Contact Insecticides Research Articles

English

Post-harvest losses of agricultural produce caused by store grain pest most especially cereals and grains to store pest require developing cheap, ecofriendly and readily available insecticide to combat this threat and achieve the goal of food security in developing countries. This study investigated the effects of Cleistopholis patens (leaf and stem bark) on Plodia interpunctella infestation in stored maize grains. Powders from the plant were administered at 0.5, 1.0, 1.5, 2.0 and 2.5 g dosages to maize grains containing developmental stages of P. interpunctella both as contact and fumigant insecticides. The insecticidal activities were monitored at 24, 48, 72 and 96 h post-treatment periods. As a contact insecticide, C. patens was significantly (PË‚0.05) more effective than as a fumigant against all developmental stages of the pest. The leaf powder was observed to be weakly effective both as contact and fumigant against P. interpunctella. At its peak, 69.17% larval mortality was achieved at 2.5 g dosage after 96 h exposure, but 1.5 g dosage of the stem bark achieved 0% egg hatchability and 100% larval and adult mortalities at the same length of exposure. Inferences from these results suggest that the plant has some bioactive constituents which if properly harnessed can be co-opted into integrated management of P. interpunctella infesting stored products. Key words: hatchability, contact, fumigant, bioactivity, Indian meal moth and post- treatment.

(Quasi)-Binomial vs. Gaussian Models to Evaluate Thiamethoxam, Pirimiphos-Methyl, Alpha-Cypermethrin and Deltamethrin on Different Types of Storage Bag Materials Against Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae).

Simple SummaryEphestia kuehniella Zeller (Lepidoptera: Pyralidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) are major stored-product pests globally. The use of contact insecticides constitutes an option of effective management of these species. Therefore, we evaluated the activity of thiamethoxam, pirimiphos-methyl, alpha-cypermethrin, and deltamethrin for the management of E. kuehniella and T. confusum larvae on three types (plastic and paper) of storage bag materials under three exposure scenarios. In addition to typical linear regression, we introduced a binomial and quasi-binomial modeling approach to analyze our data. Thiamethoxam and pirimiphos-methyl exhibited significantly higher mortality rates on E. kuehniella and T. confusum than alpha-cypermethrin and deltamethrin. Mortality rate of T. confusum larvae was significantly higher than E. kuehniella larvae. Treatments revealed significant differences in the mortalities of both species. Our results indicate that the application of contact insecticides to storage bag materials is an efficient management tool against larvae of E. kuehniella and T. confusum.The Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) are worldwide spread and notorious organisms of numerous stored-products. Both species are dangerous for bagged commodities as penetrators and invaders. The aim of the current study was to examine the efficacy of thiamethoxam, pirimiphos-methyl, alpha-cypermethrin, and deltamethrin, against E. kuehniella and T. confusum larvae, on different types of storage bag materials, i.e., woven propylene, biaxially oriented polypropylene and kraft paper through a (quasi)-binomial modeling approach. The type of the tested storage bag material did not affect the mortality rates of both species when treated with the tested insecticides. Thiamethoxam and pirimiphos-methyl showed statistically significant higher mortality rates on E. kuehniella and T. confusum (beta coefficient = 0.141; p-value < 0.05) compared to alpha-cypermethrin and deltamethrin. In addition, T. confusum exhibited significantly higher mortality rate in comparison to E. kuehniella. Our results also showed that the tested doses and surface treatments had a significant effect on the mortality E. kuehniella and T. confusum larvae. Significantly higher mortality rates were recorded when larvae were exposed on bag materials having both surfaces treated or on the single treated surface than when they were exposed on the untreated surface. Our findings can be useful towards an effective management strategy against stored-product insect pests.

