Efficacy of Modified Atmospheres on Trogoderma granarium (Coleoptera: Dermestidae) and Sitophilus zeamais (Coleoptera: Curculionidae)

Frost Damage Mitigation in Flowers and Fruitlets of Peach and Almond from the Application of a Multi-Attribute Approach Biostimulant

To prevent frost damage in fruit trees, growers employ passive and active methods, and one of these second methods is the use of biostimulant compounds against abiotic stress. In this study, two trials were conducted to evaluate the effectiveness of a multi-attribute approach biostimulant-containing α-tocopherol, boron, and glycols, in peach ('UFO-4' cultivar) and almond ('Vairo' cultivar) trees. In a first trial, one-year-old shoots with flowers were collected after 24 h, 48 h, and 96 h of the biostimulant applications. Two different application rates of the product (1000 and 2000 cc ha-1) were tested and compared to an untreated control. In a second trial, one-year-old shoots with fruitlets were collected after 24 h of the biostimulant applications. In this case, only an application rate (2000 cc ha-1) was tested. In the two trials, the collected one-year-old shoots were subjected to different frost temperatures using a controlled environment chamber. The damage level was assessed by a morphological analysis of the flowers and fruitlets 96 h after each frost cycle simulation. The lethal temperatures (LT10, LT50, and LT90) of each treatment were calculated by probit analysis. The product applied 24 h and 48 h before the frost simulations significantly decreased the LT10 and LT50 in 1.5 °C in peach flowers, and 2.5 °C in almond flowers (a temperature reduction of 50% and 75%, respectively). These results were more consistent when the application volume was 2000 cc ha-1, instead of 1000 cc ha-1. Significant differences between treated and non-treated fruitlets were observed only in almond fruitlets, with LT10 and LT50 being 0.5 °C lower in treated fruitlets (20% reduction). In conclusion, the multi-attribute approach biostimulant applied 24 or 48 h before the frost reduced the mortality of peach and almond flowers, but its effectiveness to protect fruitlets after bloom was inconsistent.

Insecticidal and Repellent Activities of Four Essential Oils Against Sitophilus zeamais (Coleoptera: Curculionidae)

Objective

This study aimed to evaluate the efficacy of Corymbia citriodora, Melaleuca alternifolia (Myrtaceae), Mentha × piperita (Lamiaceae), and Schinus terebinthifolius (Anacardiaceae) essential oils as an alternative to manage Sitophilus zeamais (Coleoptera: Curculionidae) adults.

Methods

Acute contact toxicity, acute toxicity on treated maize grain, fumigation toxicity, repellency bioassays, and GC-MS analysis of the essential oils were carried out.

Results

Corymbia citriodora, M. alternifolia, M. × piperita, and S. terebinthifolius oils were toxic at different levels to S. zeamais through residual contact, ingestion and via fumigation, and were also repellent to adults of this pest. Melaleuca alternifolia oil was the most active in contact (LC50 = 18.98 μL.mL-1), ingestion (LC50 = 1.03 μL.g-1), and fumigant (LC50 = 20.05 μL.L-1 air) bioassays. Citronelal (53.6% in C. citriodora), terpinen-4-ol (46.9% in M. alternifolia), menthol (44.8% in M. × piperita), and β-caryophyllene (16.2% in S terebinthifolius) are the major constituents of these oils.

Conclusions

Melaleuca alternifolia and M. × piperita essential oils can be used by residual contact, while those of C. citriodora, M. alternifolia, and M. × piperita by mixing with maize grains. Melaleuca alternifolia essential oil can be used as a fumigant, while those of C. citriodora and S. terebinthifolius as repellents for S. zeamais adults.

Effect of Sitophilus zeamais (Coleoptera: Curculionidae) Infestation on the Protein Physicochemical and Structural Properties of Wheat Grain

