Semiochemicals released by pecan alleviate physiological suppression in overwintering larvae of Acrobasis nuxvorella (Lepidoptera: Pyralidae)

Acrobasis nuxvorella Neunzig (pecan nut casebearer) is a monophagous herbivore of Carya illinoinensis (Wang.) K. Koch (pecan); both are indigenous to North America, where Carya has evolved for ≈60 million years. We hypothesized that this close association may have resulted in a parallel evolution allowing casebearer to use pecan volatiles to synchronize seasonality. Casebearer overwinters in diapause as a first-instar larva in a hibernaculum attached to a dormant pecan bud. Larval emergence from this structure after diapause or postdiapause quiescence coincides with the onset of pecan bud growth in the spring, and this interaction was the subject of this study. Dormant pecan twigs with hibernacula-infested buds were exposed to a water control or pecan volatiles from 'Western Schley' cultivar, and monitored to observe larval response by using a microcalorimeter. Initial testing showed that metabolic heat produced by overwintering larvae remained low and unchanged when exposed to water vapor and significantly increased within a few hours after exposure to volatiles from new pecan foliage. This shows that these larvae in hibernacula are in a physiologically suppressed state of diapause or postdiapause quiescence, from which they detect and respond to these pecan volatiles. Further studies to quantify larval responses showed that 90 and 80% of the larvae became active and emerged from their hibernacula ≈6 d after exposure to Western Schley and 'Wichita' volatiles, respectively. Mixtures of 13 sesquiterpenes from those pecan volatiles were identified to induce physiological activity within larvae after hours of exposure, followed some days later by larval emergence from hibernacula. Host volatiles, to our knowledge, have not previously been reported to induce early instar larvae in hibernacula to rouse from a state of physiological arrest to resume normal growth and development. This also has potential for use in pest management.

Indirect effects of pandemic deer overabundance inferred from caterpillar-host relations

Externally feeding phytophagous insect larvae (i.e., caterpillars, here, larval Lepidoptera and sawflies, Hymenoptera: Symphyta) are important canopy herbivores and prey resources in temperate deciduous forests. However, composition of forest trees has changed dramatically in the eastern United States since 1900. In particular, browsing by high densities of white-tailed deer (Odocoileus virginianus) has resulted in forests dominated by browse-tolerant species, such as black cherry (Prunus serotina), and greatly reduced relative abundance of other tree species, notably pin cherry (Prunus pensylvanica) and birches (Betula spp.). To quantify effects of these changes on caterpillars, we sampled caterpillars from 960 branch tips of the 8 tree species that comprise 95% of trees in Allegheny hardwood forests: red maple (Acer rubrum), striped maple (Acer pensylvanicum), sugar maple (Acer saccharum), sweet birch (Betula lenta), yellow birch (Betula allegheniensis), American beech (Fagus grandifolia), black cherry, and pin cherry. We collected 547 caterpillar specimens that belonged to 66 Lepidoptera and 10 Hymenoptera species. Caterpillar density, species richness, and community composition differed significantly among tree species sampled. Pin cherry, nearly eliminated at high deer density, had the highest density and diversity of caterpillars. Pin cherry shared a common caterpillar community with black cherry, which was distinct from those of other tree hosts. As high deer density continues to replace diverse forests of cherries, maples, birches, and beech with monodominant stands of black cherry, up to 66% of caterpillar species may be eliminated. Hence, deer-induced changes in forest vegetation are likely to ricochet back up forest food webs and therefore negatively affect species that depend on caterpillars and moths for food and pollination.

Occurrence and larval movement of Diatraea saccharalis (Lepidoptera: Crambidae) in seed mixes of non-Bt and Bt pyramid corn

BACKGROUND

Larval movement of target pest populations among Bt and non-Bt plants is a major concern in the use of a seed mixture refuge strategy for Bt resistance management. In this study, occurrence and larval movement of the sugarcane borer, Diatraea saccharalis (F.), were evaluated in four planting patterns of non-Bt and Bt plants containing Genuity® SmartStax(TM) traits in 2009-2011. The four planting patterns were: (1) a pure stand of 27 Bt plants; (2) one non-Bt plant in the center, surrounded by 26 Bt plants; (3) a pure stand of 27 non-Bt plants; (4) one Bt plant in the center, surrounded by 26 non-Bt plants. Studies were conducted under four conditions: (1) open field with natural infestation; (2) greenhouse with artificial infestations; open field with artificial infestations (3) on the center plants only and (4) on every plant. The major objective of this study was to determine whether refuge plants in a seed mixture strategy could provide a comparable refuge population of D. saccharalis to a 'structured refuge' planting.