Insecticidal efficacy of some essential oils against adults of Musca domestica L. (Diptera: Muscidae)

Nowadays, the insecticidal and acaricidal properties of plant extracts and essential oils (EOs) have been evaluated as an alternative to chemical means. This study aims to assess the insecticidal efficacy of 20 commercial EOs against the adults of Musca domestica Linnaeus (Diptera: Muscidae) by the contact of insects with the residues of EOs at the bottom of glass cups. The dose effects of seven EOs (i.e. Acorus calamus, Allium sativum, Syzygium aromaticum, Cymbopogon citratus, Juniperus communis, Cedrus atlantica, and Foeniculum vulgare) as well as the time effects of exposure to these EOs on the mortality of flies were analyzed by probit analysis. Permethrin (technical substance) was used as a reference insecticide in the positive control and pure acetone served as the negative control. The insecticidal efficacy of the tested EOs decreased in order (based on their lethal dose (LD)50 values): A. calamus > A. sativum > S. aromaticum ≥ C. citratus > J. communis > C. atlantica > F. vulgare. A. calamus EO was the most effective against flies and very fast acting with negligible reversibility of effect. The EOs of A. sativum and S. aromaticum had a significant time-dependent insecticidal effect. The time for 50% insecticidal effect (knockdown and mortality in total) of the A. sativum EO was the greatest among the seven EOs and seven times more in comparison with the positive control. Present results and literature data suggest that the aforesaid plant products could be promising as contact insecticides against adults M. domestica. The difference in the insecticidal properties of A. calamus and A. sativum EOs observed in the current study display the need for various approaches for their future application as insecticides.

Transcriptomic analysis of s-methoprene resistance in the lesser grain borer, Rhyzopertha dominica, and evaluation of piperonyl butoxide as a resistance breaker

BackgroundThe lesser grain borer, Rhyzopertha dominica is a serious pest of stored grains. Fumigation and contact insecticides play a major role in managing this pest globally. While insects are developing genetic resistance to chemicals, hormonal analogues such as s-methoprene play a key role in reducing general pest pressure as well as managing pest populations that are resistant to fumigants and neurotoxic contact insecticides. However, resistance to s-methoprene has been reported in R. dominica with some reports showing a remarkable high resistance, questioning the use of this compound and other related analogues in grain protection. The current study attempts to identify possible molecular mechanisms that contribute in resistance to s-methoprene in R. dominica.ResultsTranscriptome analysis of resistant and susceptible strains of this pest species identified a set of differentially expressed genes related to cytochrome P450s, indicating their potential role in resistance to s-methoprene. Laboratory bioassays were performed with s-methoprene treated wheat grains in presence and absence of piperonyl butoxide (PBO), a cytochrome P450 inhibitor. The results indicate that PBO, when applied alone, at least at the concentration tested here, had no effect on R. dominica adult emergence, but has a clear synergistic effect to s-methoprene. The number of produced progeny decreased in presence of the inhibitor, especially in the resistant strain. In addition, we also identified CYP complement (CYPome) of R. dominica, annotated and analysed phylogenetically, to understand the evolutionary relationships with other species.ConclusionsThe information generated in current study suggest that PBO can effectively be used to break resistance to s-methoprene in R. dominica.

Characterizing and predicting sublethal shifts in mobility by multiple stored product insects over time to an old and novel contact insecticide in three key stored commodities.

There has been a push to diversify integrated pest management (IPM) programs away from exclusive fumigant use in food facilities. Residual insecticides increasingly have been included among plans. In stored products, sublethal toxicity has been neglected in favor of evaluating direct mortality. Here, we evaluated the movement of Tribolium castaneum, Rhyzopertha dominica, Sitophilus oryzae and Sitophilus zeamais in response to aged residues of an existing (Diacon IGR+® with 11.4% methoprene + 4.75% deltamethrin) and novel (Gravista® with 2.85% methoprene + 1.2% deltamethrin + 33.3% piperonyl butoxide synergist) residual insecticide. Using the maximum labeled rate and two exposure times for each species, we assessed distance moved and velocity on wheat, rice and corn. Assessments were made from commodity residues aged between 0 and 12 months (at 3-month intervals). We found that after exposure, movement was reduced by 50-88% and equally by adults exposed to each insecticide formulation compared to untreated controls. After initial application, predicted distance moved increased from 4 to 14 m then 28 m in a 24 h period at 3 and 12 months post-application, respectively. Effectiveness of each insecticide at suppressing movement generally declined by 9-12 month post-application. Given the quick and dramatic increases in sublethal movement after initial application, our results suggest that sanitation programs in post-harvest environments are extremely important and it may be beneficial to pair chemical control with monitoring to prevent dispersal of affected insects to new areas of a facility. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Rating knockdown of flour beetles after exposure to two insecticides as an indicator of mortality

