Field trials on the efficacy of Beauveria bassiana,diatomaceous earth and Imidacloprid for the protection of wheat grains from four major stored grain insect pests

We assessed the insecticidal efficacy of Beauveria bassiana, diatomaceous earth (DE) and the neonicotinoid Imidacloprid against four major insect species of stored grain pests during field trials conducted on small farms located in four districts of Punjab, Pakistan. In each district, a 40 kg lot of wheat grain was admixed with B. bassiana (3 × 10¹⁰ conidia kg⁻¹), DE (150 ppm) and Imidacloprid (5.0 ppm) alone and in different combinations. Each lot was divided subsequently into four equal parts (10 kg each), packed in polypropylene bags, artificially infested, labeled and stored at the farms under natural environmental conditions up to 6 months. Sampling was carried out every 30 d to record the total number of dead and alive adults, as well as the percent of grain damage in treated and untreated (control) grains. Results revealed a significant difference among the treatments, test insect species and the storage period. For each district, the combined treatments provided better control of all tested insect species compared with each treatment alone. The least number of surviving adults and minimum percent grain damage was observed for Imidacloprid and DE combination, but was outperformed by the DE treatment with B. bassiana for long-term protection. For all grain protectants, we obtained the same order of susceptibility level among the test species (i.e. Liposcelis paeta > Cryptolestes ferrugineus > Rhyzopertha dominica > Tribolium castaneum). The results of the present study suggested that DE, insect pathogenic fungi and Imidacloprid can be effectively used for the protection of wheat stored at small-scale farmer's fields.     

Evaluation of two new diatomaceous earth formulations, enhanced with abamectin and bitterbarkomycin, against four stored-grain beetle species

Two new natural diatomaceous earth (DE) formulations, enhanced with abamectin (DEA-P/WP), or bitterbarkomycin (DEBBM-P/WP), were tested under laboratory conditions against adults of the rice weevil, Sitophilus oryzae, the lesser grain borer, Rhyzopertha dominica, the red flour beetle, Tribolium castaneum and the rusty grain beetle, Cryptolestes ferrugineus. The bioassays were carried out on wheat, at 30±1 °C and 70±5% r.h. The two enhanced DEs were applied either as dusts (P) or as wettable powders (WP) at the dose rates of 75, 100 125 and 150 ppm. Adult mortality was assessed after 14 and 21 d of exposure on the treated substrate. After this interval, the treated wheat was retained for an additional period of 49 d in the case of S. oryzae and 63 d in the case of the other three species, in order to evaluate progeny production. Generally, for all species tested, mortality was higher on wheat treated with powders in comparison with wettable solutions. After 14 d of exposure, all adult rice weevils were dead even at the lowest dose rate of DEA-P, while 100% mortality was noted at doses 125 ppm of DEBBM-P. For the other species, mortality was 100% on wheat treated with 75 ppm of DEBBM-P, with the exception of T. castaneum for which all adults were dead at doses 100 ppm. Progeny production was low, and no progeny were produced in the cases of R. dominica and C. ferrugineus, for both DEs. However, for S. oryzae, progeny production was high on wheat treated with WP formulations, at dose rates 100 ppm. Similar trends were noted for T. castaneum, at 100 ppm of DEBBM-WP. The results of the present study indicate that both DEA-P/WP and DEBBM-P/WP are more effective against the four beetle species examined in comparison with the currently commercially available DE formulations.     

Efficacy of diatomaceous earth formulations admixed with grain against populations of Tribolium castaneum