RESULTS

Larvae of D. saccharalis showed the ability to move from infested plants to at least four plants away, as well as to adjacent rows, but the majority remained within the infested row. However, the number of larvae found on the non-Bt plants in the mixture plantings was not significantly reduced compared with the pure stand of non-Bt corn.

CONCLUSION

The results of this study show that refuge plants in a seed mixture may be able to provide a comparable refuge population of D. saccharalis to a structured refuge planting.

Susceptibility baseline and chlorantraniliprole resistance monitoring in Chilo suppressalis (Lepidoptera: Pyralidae)

Chlorantraniliprole, a new anthranilic diamide insecticide, has been commercialized in China since 2008 for controlling of several lepidopterans, including rice stem borer, Chilo suppressalis Walker. Chemical control of this pest has become difficult because of its resistance development to many conventional insecticides. To facilitate chlorantraniliprole-resistance monitoring, seedling dip bioassays were conducted in 2011 and 2012 to assess the susceptibility of 30 populations of C. suppressalis from seven provinces in China. The assays established a larval susceptibility baseline with LC50 at 1.393 mg a.i/liter. The toxicity (LC50) of chlorantraniliprole against second-instar larvae of field populations ranged from 0.568 (SL12) to 13.547 (RA12) mg a.i/liter. Substantial variations of the susceptibility to chlorantraniliprole were detected among different geographic populations, but no significant difference was observed between years for most populations except for populations from Dong'an, Cangnan, and Lujiang. Resistance ratios to the chemical ranged from 1.0 to 9.7, indicating that most colonies remained susceptible or showed certain decrease in susceptibility. Approximately, 13.3% of the populations exhibited low levels of resistance to chlorantraniliprole. These data are useful in future monitoring program for detecting any changes in susceptibility as a result of use of the insecticide.

Multi-state trials of Bt sweet corn varieties for control of the corn earworm (Lepidoptera: Noctuidae)

Field tests in 2010-2011 were performed in New York, Minnesota, Maryland, Ohio, and Georgia to compare Bt sweet corn lines expressing Cry1A.105 + Cry2Ab2 and Cry1Ab with their non-Bt isolines, with and without the use of foliar insecticides. The primary insect pest in all locations during the trial years was Heliocoverpa zea (Boddie), which is becoming the most serious insect pest of sweet corn in the United States. At harvest, the ears were measured for marketability according to fresh market and processing standards. For fresh market and processing, least squares regression showed significant effects of protein expression, state, and insecticide frequency. There was a significant effect of year for fresh market but not for processing. The model also showed significant effects of H. zea per ear by protein expression. Sweet corn containing two genes (Cry1A.105 + Cry2Ab2) and a single gene (Cry1Ab) provided high marketability, and both Bt varieties significantly outperformed the traditional non-Bt isolines in nearly all cases regardless of insecticide application frequency. For pest suppression of H. zea, plants expressing Bt proteins consistently performed better than non-Bt isoline plants, even those sprayed at conventional insecticide frequencies. Where comparisons in the same state were made between Cry1A.105 + Cry2Ab2 and Cry1Ab plants for fresh market, the product expressing Cry1A.105 + Cry2Ab2 provided better protection and resulted in less variability in control. Overall, these results indicate Cry1A.105 + Cry2Ab2 and Cry1Ab plants are suitable for fresh market and processing corn production across a diversity of growing regions and years. Our results demonstrate that Bt sweet corn has the potential to significantly reduce the use of conventional insecticides against lepidopteran pests and, in turn, reduce occupational and environmental risks that arise from intensive insecticide use.