Boring pests such as Sitophilus zeamais (S. zeamais) are major threats in grain storage. However, how these pests affect the proteins of stored grains remains largely unknown. Here we aimed to investigate the effect of S. zeamais infestation on wheat protein during postharvest storage. In this study, wheat grain infested by S. zeamais was sampled at egg (4 d), larval (20 d), pupal (35 d), and adult stages (45 d), respectively. The protein's physicochemical and structural properties and the edible quality of whole wheat noodle were analyzed. The results showed that S. zeamais infestation significantly decreased the quality of wheat protein by altering its constitution and structure properties. Especially, compared with the control, the content of wet and dry gluten, gluten index, sodium dodecyl sulfate sedimentation volume, sulfhydryl groups, and disulfide bonds in insect-infested wheat decreased by 19.40, 5.42, 18.40, 8.12, 29.13, and 14.30%, respectively, during the storage period of one life cycle of S. zeamais. Additionally, the proportions of wheat protein fractions (albumin [1.16-fold], globulin [0.96-fold], gliadin [1.16-fold], and glutenin [0.95-fold]) and secondary structures (α-helix [0.91-fold], β-fold [0.96-fold], β-turn [1.06-fold], and random coil [1.05-fold]) of protein changed significantly, and the gluten network structure was broken in S. zeamais-infested wheat. Furthermore, the color of whole wheat noodle became darker, cooking loss rate increased, and textural properties (hardness, adhesiveness, springiness, cohesiveness, chewiness, and resilience) decreased as well. The results in the present study provided new insights for analyzing the quality deterioration mechanism and further quality improvement of boring pests-infested wheat grain.

Combination of Modified Atmosphere and Irradiation for the Phytosanitary Disinfestation of Trogoderma granarium Everts (Coleoptera: Dermestidae)

Simple Summary

The khapra beetle is defined as one of the most important quarantine pests globally, and fumigating by methyl bromide, one of the ozone-depleting substances under the Montreal Protocol, is a routine measure used for phytosanitary treatment. To protect the Ozone layer, an environmentally friendly measure is needed to be developed. The middle- to late-stage larvae and adults were treated with irradiation, modified atmosphere (MA) alone, and their combinations at room temperature of 24–26 ℃. As a result, late-stage larvae are determined as the most tolerant stage. Ionizing radiation was used to enhance the effects of 1% and 2% O₂ MA treatments that the obvious synergistic effects are presented in all combinations, resulted in saving as high as 60% of the estimated exposure times comparing with MA treatment alone. A total of 111,366 late-stage larvae were exposed to a 1% O₂ atmosphere for 14 or 15 days after a 200 Gy irradiation, resulted in no survivor in the validating tests. Therefore, the MA-irradiation combination treatment can provide quarantine security at a very high level, it may be combined with international transportation (train or sea container) to disinfest the commodities infested by khapra beetle and other stored products insect pests.

Abstract

The khapra beetle, Trogoderma granarium Everts, is defined as one of the most important quarantine pests globally, and fumigation with methyl bromide, an ozone-depleting substance, is a common phytosanitary measure currently used. The modified atmosphere (MA), irradiation, and their combination treatments of T. granarium larvae and adults were performed at room temperature (24–26 ℃) to develop an ecofriendly phytosanitary disinfestation measure and to shorten the exposure time and overcome treatment disadvantages of irradiation. Late-stage larvae are determined as the most tolerant stage resulted in large LT_99.9968 values of 32.6 (29.2–37.5) and 38.0 (35.1–41.7) days treated under 1% and 2% O₂ (with N₂ balance) atmosphere, respectively. Ionizing radiation was used to enhance the effect of MA and the mortality was highly significantly affected by all the interaction effects, indicating that the synergistic effects present in all the combined treatments. The synergistic ratios, which is defined as the estimated lethal time for MA treatment (LD₉₀, LD₉₉, and LD_99.9968), divided by that of combined treatment, were between 1.47 and 2.47. In the confirmatory tests, no individuals recovered from a sum of 111,366 late-stage larvae treated under 1% O₂ atmosphere for 14- or 15-d after 200 Gy irradiation, which resulted in validating the probit estimations and achieving an efficacy of 99.9973% mortality at 95% confidence level. Therefore, these treatment schedules are recommended to disinfest T. granarium infecting commodities for phytosanitary purposes under the warehouse, MA packaging, or in combination with international transportation by train or sea container.

