Tested Insect Species Research Articles

A winning formula: sustainable control of three stored-product insects through paired combinations of entomopathogenic fungus, diatomaceous earth, and lambda-cyhalothrin.

This research aimed to assess the effectiveness of Metarhizium robertsii, diatomaceous earth (Protect-It), and lambda-cyhalothrin, for the long-term protection of stored wheat against three destructive grain insect pests, Rhyzopertha dominica, Tribolium castaneum, and Trogoderma granarium. Different treatments were applied, both alone and in paired combinations in laboratory and persistence trials. Single treatments exhibited significantly lower mortality rates in comparison to the paired treatments for all tested insect species. Among the single treatments, lambda-cyhalothrin (Lamb) resulted in significantly higher mortality rates in laboratory trials, followed by diatomaceous earth (DE) and M. robertsii (Mr), with insignificant differences between Mr and DE. Evidently, DE exhibited the highest persistence after 120days of storage for all insect species and initial exposures, although variations in mortality rates among treatments were mostly insignificant. Overall, the most effective treatment in terms of mortality in laboratory, and persistence trials, and progeny production was DE + Lamb, followed by Mr + Lamb, and Mr + DE for all tested insect species. In general, the most susceptible insect species was R. dominica, followed by T. castaneum and T. granarium. This research highlights the effectiveness of M. robertsii, DE, and lambda-cyhalothrin in providing prolonged protection of stored wheat against all the examined grain insect species.

Efficacy of pulegone, and eugenol alone and in combination with synthetic insecticides for the management of three stored product beetle pests

The rising public concern over the safety and environmental impact of synthetic insecticides, along with the evolution of resistance, are driving entomologists to search for new pest control alternatives. Essential oils and their constituents have been proposed as the most promising alternatives due to their wide spectrum of biological activity and synergistic interaction with traditional insecticides. Therefore, the present work evaluated the toxicity of a monoterpene, pulegone (250 and 500 mg/kg), and a phenylpropene, eugenol (250 and 500 mg/kg), alone and in combination with deltamethrin (0.1 and 0.25 mg/kg), pirimiphos-methyl (2.5 and 5.0 mg/kg), and thiamethoxam (0.1 and 0.5 mg/kg) against Rhyzopertha dominica, Sitophilus oryzae, and Tribolium castaneum on wheat grains. Pulegone exerted significant toxicity at 250 and 500 mg/kg against the three beetle species, with complete mortality after 14 days of exposure, complete inhibition of progeny production, and complete protection of treated wheat grain after 75 days of treatment. While eugenol at the higher application rate tested (500 mg/kg) caused 68.3, 31.7, and 5.0 % mortality in adults of R. dominica, S. oryzae, and T. castaneum, with reduction in progeny production of 81.3, 67.7, and 79.7%, respectively. In combination treatments, pulegone reduced toxicity against tested insect species when mixed with the three insecticides, indicating an antagonistic effect. While treated wheat grains with binary mixtures of eugenol (500 mg/kg) with deltamethrin, pirimiphos-methyl, and thiamethoxam enhanced their toxicity, resulting in higher mortality rates, fewer emerged adults, and a lower loss in weight of wheat grains than those obtained in individual treatments. Based on these findings, we suggest that pulegone and eugenol might be viable options for usage in protecting stored wheat against the tested insect species. Additionally, eugenol has the potential to enhance the toxicity of synthetic insecticides, which could reduce their application rates and manage the resistance to these insecticides.

