Efficacy of Liquid Smoke to Mitigate Infestations of the Storage Mite, Tyrophagus putrescentiae, in a Model Semi-Moist Pet Food

The storage mite Tyrophagus putrescentiae infests a wide range of food products including pet food. Control of this mite depends on chemical methods such as fumigation and spraying with insecticides. Methyl bromide was used as a fumigant for high-value stored products, especially to control mite infestation in dry-cured hams and cheeses, but it is now banned for most uses in many countries because of its atmospheric ozone-depleting effects. Effective alternatives to methyl bromide are needed to develop integrated pest management programs for this pest. Liquid smoke is a naturally derived flavoring and preservative with known antimicrobial properties. The objective of this study was to investigate the efficacy of liquid smoke preparations, with varying phenol and carbonyl concentrations and pH, on the survivability and orientation behavior of T. putrescentiae in a model semi-moist pet food. The mite survivability assays using liquid smoke-treated and untreated semi-moist pet food samples indicated that there was no difference among treatments (p > 0.05) for mite infestation and survival. Two-choice behavioral assays using semi-moist pet food cubes dipped in varying concentrations (0%, 0.3%, 1%, 5%, 10%, 25%, 50%, or 100% v/v) of liquid smoke preparations found that some of the liquid smoke preparations containing medium to high carbonyl content repelled the mites. In conclusion, liquid smoke did not kill or inhibit the mite population growth in semi-moist pet food. However, some liquid smoke fractions containing medium to high carbonyl content were repellent to mites and may retard mite infestation in stored semi-moist foods.

Efficacy of the Fumigants Propylene Oxide and Ethyl Formate to Control Two Pest Species of Dry-Cured Hams

The ham mite Tyrophagus putrescentiae and the red-legged ham beetle Necrobia rufipes are harmful pests to several high-valued stored products. The regulatory phase-out of the fumigant methyl bromide necessitates the search for alternative fumigants. Propylene oxide (PPO) and ethyl formate (EF) were therefore evaluated in the laboratory for controlling these pests of dry-cured hams. Concentration-mortality studies at 25 °C of PPO and EF found that the mobile stages of the mites were very susceptible to low concentrations of 10 mg/L and less of each gas, while mite eggs were very tolerant and required 20 mg/L for PPO and 80 mg/L of EF for 100% mortality. Mixed life stage cultures of mites and beetles were treated for 24 h with either PPO or EF at 1× and 2× the estimated 99% lethal doses and confirmed effectiveness for controlling simulated pest populations. The sorptive properties of each gas in chambers with ham pieces, dog food kibbles, or fish meal were minimal for a reduction in mite toxicity when compared to treatments in empty chambers. There was no evidence that any desorbed gas occurred at a level toxic to mite eggs in any of the fumigated commodities. These fumigation studies with ham pests support further work with PPO and EF on any changes in the sensory quality of dry-cured hams for human taste and for commercial-scale fumigations toward regulatory approval.

The Effect of Residual Pesticide Application on Microbiomes of the Storage Mite Tyrophagus putrescentiae

Arthropods can host well-developed microbial communities, and such microbes can degrade pesticides and confer tolerance to most types of pests. Two cultures of the stored-product mite Tyrophagus putrescentiae, one with a symbiotic microbiome containing Wolbachia and the other without Wolbachia, were compared on pesticide residue (organophosphate: pirimiphos-methyl and pyrethroid: deltamethrin, deltamethrin + piperonyl butoxide)-containing diets. The microbiomes from mite bodies, mite feces and debris from the spent mite diet were analyzed using barcode sequencing. Pesticide tolerance was different among mite cultures and organophosphate and pyrethroid pesticides. The pesticide residues influenced the microbiome composition in both cultures but without any remarkable trend for mite cultures with and without Wolbachia. The most influenced bacterial taxa were Bartonella-like and Bacillus for both cultures and Wolbachia for the culture containing this symbiont. However, there was no direct evidence of any effect of Wolbachia on pesticide tolerance. The high pesticide concentration residues in diets reduced Wolbachia, Bartonella-like and Bacillus in mites of the symbiotic culture. This effect was low for Bartonella-like and Bacillus in the asymbiotic microbiome culture. The results showed that the microbiomes of mites are affected by pesticide residues in the diets, but the effect is not systemic. No actual detoxification effect by the microbiome was observed for the tested pesticides.

Using liquid smoke to control infestations of the ham mite, Tyrophagus putrescentiae, on dry-cured hams during aging

Eight treatments of edible coatings and nets including liquid smoke (SP and 24P) and xanthan gum (XG) were used to evaluate their effectiveness at controlling mite growth on dry-cured hams. Mite growth was controlled (P < 0.05) in both coating and netting treatments of 1% SP + 1% XG. Increasing SP concentration from 1% to 2% in the SP only treatments without XG did not control mite growth (P > 0.05) in the coating but controlled mite growth (P < 0.05) when infused in the nets. Both coating and netting treatments with 2% 24P + 1% XG controlled mite growth (P < 0.05), and ham cubes with 1% and 2% 24P in infused nets had mite numbers of 4.6 and 9.4, respectively. SP did not impact the sensory attributes of the ham. Results indicate that liquid smoke can potentially be added in coatings or ham nets to control mites and used in an integrated pest management program for dry-cured hams.

Pesticide residue exposure provides different responses of the microbiomes of distinct cultures of the stored product pest mite Acarus siro

Background

The contribution of the microbiome to pesticide breakdown in agricultural pests remains unclear. We analyzed the effect of pirimiphos-methyl (PM) on four geographically different cultures of the stored product pest mite Acarus siro (6 L, 6Tu, 6Tk and 6Z) under laboratory experiments. The effect of PM on mite mortality in the impregnated filter paper test was compared.

Results

The mite sensitivity to PM decreased in the order of 6 L, 6Tu, 6Tk, and 6Z. Then, the mites were cultured on PM residues (0.0125 and 1.25 µg·g⁻¹), and population growth was compared to the control after 21 days of exposure. The comparison showed two situations: (i) increasing population growth for the most sensitive cultures (6 L and 6Tu), and (ii) no effect on mite population growth for tolerant cultures (6Z and 6Tk). The microbiome of mites was analyzed by quantification of 16S DNA copies based on quantitative polymerase chain reaction (qPCR) and by barcode sequencing of the V4 fragment of 16S DNA on samples of 30 individuals from the control and PM residues. The microbiome comprised primarily Solitalea-like organisms in all cultures, except for 6Z, followed by Bacillus, Staphylococcus, and Lactobacillus. The microbiomes of mite cultures did not change with increasing population density. The microbiome of cultures without any differences in population density showed differences in the microbiome composition. A Sodalis-like symbiont replaced Solitalea in the 1.25 µg·g⁻¹ PM in the 6Tk culture. Sodalis and Bacillus prevailed in the microbiomes of PM-treated mites of 6Z culture, while Solitalea was almost absent.

Conclusion

The results showed that the microbiome of A. siro differs in composition and in response to PM residues in the diet. The results indicate that Sodalis-like symbionts can help recover mites from pesticide-induced stress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02661-4.

Synergism of deltamethrin with a mixture of short chain fatty acids for toxicity against pyrethroid-resistant and susceptible strains of Tribolium castaneum (Coleoptera: Tenebrionidae)

Deltamethrin is one of the most effective pyrethroid compounds used in stored product protection to control a wide range of pests. However, the development of resistance to deltamethrin in many pest species has been reported and useful research to overcome this problem is required. The present study investigated the possible synergistic effect of a commercial formulation of a mixture of the short chain fatty acids, octanoic, nonanoic and decanoic acid, in a formulation called "C8910" on the lethal activity of deltamethrin against susceptible (Lab-S) and relatively pyrethroid-resistant (Pyr-R) strains of T. castaneum. The possible mechanisms of synergism were studied by investigating the inhibitory effect of C8910 on the activity of detoxification enzymes including cytochrome P450s, esterases, and glutathione S-transferases (GST). In addition, the possible role of C8910 in enhancement of cuticular penetration of deltamethrin through insect cuticle was studied using GC analysis. The results showed that C8910 enhanced the toxicity of deltamethrin at mixing ratios of 1:5 and 1:10 against the Lab-S strain after 24 and 48 h of exposure, and synergistic factors (SF) ranged between 5.69 and 13.59. C8910 also showed greater synergism on the deltamethrin toxicity against the resistant strain than the susceptible one after 24 and 48 h of treatment at 1:5 and 1:10 ratios with SF values ranging from 22.82 and 47.16. C8910 showed strong inhibition of cytochrome P450 of rat microsomal fraction with IC₅₀ value of 6.24 mM. Meanwhile, C8910 inhibited the activity of general esterases in Lab-S and Pyr-R strains with IC₅₀ values of 26.22 and 51.73 mM, respectively. However, weak inhibition of GST activity was observed with inhibition of 52.0 and 22.6% at concentration of 100 mM of C8910 for Lab-S and Pyr-R, respectively. In addition, the results showed no significant difference between the unpenetrated amounts of deltamethrin when insects were treated with deltamethrin alone or with deltamethrin+C8910 (1:20) through the insect cuticle. Results suggested that the synergism between C8910 and deltamethrin could be related to the ability of C8910 to inhibit the detoxification enzymes such as cytochrome P450 and esterases. Therefore, C8910 could be a promising synergist to enhance deltamethrin toxicity and to be a possible natural alternative for conventional synergists such as piperonyl butoxide.