The efficacy of diatomaceous earth (DE) to control stored-products Coleoptera on stored grain was examined against several populations of the red flour beetle, Tribolium castaneum (Herbst). Four commercially available DE formulations were tested: INSECTO^®, Perma-Guard™, Protect-It^® and the diatomite used for the production of Dryacide^®, each at six concentrations (100-1000 ppm). A great variation of efficacy was observed among the DE formulations tested. Protect-It at concentrations up to 400 ppm was found to be the most effective formulation to control red flour beetle populations. However, a concentration of 1000 ppm of Protect-It was necessary to control all adults of all populations. Most T. castaneum populations, except one from Ivory Coast (Asm), were more than 90% controlled with INSECTO and Dryacide DE at 600 ppm. At this concentration, about 88% and 22% Asm adults died with INSECTO and Dryacide DE, respectively. Perma-Guard was the least efficient DE formulation to control T. castaneum adults with three populations exhibiting some survival at 1000 ppm. Reduced susceptibility to DE was observed in two populations, Asm and Lab susceptible from Kansas (Lab-S). As neither population had been previously exposed to DE, it is suggested that red flour beetles may naturally vary in susceptibility to DE. In addition, it was found that some populations can be satisfactorily controlled with some DE formulations but not with others.     

Susceptibility of stored-product insects to enhanced diatomaceous earth

Mortality of adult Rhyzopertha dominica (F.), Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) was recorded after exposure for different times to application rates of 0, 0.5, 1, 1.5 or 2 g/m² of the diatomaceous earth (DE) DEBBM-P/WP and to 0, 3, 4, 5 or 6 g/m² of the DE Protect-It^®. Mortality of all insects increased with increasing exposure interval; dry dusts were more effective than slurries, and overall mortality was greater for DEBBM-P/WP than Protect-It^®.     

Physiological and behavioral effects of different concentrations of diatomaceous earth on common stored product pest Callosobruchus maculatus

The presented research focuses on the assessment of the changes in the behavioral and physiological parameters of Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae), treated with amorphous diatomaceous earth (DE) (Perma- Guard™). During the experiments, parameters such as stimulated and spontaneous locomotor activity, oxygen consumption and fecundity were tested. Increasing DE concentration caused significant inhibition in both oxygen consumption and locomotor activity. Moreover, the treated insects had significantly lower fecundity, due to decreased egg laying, lower number of infested beans as well as lowered hatchability. By limiting the progeny number, DE possibly prevents or at least reduces the size of the C. maculatus outbreak. Additionally, scanning electron microscope (SEM) micrographs revealed that DE particles accumulate especially in joints or hairy regions of the insect body close to the sensilla. This, along with data on locomotor activity, indicates a possible presence of additional, previously undescribed, mode of DE action - as an irritant. In conclusion, the presented results contribute to the understanding of the insecticidal activity of DE and provide novel data on the potential application of oxygen consumption as a pesticide efficiency marker.     

Laboratory assessment of insecticidal effectiveness of natural zeolite and diatomaceous earth formulations against three stored-product beetle pests

The insecticidal effectiveness of two natural zeolite formulations (Minazel plus and Minazel), applied to wheat at selected rates of 0.25, 0.50 and 0.75 g/kg, and a diatomaceous earth formulation (DE) (Protect-It™), applied at the recommended rates of 0.15 g/kg for Sitophilus oryzae, 0.20 g/kg for Rhyzopertha dominica and 0.30 g/kg for Tribolium castaneum, were tested under laboratory conditions (24 ± 1 °C temperature and 45 ± 5% relative humidity). The highest adult mortality was observed after the longest exposure period of 21 days and 7 days of recovery, when all three zeolite dosage rates and the recommended DE dosage caused 97-100% mortality of S. oryzae and 94-100% of T. castaneum. On the other hand, 100% mortality was not achieved in any test variant involving R. dominica; the highest (about 92%) was detected for DE, while 52% and 79% mortality was achieved with the zeolites at the highest rate of 0.75 g/kg. Progeny reduction by >90% was achieved after 21 days of contact of all three beetle pests with DE-treated wheat, while the same level of reduction was achieved for S. oryzae and T. castaenum only after contact with the highest rate of the zeolite product, Minazel. Thus the two zeolite formulations are comparable to diatomaceous earth in controlling adult S. oryzae, R. dominica and T. castaneum, but only the Minazel formulation could effectively protect wheat from attack by S. oryzae or T. castaneum, and only with a higher rate of application than for the DE formulation.     