Cloning, expression and characterization of an insect geranylgeranyl diphosphate synthase from Choristoneura fumiferana

Geranylgeranyl diphosphate synthase (GGPPS) catalyzes the condensation of the non-allylic diphosphate, isopentenyl diphosphate (IPP; C5), with allylic diphosphates to generate the C20 prenyl chain (GGPP) used for protein prenylation and diterpenoid biosynthesis. Here, we cloned the cDNA of a GGPPS from the spruce budworm, Choristoneura fumiferana, and characterized the corresponding recombinant protein (rCfGGPPS). As shown for other type-III GGPPSs, rCfGGPPS preferred farnesyl diphosphate (FPP; C15) over other allylic substrates for coupling with IPP. Unexpectedly, rCfGGPPS displayed inhibition by its FPP substrate at low IPP concentration, suggesting the existence of a mechanism that may regulate intracellular FPP pools. rCfGGPPS was also inhibited by its product, GGPP, in a competitive manner with respect to FPP, as reported for human and bovine brain GGPPSs. A homology model of CfGGPPS was prepared and compared to human and yeast GGPPSs. Consistent with its enzymological properties, CfGGPPS displayed a larger active site cavity that can accommodate the binding of FPP and GGPP in the region normally occupied by IPP and the allylic isoprenoid tail, and the binding of GGPP in an alternate orientation seen for GGPP binding to the human protein. To begin exploring the role of CfGGPPS in protein prenylation, its transcripts were quantified by qPCR in whole insects, along with those of other genes involved in this pathway. CfGGPPS was expressed throughout insect development and the abundance of its transcripts covaried with that of other prenylation-related genes. Our qPCR results suggest that geranylgeranylation is the predominant form of prenylation in whole C. fumiferana.

Allocation of cysteine for glutathione production in caterpillars with different antioxidant defense strategies: a comparison of Lymantria dispar and Malacosoma disstria

Sulfur amino acids [cysteine (Cys) and methionine (Met)] play two major roles during animal development: protein synthesis for growth and glutathione synthesis for defense. For caterpillars, the levels of sulfur amino acids found in foliar protein can be especially low relative to their nutritional needs. Previous work has measured concentrations of glutathione (GSH; containing Cys) in specific animal tissues, but has not examined whole-body levels to ascertain the costliness of this defense in terms of Cys allocation. This study examined whether the production of GSH varies between species and within individuals in accordance with an insect's need for antioxidant defense. Secondly, we quantified the allocation of total Cys (peptide-bound plus free Cys) to GSH in caterpillars as an estimate of its cost. Two contrasting species were compared: Lymantria dispar (Lymantriidae), a species that is highly defended, and Malacosoma disstria (Lasiocampidae), a species that is less defended. As expected, GSH levels were significantly higher in L. dispar than in M. disstria. Consistent with the function of the midgut as a first line of defense against ingested toxins, GSH levels were significantly higher in these tissues than in the whole bodies of both species. A major finding in this study was that a large fraction of total Cys is used to produce GSH: GSH in the midguts of L. dispar and M. disstria contained 23 and 21%, respectively, of the total Cys in these tissues, and the GSH in their remaining body tissues contained 19 and 17% of the total Cys in these tissues. Levels of total Cys in caterpillar tissues followed the same pattern of distribution as did GSH, producing a strong association between GSH and total Cys (R(2) = 0.794). We conclude that GSH is a costly defense, especially in generalist tree-feeding species such as L. dispar. These results further suggest that the large allocation of Cys to GSH in highly defended species might produce a tradeoff by limiting the amount of Cys available for rapid growth.

Tent caterpillars are robust to variation in leaf phenology and quality in two thermal environments

The synchrony between emergence of spring-active, insect herbivores and the budburst of their host plants could be affected by warming temperatures with influences on the availability and quality of foliage as it undergoes physical and chemical changes. This can affect the growth and survival of insects. Here, we used sun-exposed and shaded trees to determine whether the synchrony between egg hatch of western tent caterpillar, Malacosoma californicum pluviale Dyar (Lepidoptera:Lasiocampidae) and budburst of its host red alder, Alnus rubra Bongard (Betulaceae)changes with different thermal environments (temperature and light together). To explore the potential outcome of a shift in phenological synchrony, we used laboratory assays of larval growth and survival to determine the effect of variation in young, youthful and mature leaves from sun-exposed and shaded trees. While the average higher temperature of sun-exposed trees advanced the timing of budburst and egg hatch, synchrony was not disrupted. Leaf quality had no significant influence on growth or survival in the laboratory for early instars reared as family groups. Later instar larvae, however, performed best on mature leaves from sun-exposed trees. The robust relationship between leaf and larval development of western tent caterpillars suggests that warming climates may not have a strong negative impact on their success through shifts in phenological synchrony, but might influence other aspects of leaf quality and larval condition.