Nitric Oxide Fumigation for Control of Ham Mite, Tyrophagus putrescentiae (Sarcoptiformes: Acaridae)

The ham mite, Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae), is a common pest infesting several stored products, particularly the aged hams. In this study, we reported the efficacy of nitric oxide (NO) fumigation, a recently discovered fumigation treatment under the ultra-low oxygen environment, at various concentrations and time under the laboratory conditions at 25°C against different mite stages on both dietary media and ham meat. Our results showed that NO fumigation was effective against all mite stages and 100% control was achieved. Generally, the egg was the most tolerant stage and required 48-, 24-, 16-, and 8-h treatments to achieve 100% mortality at 0.5, 1, 1.5, and 2% NO concentration on dietary media, respectively. Tyrophagus putrescentiae mobile immatures and adult stages were less tolerant, and 100% mortality was achieved after 16-, 8-, 8-, and 4-h treatment at 0.5, 1, 1.5, and 2% NO, respectively. The median lethal concentration (LC50) of NO on egg was 0.86, 0.68, and 0.32% for 8-, 16-, and 24-h treatments. In addition, a confirmatory test was conducted on ham meat at 0.5 and 1.0% of NO and similar efficacy was found. Complete control of egg was achieved after 48- and 24-h treatment at 0.5 and 1.0% of NO, respectively, and larvae and adult mites were 100% controlled after 16 and 8 h at 0.5 and 1.0% of NO, respectively. Our results demonstrated that NO fumigation was effective against T. putrescentiae and can be a potential alternative treatment to methyl bromide for cured-ham pest control.

Effects of Diet and Temperature on the Life History of the Redlegged Ham Beetle (Coleoptera: Cleridae)

We investigated the effects of various foods and different rearing temperatures on the survival and development of the redlegged ham beetle Necrobia rufipes (De Geer) (Coleoptera: Cleridae), a serious pest of dry-cured hams. The diets tested were dried pet food, finely shredded copra, shredded cheese, dry-cured ham, ground fish meal, and mature larvae of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). As indicated by the growth index and k-values, N. rufipes populations grew fastest on the pet food and slowest on the copra. On the other hand, N. rufipes fed both ham and T. castaneum larvae produced significantly heavier larvae. The adult beetles lived significantly longer on cheese compared to other foods. Studies conducted to determine the developmental rates of N. rufipes fed pet food at temperatures of 22, 25, 28, and 31°C showed that the total developmental time and longevity of N. rufipes significantly varied at different temperatures tested. The shortest developmental time (93.32 d) was observed at 28°C. Oviposition rate was highest for females reared at 25°C while lowest at 22°C. Based on the development, reproduction, and thermal requirements, the most suitable temperature for N. rufipes was between 28 and 31°C. The results also revealed that larval cannibalism prevailed among adult beetles.

A Combination Sulfuryl Fluoride and Propylene Oxide Treatment for Trogoderma granarium (Coleoptera: Dermestidae)

The khapra beetle, Trogoderma granarium, is an important quarantine pest of stored-products. While it is not established in the North America, frequent interceptions highlight the need for treatments to eradicate isolated populations if they occur. Methyl bromide has long been the standard fumigant used for this purpose; however, increasing restrictions on its use necessitate the development of new treatment options. Here we evaluate a treatment for khapra beetle using a combination of sulfuryl fluoride (SF) and propylene oxide (PPO). Experiments were conducted to determine the most tolerant stages and the effective rates for each compound. Combination treatments using both products were then evaluated at several temperatures to determine effective doses for quarantine level control. The egg stage was by far the most tolerant to SF, requiring concentration × time (CT) products roughly 10-fold greater than the next most tolerant stage, diapausing larvae. Diapausing larvae were significantly more tolerant to SF than non-diapausing larvae in a recently collected 'field' strain, but not in a more than 30-yr-old 'laboratory' culture. PPO treatments were shown to completely control the egg stage at CTs greater than 155 hr-mgL-1 at both 10 and 20°C. Resulting combination treatments with initial dose rates of 96 and 40 mgL-1 at 10°C and 80 and 40 mgL-1 at 20°C are proposed for SF and PPO, respectively. These combination treatments utilize SF's efficacy against the larval stage along with PPO's superior ovicidal properties to provide enhanced treatment efficacy over each product alone against all life stages of khapra beetle.

Responses of Red Flour Beetle Adults, Tribolium castaneum (Coleoptera: Tenebrionidae), and Other Stored Product Beetles to Different Pheromone Trap Designs

Simple Summary

Traps are used to monitor insect pests in stored food product habitats, and information on insects trapped can be used for making control decisions in pest control programs. A special trap is used for adults of the red flour beetle, one of the most serious pests of flourmills worldwide. The red flour beetle trap is a “pitfall” design wherein a walking beetle orients to the trap, it climbs up the inclined side of the trap to the top of a cup, it then slips or walks over the edge of the cup. The beetle falls into the bottom of the cup, where it is retained and killed inside the food oil placed in the bottom of the cup. However, dusty environments can result in the pitfall trap operating poorly and not capturing beetles at an optimum level. This research showed that a dust cover can be applied to the top of a baited pitfall trap and significantly improve capture of beetles in dusty environments of a flourmill. The dust cover was incorporated into the commercial pitfall trap product and now is known as the Dome trap, which is widely used for pest management of flour beetles and other stored product insects throughout the grain and food industries in many countries.

Abstract

A series of laboratory and field experiments were performed to assess the responses of Tribolium castaneum (Herbst) and other stored-product beetles to pheromone-baited traps and trap components. A commercial Tribolium pitfall trap called the Flit-Trak M², the predecessor to the Dome trap, was superior in both laboratory and field experiments over the other floor trap designs assessed at capturing walking T. castaneum. In field experiments, Typhaea stercorea (L.) and Ahasverus advena (Stephens) both preferred a sticky trap to the pitfall trap. Although the covered trap is effective at capturing several other species of stored product beetles, the synthetic Tribolium aggregation pheromone lure is critical for the pitfall trap’s efficacy for T. castaneum. Although the food-based trapping oil used in the pitfall trap was not found to be attractive to T. castaneum when assayed alone, it had value as an enhancer of the pheromone bait when the two were used together in the trap. A dust cover modification made to go over the pitfall trap was effective in protecting the trap from dust, although the trap was still vulnerable to dust contamination from sanitation techniques that used compressed air to blow down the mill floors. Capture of T. castaneum in the modified trap performed as well as the standard trap design in a non-dusty area of a flour mill, and was significantly superior over the standard trap in a dusty area. T. castaneum responded in flight outside a flourmill preferentially to multiple funnel traps with pheromone lures compared to traps without pheromone.