Efficacy of heat treatment on phosphine resistant and susceptible populations of stored product insects

In this study we evaluated the efficacy of heat treatment on phosphine resistant and susceptible populations of stored product insects at twenty three different commercial facilities in Greece. Heat treatments were carried out by using special equipment, such as Therminate, TempAir and ThermoNox, applied alone or in combination. The overall temperature range was between 33 and 55 °C and the duration of the heat treatments was between 20 and 39 h. Adults of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), and the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), were used in the experiments. The field populations were collected from different storage facilities in Greece and were characterized as resistant populations by using the Detia Degesch Phosphine Tolerance Test Kit. Insect mortality was measured at the termination of each trial. Then, the vials were kept in incubator chambers at 25 °C and 65% relative humidity and 65 d later the progeny production was measured in the treated substrate. In light of our findings, in the vast majority of the cases, complete control was observed for both resistant and susceptible populations at all facilities. In general, in the few cases where survival and progeny production was recorded, there was no specific trend towards specific species or population. Overall, based on the current results, heat treatment can be used by the industry as an alternative method for the control of phosphine-resistant adults of R. dominica and O. surinamensis.     

Insecticidal effect of contact insecticides against stored product beetle populations with different susceptibility to phosphine

In the present work we evaluated the effect of alpha-cypermethrin, pirimiphos-methyl and spinetoram on field and laboratory strains of Sitophilus oryzae (L.) and Oryzaephilus surinamensis (L.) with different susceptibility levels to phosphine. The field populations were collected from storage facilities in Greece and were characterized as resistant by using the Food and Agriculture Organization (FAO) protocol, based on the same protocol, populations were characterized as susceptible to phosphine. The insecticides were applied at three dose rates (0.1, 1 and 10 ppm) on wheat and adult mortality was measured after 7, 14 and 21 days of exposure, while progeny production was assessed 65 days later. For S. oryzae populations, complete control was noted at the highest dose on pirimiphos-methyl and spinetoram, while mortality caused by alpha-cypermethrin was 62 and 100% for the field and laboratory populations, respectively. For O. surinamensis, complete control was recorded at the highest dose only on alpha-cypermethrin for the laboratory population, in contrast with the field population, where mortality was only 32% after 21 days of exposure. In general, the variations among populations were negligible for spinetoram, probably due to the fact that the populations tested were not previously exposed to this active ingredient. In contrast, the lowest susceptibility of the field populations to the other two insecticides can be attributed to the fact that these populations might have been exposed to these active ingredients, while any hypothesis for cross-resistance with phosphine has to be examined more thoroughly.     

Diatomaceous earth low-lethal dose effects on the fitness of entomopathogenic fungus,Beauveria bassiana,against two coleopteran stored product pests

Efficacy of different doses of the Beauveria bassiana-IRAN441C alone (66,125, 250, 500, 1000 mg conidia. Kg⁻¹ grains) and combined with a low-lethal dose (LD₂₅) of diatomaceous earth (DE) SilicoSec® as lethal agents were assessed against the adults of Callosobruchus maculatus (F.) (Chrysomelidae) on mung, and cowpeas, and Oryzaephilus surinamensis (L.) (Silvanidae) on wheat and barley seeds. In both species, mortality reached 60–73% in B. bassiana alone and 83–100% in fungus combined with the DE at the highest dose. A synergistic effect between B. bassiana conidia and the DE was confirmed. The DE low-lethal dose alters fungal mycosis and sporogenesis (conidia mL⁻¹) rates in the infected cadavers. The adult populations of both species were suppressed desirably despite a decrease in the number of cadaver-derived mycosis and their spore production at the highest combination doses (1000 mg kg⁻¹+ LD₂₅ of DE). Seed type had no significant effect on mycosis and sporogenesis on both insects in several combination doses. The cadaver-derived aerial conidia germination rate was increased in the presence of DE low-lethal dose, but it declined by increasing the fungal dose. Type of commodity failed to affect the germination rate of O. surinamensis-derived conidia; however, the mung bean intensified this case for another insect. In both beetles, offspring's emergence was suppressed dose-dependently seven weeks after removing exposed parents to the lethal agents as well it was more in doses mixed with DE. The most significant reduction in progeny production of treated C. maculatus occurred on cowpeas and that of treated O. surinamensis on wheat seeds. Our findings demonstrate that DE's low-lethal dose enhances the virulence of B. bassiana in the various mixtures synergistically, and co-applications of the two substances were feasible. As well, the lethal agents' adverse effects were found to carry over onto both species' offspring during two-month storage time.     