Efficacy of entomopathogenic fungi against three major stored insect pests, Rhyzopertha dominica, Sitophilus zeamais and Trogodermagranarium

The use of biological control agents such as pathogens and natural enemies could be helpful in reducing reliance on synthetic non-selective insecticides and environmental pollution. Entomopathogenic fungi act as pathogens for insect pests and could be a good alternative to insecticides. In the present work, control potential of six native entomopathogenic fungi: Aspergillus nidulans, Aspergillus fumigatus, Cladosporium cladosporioides, Metarhizium flavoviride, Penicillium citrinum and Trichoderma harzianum, was evaluated against three major stored insect pests, Rhyzopertha dominica, Sitophilus zeamais and Trogoderma granarium, under laboratory conditions. Four doses of each fungal isolate viz., 1 × 104, 1 × 106, 1 × 108 and 1 × 1010 conidia/kg wheat grains were evaluated in terms of adult mortality and progeny suppression of subsequent generation. Bioassays were performed in an incubator with 30 °C, 65% relative humidity and without lighting, and the vials were observed after 7, 14, and 21 d post exposure to calculate mortality of introduced adults. The results revealed that insects’ mortality was dose and time dependent. In most of the cases, M. flavoviride caused the highest mortality and progeny suppression of all tested insect species followed by T. harzianum and C. cladosporioides, while the lowest were observed against A. nidulans followed by A. fumigatus and P. citrinum. Overall, R. dominica was the most susceptible species to all fungal isolates followed by S. zeamais and T. granarium. In summary, the data of the present work indicate a significant potential of tested entomopathogenic fungi as biological control agents against R. dominica, S. zeamais and T. granarium. Further studies are recommended to evaluate control potential of these entomopathogenic fungi against stored insect pests under storage environment. Evaluation of more virulent strains of entomopathogenic fungi and their isolates, development of suitable formulation(s), and standardizing mode application will also be the questions for future research.

Fabrication of Carum copticum essential oil-loaded chitosan nanoparticles and evaluation its insecticidal activity for controlling Rhyzopertha dominica and Tribolium confusum.

Plant essential oils (EOs) can be used as a feasible tool for insect pest control. Nanoparticle formulations of plant EOs can improve the efficiency and stability of EOs, as well as insecticidal potential. In this study, Carum copticum L. essential oil-loaded nanoparticles (OLNs) were prepared via an oil-in-water emulsion, followed by droplet solidiffication via ionic gelation using a cross-linker, sodium tripolyphosphate (TPP). The nanoparticles were characterized by ultraviolet and visible (UV-Vis) spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), laser light scattering (LS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Moreover, the insecticidal activity of C. copticum EO and OLNs was evaluated against Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) and Tribolium confusum Jacquelin du Val. (Coleoptera: Tenebrionidae). In addition, their effectiveness was assessed on the progeny production of tested insect species. The loading efficiency ranged from 34.33 to 84.16% when the chitosan to EO weight ratio was 1:1.25 and 1:0.5, respectively. The loading efficiency decreased with increasing EO content in the nanoparticles. The OLN particles exhibited spherical shape. The particle size was in the range 120-223.6 nm and increased with the increase of EO to chitosan ratio. So that the largest mean particle size (223.6 nm) was reported in the 1:1.25 weight ratio of chitosan to the EO. The mortality percentage of R. dominica and T. confusum adults were 74 and 57% when exposed for 7 days to 2000 mg/kg of OLNs at the 1:1.25 weight ratio, while EO caused 62 and 44% mortality on both insect species, respectively. Therefore, OLNs can potentially improve the insecticidal activity of C. copticum EO and could be applied to facilitate control of stored-product insect pests.

Combinations of Beauveria bassiana and spinetoram for the management of four important stored-product pests: laboratory and field trials

The current study examines the efficacy of the semi-synthetic insecticide spinetoram and entomopathogenic fungi Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae) as wheat protectants against the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), the granary weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae), and the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), under laboratory and field trials. One dose of B. bassiana, i.e., 1 × 107 conidia/kg wheat, two doses of spinetoram, i.e., spine1: 0.05 ppm (mg/kg wheat), spine2: 0.1 ppm, and their combinations (Bb + spine1, Bb + spine2) were evaluated at 20, 25, and 30 °C. All treatments provided significantly higher mortality at 30 °C compared with the other two temperatures. Maximum mortality levels were observed in the treatments where B. bassiana was combined with the higher dose of spinetoram (0.1 ppm). All treatments reduced progeny production in comparison with the control groups. Maximum progeny reduction was observed at 30 °C, on wheat treated with the Bb + spine2 combination. The combination Bb + spine2 also provided elevated mortality rates in both laboratory and field persistence trials, but at 180 days caused moderate mortality to all tested insect species. Concerning progeny, at laboratory persistence trials, the combination Bb + spine2 exhibited the lowest offspring emergence to all tested species compared to the other treatments and control. Overall, our study showed that R. dominica was the most susceptible species followed by S. granarius, T. castaneum, and T. granarium. Our findings revealed that the combination of B. bassiana and spinetoram may be a useful tool for efficient and advanced integrated pest management strategies for long storage periods under multiple temperatures.