Development of a new method to prepare nano-/microparticles loaded with extracts of Azadirachta indica, their characterization and use in controlling Plutella xylostella

Biodegradable nanoparticles have been widely explored as carriers for controlled delivery of therapeutic molecules; however, studies describing the development of nanoparticles as carriers for biopesticide products are few. In this work, a new method to prepare nanoparticles loaded with neem (Azadirachta indica) extracts is presented. In this study, nanoparticles were formulated as colloidal suspension and (spray-dried) powder and characterized by evaluating pH, particle size, zeta potential, morphology, absolute recovery, and entrapment efficiency. A high-performance liquid chromatography method was used for nanoparticle characterization. The best formulations presented absolute recovery and entrapment efficiencies of approximately 100% and a release profile based on swelling and relaxation of the polymer or polymer erosion. The biological data of the formulated products against Plutella xylostella showed 100% larval mortality. The nanoparticle information improved the stability of neem products against ultraviolet radiation and increased their dispersion in the aqueous phase.

Functional characterization of a juvenile hormone esterase related gene in the moth Sesamia nonagrioides through RNA interference

Juvenile hormone esterase (JHE) is a carboxylesterase that has attracted great interest because of its critical role in regulating larval to adult transition in insects and other arthropods. Previously, we characterized an ecdysteroid sensitive and juvenile hormone non-susceptible juvenile hormone esterase related gene (SnJHER) in the corn stalk borer, Sesamia nonagrioides. SnJHER was rhythmically up-regulated close to each molt during the corn stalk borer's larval development. In this paper we attempted to functionally characterize SnJHER using several reverse genetics techniques. To functionally characterize SnJHER, we experimented with different dsRNA administration methods, including hemolymph, bacterial or baculovirus-mediated RNA interference, (RNAi). Our findings indicate the potential implication of SnJHER in the developmental programming of Sesamia nonagrioides. It is still unclear whether SnJHER is closely related to the authentic JHE gene, with different or similar biological functions.

Geographic variation in diapause induction and termination of the cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Overwintering diapause in Helicoverpa armigera, a multivoltine species, is controlled by response to photoperiod and temperature. Photoperiodic responses from 5 different geographical populations showed that the variation in critical photoperiod for diapause induction was positively related to the latitudinal origin of the populations at 20, 22 and 25°C. Diapause response to photoperiod and temperature was quite different between northern and southern populations, being highly sensitive to photoperiod in northern populations and temperature dependence in southern populations. Diapause pupae from southern population showed a significantly shorter diapause duration than from northern-most populations when they were cultured at 20, 22, 25, 28 and 31°C; by contrast, overwintering pupae from southern populations emerged significantly later than from northern populations when they were maintained in natural conditions, showing a clinal latitudinal variation in diapause termination. Diapause-inducing temperature had a significant effect on diapause duration, but with a significant difference between southern and northern populations. The higher rearing temperature of 22°C evoked a more intense diapause than did 20°C in northern populations; but a less intense diapause in southern population. Cold exposure (chilling) is not necessary to break the pupal diapause. The higher the temperature, the quicker the diapause terminated. Response of diapause termination to chilling showed that northern populations were more sensitive to chilling than southern population. All results demonstrate that H. armigera is not genetically homogeneous throughout its range, but rather is composed of distinct populations genetically adapted to local environmental conditions despite the potential for gene flow via seasonal migration of adults.

Response of multiple generations of semilooper, Achaea janata feeding on castor to elevated CO2

The growth, development and consumption of four successive generations of semilooper, Achaea janato reared on castor (Ricinus communis L.) foliage grown under elevated carbon dioxide (550 and 700 parts per million ) concentrations in open top chambers were estimated at Hyderabad, India. Significantly lower leaf nitrogen, higher carbon, higher relative proportion of carbon to nitrogen (C: N) and higher polyphenols expressed in terms of tannic acid equivalents were observed in castor foliage under elevated CO2 levels. Significant influence on life history parameters of A. jonata viz., longer larval duration, increased larval survival rates and differential pupal weights in successive four generations were observed under elevated over ambient CO2 levels. The consumption per larva under elevated CO2 increased from first to fourth generation. An increase in approximate digestibility and relative consumption rate, decreased efficiency of conversion of ingested food and digested food and relative growth rate of the four generations under elevated CO2 levels was noticed. Potential population increase index was lower for successive generations under both elevated CO, over ambient. The present findings indicated that elevated CO2 levels significantly alter the quality of castor foliage resulting in higher consumption and better assimilation by larvae, slower growth and longer time to pupation besides producing less fecund adults over generations.