Ethanedinitrile as a Fumigant for Lasioderma serricorne (Coleoptera: Anobiidae), and Rhyzopertha dominica (Coleoptera: Bostrichidae): Toxicity and Mode of Action

This study evaluated the fumigant ethanedinitrile (EDN) against the cigarette beetle, Lasioderma serricorne, and phosphine-resistant and susceptible lesser grain borer, Rhyzopertha dominica, life stages under laboratory conditions. Eggs of both species were the most susceptible stage to EDN. EDN is, therefore, a promising alternative because eggs are generally tolerant to most common fumigants. Lasioderma serricorne eggs were the most susceptible with an LC50 estimated of 50.4 ppm, followed by adults, pupae and larvae with LC50 values of 160.2, 192.5, and 446.6 ppm, respectively, after 24-h exposure at 25°C. Eggs of phosphine-susceptible (LC50 = 11.2 ppm) and resistant (LC50 = 12.0 ppm) R. dominica strains were more susceptible to EDN than were adults of both strains, with LC50 values of 27.7 and 36.0 ppm, respectively. Lasioderma serricorne mixed life stage cultures were completely controlled at concentrations ≥2,000 ppm at 24 h. Fumigation with 600 ppm was enough to suppress adult emergence in the case of the phosphine-susceptible R. dominica strain (USDA), while an average of only 4.0 adults emerged from the phosphine-resistant R. dominica strain (Belle Glade) compared with 514.3 adults in the control. Lasioderma serricorne was more tolerant to EDN than both R. dominica strains. EDN caused 61.8 and 68.2 % inhibition of R. dominica (USDA) cytochrome c oxidase activity at concentrations of 0.0038 and 0.0076 mM in vitro, respectively, and it did not inhibit its activity in the case of an in vivo assay. These results suggest that cytochrome c oxidase may not be the main target for EDN toxicity.

Efficacy of Sulfuryl Fluoride Against Fourth-Instar Pecan Weevil (Coleoptera: Curculionidae) in Pecans for Quarantine Security

The efficacy of sulfuryl fluoride was evaluated for control of fourth-instar pecan weevil, Curculio caryae (Horn), at 25°C for a 24-h exposure. Larvae, collected as they naturally emerged from pecans, were used to artificially infest pecan nuts. Infested nuts were fumigated with six concentration by time (CT) treatment dosages of sulfuryl fluoride (0-750 g-h/m3) within air-tight, glass containers. The sulfuryl fluoride concentration in each fumigation container was analyzed 30 min after sulfuryl fluoride introduction and just prior to termination of the experiment. Mean sulfuryl fluoride CT dosages were calculated from sulfuryl fluoride measurements and were used for probit analysis. The lethal accumulated dosage (LAD99) of sulfuryl fluoride for pecan weevil was 1052.0 g-h/m3 with a 95% C.I. of 683.21-2,573.0 g-h/m3. For the confirmatory trial, we used two sulfuryl fluoride CT dosage treatments, 1,100 and 1,300 g-h/m3, and a nonfumigated control. All larvae were dead in both fumigation treatments by 14-d postfumigation. Due to higher mortality in the nonfumigated control in the confirmatory trial compared to that of the dose-response trial, 1300 g-h/m3 was selected as the sulfuryl fluoride CT dosage for a proposed quarantine treatment schedule. Fumigating pecans with sulfuryl fluoride can control larval pecan weevil infestations in commercially traded nuts and maintain compliance with quarantine regulations both within and outside the United States.

High-dose strategies for managing phosphine-resistant populations of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

BACKGROUND

Rhyzopertha dominica is a serious pest of stored grains and many populations have resistance to the fumigant phosphine. Some populations contain beetles with a 'strong resistance' phenotype. Recent work found the LC₅₀ values for two strong-resistant populations recently studied in North America, Belle Glade and Minneapolis were 100- and 595-fold higher, respectively, compared to LC₅₀ of a lab-susceptible strain. Populations with 'weak-resistant' phenotypes had LC₅₀ values 5- to 10-fold that of a susceptible strain. The work reported below aimed to determine the minimum phosphine concentrations and number of days of exposure needed to effectively control all life stages of representative weak- and strong-resistant strains, and then to recommend the treatment conditions needed to control strongly phosphine-resistant R. dominica in pest populations.

RESULTS

A dose-mortality assay estimated that phosphine fumigation over 48 h using 730-870 ppm at 25° C would control adults of both strongly resistant R. dominica populations. Fumigations with mixed life stage cultures found 200 ppm killed all susceptible and weak-resistant beetles in 2 days, but the strong-resistant Minneapolis and Belle Glade strains had substantial survivors at 200 ppm. Furthermore, the Belle Glade strain had beetles that survived 1000 ppm in 2-day fumigations. The strong-resistant Belle Glade strain needed nearly 10 days at over 400 ppm to have acceptable levels of control.

CONCLUSION

This study recommends protocols to manage strongly resistant R. dominica populations provided that a minimum phosphine concentration of 400 ppm be maintained at 25° C or higher for up to 10 days. © 2019 Society of Chemical Industry.

Comparison of Methyl Bromide and Phosphine for Fumigation of Necrobia rufipes (Coleoptera: Cleridae) and Tyrophagus putrescentiae (Sarcoptiformes: Acaridae), Pests of High-Value Stored Products

Fumigation with methyl bromide has been a long established and effective method for controlling many pests of stored products, including the key major pests that infest dry-cured hams, aged cheese, and other value-added durable stored products. Methyl bromide had been widely used for the disinfestation of dry-cured ham facilities in the United States, but is now phased out of use since it is an ozone-depleting substance. This paper reports laboratory studies to evaluate the efficacies of methyl bromide and phosphine for controlling two of the key arthropod pests of dry-cured hams and aged cheeses. Larvae of the red-legged ham beetle, Necrobia rufipes (Fabricius), were the most tolerant life stages when treated with either phosphine or methyl bromide for 48 h exposure at 23°C, whereas eggs of the mold mite, Tyrophagus putrescentiae (Schrank), were slightly more tolerant than mobile stages for both compounds. Under laboratory conditions, complete control was achieved for the both species with concentrations of 0.85 and 4.0 g/m3 of phosphine and methyl bromide, respectively, at 48 h exposure. The results give new information for judicious use of the existing stocks of methyl bromide, whether for pest mitigation or to help in developing a quarantine treatment schedule with that gas. Phosphine shows good potential as an effective alternative to methyl bromide, but if it was to be adopted as a fumigant in the dry-cured ham industry, methods to prevent metal corrosion would need to be designed and effectively implemented.

Resistance to the Fumigant Phosphine and Its Management in Insect Pests of Stored Products: A Global Perspective

Development of resistance in major grain insect pest species to the key fumigant phosphine (hydrogen phosphide) across the globe has put the viability and sustainability of phosphine in jeopardy. The resistance problem has been aggravated over the past two decades, due mostly to the lack of suitable alternatives matching the major attributes of phosphine, including its low price, ease of application, proven effectiveness against a broad pest spectrum, compatibility with most storage conditions, and international acceptance as a residue-free treatment. In this review, we critically analyze the published literature in the area of phosphine resistance with special emphasis on the methods available for detection of resistance, the genetic basis of resistance development, key management strategies, and research gaps that need to be addressed.

Development of a Quick Knockdown Test for Diagnosing Resistance to Phosphine in Sitophilus oryzae (Coleoptera: Curculionidae), a Major Pest of Stored Products

A key component in the management of resistance to fumigant phosphine in stored products pests is their early detection and implementation of control strategies. Currently, resistance testing involves exposing adults to a specific discriminating concentration over a fixed time period (20-48 h). Although it is widely adopted, this test takes significant time for assay preparation (up to 4 wk) as well as diagnosis (1-2 wk). To address these lacunae, we have established a 'quick knockdown test' using a key grain insect pest, rice weevil, Sitophilus oryzae (L.). Susceptible, weakly and strongly phosphine-resistant reference strains were exposed to a threshold concentration of phosphine over short exposure periods (min to h). The time to knockdown (KT) responses to phosphine were characterized at 2 (1,440 ppm) and 5 mg/liter (3,600 ppm). The time to 99.9% KT (KT99.9) at 2 mg/liter was 12.52 min for the susceptible adults, compared with 167.9 and 1,510 min in the case of weakly and strongly resistant phenotypes, respectively. As anticipated, increasing the concentration of phosphine to 5 mg/liter halved the KT99.9 (81.57 min) to separate weakly and strongly resistant populations than it was required at 2 mg/liter. We validated the KT99.9 value for the 5 mg/liter against field-derived populations of S. oryzae. The results were aligned with the existing Food and Agriculture Organization approach, confirming that the proposed 'quick test' is a reliable tool to rapidly diagnose resistance in this species.