Laboratory and field studies on the combined application of Beauveria bassiana and fipronil against four major stored-product coleopteran insect pests.

In the current study we have tested the application of Beauveria bassiana (Hypocreales: Cordycipitaceae) alone and in combination with fipronil at two doses against Tribolium castaneum (Coleoptera: Tenebrionidae), Rhyzopertha dominica (Coleoptera: Bostrychidae), Sitophilus granarius (Coleoptera: Curculionidae), and Trogoderma granarium (Coleoptera: Dermestidae) under laboratory and field conditions. At laboratory conditions, the combination of B. bassiana with the highest dose of fipronil produced the highest mortality. At different temperatures, mortality was increased with the increase in temperature. Maximum mortality was observed at 30°C, followed by 25°C and 20°C for all tested species. Different treatments significantly reduced the progeny number in comparison to control groups for all tested species at all temperatures. In the persistence trial, all treatments that included the combinations of B. bassiana with fipronil produced significantly higher mortalities than the single treatments for all tested species over a period of 6months. Furthermore, all treatments significantly reduced the number of progenies of all insect species in comparison with the control groups over the same storage period. In field trials, mortalities of all tested insect species were significantly higher on wheat treated with B. bassiana, fipronil, or their combinations than on controls for an entire storage period of 180days. Overall, R. dominica was found the most susceptible species followed by S. granarius, T. castaneum, and T. granarium. The findings of the current study suggest that the use of B. bassiana and fipronil as grain protectants may provide elevated control against major stored-grain insect species during a prolonged period of storage.

A Pilot Study of Natural Formulation Activity in the Protection of Stored Wheat and Barley Against the Stored-Product Insects

The stored-product insects are one of the major causes of losses in the stored cereals. Most of control measures still rely on a synthetic pesticide usage, but due to its negative side effects on the goods, human health, and the environment, there is an urgent need for an alternative control. A natural formulation based on the diatomaceous earth (DE) SilicoSec®, enhanced with the botanicals (essential oil lavender, corn oil, and bay leaves dust) and the silica gel was developed. The aim of the study was to test the activity of the developed formulation as a postharvest protectant of seed wheat and barley in the suppression Sitophilus oryzae (L.), Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst). As a reference comparative value, the DE SilicoSec® was applied. Subsequent to the six months of storage under the simulated warehouse conditions, the formulation has completely suppressed the initial population development of all three tested insect species, both in wheat and barley. In wheat, a complete suppression was detected at the dose of 500 ppm against T. castaneum and 600 ppm against both R. dominica and S. oryzae. In barley, a complete suppression was detected at the doses of 500 ppm, 400 ppm, and 600 ppm against R. dominica, T. castaneum and S. oryzae, respectively. Conclusively, the results of this study indicate that the developed natural formulation based on the DE, botanicals, and silica gel was highly effective against the three major stored‐product insect species, providing a long-term safe storage of wheat and barley seeds.