Characterization and biocontrol potential of entomopathogenic fungus, Beauveria bassiana isolates against Spilarctia obliqua

Beauveria bassiana is a known natural enemy of a number of insect pests of crop plants. In order to screen different isolates of any given entomopathogens molecular markers provide a means for constructing the molecular phylogeny, diversity and link to virulent phenotypes. Eight isolates of B. bossiona isolated from different insect hosts and from different location at Pantnagar (Uttrakhand) were characterized by PCR-based RAPD markers. Bioassays were conducted by using first, second and third instar larvae of Spilarctia oblique in order to categorize the isolates based on virulence. The isolates were arbitrarily rated as more virulent, moderately virulent and less virulent based on the speed of killing. A wide range of variation in virulence was observed and the isolates of same insect origin and location showed differences in their aggressiveness. No correlation was found between the pathogenicity of the isolates and the relatedness of the original insect host. The pathogenicity against first, second and third instar larva of Spilarctia obliqua did not reveal any relatedness with the clustering pattern.

Implications of European corn borer, Ostrinia nubilalis, infestation in an Aspergillus flavus-biocontrolled corn agroecosystem

BACKGROUND

A novel biocontrol strategy consisting of field application of bioplastic-based granules inoculated with a non-toxigenic Aspergillus flavus L. strain has recently been shown to be effective for reducing aflatoxin contamination in corn. This study focused on other factors that may affect the feasibility of this biocontrol technique, and more specifically the role of the European corn borer (ECB), Ostrinia nubilalis H., in the dispersal and infestation of A. flavus in corn and its impact on crop yield.

RESULTS

In spite of the high percentage of corn ears showing larval feeding damage, ECB-bored kernels accounted for only 3 and 4% in 2009 and 2010 respectively. Most of the damaged kernels were localised in the ear tip or immediately below. More precisely, the average incidence of ECB-bored kernels in the upper end of the ear was 32%. However, less than 5% of kernels from the central body of the ear, which includes the majority of kernels, were injured by ECB.

CONCLUSIONS

Although ECB larvae showed a high tolerance to aflatoxin B1 and thus had the potential to serve as vectors of the mould, fungal infection of kernels was poorly associated with insect damage. ECB infestation resulted in grain yield losses not exceeding 2.5%.

Biochemical responses of Anticarsia gemmatalis (Lepidoptera: Noctuidae) in soybean cultivars sprayed with the protease inhibitor berenil

The damage caused by Anticarsia gemmatalis motivates this study on the adaptive mechanisms of the insect to soybean. The lipoxygenase pathway produces and releases jasmonic acid, involved in the regulation of the plant defense genes, which encodes protease inhibitor (PI) production. Three soybean cultivars IAC-18, IAC-24, and Foscarin-31 were sprayed with water and berenil, a synthetic inhibitor, at 0.60 and 1.0% (w/v) and then infested with A. gemmatalis larvae. The lipoxygenase (LOX) activity increased in the leaves of Foscarin-31, IAC-18, and IAC-24 by 87, 81, and 78%, respectively, after 24 h of A. gemmatalis damage. IAC-18 revealed the lowest increase in PI when compared to the other cultivars. Protease, amidase, and esterase activities in soybean larvae dropped drastically after berenil application. PIs may be included in the control strategies of A. gemmatalis in soybean by lowering the digestive enzyme activity in the larval midgut, thus affecting insect growth and development.