Evaluation of Knockdown Bioassay Methods to Assess Phosphine Resistance in the Red Flour Beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Resistance to the fumigant phosphine in Tribolium castaneum occurs worldwide. This study evaluated tests based on adult knockdown time, the time for a beetle to become immobile, when exposed to a high concentration of phosphine. We recorded knockdown times of beetles that remained completely still for 30 s when exposed to 3000 ppm of phosphine in a large, gas-tight glass tube. Beetles were used from 12 populations, of which six were 'susceptible' to phosphine, three were 'weakly resistant', and three were 'strongly resistant'. Knockdown times were determined for single beetles, as well as for groups of ten beetles for which the time to knockdown for either five beetles (KT50) or ten beetles (KT100) were recorded. Similar knockdown times occurred across susceptible and resistant populations. However, the KT100 tests generated conservative times for diagnosing strong vs. weak resistance. The strong resistant populations were all over 100 min with KT100, compared to 60 min or less for susceptible and weak resistant populations. Special tests on single beetles revealed higher knockdown times in insects that were deliberately disturbed compared to those without any disturbances. Work reported here suggests a knockdown test conducted on beetles in a matter of minutes or hours could help classify phosphine resistance status prior to decisions on phosphine fumigation.

Biology and Control of the Khapra Beetle, Trogoderma granarium, a Major Quarantine Threat to Global Food Security

The khapra beetle, Trogoderma granarium, is a voracious feeder of stored products and is considered one of the most important quarantine pests globally. Its ability to survive for long periods under extreme conditions facilitates its spread through international commerce, which has led to invasions of new geographic regions. The khapra beetle is an important quarantine pest for many countries, including the major wheat-producing countries the United States, Canada, Russia, and Australia, and has been classified as one of the 100 worst invasive species worldwide. This species cannot always be controlled by insecticides and other nonchemical methods that are usually effective against other pests of stored products, particularly owing to its diapausing late larval stage. It can rapidly develop at elevated temperatures and under dry conditions, which are not favorable for many major stored-product insects. We synthesize key published work to draw attention to advances in biology, detection and control of the khapra beetle, and directions to consider for future research.

Evaluation of Light Attraction for the Stored-Product Psocids, Liposcelis entomophila, Liposcelis paeta, and Liposcelis brunnea

Psocids have become global pests of stored commodities as they can cause considerable economic losses. These insects are difficult to control because they have developed resistance to many chemical insecticides. Therefore, it is crucial to investigate alternative integrated pest management (IPM) approaches, such as the use of light attraction for monitoring and/or controlling psocids. Light attraction has been studied for Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae) but not for other psocid species. In this study, we investigated the response of adults of three psocid species (Psocoptera: Liposcelididae), Liposcelis entomophila (Enderlein), Liposcelis paeta Pearman, and Liposcelis brunnea Motschulsky, to six wavelengths of light from light-emitting diode (LED) in paired-choice pitfall tests. L. entomophila females and males were not attracted to any of the wavelengths tested. L. paeta females responded positively to two ultraviolet (UV) wavelengths (351 and 400 nm) and to green light (527 nm), while males did not respond to any light. L. brunnea females and males responded positively to all six wavelengths evaluated. Most of the LEDs that elicited positive responses to L. paeta females and L. brunnea females and males were also preferred when these lights were presented against brewer's yeast, a food attractant highly preferred by several psocid species. Females of L. paeta and L. brunnea were attracted to white light when compared with a blank, but females of L. entomophila were not attracted to white light compared to a blank.

Phosphine Resistance in North American Field Populations of the Lesser Grain Borer, Rhyzopertha dominica (Coleoptera: Bostrichidae)

Phosphine is the most widely used fumigant for stored grain insect pests, and resistance to phosphine has evolved in several species worldwide. This study was designed to determine the presence of phosphine resistance in 34 populations of Rhyzopertha dominica (F.) collected from the United States and Canada. Adult R. dominica were sampled and subjected to a discriminatory dose toxicity assay of exposure to 20 ppm of phosphine for 20 h of exposure to distinguish a susceptible R. dominica adult by death from a resistant beetle that survives the treatment. All but two of the 34 geographic populations surveyed had some beetles that were resistant to phosphine, and the frequency of resistance varied from 97% in a population from Parlier, California to 0% in beetles from both Carnduff, Saskatchewan and Starbuck, Manitoba. Probit analyses of dose-mortality bioassays with beetles from a laboratory-susceptible strain and those from five of the populations sampled were used to calculate resistance ratio factors (RRs) based on the ratio of LC50 (estimate for the concentration to kill 50% of a test group) in the sampled population to the LC50 for the susceptible strain. The highest RR for the five resistant populations was nearly 596-fold in beetles from Belle Glade, Florida, whereas the lowest RR in that group was 9-fold in Wamego, Kansas. This study revealed that phosphine resistance in R. dominica is common across North America and some populations have levels of resistance that may pose challenges for continued use of phosphine for their management.

Use of Lard, Food Grade Propylene Glycol, and Polysaccharides in Infused Nets to Control Tyrophagus putrescentiae (Schrank; Sarcoptiformes: Acaridae) Infestation on Dry Cured Hams

Tyrophagus putrescentiae (Schrank) is controlled in the U.S. dry cured ham industry with methyl bromide (MB) fumigation. However, MB fumigation is being phased out of use since it is an ozone depleting substance. The objective of this research was to evaluate ham nets that were infused with lard, propylene glycol (PG) and polysaccharide coating for their efficacy at controlling mite infestations on dry cured ham cubes from hams that were aged for 4 to 6 mo. Results indicated that fewer T. putrescentiae (P < 0.05) were on ham cubes with treated nets containing PG when compared to the number of mites on ham cubes with untreated nets over 10 wk of storage. Lard infused nets without PG did not decrease the mite population (P > 0.05). The net without coating slowed the growth and reproduction of T. putrescentiae since net controls had fewer mites (P < 0.05) than controls without nets. Fungi were not present on ham cubes that were treated with PG-containing nets over 10 wk of storage with a few exceptions. In conclusion, lard and xanthan gum, or carrageenan + propylene glycol alginate treated nets containing the medium concentration of PG effectively inhibited mite reproduction and fungal growth on dry cured ham and could potentially be used in an integrated pest management program to control mites on dry cured hams.

Application of Food-Grade Ingredients to Nets for Dry Cured Hams to Control Mite Infestations

Infestations of Tyrophagus putrescentiae (Schrank; Sarcoptiformes: Acaridae), known as the ham mite, may occur on dry cured hams during the aging process. The fumigant methyl bromide is currently used to control mite infestations, but it will eventually not be available for use since it contributes to the depletion of the ozone layer. The use of ham nets treated with xanthan gum, carrageenan, propylene glycol alginate, and propylene glycol food-grade ingredients on mite orientation to or oviposition on treated or untreated ham cubes, and mite reproduction and population growth over a 10-wk period was evaluated. Behavioral tests indicated that more than 95% of the mites oriented to the ham cubes that were wrapped in untreated nets when compared to treated nets and no eggs were laid on the latter. The reproduction assays demonstrated that there were fewer (P < 0.05) T. putrescentiae produced over a 2-wk period on ham cubes covered with both gum and propylene glycol treated nets, when compared to the untreated or gum-only treated nets over the 10-wk storage period of the experiment. Medium and high concentrations of propylene glycol treatments showed the lowest reproductive rates of mites. No more than 4 mites could be found on each of these treatments in comparison to 200 to 300 mites that were recorded on the untreated hams. This study demonstrated efficacy of using the nets treated with food-grade ingredients during ham aging to control mite infestations on a laboratory scale. Further research will be conducted to determine the effectiveness of the same treated nets on whole hams in commercial aging rooms.

Geographic Variation in Phosphine Resistance Among North American Populations of the Red Flour Beetle (Coleoptera: Tenebrionidae)

The red flour beetle, Tribolium castaneum (Herbst), is a common stored-product pest found worldwide. Phosphine, hydrogen phosphide (PH3), is the most commonly used fumigant for stored grains, for which genetically based resistance has been recorded for several pest species. This study assessed phosphine resistance in 25 T. castaneum populations from across the United States and Canada using a discriminating dose bioassay. Dose-mortality assays were conducted with adults from seven of these populations to categorize weak and strong resistance phenotypes. Phosphine resistance was detected in 12 out of the 25 populations, and the frequency of resistance within populations varied from 2% in Victoria, TX, to 100% in Red Level, AL. Two resistant populations from Kansas that had been sampled three years earlier were found to have similar resistance frequencies in the current study. None of the four Canadian populations had any detectable resistance among the insects tested. Resistance ratio calculations from LC50 value in resistant populations relative to the LC50 for the laboratory susceptible strain allowed resistance phenotypes to be assigned as either weak resistance, at 5- to 26-fold resistance relative to susceptible, or strong resistance at 95- to 127-fold relative to susceptible. This study suggests that proper resistance assessment techniques can help to determine occurrence of phosphine resistance in populations of T. castaneum and can further characterize the strength of resistance present. These data can be used to support resistance management programs that consider either cessation or modification of phosphine fumigation to control T. castaneum.