Effect of packaging chickpeas with CO2 modified atmospheres on mortality of Callosobruchus chinensis (Coleoptera: Chrysomelidae)

High CO2 modified atmosphere packaging (MAP) is a sustainable alternative for pest control in stored products. The effectiveness of this method varies depending on the CO2 concentration used, insect exposure time, temperature, humidity, the tested insect species, and the insect's stage of development. One factor that substantially influences the concentration of CO2 available inside the packages, and therefore the effectiveness of the treatment, is the sorption of gas in the commodity. This study evaluated the impacts of packaging chickpeas in modified atmospheres of 50% and 90% CO2 with filling ratios (proportion of grain relative to the volume of the package) of 1% and 96% grain on the mortality of C. chinensis eggs and pupae and on the fecundity of the females emerging from the surviving individuals. In packages with a 96% filling ratio, CO2 concentration in the headspace of packages reduced to 60% and 30% from initial concentrations of 90% and 50% (respectively) in the first 24 h of exposure. Despite this reduction in CO2 concentrations, no differences in the mortality of C. chinensis eggs and pupae were observed between these packages and those with a 1% filling ratio. The estimated exposure time to achieve 95% mortality (LT95) of the eggs ranged from 38 to 68 h; for pupae, it ranged from 142 to 248 h. The fecundity of females that emerged from the surviving pupae decreased after 48 h of exposure to CO2, but the fecundity of females that emerged from surviving eggs was not affected by exposure time, MAPs, or filling ratio. Therefore, effective pest control can be accomplished with the use of sufficient treatment times to eradicate the most tolerant developmental stages, regardless of whether the packages are full or not.

Dickeya dianthicola Is Not Vectored by Two Common Insect Pests of Potato

Dickeya dianthicola (Samson) is an important pathogen causing blackleg disease of potato. Previous work suggested that insects might vector species of Pectobacteriaceae between plants but no conclusive work has confirmed this. Green peach aphids (Myzus persicae Sulzer) and Colorado potato beetles (Leptinotarsa decemlineata Say) are aggressive potato pests and related to known vectors of several species of bacteria other than D. dianthicola. This study sought to determine whether these insects vector D. dianthicola for potato infection. Neither insect species showed olfactory discrimination based on the presence of infection in laboratory tests but beetles were repelled by uninfected foliage treated with 2,3-butanediol, a primary Dickeya metabolite. Beetle recruitment to plants was not affected by their infection status; however, aphids preferred uninfected foliage when conspecifics were present. In the laboratory, neither insect acquired or transmitted D. dianthicola through feeding. In the field, neither insect’s abundance was significantly correlated with disease spread. Overall, this study did not find indications that D. dianthicola is vectored by the tested insect species. Therefore, efforts to limit Dickeya spread should focus on sanitation, water management, and seed screening—not on the control of these insect species. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Pathogenicity against hemipteran vector insects of a novel insect pathogenic fungus from Entomophthorales (Pandora sp. nov. inedit.) with potential for biological control

A new but still unpublished entomopathogenic fungus (ARSEF13372) in the genus Pandora (Entomophthorales: Entomophthoraceae) was originally isolated from Cacopsylla sp. (Hemiptera: Psyllidae). Several species of the genus Cacopsylla vector phloem-borne bacteria of the genus ‘Candidatus Phytoplasma‘, which cause diseases in fruit crops such as apple proliferation, pear decline and European stone fruit yellows. To determine Pandora’s host range and biocontrol potential we conducted laboratory infection bioassays; Hemipteran phloem-feeding insects were exposed to conidia actively discharged from in vitro produced mycelial mats of standardized area. We documented the pathogenicity of Pandora sp. nov. to species of the insect families Psyllidae and Triozidae, namely Cacopsyllapyri L., C.pyricola (Foerster), C.picta (Foerster, 1848), C.pruni (Scopoli), C.peregrina (Foerster), and Trioza apicalis Foerster. The occurrence of postmortem signs of infection on cadavers within 10 days post inoculation proved that Pandora sp. nov. was infective to the tested insect species under laboratory conditions and significantly reduced mean survival time for C.pyri (summer form and nymph), C.pyricola, C.picta, C.pruni, C.peregrina and T.apicalis. Assessing a potential interaction between phytoplasma, fungus and insect host revealed that phytoplasma infection (‘Candidatus Phytoplasma mali’) of the vector C.picta and/or its host plant apple Malus domestica Borkh. did not significantly impact the survival of C.picta after Pandora sp. nov. infection. The results from infection bioassays were discussed in relation to Pandora sp. nov. host range and its suitability as biocontrol agent in integrated pest management strategies of psyllid pests, including vector species, in orchards.