Synthesis of novel 4α-(acyloxy)-2'(2',6')-(di)halogenopodophyllotoxin derivatives as insecticidal agents

In continuation of our program aimed at the discovery and development of natural-product-based insecticidal agents, we have prepared three series of novel 4α-(acyloxy)-2'(2',6')-(di)halogenopodophyllotoxin derivatives modified in the C and E rings of podophyllotoxin, which is a naturally occurring aryltetralin lignan isolated from the roots and rhizomes of Podophyllum hexandrum . Their structures were well characterized by (1)H NMR, HRMS, ESI-MS, optical rotation, and mp. The stereochemical configurations of compounds 5s, 6b, 6d, and 7q were unambiguously confirmed by single-crystal X-ray diffraction. Their insecticidal activity was evaluated against the pre-third-instar larvae of oriental armyworm, Mythimna separata Walker, in vivo at a concentration of 1 mg/mL. These derivatives likely displayed the antimolting hormone effect. Among all the derivatives, especially compounds 5a, 5n, 7f, 7n, and 7w exhibited the most potent insecticidal activity with final mortality rates of 70% or so. This suggested that a chlorine or bromine atom introduced at the C2' or C2' and C6' positions on the E ring of podophyllotoxin was necessary for obtaining the potent compounds. This will pave the way for further design, structural modification, and development of podophyllotoxin derivatives as insecticidal agents.

Characterization of a spruce budworm chitin deacetylase gene: stage- and tissue-specific expression, and inhibition using RNA interference

Chitin deacetylase (CDA) catalyzes the conversion of chitin into chitosan, thereby modifying the physical properties of insect cuticles and peritrophic matrices. A lepidopteran chitin deacetylase gene (CfCDA2) was cloned from the spruce budworm, Choristoneura fumiferana, and found to generate two alternatively spliced transcripts, CfCDA2a and CfCDA2b. Transcriptional analysis using isoform-specific RT-PCR primers indicated that both isoforms were upregulated during the molt. Interestingly, CfCDA2b transcripts were most abundant in the head during the molting stage while those of CfCDA2a were predominant in the epidermis during the feeding period. Injection of CfCDA2-specific dsRNA into C. fumiferana larvae or pre-pupae induced both abnormal phenotypes and high mortality, which resulted from an inability to shed the old cuticle. These results suggest that CfCDA2 plays an important role in the molting process, and that the two alternatively spliced transcripts have different functions during insect development. This is the first detailed characterization of lepidopteran chitin deacetylase gene.

The glutathione-related detoxication responses to juvenile and ecdysone hormones in Galleria mellonella

The effect of 20-hydroxyecdysone (20E) and juvenile hormone (JH) on the glutathione pathway of the greater wax moth Galleria mellonella (Lepidoptera: Pyralidae) was determined by investigating glutathione peroxidase (GSH-Px), glutathione S-transferases (GST), and glutathione reductase (GR) activities as well as reduced and oxidized glutathione (GSH and GSSG) content with respect to developmental stage. The continuous decreases of GSH-Px and GST activities dependent on the growth period of G. mellonella occurred in JH and 20E groups over and under their controls, respectively. While the GR activities of G. mellonella showed increases in young pupa (YP) for both control and in old larvae (OL) for the 20E groups after the minimum at these periods, they also increased after old pupa (OP) for the JH group with a maximum in OL period. Although GR activity levels in the JH group were significantly higher compared with controls and 20E groups up to OP period, the activity levels for the control and 20E groups were higher than those of the JH group at adult (AD) and old pupa (OP) periods, respectively. In spite of increases in the GR activity of 20E and control groups of G. mellonella, decreased GSH and increased GSSG levels were observed at aging period. GSH levels in the JH group reached a maximum at prepupa (PP) and then decreased with non-significant changes from OL to AD period. According to the results, GSH and GSSG levels, as well as GSH/GSSG ratios, were below and over control levels in 20E and JH groups, respectively, during all of the investigated developmental stages. On the contrary, the LPO levels were higher than the control for 20E and lower for the JH groups during the developmental period. These results show that while ecdysone hormone has a negative effect on the glutathione-related detoxication capacity of G. mellonella, the juvenile hormone has a positive effect on this process.