Bright conjugated polymer nanoparticles containing a biodegradable shell produced at high yields and with tuneable optical properties by a scalable microfluidic device

This study compares the performance of a microfluidic technique and a conventional bulk method to manufacture conjugated polymer nanoparticles (CPNs) embedded within a biodegradable poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) (PEG_5K-PLGA_55K) matrix. The influence of PEG_5K-PLGA_55K and conjugated polymers cyano-substituted poly(p-phenylene vinylene) (CN-PPV) and poly(9,9-dioctylfluorene-2,1,3-benzothiadiazole) (F8BT) on the physicochemical properties of the CPNs was also evaluated. Both techniques enabled CPN production with high end product yields (∼70-95%). However, while the bulk technique (solvent displacement) under optimal conditions generated small nanoparticles (∼70-100 nm) with similar optical properties (quantum yields ∼35%), the microfluidic approach produced larger CPNs (140-260 nm) with significantly superior quantum yields (49-55%) and tailored emission spectra. CPNs containing CN-PPV showed smaller size distributions and tuneable emission spectra compared to F8BT systems prepared under the same conditions. The presence of PEG_5K-PLGA_55K did not affect the size or optical properties of the CPNs and provided a neutral net electric charge as is often required for biomedical applications. The microfluidics flow-based device was successfully used for the continuous preparation of CPNs over a 24 hour period. On the basis of the results presented here, it can be concluded that the microfluidic device used in this study can be used to optimize the production of bright CPNs with tailored properties with good reproducibility.

Evolution of Stored-Product Entomology: Protecting the World Food Supply

Traditional methods of stored-product pest control were initially passed from generation to generation. Ancient literature and archaeology reveal hermetic sealing, burning sulfur, desiccant dusts, and toxic botanicals as early control methods. Whereas traditional nonchemical methods were subsequently replaced by synthetic chemicals, other traditional methods were improved and integrated with key modern pesticides. Modern stored-product integrated pest management (IPM) makes decisions using knowledge of population dynamics and threshold insect densities. IPM programs are now being fine-tuned to meet regulatory and market standards. Better sampling methods and insights from life histories and ecological studies have been used to optimize the timing of pest management. Over the past 100 years, research on stored-product insects has shifted from being largely concentrated within 10 countries to being distributed across 65 countries. Although the components of IPM programs have been well researched, more research is needed on how these components can be combined to improve effectiveness and assure the security of postharvest food as the human population increases.

Time-Mortality Relationships to Control Tyrophagus putrescentiae (Sarcoptiformes: Acaridae) Exposed to High and Low Temperatures

Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae) is a widely distributed pest species that is of significant economic importance for dry-cured country hams. Methyl bromide was used for decades in country ham plants to control this pest, but now this fumigant is recognized as an atmospheric ozone-depleting compound and will be phased out for all uses in the near future. Of various chemical and nonchemical alternatives to methyl bromide, extreme temperatures are viable and straightforward nonchemical methods to control pests. This study evaluated the efficacy of high and low temperatures on mortality of mold mite in the laboratory. Ten eggs and a mixture of 40 adults and nymphs were separately exposed to different high and low temperatures, ranging from +35 to 45 °C and from -20 to +5 °C, for several periods of time. Mortality was assessed after a recovery period for each life stage. Tyrophagus putrescentiae eggs were found to be more tolerant to both high and low temperatures than were the mobile stages. Results showed that high temperatures from 40-45 °C killed all mites within 4 to 1 d, respectively, while -10 °C or lower killed all mites in less than 1 d. Regression analyses of mortality data as a function of exposure predicted times for achieving desired levels of mite mortality. This study suggests that extreme temperature treatment can play an important role in integrated pest management programs for dry-cured ham as an alternative to methyl bromide or other chemical treatments.

Monitoring Tyrophagus putrescentiae (Acari: Acaridae) With Traps in Dry-Cured Ham Aging Rooms

Methyl bromide is the most effective fumigant for controlling the mold (or ham) mite, Tyrophagus putrescentiae (Schrank) (Acari: Acaridae), the most significant pest of dry-cured ham. However, methyl bromide is being phased out of use. Therefore, integrated pest management (IPM) methods should be developed to help control mites in dry-cured ham plants. The foundation of a successful IPM program is an effective monitoring program that provides information on pest presence and abundance over time. By using food-baited traps fabricated from disposable petri dishes and a dog food-based bait, mite activity over time and space was monitored in five dry-cured ham aging rooms from three commercial processing facilities that differed in their fumigation frequencies. Weekly sampling of the mite was conducted from June 2012 to September 2013. There were significant differences in the average weekly trap captures in all facilities, especially before and after fumigation, with the majority of mites in traps prior to fumigation. Mite numbers had a pattern of sharp decline after fumigation, followed by a steady increase until the next fumigation. Average trap captures varied due to trap location over the study period at all study sites, indicating that traps could be used to identify specific locations within an aging room where mite infestation of hams was more likely to occur. These findings can inform facility managers of mite population changes that can be used as one factor toward making pest management decisions and assessing the impact of fumigation or other pest mitigation actions.

Efficacy of selected food-safe compounds to prevent infestation of the ham mite, Tyrophagus putrescentiae (Schrank) (Acarina: Acaridae), on southern dry-cured hams

BACKGROUND

Tyrophagus putrescentiae (Schrank) is a serious mite pest of dried meats and cheeses. Infestations of T. putrescentiae are controlled with the fumigant methyl bromide, which is an ozone-depleting substance and is currently being banned in most countries. Effective alternatives to methyl bromide are needed. The objective of this research was to use laboratory assays to investigate the effectiveness of food-safe compounds for preventing infestation of T. putrescentiae on dry-cured hams.

RESULTS

Ham pieces dipped in solutions of either propylene glycol (1,2-propanediol), lard, ethoxyquin or butylated hydroxytoluene prevented or significantly reduced mite population growth. Behavioral assays revealed that more mites oriented to the untreated control ham cubes, and more eggs were laid on these untreated ham cubes, compared with cubes treated with various dips. Our results also indicated that a combination of carrageenan + propylene glycol alginate + 40% propylene glycol was effective in reducing mite numbers on whole aging hams compared with untreated whole hams.

CONCLUSIONS

Several food-safe compounds can prevent infestation of T. putrescentiae on dry-cured hams and may represent alternatives for managing this pest. © 2015 Society of Chemical Industry.

Populations of Stored Product Mite Tyrophagus putrescentiae Differ in Their Bacterial Communities

Background:Tyrophagus putrescentiae colonizes different human-related habitats and feeds on various post-harvest foods. The microbiota acquired by these mites can influence the nutritional plasticity in different populations. We compared the bacterial communities of five populations of T. putrescentiae and one mixed population of T. putrescentiae and T. fanetzhangorum collected from different habitats.

Material: The bacterial communities of the six mite populations from different habitats and diets were compared by Sanger sequencing of cloned 16S rRNA obtained from amplification with universal eubacterial primers and using bacterial taxon-specific primers on the samples of adults/juveniles or eggs. Microscopic techniques were used to localize bacteria in food boli and mite bodies. The morphological determination of the mite populations was confirmed by analyses of CO1 and ITS fragment genes.

Results: The following symbiotic bacteria were found in compared mite populations: Wolbachia (two populations), Cardinium (five populations), Bartonella-like (five populations), Blattabacterium-like symbiont (three populations), and Solitalea-like (six populations). From 35 identified OTUs₉₇, only Solitalea was identified in all populations. The next most frequent and abundant sequences were Bacillus, Moraxella, Staphylococcus, Kocuria, and Microbacterium. We suggest that some bacterial species may occasionally be ingested with food. The bacteriocytes were observed in some individuals in all mite populations. Bacteria were not visualized in food boli by staining, but bacteria were found by histological means in ovaria of Wolbachia-infested populations.

Conclusion: The presence of Blattabacterium-like, Cardinium, Wolbachia, and Solitalea-like in the eggs of T. putrescentiae indicates mother to offspring (vertical) transmission. Results of this study indicate that diet and habitats influence not only the ingested bacteria but also the symbiotic bacteria of T. putrescentiae.