Efficacy of Clonostachys rosea, as a promising entomopathogenic fungus, against coleopteran stored product insect pests under laboratory conditions

BackgroundEfficacy of new isolates of the entomopathogenic fungus (EPF), Clonostachys rosea, against adult stage of the most serious coleopteran stored product insect pests in Iraq, Trogoderma granarium Everts (Coleoptera: Dermestidae), Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) and Callosobruchus maculatus Fabricius (Coleoptera: Chrysomelidae), was evaluated under laboratory conditions. Two isolates of C. rosea, associated with the green peach aphid (Myzus persicae Sulz.), were isolated and investigated. Efficacy of C. rosea isolates was evaluated by two concentrations (1 × 108 and 1 × 106 conidia ml−1).ResultsCorrected mortality rates caused by both C. rosea isolates, 6 days post-treatment, with 1 × 108 conidia ml−1, ranged from 70.7 to 75.7%. Fungal infection caused 37–53% reduction in total fecundity of the adult females of the three tested insect species, 6 days post-treatment.ConclusionObtained results demonstrated that C. rosea isolates had potentials as a biological control agent against coleopteran stored product insect pests. However, further studies under commercial storage conditions are required.

Persistence and efficacy of enhanced diatomaceous earth, imidacloprid, and Beauveria bassiana against three coleopteran and one psocid stored-grain insects.

The residual efficacy of the enhanced diatomaceous earth (DE) formulation DEBBM alone and in combination with Beauveria bassiana (Hypocreales: Cordycipitaceae) or with the neonicotinoid insecticide imidacloprid against Tribolium castaneum (Coleoptera: Tenebrionidae), Rhyzopertha dominica (Coleoptera: Bostrychidae), Cryptolestes ferrugineus (Coleoptera: Laemophloeidae), and Liposcelis paeta (Psocoptera: Liposcelididae) was investigated in the laboratory. The combination treatments were more effective compared to the single treatments against all examined species. The combinations of DEBBM and imidacloprid and imidacloprid with the highest dose rate of B. bassiana provided the highest mortality values against all tested species for 90days of storage period. The combination of DEBBM plus B. bassiana resulted to the highest mortalities and to the lowest offspring production of all combinations tested after 180days of storage. Mortality of adults for each test insect species was decreased over the storage period of 6months, and the progeny production was increased with the extended storage period. Among the tested insect species, L. paeta was the most susceptible to all three grain protectants followed by C. ferrugineus, R. domina, and T. castaneum. The findings of the current study suggest that the use of DEBBM, imidacloprid, and B. bassiana as grain protectants may provide elevated control of major stored-grain insect species during a prolonged period of storage.

Potential of two insectivorous avian species and two insect predators for spreading Spodoptera littoralis nucleopolyhedrovirus (SlNPV) in Egyptian ecosystem

The polyhedral inclusion bodies (PIBs) of Spodoptera littoralis nucleopolyhedrosis virus (SlNPV) were extracted from droppings of both the house sparrow Passer domesticus Raf. and the cattle egret Bubulcus ibis Bon. Due to the wide host range of the SlNPV, the extracted PIBs were bioassayed versus newly hatched larvae (L1) of S. littoralis, S. exigua, Trichoplusia ni, and Autographa circumflexa belonging to the insect fauna of the Egyptian clover Trifolium alexandrinum L. and the greater wax moth Galleria mellonella. Mortality of treated neonates of the 5 tested insect species ranged between 80 and 100 % after 7 days from ingesting the PIB-contaminated diet. Feeding nymphs and adults of the earwig Labidura riparia Pallas on S. littoralis larvae infected with the nuclear polyhedrosis virus (SlNPV) passed viable PIBs in feces which were extracted and bioassayed versus lepidopteran larvae of L1. All of the virus-treated 5 lepidopteran species became infected with the virus and showed mortality of 44–96% at the 7th day post ingestion of the extracted PIBs. On the other hand, feces extract of the 3rd larval instar (L3) of the lacewing Parachrysopa pallens (R.) fed on the virus-diseased larvae of S. littoralis caused no mortality when assayed versus the 5 tested lepidopteran larvae proving absence of viable PIB polyhedra that might be due to the mode of larval feeding by external digestion of its host contents including the polyhedra. Results explain the potential role played by insectivorous birds in spreading the nucleopolyhedrosis viruses in the agroecosystem as well as certain predatory insects.