Knockdown and mortality of adults of the red flour beetle, Tribolium castaneum (Herbst) and the confused flour beetle, Tribolium confusum Jacquelin du Val, were assessed after exposure to two contact insecticides, chlorfenapyr and cyfluthrin, on a concrete surface. Individuals were rated on a scale for knockdown of exposed adults according to their mobility from 1, representing immobilized adults to 5, representing normally moving (similar to the controls). Only cyfluthrin gave immediate knockdown. Adults were rated at 1, 3 and 7 days post-exposure. After the final assessment, adults were discarded and the same procedure was repeated for 5 consecutive weeks with new adults exposed on the same treated surfaces. Despite initial knockdown, many individuals did not eventually die after exposure to cyfluthrin. In contrast, adults exposed to chlorfenapyr were not initially knocked down after exposure but most died after 7 days. These trends were similar during the entire 5-week residual testing period. The storage of the treated dishes in illuminated or non-illuminated conditions did not affect the insecticidal effect of either insecticide. The results of the present study can be further implemented towards the design of a “lethality index” that can serve as a quick indicator of knockdown and mortality rates caused after exposure to insecticides.

Effect of Pheromones, Plant Volatiles and Spinosad on Mating, Male Attraction and Burrowing of Cadra cautella (Walk.) (Lepidoptera: Pyralidae).

Simple SummarySex pheromones used at higher concentrations than their availability in insects have been successful in decreasing the insect population. Furthermore, botanical oils have also had negative impacts on the insect population level. In the first study, we investigated the combined effect of sex pheromones and plant oils on mating of almond moth. The second study sought the burrowing ability of almond moth larvae through different flour media. Mating declined on the presence of pheromones and botanical oils, whereas burrowing ability differed with flour type. Exposure to spinosad affected both mating success and larval penetration through flour media. The findings of this study reveal that various applications of sex pheromones, plant oils and spinosad ensure the better protection of cereal-based agricultural produce from insect infestation during storage.Mating disruption of Cadra cautella (Walk.) (Lepidoptera: Pyralidae) using its sex pheromone components, (Z, E)-9,12-tetradecadienyl acetate (ZETA) and (Z)-9-tetradecadien-1-yl acetate (ZTA), is successful in its population management. In addition, botanical oils have extensively been investigated in stored product pest management, but the effect of synthetic sex pheromones on the mating of C. cautella in the presence of plant volatiles is still unknown. Spinosad is used in food facilities as a contact insecticide but, if C. cautella larvae burrow into food, they may escape from spinosad. Importantly, the impact of spinosad on burrowing ability of C. cautella remains unknown. Therefore, the objectives of this study were to determine the effects of sex pheromone components ZETA and ZTA in the presence of botanical oils on the mating of C. cautella and the burrowing ability of C. cautella larvae in different types of flour treated with spinosad. In the first study, male and female moths were introduced into the cubicle having botanical oils and pheromone components. The mating status of female moths and male moth attraction to the trap was determined. The control experiments had only the botanical oils or pheromones. In the second study, burrowing ability of C. cautella larvae through different flour types was evaluated over 10 d. The flour was sprayed with spinosad (treatments) or water (controls). The mating success was higher with botanical oils alone but declined with exposure to pheromone either alone or combined with botanical oils. No differences in male attraction to traps were observed in botanical only, pheromone only or pheromone + botanical oil treatments. The burrowing of C. cautella larvae differed with flour type and spinosad altered burrowing ability. Thus, we conclude that the mating and burrowing of C. cautella is influenced by its pheromone and by exposure to botanicals and spinosad.