Effectiveness of Sulfuryl Fluoride Fumigation for the Control of Phosphine-Resistant Grain Insects Infesting Stored Wheat

A field experiment was conducted in eight 13.6-MT steel bins containing 6.8 MT each of wheat to assess efficacy of sulfuryl fluoride or SF fumigant to control phosphine-resistant and susceptible Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst). Approximately 400 adults of each type of beetle were added to each bin. Additionally, muslin bags containing immature stages and adults, with their respective diets, were also placed in bins. Four bins were fumigated with SF and others were untreated control bins. The SF dosages in treated bins ranged from 1,196–1,467 mg-h/liter. Mortality of adults in each bag was assessed 5 d postfumigation; diet minus adults was incubated in a jar, and number of adults counted after 8 wk. No significant change occurred in number of insect-damaged kernels in SF-treated bins. In trier samples from SF-treated bins, R. dominica numbers declined from 24 prefumigation to 0 at 3- and 6-wk postfumigation; T. castaneum numbers were unchanged. In WBII traps from SF-treated bins, numbers R. dominica and T. castaneum declined from 25 and 33, respectively, prefumigation to 0 or near 0 at 3- and 6-wk postfumigation. Mortalities of resistant and susceptible adult R. dominica, and adult and large larvae of T. castaneum in SF-treated bags was 100%. For all four types of beetles, adult numbers in jars associated with SF-treated bins were 0 or near 0. Results show SF is effective against all life stages of phosphine-resistant R. dominica and T. castaneum, and can be used for phosphine resistance management.

Movement and Orientation Decision Modeling of Rhyzopertha dominica (Coleoptera: Bostrichidae) in the Grain Mass

Grain stored in bins is initially a relatively homogenous resource patch for stored-product insects, but over time, spatial pattern in insect distribution can form, due in part to insect movement patterns. However, the factors that influence stored-product insect movement patterns in grain are not well-understood. This research focused on the movement of the lesser grain borer, Rhyzopertha dominica (F.), within a simulated wheat grain mass (vertical monolayer of wheat) and the identification of factors that contribute to overall and upward movement (age since adult emergence from an infested kernel [1, 7, and 14 d], sex, strain, and different levels of environment quality). We also used the model selection approach to select the most relevant factors and determine the relationships among them. Three-week-old adults tended to stay closer to the surface compared with 1- or 2-wk-old insects. Also, females tended to be more active and to explore a larger area compared with males. Explored area and daily displacement were also significantly strain-dependent, and increasing grain infestation level decreased daily displacement and explored area. Variation in movement pattern is likely to influence the formation of spatial pattern and affect probability to disperse. Understanding movement behavior within a grain bin is crucial to designing better strategies to implement and interpret monitoring programs and to target control tactics.

Oviposition by Female Plodia interpunctella (Lepidoptera: Pyralidae): Description and Time Budget Analysis of Behaviors in Laboratory Studies

The oviposition behavior of the Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), a major insect pest of durable stored foods, was studied in small experimental arenas under laboratory conditions using videography, and a time budget analysis of its behaviors was documented. Resting gravid females typically became active shortly after the start of the scotophase. The characteristic behaviors exhibited by mated females prior to oviposition included antennal movement, grooming of antennae and mouth parts using the forelegs, walking or flying, and abdomen bending and dragging. Pre-oviposition behaviors such as antennal grooming and walking or flying were observed to alternate several times before females commenced the abdominal dragging behavior that preceded egg laying. Eggs were laid singly or sometimes in groups, either freely or stuck to food material. Gravid females showed little or no movement during the photophase; however, they actively flew and oviposited during the scotophase. Females allocated only a small portion of their time to oviposition while the rest of the time was spent away from food. Females oviposited on food material by making repeated visits, predominantly during the first four hours of the scotophase. Visits and time spent on food declined as the scotophase advanced.

Developing food-grade coatings for dry-cured hams to protect against ham mite infestation

Dry-cured hams may become infested with ham mites, Tyrophagus putrescentiae, during the aging process. Methyl bromide is the only known available fumigant pesticide that is effective at controlling ham mite infestations in dry cured ham plants. However, methyl bromide will be phased out of all industries as early as 2015 due to its status as an ozone-depleting substance. Research was conducted to develop and evaluate the potential of using food-grade film coatings to control mite infestations, without affecting the aging process and sensory properties of the dry-cured hams. Cubes coated with xanthan gum+20% propylene glycol and carrageenan/propylene glycol alginate+10% propylene glycol were effective at controlling mite infestations under laboratory conditions. Water vapor permeability was measured to estimate the impact of coatings during the aging process. It was evident that carrageenan/propylene glycol alginate coatings were permeable to moisture, which potentially makes them usable during aging.

Resistance of Lasioderma serricorne (Coleoptera: Anobiidae) to Fumigation with Phosphine

Lasioderma serricorne (F.) is a serious pest of stored products that is known to be resistant to the fumigant pesticide gas phosphine. This study investigated resistance in populations from the southeastern United States, and determined if a recommended treatment schedule could kill resistant insects. A laboratory assay for adult insects was developed that used a discriminating concentration of 50 ppm phosphine applied to insects for 20 h at 25°C followed by 7 d of recovery in air. Survivors were classified as resistant. L. serricorne from six different field populations associated with stored tobacco were surveyed with the assay and all had resistant individuals. Four populations had greater than 90% of their insects resistant. Two industry-recommended treatment schedules were evaluated in laboratory fumigations against mixed life stage cultures of the four most resistant populations: the first at 200 ppm for 4 d at 25°C for controlling phosphine-susceptible L. serricorne and the second at 600 ppm for 6 d at 25°C intended to control phosphine-resistant beetles. The four populations with the highest frequency of resistant individuals from the field sampling study were not controlled by the "normal" treatment intended for susceptible insects. The higher concentration treatment greatly reduced beetle progeny from mixed-stage colony jars, but there were substantial numbers of surviving adults from all four highly resistant populations that represented unacceptable levels of control.

Ecological Networks in Stored Grain: Key Postharvest Nodes for Emerging Pests, Pathogens, and Mycotoxins

Wheat is at peak quality soon after harvest. Subsequently, diverse biota use wheat as a resource in storage, including insects and mycotoxin-producing fungi. Transportation networks for stored grain are crucial to food security and provide a model system for an analysis of the population structure, evolution, and dispersal of biota in networks. We evaluated the structure of rail networks for grain transport in the United States and Eastern Australia to identify the shortest paths for the anthropogenic dispersal of pests and mycotoxins, as well as the major sources, sinks, and bridges for movement. We found important differences in the risk profile in these two countries and identified priority control points for sampling, detection, and management. An understanding of these key locations and roles within the network is a new type of basic research result in postharvest science and will provide insights for the integrated pest management of high-risk subpopulations, such as pesticide-resistant insect pests.

Controlling pests in dry-cured ham: A review

Dry-cured hams can become infested with ham mites, red-legged beetles, cheese skippers, and larder beetles during the aging process. Though other methods may be used for beetles and cheese skippers, methyl bromide is the only available fumigant that is effective at controlling ham mites in dry-cured ham plants in the United States. However, methyl bromide will be phased out of all industries by approximately 2015. This paper will review and explore potential alternatives that have been investigated to determine their feasibility for replacing methyl bromide to control pest infestations in dry-cured ham plants in the United States. Potential alternatives include: 1) fumigants such as phosphine and sulfuryl fluoride; 2) physical control approaches through cold treatment, modified atmosphere, inert dusts, etc.; 3) pesticides and bioactive compounds; 4) food-grade processing aids. The most promising potential alternatives to date include the use of propylene glycol on the ham surface, the exploration of alternative fumigants, and implementation of an integrated pest management plan.

Microscale extraction and phase separation using a porous capillary

We report the use of a porous polytetrafluoroethylene capillary for the inline separation of liquid-liquid segmented flows, based on the selective wetting and permeation of the porous capillary walls by one of the liquids. Insertion of a narrow flow restriction at the capillary outlet allows the back pressure to be tuned for multiple liquid-liquid combinations and flow conditions. In this way, efficient separation of aqueous-organic, aqueous-fluorous and organic-fluorous segmented flows can be readily achieved over a wide range of flow rates. The porous-capillary-separator enables the straightforward regeneration of a continuous flow from a segmented flow, and may be applied to various applications, including inline analysis, biphasic reactions, and purification. As a demonstration of the latter, we performed a simple inline aqueous-organic extraction of the pH indicator 2,6-dichloroindophenol. An aqueous solution of the conjugate base was mixed with hydrochloric acid in continuous flow to protonate the indicator and render it organic-soluble. The indicator was then extracted from the aqueous feed into chloroform using a segmented flow. The two liquids were finally separated inline using a porous PTFE capillary, with the aqueous phase emerging as a continuous stream from the separator outlet. UV-visible absorption spectroscopy showed the concentration of indicator in the outflowing aqueous phase to be less than one percent of its original value, confirming the efficacy of the extraction and separation process.