Residual Efficacy of Pyriproxyfen on Grain Commodities Against Stored Product Insect Pests

Studies on residual efficacy of insecticides with reduced risk are necessary for strategies on their use and application frequency. Within these insecticides, insect growth regulators, such as pyriproxyfen, have been successfully used to control stored grain pests. The objective of this study was to evaluate the residual efficacy of pyriproxyfen in larvae of the stored grain pests Oryzaephilus surinamensis, Tribolium castaneum and Trogoderma granarium. Grains of wheat, maize, rice, and oats were exposed to pyriproxyfen at concentrations of 1, 2 or 4 mg kg−1. Six bioassays were performed by releasing the insects on treated grains after different post treatment periods (0, 2, 4, 8, 12 and 16 weeks). Adult emergence of the three insect species was reduced at tested concentrations in all treated grains. For all bioassays the residual efficacy of pyriproxyfen decreased with increase in the post treatment period. At 4 mg kg−1, the adult emergence did not exceed 16% at week 0 and it was <40% at week 12 in all tested insect species on all grains, but it increased at week 16. The residual effect of pyriproxyfen was more effective in wheat followed by oats, maize and rice for T. castaneum and T. granarium, whereas against O. surinamensis pyriproxyfen was more effective in oats followed by wheat, maize and rice. Results show that pyriproxyfen has potential for residual control of O. surinamensis, T. castaneum and T. granarium, and may be used for replacement of conventional neurotoxic insecticides for managing the insect pests of stored commodities.

Three-dimensional wing structure attenuates aerodynamic efficiency in flapping fly wings.

The aerial performance of flying insects ultimately depends on how flapping wings interact with the surrounding air. It has previously been suggested that the wing's three-dimensional camber and corrugation help to stiffen the wing against aerodynamic and inertial loading during flapping motion. Their contribution to aerodynamic force production, however, is under debate. Here, we investigated the potential benefit of three-dimensional wing shape in three different-sized species of flies using models of micro-computed tomography-scanned natural wings and models in which we removed either the wing's camber, corrugation, or both properties. Forces and aerodynamic power requirements during root flapping were derived from three-dimensional computational fluid dynamics modelling. Our data show that three-dimensional camber has no benefit for lift production and attenuates Rankine-Froude flight efficiency by up to approximately 12% compared to a flat wing. Moreover, we did not find evidence for lift-enhancing trapped vortices in corrugation valleys at Reynolds numbers between 137 and 1623. We found, however, that in all tested insect species, aerodynamic pressure distribution during flapping is closely aligned to the wing's venation pattern. Altogether, our study strongly supports the assumption that the wing's three-dimensional structure provides mechanical support against external forces rather than improving lift or saving energetic costs associated with active wing flapping.

Susceptibility of different species of lepidoptera insects to strain Bacillus thuringiensis ssp. aizawai