Tenebenal: a meta-diamide with potential for use as a novel mode of action insecticide for public health

BackgroundThere is an urgent need for insecticides with novel modes of action against mosquito vectors. Broflanilide is a meta-diamide, discovered and named Tenebenal™ by Mitsui Chemicals Agro, Inc., which has been identified as a candidate insecticide for use in public health products.MethodsTo evaluate its potential for use in public health, Tenebenal™ was screened using an array of methodologies against Anopheles and Aedes strains. Initially it was assessed for intrinsic efficacy by topical application. Tarsal contact bioassays were then conducted to further investigate its efficacy, as well as its potency and speed of action. The potential of the compound for use in indoor residual spray (IRS) applications was investigated by testing the residual efficacy of a prototype IRS formulation on a range of typical house building substrates, and its potential for use in long-lasting insecticidal nets (LLIN) was tested using dipped net samples. Finally, bioassays using well-characterized insecticide-resistant mosquito strains and an in silico screen for mutations in the insecticide’s target site were performed to assess the risk of cross-resistance to Tenebenal™.ResultsTenebenal™ was effective as a tarsal contact insecticide against both Aedes and Anopheles mosquitoes, with no apparent cross-resistance caused by mechanisms that have evolved to insecticides currently used in vector control. Topical application showed potent intrinsic activity against a Kisumu reference strain and an insecticide-resistant strain of Anopheles gambiae. Applied to filter paper in a WHO tube bioassay, Tenebenal™ was effective in killing 100% of susceptible and resistant strains of An. gambiae and Aedes aegypti at a concentration of 0.01%. The discriminating concentration of 11.91 µg/bottle shows it to be very potent relative to chemistries previously identified as having potential for vector control. Mortality occurs within 24 h of exposure, 80% of this mortality occurring within the first 10 h, a speed of kill somewhat slower than seen with pyrethroids due to the mode of action. The potential of Tenebenal™ for development in LLIN and IRS products was demonstrated. At least 12 months residual efficacy of a prototype IRS formulation applied at concentrations up to 200 mg of AI/sq m was demonstrated on a range of representative wall substrates, and up to 18 months on more inert substrates. A dipped net with an application rate of around 2 g/sq m Tenebenal™ killed 100% of exposed mosquitoes within a 3-min exposure in a WHO cone test.ConclusionsTenebenal™ is a potent insecticide against adult Aedes and Anopheles mosquitoes, including strains resistant to classes of insecticide currently used in vector control. The compound has shown great potential in laboratory assessment and warrants further investigation into development for the control of pyrethroid-resistant mosquitoes.

Naturally Occurring Compounds/Materials as Alternatives to Synthetic Chemical Insecticides for Use in Fire Ant Management.

Simple SummaryRed imported fire ants are a notorious pest, impacting humans, livestock, pets and wildlife due to their venomous stings and causing billions of dollars in damages annually. Synthetic insecticides are a major tool used to control this pest. There is an ever-increasing public concern about the potential adverse effects of synthetic insecticides. Extensive effort has been made in searching for alternatives. In addition to biological control, physical and cultural practices, and semiochemicals, natural products continue to be one of the most attractive sources of alternatives. Naturally occurring compounds/materials have been successfully used as active ingredients in fire ant baits, contact-based control products, repellants and fumigants. In this article, we summarized the synthetic insecticides that are currently used in managing fire ants, available alternative products in the current USA market, and academic efforts in searching for fire ant natural toxins, repellants and fumigants.The invasive red imported fire ant, Solenopsis invicta Buren (hereafter, fire ants), is a significant threat to public health and a danger to livestock, pets and wildlife due to their venomous stings. The fire ant has invaded many countries and regions and has become a globally significant pest. The current major tool to manage fire ants are synthetic insecticides that are used largely as stomach poisons in bait products or contact insecticides in spray, broadcast, drench, and dust products for area and nest treatments. In addition to these insecticide products, repellants and fumigants can also be useful in some unique scenarios. The ever-increasing public concern about the potential adverse effects of synthetic insecticides on health and the environment has been a driving force for searching for safer alternatives to control fire ants. Tremendous effort has been made in developing biologically-based control for managing fire ants; however, natural products continue to be one of the most attractive sources of safe alternatives to synthetic insecticides. Here, we summarized the synthetic insecticides that are currently used in managing fire ants, available alternative products in the current market, and academic efforts in searching for fire ant natural toxins, repellants and fumigants.