Evaluation of methoprene alone and in combination with diatomaceous earth to control Rhyzopertha dominica (Coleoptera: Bostrichidae) on stored wheat

A series of experiments were conducted in which different formulations of the insect growth regulator methoprene were evaluated for control of Rhyzopertha dominica (F.), the lesser grain borer, a major internal insect pest of stored wheat. In the first test, application rates of 10-ppm R,S-methoprene (a racemic mixture of the R and S isomers of methoprene) and 1 and 5-ppm S-methoprene (S-isomer only) gave 100% suppression of F₁ adult progeny of R. dominica for 24 weeks. In the second test, adult R. dominica were exposed at 27°C and 32°C, 57% and 75% relative humidity (r.h.) on untreated wheat and wheat treated with 1- to 10-ppm S-methoprene dust. Survival after a 3-week exposure decreased with increasing concentration of dust, and ranged from 69% to 99%, but no F₁ adult progeny were produced in treated wheat. In the final test, concentrations of 0, 0.25, 0.50, 0.75, and 1.0 ppm S-methoprene EC were combined with concentrations of 0, 75, 150, 225, and 300 ppm of the commercial diatomaceous earth (DE) Protect-It^®. Within each methoprene concentration, survival generally decreased with increasing concentration of DE, and was generally greater at 75% than at 57% r.h. Only the wheat treated with 0-ppm methoprene contained an appreciable number of F₁ adults. In summary, both the dust and EC formulations of S-methoprene gave 100% suppression of F₁ adult progeny R. dominica at application rates of 1 ppm, and combination treatments involving reduced rates of methoprene and DE gave effective control of R. dominica.     

Evaluation of three new insecticide formulations based on inert dusts and botanicals against four stored-grain beetles

Three new insecticide formulations were developed that combine diatomaceous earth (Celatom MN 23) with compounds with low mammalian toxicity. Sitophilus oryzae, Sitophilus granarius, Rhyzopertha dominica and Tribolium castaneum were held on wheat (13.5% moisture content) treated with different doses of the formulations at 28 ± 1 °C and 60 ± 5% RH for 2–7 days, and then held for progeny emergence. The three formulations were made up of: dill essential oil, bait, silica gel and DE (Dill-DE); pyrethrin, PBO, dill essential oil, silica gel and DE (Py-Dill-DE); and disodium octaborate tetrahydrate (DOT), pyrethrin, PBO, dill essential oil, silica gel and DE (DOT-PY-Dill-DE). They were applied either as powders or as slurries. Applying the formulations as powders over a range of concentrations showed that pure DE is the least effective insecticide, with 50% mortality ranging from 430 to 1000 ppm depending on the species after 2–3 days. Dill-DE formulation was the next least effective formulation. The Py-Dill-DE and DOT-Py-Dill-DE formulations had similar activity and being the most effective formulations with 50% mortality from 40 to 260 ppm depending on the species. Bioassays were also run at single doses. Dill-DE was applied at 300 ppm, Py-Dill-DE at 150 ppm and DOT-PY-Dill-DE at 200 ppm. After 3 days, Py-Dill-DE and DOT-PY-Dill-DE formulations there was 100% mortality for S. oryzae, S. granarius and R. dominica. After 7 days the mortality of T. castaneum was from 96 to 100%. Both formulations reduced the progeny almost by 100%. There was survival for all insects with Dill-DE formulation. The concentrations of 150 ppm of Py-Dill-DE, 200 ppm of DOT-PY-Dill-DE and 300 ppm of Dill-DE reduced bulk densities by 0.7, 0.8 and 5.7 kg/hL, respectively.     