Field evaluation of hermetic and synthetic pesticide-based technologies in smallholder sorghum grain storage in hot and arid climates

Field evaluation of six grain storage technologies under hot and arid conditions (32–42 °C; rainfall < 450 mm/year) in two locations in Zimbabwe were conducted over two storage seasons. The treatments included three hermetic technologies (Purdue Improved Crop Storage bags, GrainPro Super Grainbags, metal silos); three synthetic pesticide-based treatments; and an untreated control, all using threshed sorghum grain. Sampling was at eight-week intervals for 32 weeks. Highly significant differences (p < 0.01) occurred between hermetic and non-hermetic treatments regarding grain damage, weight loss, insect pest populations, and grain moisture content; with the hermetic containers exhibiting superior grain protection. Weight losses were low (< 3%) in hermetic treatments compared to pesticide-based treatments (3.7 to 14.2%). Tribolium castaneum developed in metal silos, deltamethrin-incorporated polypropylene bags and a pesticide treatment containing deltamethrin 0.13% and fenitrothion 1% while Sitotroga cerealella developed in a pesticide treatment containing pirimiphos-methyl 0.16% + thiamethoxam 0.036%. Mechanisms of survival and development of these pests in the tested treatments and under similar climatic conditions need further elucidation. These hermetic technologies can be successfully used by smallholder farmers in developing countries as alternatives to synthetic pesticides for protecting stored-sorghum grain under hot and arid climatic conditions to attain household food security. To our knowledge, this is the first published study on modern hermetic storage of sorghum grain under typical smallholder storage conditions and involving stakeholders.

Sublethal exposure of Trogoderma granarium everts (Coleoptera: Dermestidae) to insecticide-treated netting alters thigmotactic arrestment and olfactory-mediated anemotaxis

Long-lasting insecticide treated netting (LLIN) has a number of potential uses for the control of insect pests. Using such netting, stored products may be protected from insects including the khapra beetle (Trogoderma granarium Everts, Coleoptera: Dermestidae) a widespread pest of many agricultural commodities. Here we first examined whether brief exposures of larvae to LLIN, for less than 30 min, decreased the chance of eventual adult emergence compared to larvae exposed on untreated netting. Next, we observed the responses of larvae that were either not exposed to any netting, exposed to untreated netting, or exposed to LLIN for 10 min and then placed in a wind tunnel and monitored for movement toward a stimulus. The wind-tunnel assay was performed either with or without a lure containing kairomones and pheromones known to be attractive to larvae of this species. There was little effect of the LLIN on adult emergence of exposed larvae. However, there were interacting effects of untreated netting and LLIN relating to thigmotaxis and anemotaxis. Larvae not exposed to netting showed increased likelihood of walking upwind if the semiochemical lure was provided, as expected. A similar pattern was observed when the untreated netting was used, but the larvae became more likely to remain stationary in the assay after acclimating to the net. When LLIN was used, the larvae became more likely to move and there was a baseline increase in the likelihood of moving upwind. However, upwind walking was no longer related to semiochemical presentation. These observations suggest that particular care should be used in relation to the airflow patterns and semiochemical landscape of the warehouse settings in which LLIN is deployed.

Effect of Nitrogen on Phosphine-Susceptible and -Resistant Populations of Stored Product Insects

Simple Summary

The sawtoothed grain beetle, the red flour beetle and the rice weevil are three major stored product insects that attack different stored products worldwide. Limited chemical options are available, and eco-friendlier management strategies are needed. Low oxygen treatment can be used as an alternative method to limit chemical treatments. Therefore, we conducted nine trials in commercial nitrogen chambers with phosphine susceptible and resistant populations. The vials with insects were placed in different locations inside the chambers and mortality was recorded after the termination of each trial. The vials were kept at laboratory conditions for 65 days in order to measure progeny production. Low or no survival was recorded in all cases for all species. Moreover, progeny production was suppressed with some exceptions for some species and populations. The current study indicates that low oxygen is effective against phosphine susceptible and resistant populations and can be used as alternative method to chemicals.

Abstract

In this study, we evaluated nitrogen treatment on phosphine-resistant field and -susceptible laboratory populations of different stored product beetles. Nine trials were conducted in commercial nitrogen chambers with the O₂ level set at 1.0%. Two different temperatures—i.e., 28 and 40 °C—and three exposure intervals—i.e., 2.5, 3 and 9 d—were used in our tests. Adults of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae); the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae); and the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) were used in the trials. The insects were placed in vials with different commodities per species and population, and their mortality was measured after the termination of each trial. Then, the vials were kept in incubator chambers at 25 °C and 65% relative humidity for 65 d to measure progeny production. Complete parental mortality was observed in all cases for O. surinamensis and S. oryzae, but there was some survival for T. castaneum at 28 °C and 3 d of exposure. In general, progeny production was completely (100%) suppressed, with some exceptions for all species and populations. The results indicate that low oxygen is effective for all species tested, regardless of their resistance status to phosphine, and can be further adopted as an alternative method to mitigate resistance in stored product beetles.