Field efficacy of selected insecticides for control of mint rhizome borer, Datonychus melanostictus (Marsham, 1802) (Coleoptera: Curculionidae) in Morocco

The weevil, Datonychus melanostictus, is one of the most damaging insect pest of mint crop Mentha spicata L. in Morocco. This insect causes significant damage by larval feeding on mint rhizomes. The effectiveness of systemic and contact insecticides for controlling larvae and adults of D. melanostictus was investigated in spearmint field trials, during three cropping seasons in the Chaouia region. The contact insecticide lambda-cyhalothrin (250 ml/ha) caused the highest mortality (87.5%) against adult weevils three days after treatment, reducing the damaged rhizomes by 61% and significantly increased the fresh yield by 48.7% over the check. However, the use of neonicotinoid insecticides imidacloprid and thiacloprid after mint cuts showed a negative effect to reduce the larval infestation on rhizomes. These findings revealed that the use of lambda-cyhalothrin as foliar application in early summer, could be an excellent candidate to control the adult weevils D. melanostictus on mint crop.

A deltamethrin crystal polymorph for more effective malaria control

Pyrethroid contact insecticides are mainstays of malaria control, but their efficacies are declining due to widespread insecticide resistance in Anopheles mosquito populations, a major public health challenge. Several strategies have been proposed to overcome this challenge, including insecticides with new modes of action. New insecticides, however, can be expensive to implement in low-income countries. Here, we report a simple and inexpensive method to improve the efficacy of deltamethrin, the most active and most commonly used pyrethroid, by more than 10 times against Anopheles mosquitoes. Upon heating for only a few minutes, the commercially available deltamethrin crystals, form I, melt and crystallize upon cooling into a polymorph, form II, which is much faster acting against fruit flies and mosquitoes. Epidemiological modeling suggests that the use of form II in indoor residual spraying in place of form I would significantly suppress malaria transmission, even in the presence of high levels of resistance. The simple preparation of form II, coupled with its kinetic stability and markedly higher efficacy, argues that form II can provide a powerful, timely, and affordable malaria control solution for low-income countries that are losing protection in the face of worldwide pyrethroid resistance.

Hydrogels: From Controlled Release to a New Bait Delivery for Insect Pest Management.

Here, we review the literature on the development and application of hydrogel compounds for insect pest management. Researchers have used hydrogel compounds for the past few decades to achieve the controlled release of various contact insecticides, but in recent years, hydrogel compounds have also been used to absorb and deliver targeted concentrations of toxicants within a liquid bait to manage insect pests. The highly absorbent hydrogel acts as a controlled-release formulation that keeps the liquid bait available and palatable to the target pests. This review discusses the use of various types of hydrogel compounds in pest management based on different environmental settings (e.g., agricultural, urban, and natural areas), pest systems (e.g., different taxa), and modes of insecticide delivery (e.g., spray vs bait). Due to their unique physicochemical properties, hydrogel compounds have great potential to be developed into new and efficacious pest management strategies with minimal environmental impact. We will also discuss the future research and development of hydrogels in this review.

Transcriptional Control of Quality Differences in the Lipid-Based Cuticle Barrier in Drosophila suzukii and Drosophila melanogaster.