Efficacy of Methyl Bromide for Control of Different Life Stages of Stored-Product Psocids

The psocid species Liposcelis paeta Pearman, Liposcelis entomophila (Enderlein), Liposcelis decolor (Pearman), Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae), and Lepinotus reticulatus Enderlein (Psocoptera: Trogiidae) were evaluated in laboratory bioassays to determine their susceptibility to six concentrations of methyl bromide (0.027, 0.113, 0.280, 0.393, 0.452, and 0.616 g/m3) after 48 h of exposure at 27.5°C. The life stages that were evaluated were adults (for all species), nymphs (for all species except Lep. reticulatus), and eggs (for L. entomophila, L. decolor, and L. bostrychophila). Adults and nymphs were very susceptible, and complete mortality was recorded at concentrations between 0.027 and 0.280 g/m3. In contrast, eggs were by far more tolerant than adults and nymphs for all species tested. At 0.027 g/m3, mortality did not exceed 53%, while survival was high even at 0.113 g/m3. Complete (100%) egg mortality was recorded at 0.393 g/m3 for L. decolor and at 0.452 g/m3 for L. entomophila and L. bostrychophila; concentrations estimated to give 99% mortality for eggs of these three species were 0.710, 1.044, and 0.891 g/m3, respectively. These results show that stored-product psocids are susceptible to methyl bromide, but concentrations of ≥0.452 g/m3 should be used to control all life stages.

Evaluation of Potential Attractants for Six Species of Stored-Product Psocids (Psocoptera: Liposcelididae, Trogiidae)

Psocids have emerged as worldwide pests of stored commodities during the past two decades, and are difficult to control with conventional management tactics such as chemical insecticides. Therefore, it is necessary to investigate alternative management strategies, such as the use of attractants for monitoring and controlling psocids, which can be incorporated into integrated pest management programs for psocids. Using a two-choice pitfall test, we studied the response of adults of different ages and sexes of Liposcelis entomophila (Enderlein) (Psocoptera: Liposcelididae), Liposcelis paeta Pearman, Liposcelis decolor (Pearman), Liposcelis brunnea Motschulsky, Liposcelis corrodens (Heymons), and Lepinotus reticulatus Enderlein (Psocoptera: Trogiidae) to volatiles from different potential attractants including grains, grain-based oils, brewer's yeast, wheat germ, and commercially available kairomone lures. For all species tested, sex and age did not have a major influence on response to the different potential attractants. Brewer's yeast most consistently elicited the strongest response for psocids, but this response frequently was not different from that to wheat germ and wheat germ oil. The percentage response to brewer's yeast varied among the psocid species tested: L. decolor (73-78%), L. entomophila (62-73%), L. brunnea (64-68%), L. paeta (42-57%), Lep. reticulatus (40%), and L. corrodens (15-19%). Two psocids species (L. corrodens and Lep. reticulatus) had low responses to all the potential attractants evaluated compared with the other four species. These results show there is high potential for using these attractants in a psocid-monitoring program.

Diagnostic molecular markers for phosphine resistance in U.S. populations of Tribolium castaneum and Rhyzopertha dominica

Stored product beetles that are resistant to the fumigant pesticide phosphine (hydrogen phosphide) gas have been reported for more than 40 years in many places worldwide. Traditionally, determination of phosphine resistance in stored product beetles is based on a discriminating dose bioassay that can take up to two weeks to evaluate. We developed a diagnostic cleaved amplified polymorphic sequence method, CAPS, to detect individuals with alleles for strong resistance to phosphine in populations of the red flour beetle, Tribolium castaneum, and the lesser grain borer, Rhyzopertha dominica, according to a single nucleotide mutation in the dihydrolipoamide dehydrogenase (DLD) gene. We initially isolated and sequenced the DLD genes from susceptible and strongly resistant populations of both species. The corresponding amino acid sequences were then deduced. A single amino acid mutation in DLD in populations of T. castaneum and R. dominica with strong resistance was identified as P45S in T. castaneum and P49S in R. dominica, both collected from northern Oklahoma, USA. PCR products containing these mutations were digested by the restriction enzymes MboI and BstNI, which revealed presence or absence, respectively of the resistant (R) allele and allowed inference of genotypes with that allele. Seven populations of T. castaneum from Kansas were subjected to discriminating dose bioassays for the weak and strong resistance phenotypes. Application of CAPS to these seven populations confirmed the R allele was in high frequency in the strongly resistant populations, and was absent or at a lower frequency in populations with weak resistance, which suggests that these populations with a low frequency of the R allele have the potential for selection of the strong resistance phenotype. CAPS markers for strong phosphine resistance will help to detect and confirm resistant beetles and can facilitate resistance management actions against a given pest population.

Nanocrystal synthesis in microfluidic reactors: where next?

The past decade has seen a steady rise in the use of microfluidic reactors for nanocrystal synthesis, with numerous studies reporting improved reaction control relative to conventional batch chemistry. However, flow synthesis procedures continue to lag behind batch methods in terms of chemical sophistication and the range of accessible materials, with most reports having involved simple one- or two-step chemical procedures directly adapted from proven batch protocols. Here we examine the current status of microscale methods for nanocrystal synthesis, and consider what role microreactors might ultimately play in laboratory-scale research and industrial production.

Fumigation of bed bugs (Hemiptera: Cimicidae): effective application rates for sulfuryl fluoride

The bed bug, Cimex lectularius L. (Hemiptera: Cimicidae), has resurged recently as a domestic pest in North America with very limited options for decisive control. We report efficacy studies with sulfuryl fluoride (SF) toward use as a structural fumigant to control bed bugs. Laboratory studies were conducted in which eggs, adults, and nymphs from a pesticide susceptible laboratory population were fumigated for 24 h using SF at 99.8% purity in airtight, 3.8-liter glass containers under two temperatures, 25 degrees C and 15 degrees C. Bed bugs were placed in separate ventilated glass vials and wrapped in mattress padding before fumigation. The gas concentration within each jar was determined using quantitative gas chromatography-mass spectrometry. Dose-response trials using eggs of known age (48-96 h) were conducted at five or six target concentrations measured as concentration x time accumulated dosages (g-h/m3) and one untreated control at each temperature. Each target dose was replicated in four different fumigation containers (replicates), with at least 32 eggs per replicate. The number of hatched and unhatched eggs postfumigation, and number of live and dead nymphs that resulted from hatched eggs, were evaluated daily for at least 1 wk after egg hatch. The lethal accumulated dosage (LAD99) for bed bug eggs was 69.1 (95% fiducial limits [FLs] of 62.9-79.5) g-h/m3 at 25 degrees C and 149.3 (95% FLs of 134.4-177.9) g-h/m3 at 15 degrees C. Confirmatory trials with dosages of 1.5x the LAD99 were conducted at 25 degrees C and 1.5x the threshold mortality dose at 15 degrees C with at least 15 adults, 13 late-instar nymphs and 79 eggs of known age per replicate. At 25 degrees C, a target dosage of 103.7 g-h/m3 resulted in 100% mortality of adults and late-instar nymphs. Nymphs emerged and survived from two of 439 eggs treated with SF dosages that were 6-7 g-h/m3 less than the target dosage. No nymphs emerged from eggs fumigated with dosages > 97.9 g-h/m3 in the validation study. Therefore, the threshold dosage for complete egg mortality (97.9 g-h/m3) was used, rather than the LAD99, to calculate the monitored field dosage rate of 148.2 g-h/m3 (= 1.5 x 97.9 g-h/m3) for control of all life stages of bed bugs at 25 degrees C. Based on these results, at 15 degrees C, 1.5x the threshold dosage for complete egg control (189.7 g-h/m3) was used to calculate a target dosage of 285 g-h/m3 for the confirmatory trial, which resulted in 100% mortality of adults, late-instar nymphs, and eggs.