The results of assessing the effect of Bacillus thuringiensis ssp. aizawai strain on fi ve species of lepidopteran pests (Lepidoptera) belonging to different families are presented. The mortality of larvae infected with B. thuringiensis strain varied signifi cantly depending on the species of insect. In four species: the cabbage white butterfl y (Pieris brassicae L.), the cabbage moth (Mamestra brassicae L.), the greater wax moth (Galleria melonella L.) and the black-veined white (Aporia crataegi L.), death of individuals was noted on the second day of the experiment. However, mortality rate was signifi cantly different between species and increased over time. The diamondback moth (Plutella xylostella L.) was more susceptible to the pathogen. Signifi cant mortality of the larvae of this phytophage was observed already on the fi rst day after infection; while on the second day of the experiment all individuals died. Lethal time LT90 of more resistant species (black-veined white) and more sensitive ones (diamondback moth) differed sevenfold. Semi-lethal concentrations of B. thuringiensis strain for the tested insect species were determined: on the third day of the experiment, lethal concentration LC50 for the cabbage moth larvae, the greater wax moth and blackveined white ranged from 1.7 to 4.5 × 108 spores/ ml. For the cabbage white butterfl y, it was much lower (1.8×107 spores/ml). For diamondback moth caterpillars, LC50 was 4.25×107 spores/ml already one day after infection. It was noted that the specifi city of B. thuringiensis strain is associated with various mechanisms of insect protection from pathogens, and is due to individual characteristics of the species. In particular, the pH of excrement of intact caterpillars of the cabbage white butterfl y, a species sensitive to B. thuringiensis, was 2 times higher than that of caterpillars of the greater wax moth – 8.9 and 4.3, respectively, which is one of the reasons for the susceptibility (or resistance) of the species to bacterial entomopathogen.

Evaluation of diatomaceous earth formulations enhanced with natural products against stored product insects

The insecticidal effect of prepared insecticide formulations labelled as Natural P, Inert Natural P and Py EC on Sitophilus oryzae, Rhyzopertha dominica and Tribolium castaneum have been evaluated on wheat grains. Formulation Natural P contains diatomaceous earth (DE), amorphous silica gel (3%), pyrethrin, flax oil, lavandin essential oil (EO) and un-activated yeast. Formulation Inert Natural P contains DE, amorphous silica gel, lavandin EO and food grade bait whereas formulation Py EC contains pyrethrin, piperonyl butoxide (PBO), flax oil, polysorbate, methyl oleate and amorphous silica gel (5%). Celatom® MN-51 (diatomaceous earth – DE) was used as a standard insecticide. Inert Natural P and Natural P were applied as dust at four different doses and Py EC was applied as emulsions on grain by spraying. All three formulations showed higher insecticidal efficacy and higher progeny inhibition on all three tested insect species and had lower impact on wheat bulk density reduction compared with Celatom® MN-51. The LD50 and LD90 values of Inert Natural P were 48.7 and 163.7 ppm respectively for S. oryzae, 15.2 and 178.0 ppm for R. dominica and 115.2 and 171.3 ppm for T. castaneum. The LD50 and LD90 values of Natural P were 83.6 and 97.9 ppm respectively for S. oryzae, 19.5 and 97.9 ppm for R. dominica and 75.4 and 105.6 ppm for T. castaneum. Applied Py EC at concentration of 2.0 ppm a.i. pyrethrin exhibited 100% mortality after 2 d of S. oryzae and T. castaneum and after 6 d of R. dominica. In addition, all three formulations caused significant reduction of progeny (F1) population compared to control, providing promising approach of integrated pest management strategy.

Residual efficacy of methoxyfenozide applied on different grain commodities for the control of three stored-product insect pests

The residual efficacy of methoxyfenozide was assessed by exposing last instar larvae of Oryzaephilus surinamensis (Linnaeus, 1758) (Coleoptera: Silvanidae) , Tribolium castaneum Herbst, 1797 (Coleoptera: Tenebrionidae) and Trogoderma granarium Everts, 1898 (Coleoptera: Dermestidae) to the treated grain commodities (maize, oat, rice and wheat) at concentrations of 1, 2 and 4 mg kg -1 of active ingredient under laboratory conditions. This trial was performed at the Department of Entomology, University of Agriculture, Faisalabad, Pakistan during the year 2018. Six bioassays were conducted by releasing the insects on treated commodities after different post treatment periods (0, 2, 4, 8, 12 and 16 weeks). At 4 mg kg -1 , the adult emergence from larvae exposed to treated commodities did not exceed 15% at week 0 and it was less than 36% at week 12 in all the tested insect species on all the tested commodities. The methoxyfenozide was generally more effective on oats followed by wheat, maize and rice in the O. surinamensis and T. castaneum while against T. granarium it was more effective in wheat followed by oats, maize and rice. Results show that methoxyfenozide possess great potential for residual control of O. surinamensis, T. castaneum and T. granarium , and can be used for replacement of conventional neurotoxic insecticides.