Cuticle barrier efficiency in insects depends largely on cuticular lipids. To learn about the evolution of cuticle barrier function, we compared the basic properties of the cuticle inward and outward barrier function in adults of the fruit flies Drosophila suzukii and Drosophila melanogaster that live on fruits sharing a similar habitat. At low air humidity, D. suzukii flies desiccate faster than D. melanogaster flies. We observed a general trend indicating that in this respect males are less robust than females in both species. Xenobiotics penetration occurs at lower temperatures in D. suzukii than in D. melanogaster. Likewise, D. suzukii flies are more susceptible to contact insecticides than D. melanogaster flies. Thus, both the inward and outward barriers of D. suzukii are less efficient. Consistently, D. suzukii flies have less cuticular hydrocarbons (CHC) that participate as key components of the cuticle barrier. Especially, the relative amounts of branched and desaturated CHCs, known to enhance desiccation resistance, show reduced levels in D. suzukii. Moreover, the expression of snustorr (snu) that encodes an ABC transporter involved in barrier construction and CHC externalization, is strongly suppressed in D. suzukii. Hence, species-specific genetic programs regulate the quality of the lipid-based cuticle barrier in these two Drosophilae. Together, we conclude that the weaker inward and outward barriers of D. suzukii may be partly explained by differences in CHC composition and by a reduced Snu-dependent transport rate of CHCs to the surface. In turn, this suggests that snu is an ecologically adjustable and therefore relevant gene in cuticle barrier efficiency.

Insecticidal Activities of Some Botanicals on the Three Species of Callosobruchus

Nine medicinal and aromatic plants were evaluated for their efficacy as contact insecticides on the three species of Callosobruchus, i. e. C. maculatus, C. analis and C. chinensis. Aqueous extract of twelve plants, i. e. Synzgium aromaticum (clove floral buds), Azadirachta indica (neem leaves), Allium sativum (garlic bulbs), Piper nigrum (black pepper seeds), Thevetia peruviana (kaner leaves), Moringa oliefera (moringa leaves, flowers, drumstick and root), Prosopis cineraria (khejri leaves), Eucalyptus globulus (eucalyptus leaves) and Curcuma longa (turmeric rhizome) were tested against all the three species of bruchids. The extracts were applied at doses of 0.5, 1.5, 2.5, 3.5 and 4.5 ml/20 g to cowpea seeds by filter paper diffusion method. The higher dose of flower and leaf extracts from M. oleifera, seed extract from P. nigrum and leaves extract from A. indica have shown potent insecticidal activity against all the three Callosobruchus species. Use of these botanicals can be an ecofriendly alternative to the chemical insecticides against the Callosobruchus species.

Essential oil composition and insecticidal activity of Satureja boissieri against Sitophilus granarius (Coleoptera:Curculionidae) and Spodoptera littoralis (Lepidoptera: Noctuidae)

In the scope of this study, we have investigated fumigant and contact toxicity effects of Satureja boissieri Hausskn. ex Boiss. essential oil against Sitophilus granarius L. (Coleoptera: Curculionidae) and Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). The fumigant and contact toxicity experiments were carried out with the adults of Sitophilus granarius whereas the contact toxicity experiment was carried out with the 3rd, 4th and 5th larvae of S. littoralis. Also, various fractions of S. boissieri essential oil were investigated for fumigant activity against S. granarius. In fumigant toxicity studies, the highest activity was obtained at 36 hours with a dose of 0.1 μl/ml with a 100% mortality rate. Fractions of the essential oil had significant fumigant activity on S. granarius (100% fumigant activity at 0.1 μl/ml). Contact toxicity of 100 μl/ml essential oil on the 3rd and 4th larval stage of S. littoralis, was determined to be 100%, however, on the 5th larval stage it was 90.17%. The activity at 25 μl/ml dose was 71.12% in the 3rd larval stage whereas the activity remained very low (6.39- 22.20%) in other larval stages. These results indicated that essential oil of S. boissieri have significant potential which merits to be studied further in possible applications as fumigant and contact insecticide in the control of S. granarius and S. littoralis.