Beauveria bassiana (Ascomycota: Hypocreales) wound dressing for the control of Euzophera pinguis (Lepidoptera: Pyralidae)

Injury to olive tree trunks and branches because of biotic and abiotic factors, such as pruning and mechanical harvesting, attracts the olive pyralid moth Euzophera pinguis Haworth (Lepidoptera: Pyralidae). This moth has become increasingly important in the Mediterranean region during recent years. The use of an entomopathogenic fungus for wound dressing for pest control is reported for the first time in this study. Beauveria bassiana (Ascomycota: Hypocreales) strain EABb 08/04-Ep was originally obtained from a diseased E. pinguis larva and has shown effective E. pinguis control in an olive crop in Jaén, Andalusia, Spain, under field conditions during the spring and fall of 2008 and 2009 and the spring of 2011. Experimental artificial 30 by 30-mm square wound cages were large enough to allow the E. pinguis females to oviposit. Approximately 80 and 40-60% of the control wounds contained live larvae in the experiments that occurred during the spring and fall, respectively. The B. hassiana wound dressing gave similar results as the chlorpyrifos wound dressing throughout the experiment, with efficacies reaching 80-85% in the spring and 90-95% in the autumn. The B. bassiana fungus was recovered from 60-90% of the wounds at the completion of the experiments and after 60 d of treatment. These data indicate that strain EABb 08/04-Ep applied to the pruning wounds can be an effective tool for the microbial control of E. pinguis in olive crops. Moreover, B. bassiana may be used within integrated pest management strategies to minimize chemicals, depending on the population density of the pyralid moth.

The effect of rearing in different temperature regimes on the reproduction of Anagasta kuehniella (Lepidoptera: Pyralidae)

Eggs of Anagasta kuehniella (Zeller) are widely used in mass rearing of parasitoids, especially Trichogramma spp. and predators in many biological-control programs. The objective of this study was to improve the efficiency of mass rearing of A. kuehniella through determining the optimal temperature conditions for rearing, by assessing the effect of temperature during the developmental stages on the reproduction of A. kuehniella. We evaluated 1) the effect of temperature at which A. kuehniella was kept from egg to adult death, on reproduction; 2) the effect of temperature during the larval and pupal stages on oviposition; and 3) the effect of different temperatures on adults that originated from larvae kept in a constant temperature of 25°C. The results indicated that the optimal temperature range for the development of A. kuehniella is between 20-30°C, as at 30°C there was a marked decrease in viability of the egg and larval stages. The best temperature for maintaining A. kuehniella from egg to adult death is 25°C. Temperatures of 30 and 32°C lead to deformations in genitalia of males, reducing the viability of eggs, and also eggs and females from these temperatures have lower weights. The rearing temperature of immatures affects the egg-laying capacity of adults and the egg viability. The oviposition capacity of adults kept in different temperatures ranging from 18 to 32°C, after being reared in constant temperature (25°C) during the larval stages, was not affected.

Regression analysis of dynamics of insecticide resistance in field populations of Chilo suppressalis (Lepidoptera: Crambidae) during 2002-2011 in China

To understand the evolution of insecticide resistance in the Asiatic rice borer, Chilo suppressalis (Walker) (Lepidoptera: Crambidae), in field, regression analysis based on a linear or nonlinear model was adopted for analyzing resistance dynamics to six insecticides of two field populations of the Lianyungang (LYG) and Ruian (RA) populations during 2002-2011. For the low-level resistance population, LYG population, sustained susceptibilities to abamectin and fipronil were seen for 10 yr; a polynomial curve regression model showed an increase in resistance to chlorpyrifos; exponential growth models fit to the resistance dynamics to triazophos and deltamethrin, and a sigmoidal growth curve for monosultap. For the high-level multiple resistance population, RA population, a slight increase from susceptible to a minor resistance to abamectin could be modeled by a polynomial cubic equation; an exponential growth model fit to the increase of resistance to fipronil from 8.7-fold to 33.6-fold; a sine waveform model fit to the vibrating tendency of resistance to chlorpyrifos; the dynamics of resistance to triazophos could be modeled by two combined curves, with a polynomial growth model and a sine waveform model; the high level of resistance to monosultap could be modeled with a sine waveform model; and a significant linear growth relationship of the resistance to deltamethrin of the RA population over years was found. Then, the relationship between dynamics of resistance development to insecticides among the field populations of C. suppressalis and the application history of pesticides for controlling rice borers was discussed.