Impact of certain nano oils against Ephestia kuehniella and Ephestia cutella (Lepidoptera-Pyralidae) under laboratory and store conditions

BackgroundFor the purpose of environmental safety, many essential oils were recommended in many Integrated Pest Management (IPM) programs to protect plants from insect’s infestations and have few effects on non-target organisms and the environment. This study was aimed to investigate and estimate the activity of four nano essential oils against tested insects under laboratory and store conditions.MethodsThe nano encapsulation process was carried out by polymerization technology. The tested nano oils were experimented at tested concentration (0.5%) for their insecticidal activities against the third-instar larvae of tested insects. After 7 days of exposure, accumulative mortality percentages were calculated in the treated and untreated control. Also, the tested nano oils were sprayed to the foam granules and were mixed with wheat (2 g foam/100 g wheat) for testing the oviposition inhibitory effects of tested oils. Additionally, the experiment was designed to test the persistent effect of tested oils against Ephestia kuehniella and E. cautella on foam as surface protectant after 90-day intervals.ResultsThe larval accumulative mortality of tested insect species enhanced progressively with the increase of exposition times (7 days). In the case of tested insects, rosemary oil gave the highest accumulative mortality percentages. The persistence effects of tested nano oils on foam and covering gunny bags showed various biological activates by reducing number of eggs, almost suppressing the percentages of progeny emergence (F1) and high percentages of malformation of tested insects. The efficacy of the tested nano oils on the weight loss of wheat grains after 90 days of storage was experimented.ConclusionResults of this work and that of other researchers indicate that some essential oils might be useful for managing insects in enclosed spaces because of their fumigant action. Plant essential oils and their active ingredient have potentially high bioactivity against a range of insects. Furthermore, they are highly selective to insects. Incorporation of essential oils into a controlled release nanoformulation prevents rapid vaporization and degradation, increases constancy, and preserves the lower effective dosage/application. Treated foam with nano rosemary and nano eucalyptus oil and covering gunny bags provided many efficient effects against tested insects.

Lethal and behavioral effects of synthetic and organic insecticides on Spodoptera exigua and its predator Podisus maculiventris.

BackgroundThe beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), is a key insect pest of edible vegetables around the world and it is resistant to insecticide of different classes. Insecticides that are effective to this pest and selective to predator stinkbugs are required for the integrated management of S. exigua.MethodsThe toxicity of four commercial insecticide formulations azadirachtin + pyrethrin, spinosad, pyrethrin and chlorantraniliprole was tested on the target pest and their side effect were evaluated on the spined soldier bug, Podisus maculiventris (Heteroptera: Pentatomidae) through different bioassays.ResultsSpinosad and chlorantraniliprole were more toxic to S. exigua than to the predator P. maculiventris but opposite results were obtained for pyrethrin and azadirachtin + pyrethrin in contact toxicity bioassay. Chlorantraniliprole was the most toxic to S. exigua in oral toxicity bioassay, followed by spinosad, pyrethrin and azadirachtin + pyrethrin. Spinosad in oral toxicity bioassay was the most toxic to P. maculiventris, followed by pyrethrin, azadirachtin + pyrethrin and chlorantraniliprole. Spinosad caused irritability to the predator while pyrethrin to the pest. The insecticide repellency was not observed over the tested insect species. The synthetic insecticide chlorantraniliprole was less toxic than the natural pyrethrin, azadirachtin + pyrethrin and spinosad to the predator.ConclusionsThis work provides useful information on the combination of commercial insecticides with the predator P. maculiventris to controlling S. exigua in integrated pest management (IPM) programs.