Efficacy of Eucalyptus Leaf (Eucalyptus camaldulensis), Moringa Seed (Moringa oleifera) and Pirimiphos-methyl Powders against Maize Weevil (Sitophilus zeamais) in Stored Maize

Annually, Nigeria loses 20–40% of maize grain due to insect pests attack. However, insect pest control in stored products relied heavily on the use of gaseous fumigants and residual contact insecticides. The control method is limited as it is toxic to beneficials and humans. Efforts have now shifted to the use of edible plant materials as protectants of which the tropics are well endowed with. Therefore, a study was conducted in laboratory in order to evaluate the effectiveness of powders of eucalyptus leaf (Eucalyptus camaldulensis Schlecht,) moringa seed (Moringa oleifera Lam.) and Pirimiphos-methyl against maize weevil (Sitophilus zeamais) on stored maize (Zea mays L.).&#x0D; &#x0D; camaldulensis leaf powder showed 100% repellence effect at a concentration of 2.0 g / 20 g maize seeds while M. oleifera seed powder had 75% repellence effect against S. zeamais. Contact toxicity of E. camaldulensis leaf powder on S. zeamais was 65% at 1.0 g/20 g maize seeds after 96 hours of exposure. Contact toxicity of M. oleifera seed powder on S. zeamais was 60% at 96 hours of exposure at a concentration of 1.0 g/20 g maize seeds. The powders of E. camaldulensis leaf and M. oleifera seed showed promising effects against S. zeamais in stored maize, hence could be incorporated in an integrated approach as alternative to synthetic pesticides when used in reducing weevil infestation in stored maize seeds.&#x0D;

Evaluation of boric acid as toxic sugar bait against resistant Aedes aegypti mosquitoes.

Current methods of broad area application of contact insecticides used in mosquito control are becoming less effective, primarily due to resistance within mosquito populations. New methods that can deliver ingestible insecticides are being investigated as a means to mitigate resistance. This study evaluated insecticide delivery through toxic sugar baits (TSB) and resulting mortality of susceptible and resistant strains of Aedes aegypti. Two Ae. aegypti strains were evaluated using a 1% boric acid TSB: the susceptible Orlando 1952 (ORL) strain and the resistant Puerto Rican (PR) strain. The TSB resulted in high mortality for both ORL and PR strain of Ae. aegypti. Average mortality of female mosquitoes given TSB was 90.8% for PR and 99.3% for ORL. Our study suggests that targeting resistant mosquitoes with ingestible insecticides through TSBs could be a viable alternative to current mosquito control strategies and should be considered when developing an integrated vector management program.

Effect of Six Insecticides on Egg Hatching and Larval Mortality of Trogoderma granarium Everts (Coleoptera: Dermestidae).

The khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is one of the most destructive insect species of stored food worldwide and is subjected to strict phytosanitary legislations. In the present study, we evaluated the egg hatching and larval mortality of T. granarium on concrete surfaces treated with six insecticides (i.e., α-cypermethrin, chlorfenapyr, deltamethrin, pirimiphos-methyl, pyriproxyfen, and s-methoprene) that are registered in Greece for surface treatment and exhibit a broad spectrum of different modes of action. Furthermore, we investigated the influence of the presence of food on egg hatching and larval mortality. Egg hatchability on treated concrete was higher in tests with the presence of food for all tested insecticides, with the exception of s-methoprene. In contrast, larval mortality was lower in treatments where there was nourishment for all insecticides. No egg hatching was recorded on concrete treated with pirimiphos-methyl where there was no food, while with the addition of food, the egg hatching did not exceeded 26.7% after 6 days of exposure. The highest percentage of hatched eggs was recorded on concrete treated with chlorfenapyr (87.7% with food vs. 76.7% without food), followed by deltamethrin (76.7% with food vs. 63.3% without food), pyriproxyfen (50.0% with food vs. 42.2% without food), and α-cypermethrin (28.9% with food vs. 6.7% without food). In the case of s-methoprene, more eggs were hatched in the absence of food (91.1%) in contrast to in the presence of food (86.7%). Regarding mortality, all larvae were dead after 5 days of exposure on pirimiphos-methyl-treated concrete with food. Furthermore, larvae died faster in treatments without food. For α-cypermethrin, 100% mortality was recorded after 4 days of exposure, while with presence of food, all larvae died after 6 days. Chlorfenapyr caused complete mortality of larvae after 5 days of exposure on concrete without food and after 8 days with food. In the case of deltamethrin, 100% mortality was recorded after 7 days in the absence of food and 8 days in the presence of food. Regarding pyriproxyfen, complete mortality was not recorded when food was present, reaching 94.1% 14 days postexposure. However, after 12 days, all larvae died in treatments without food. Although egg hatching was higher in the case of s-methoprene on concrete without food, larval mortality was 100% after 8 days of exposure. Nevertheless, when there was food, 87.3% of the exposed larvae died after 13 days. Therefore, it becomes evident that sanitation of storage facilities before the application of contact insecticides is a key factor for the successful control of T. granarium in the egg stage.