Controlled multistep synthesis in a three-phase droplet reactor

Channel-fouling is a pervasive problem in continuous flow chemistry, causing poor product control and reactor failure. Droplet chemistry, in which the reaction mixture flows as discrete droplets inside an immiscible carrier liquid, prevents fouling by isolating the reaction from the channel walls. Unfortunately, the difficulty of controllably adding new reagents to an existing droplet stream has largely restricted droplet chemistry to simple reactions in which all reagents are supplied at the time of droplet formation. Here we describe an effective method for repeatedly adding controlled quantities of reagents to droplets. The reagents are injected into a multiphase fluid stream, comprising the carrier liquid, droplets of the reaction mixture and an inert gas that maintains a uniform droplet spacing and suppresses new droplet formation. The method, which is suited to many multistep reactions, is applied to a five-stage quantum dot synthesis wherein particle growth is sustained by repeatedly adding fresh feedstock.

Evaluation of potential attractants for Liposcelis bostrychophila (Psocoptera: Liposcelididae)

The psocid, Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae), can cause significant damage to stored commodities, and its pest status in the United States has been increasing over the last decade. Because L. bostrychophila is difficult to control with conventional methods, it is critical to explore alternative approaches such as the use of attractants that can be incorporated into integrated pest management programs for monitoring psocids. The orientation response of several L. bostrychophila life stages (first and second instars, third and fourth instars, 0- to 7-d-old adults, 21- to 28-d-old adults, and adults of mixed ages) to a range of potential attractants (including whole and cracked grains, grain-based oils, wheat germ, brewer's yeast, and commercially available kairomone lures) was studied using a two-choice pitfall test to identify candidates for further development as lures in traps. Among the potential attractants evaluated, the strongest response by all stages of L. bostrychophila was to brewer's yeast. Other materials for which there was consistently a strong response were psocid diet, wheat germ, and wheat germ oil. These results show the potential for developing monitoring tools for integrated pest management programs for L. bostrychophila and other psocid species.

Attract-and-Kill and other pheromone-based methods to suppress populations of the Indianmeal moth (Lepidoptera: Pyralidae)

Three attract-and-kill formulations, a gel, a wax panel, and a plastic cylinder were tested in simulated warehouses at three densities of devices and at three densities of moths, Plodia interpunctella Hübner, per room. Wax panels and the cylinder formulations suppressed all the densities of moths with only one device per room. Two field experiments were then conducted during 2005 and 2006 in replicated commercial pet food and grocery stores that harbored natural populations of P. interpunctella. In the summer of 2005, the wax panel formulation suppressed adult male response to monitoring traps and also reduced the numbers of larvae in food bait oviposition cups after the first month of being established. This suppression was maintained until the third month. The second field experiment in 2006 compared three pheromone-based methods of moth suppression in buildings with moth populations in untreated buildings. The mass-trapping treatment showed the lowest adult moth capture after the first month of the experiment until the end of the third month. However, this treatment was similar statistically to use of attract-and-kill panels, mating disruption, and untreated control establishments in most of the weeks. Monitoring of larvae in food cups revealed the pheromone-based methods were not significantly different from each other, but that they suppressed moth populations in most of the weeks when compared with untreated control buildings. This research shows potential for successful pheromone-based suppression methods for Indianmeal moths in commercial applications.

Aggregation pheromone components of two species ofPissodes weevils (Coleoptera: Curculionidae) Isolation, identification, and field activity

Two related volatile compounds were identified from each of two species ofPissodes bark weevils and implicated as components of their aggregation pheromones. Grandisol (cis-2-isopropenyl-1-methylcyclobutaneethanol), and its corresponding aldehyde, grandisal, were isolated from males of bothP. strobi andP. approximatus and were found in the abdomens and hindguts of the respective species. In field tests synthetic grandisol and grandisal together with odors from cut pine acted synergistically in attracting both sexes ofP. approximatus. This response was similar to that elicited by maleP. approximatus feeding on cut pine. Males and females of natural populations ofP. strobi were more responsive to caged males feeding on leaders of white pine than they were to leaders alone. The combination of grandisol, grandisal, and leaders was less attractive than males on leaders, but more attractive than leaders alone. From isolation of pheromone components at different times of the year, it was determined that males of both species produced grandisol and grandisal only at times when cohort females were reproductively mature.

Potential for hypobaric storage as a phytosanitary treatment: mortality of Rhagoletis pomonella (Diptera: Tephritidae) in apples and effects on fruit quality

The efficacy of low-oxygen atmospheres using low pressure, referred to as hypobaric conditions, to kill egg and third-instar Rhagoletis pomonella (Walsh) in apples was investigated. Infested apples were exposed to 3.33 and 6.67 kPa in glass jars at 25 and 30 degrees C for times ranging from 3 to 120 h. Probit analyses and lethal dose ratio tests were performed to determine differences in lethal time values. Eggs were more tolerant of low pressure compared with third-instar R. pomonella. Mortality of eggs and larvae increased with increase in time of exposure to low pressure and temperature. Lower pressures increased percent mortality of eggs, but these values were not significantly different at the pressures tested in this investigation. The LT99 for R. pomonella eggs at 3.33 kPa was 105.98 and 51.46 h, respectively, at 25 and 30 degrees C, which was a significant effect of the higher temperature on egg mortality. Investigation into consumer acceptance of low-pressure-treated apples was done with 'Red Delicious' and 'Golden Delicious'. Apples exposed to 3.33 kPa at 25 and 30 degrees C for 3 and 5 d were stored at 1 degrees C for 2 wk and presented to a sensory panel for evaluation. The panelists rated treated apples with untreated controls for external and internal appearance and taste. Golden Delicious apples were unaffected for all three sensory factors across both temperatures and exposure times. Although taste was unaffected for Red Delicious, the internal and external appearances deteriorated. Use of low pressure for disinfestation and preservation of apples is a potential nonchemical alternative to chemical fumigants such as methyl bromide and phosphine.

Phosphine resistance in Tribolium castaneum and Rhyzopertha dominica from stored wheat in Oklahoma

Phosphine gas, or hydrogen phosphide (PH3), is the most common insecticide applied to durable stored products worldwide and is routinely used in the United States for treatment of bulk-stored cereal grains and other durable stored products. Research from the late 1980s revealed low frequencies of resistance to various residual grain protectant insecticides and to phosphine in grain insect species collected in Oklahoma. The present work, which used the same previously established discriminating dose bioassays for phosphine toxicity as in the earlier study, evaluated adults of nine different populations of red flour beetle, Tribolium castaneum (Herbst), and five populations of lesser grain borer, Rhyzopertha dominica (F.) collected from different geographic locations in Oklahoma. One additional population for each species was a laboratory susceptible strain. Discriminating dose assays determined eight out of the nine T. castaneum populations, and all five populations of R. dominica, contained phosphine-resistant individuals, and highest resistance frequencies were 94 and 98%, respectively. Dose-response bioassays and logit analyses determined that LC99 values were approximately 3 ppm for susceptible and 377 ppm for resistant T. castaneum, and approximately 2 ppm for susceptible and 3,430 ppm for resistant R. dominica. The most resistant T. castaneum population was 119-fold more resistant than the susceptible strain and the most resistant R. dominica population was over 1,500-fold more resistant. Results suggest a substantial increase in phosphine resistance in these major stored-wheat pests in the past 21 yr, and these levels of resistance to phosphine approach those reported for other stored-grain pest species in other countries.

Effectiveness of sulfuryl fluoride for control of different life stages of stored-product psocids (Psocoptera)

With the phase-out and impending ban of methyl bromide, sulfuryl fluoride is among the most promising alternative fumigant insecticides for control of stored-product insect pests. It has been evaluated for control of several stored-product insect pests, but there are few data available on its efficacy for control of stored-product psocids (Psocoptera). We evaluated sulfuryl fluoride for control of different life stages of the psocids Liposcelis paeta Pearman, L. entomophila (Enderlein), L. bostrychophila Badonnel, L. decolor Pearman, and Lepinotus reticulatus Enderlein (Trogiidae) in 48-hr trials at 27.5 degrees C. Adults and nymphs were susceptible to sulfuryl fluoride. Complete (100%) adult and nymphal mortality was recorded at concentrations between 4 and 8 g/m3, except for L. decolor for which all adults were only killed at 24 g/m3. Eggs were tolerant to sulfuryl fluoride. Complete egg mortality was achieved at 24 and 72 g/m3 for L. reticulatus and L. decolor, respectively. Survival of L. paeta eggs was recorded even after exposure to 96 g/m3. Given that the highest United States label concentration for sulfuryl fluoride for a 48-h exposure interval is 31.25 g/m3, our study indicates that high doses and/or longer exposures are needed for complete mortality of eggs of L. decolor and L. paeta. Moreover, the present work suggests that there is considerable variation in efficacy of sulfuryl fluoride for control of different psocid species.