Baseline susceptibility to Cry1Ac insecticidal protein in Heliothis virescens (Lepidoptera: Noctuidae) populations in Brazil

The tobacco budworm, Heliothis virescens (F.), is one of the target pests of genetically modified cotton expressing Cry1Ac insecticidal protein (Bt cotton) derived from Bacillus thuringiensis Berliner. This study was conducted to evaluate the susceptibility of field-collected populations of H. virescens to Cry1Ac to establish a baseline for use in an insect resistance management program for Bt cotton in Brazil. Insects were sampled from the main Brazilian cotton-growing regions (Bahia, Mato Grosso, Mato Grosso do Sul, and Goiás) during the cropping seasons of 2007/08 and 2008/09. Cry1Ac susceptibility was estimated by using diet incorporation bioassays. H. virescens was highly susceptible to Cry1Ac protein. The estimated LC50 values varied from 0.18 to 0.66 microg of Cry1Ac/ml of diet among the 2007-2008 populations (approximately 3.7-fold variation). Similarly, the EC50 values based on growth inhibition ranged from 0.0053 to 0.0161 microg of Cry1Ac/ml of diet for the 2007-2008 populations (approximately 3.0-fold variation). A joint analysis of the mortality data across all tested populations was used to develop and validate the diagnostic concentrations of 3.1 and 5.6 microg of Cry1Ac/ml of diet, the upper bound of the confidence interval and twice the LC99 were selected, for resistance monitoring programs of H. virescens to Cry1Ac protein in Brazil.

Effect of chemical additives on Bacillus thuringiensis (Bacillales: Bacillaceae) against Plutella xylostella (Lepidoptera: Pyralidae)

To examine the effect of chemical additives on Bacillus thuringiensis (Berliner) against Plutella xylostella (L.), inorganic salts, nitrogenous compounds, protein solubilizing agents, and organic acids were selected and tested. The chosen materials are low in cost and environmentally safe. Results show that many inorganic salts can increase the activity of B. thuringiensis in a range of 1.31- to 3.08-fold. These include calcium acetate, calcium chloride, calcium hydroxide, calcium sulfate, calcium carbonate, sodium carbonate, sodium acetate, potassium hydroxide, potassium carbonate, potassium acetate, magnesium chloride, magnesium sulfate, and zinc sulfate. Nitrogenous compounds, including peptone, sodium nitrate, and ammonium nitrate, can enhance the activity of B. thuringiensis 1.62-, 1.32-, and 1.37-fold, respectively. Among the protein solubilizing agents, EDTA, urea, mercaptoethanol and dipotassium hydrogen phosphate increased the activity of B. thuringiensis 1.62- to 2.34-fold. Among the organic acids, maleic and citric acids boosted the activity 1.45- and 1.55-fold, respectively. Meanwhile, sodium benzoate and resorcinol led to 1.74- and 1.44-fold activity gains, respectively. Use of appropriate additives could provide great benefit not only in reducing the costs for field applications of biological insecticides but also by boosting the efficacy of B. thuringiensis.

Effects of elevated CO2 leaf diets on gypsy moth (Lepidoptera: Lymantriidae) respiration rates

Elevated levels of CO2 affect plant growth and leaf chemistry, which in turn can alter host plant suitability for insect herbivores. We examined the suitability of foliage from trees grown from seedlings since 1997 at Aspen FACE as diet for the gypsy moth (Lymantria dispar L.) Lepidoptera: Lymantriidae: paper birch (Betula papyrifera Marshall) in 2004-2005, and trembling aspen (Populus tremuloides Michaux) in 2006-2007, and measured consequent effects on larval respiration. Leaves were collected for diet and leaf chemistry (nutritional and secondary compound proxies) from trees grown under ambient (average 380 ppm) and elevated CO2 (average 560 ppm) conditions. Elevated CO2 did not significantly alter birch or aspen leaf chemistry compared with ambient levels with the exception that birch percent carbon in 2004 and aspen moisture content in 2006 were significantly lowered. Respiration rates were significantly higher (15-59%) for larvae reared on birch grown under elevated CO2 compared with ambient conditions, but were not different on two aspen clones, until larvae reached the fifth instar, when those consuming elevated CO2 leaves on clone 271 had lower (26%) respiration rates, and those consuming elevated CO2 leaves on clone 216 had higher (36%) respiration rates. However, elevated CO2 had no apparent effect on the respiration rates of pupae derived from larvae fed either birch or aspen leaves. Higher respiration rates for larvae fed diets grown under ambient or elevated CO2 demonstrates their lower efficiency of converting chemical energy of digested food stuffs extracted from such leaves into their biosynthetic processes.