Stored grain pest prevalence and insecticide resistance in Egyptian populations of the red flour beetle Tribolium castaneum (Herbst) and the rice weevil Sitophilus oryzae (L.)

As a consequence of the widespread use of insecticides against insect pests in grain warehouses and in the food industry, insecticide resistance has greatly increased among these species all over the world. Nonetheless, insecticide resistance in stored grain insects in Egypt was little studied. Therefore, our study aimed to forecast infestation risks and determine the insecticide resistance level in Egyptian populations of the main insect pests of stored grains. To achieve this goal, we surveyed the populations of stored-product insects in wheat in two different sites in the Alexandria governorate (Egypt) between June and August 2017. Moreover, insecticide resistance levels in Egyptian populations of Tribolium castaneum (Herbst) and Sitophilus oryzae (L.) collected from wheat storage facilities (granaries and flour mills) in Alexandria governorate were also determined. Three contact insecticides, namely malathion, pirimiphos-methyl and cypermethrin, were tested. Tarsal contact bioassays on filter paper were carried out on adults following FAO methods and concentration-mortality lines were estimated to determine the resistance ratios for each insecticide and population. The data from the monitoring of insects revealed that T. castaneum and S. oryzae were the most common species infesting wheat in both Alexandria granaries and mills. Populations of S. oryzae were generally more resistant to malathion than the populations of T. castaneum. However, T. castaneum populations were more resistant to pirimiphos-methyl than the S. oryzae populations. Both populations of T. castaneum and S. oryzae were susceptible to cypermethrin. The detected levels of insecticide resistance indicate that this phenomenon takes place and should be a concern in Egyptian populations of T. castaneum and S. oryzae requiring monitoring and design of resistance management practices.

Foliar- and Soil-Applied Pesticide Compatibility with Aphidius colemani1 Parasitoids

When using predators or parasitoids for biological control of target pests, pesticides might be required to manage other arthropod pests and plant diseases. To minimize risk to natural enemies, growers need to be aware of which pesticides cause direct and indirect toxicity when combining biological and chemical controls. Aphidius colemani Viereck (Hymenoptera: Braconidae), an endoparasitoid of green peach aphid, Myzus persicae Sulzer (Hemiptera: Aphididae), and other aphid pests, killed after exposure for 6, 12, 24, and 48 hours to 13 contact insecticides and two fungicides at medium and high rates were assessed in a laboratory. In addition, percentage of parasitism of green peach aphid, Myzus persicae Sulzer (Hemiptera: Aphididae), after plants were treated with five soil-applied systemic insecticides was determined in a greenhouse. Using standards set by the International Organization for Biological Control-West Palearctic Regional Section (IOBC-WPRS), most foliar-applied pesticides tested were “slightly harmful” or “moderately harmful” to A. colemani. However, permethrin, spinetoram + sulfoxaflor, dinotefuran, tolfenpyrad, and acetamiprid killed ≥70% of A. colemani. In addition, the systemic insecticides cyantraniliprole, dinotefuran, flupyradifurone, imidacloprid, spirotetramat killed 100% of green peach aphids, thereby eliminating hosts for A. colemani to parasitize. Results underscore the need to develop new, practical guidelines for evaluating pesticide toxicity to natural enemies.