The efficacy and persistence of diatomaceous earths admixed with commodity against four tropical stored product beetle pests

The efficacy and persistence of two commercially available enhanced diatomaceous earth (DE) products (Dryacide^® and Protect-It^®) against four common tropical storage pests (Prostephanus truncatus, Sitophilus zeamais, Callosobruchus maculatus and Acanthoscelides obtectus) were studied when admixed with typical host commodities at different application rates and relative humidities. Persistence of the enhanced DE treatments was considered after 3 and 6 months storage by assessment of both adult mortality and F1 progeny emergence. Both DEs usually increased parental mortality and reduced progeny emergence of all four insect species in comparison with the untreated control at both 50% and 60% r.h., and at all storage periods. However, efficacy was inversely related to duration of storage and over time the host commodity also became less suitable for insect development. Each insect species differed in its susceptibility to the DE treatments, highlighting the need for field application rates to be based upon the entire spectrum of pest species likely to be present during storage.     

Fumigation toxicity of monoterpenoids to several stored product insects

Twenty naturally occurring monoterpenoids were evaluated in a preliminary fumigation screening test on some important stored-product pest insects, including the rice weevil, Sitophilus oryzae, the red flour beetle, Tribolium castaneum, the sawtoothed grain beetle, Oryzaephilus surinamensis, the house fly, Musca domestica, and the German cockroach, Blattella germanica. Cineole, l-fenchone, and pulegone at 50 μg/ml air caused 100% mortality in all five species tested. Ketone compounds were generally more toxic than other monoterpenoids. Three monoterpenoids, the ketones pulegone, l-fenchone, and the aldehyde perillaldehyde, were selected for further study. They were effective against T. castaneum in the fumigation assay; however the toxicity was relatively low in comparison to dichlorvos. LC₅₀ values of these three monoterpenoids tended to decrease at longer exposure times and higher temperatures. Inclusion of either maize kernels or house fly medium (HFM) increased LC₅₀ values, HFM more so than maize kernels. Monoterpenoids may be suitable as fumigants or vapor-phase insecticides because of their high volatility, fumigation efficacy, and their safety.     

Effectiveness of diatomaceous earth for control of Sitophilus zeamais (Coleoptera: Curculionidae), Tribolium castaneum and Palorus subdepressus (Coleoptera: Tenebrionidae)

The effectiveness of diatomaceous earth (DE) or diatomite has been assessed against three major beetle pests of stored maize: Sitophilus zeamais (the maize weevil), Tribolium castaneum (the red flour beetle) and Palorus subdepressus (the depressed flour beetle). Maize has been treated with four doses of DE (1.5, 3, 4.5 and 6 g/kg) and four doses of Actellic Super™ Dust a chemical insecticide used as a reference (0.25, 0.5, 0.75 and 1 g/kg). The effective mortality was measured for each treatment after 1, 2, 4, 7 and 14 d of exposure. The corrected mortality rates were calculated by considering the mortality in the control group. Diatomaceous earth was as effective as Actellic Super™ Dust but required higher doses. Diatomaceous earth acted faster on S. zeamais and P. subdepressus compared to T. castaneum. The highest dose tested for DE caused the same mortality in T. castaneum as the recommended dose of Actellic Super™ Dust. Diatomaceous earth is a good alternative for the control of these three devastating insect pests of maize stocks and can readily be incorporated into integrated stored products pest management programs.     

Enhancement the efficacy of spinosad for the control Sitophilus oryzae by combined application with diatomaceous earth and Trichoderma harzianum

Laboratory tests were carried out to evaluate the effect of diatomaceous earth (DE) originated from Egypt and Trichoderma harzianum on the efficacy of spinosad applied at low application rates against Sitophilus oryzae adults in stored wheat. Spinosad was assessed at 0.05, 0.1 and 0.5 mg/kg (ppm) alone or combined with DE at 100, 500 and 1000 mg/kg (ppm) or with T. harzianum at 3.3 × 10⁶, 6.6 × 10⁶ and 2.1 × 10⁷ spores/kg. Adult mortality after 7, 14 and 21 days, progeny reduction after 45 and 90 days, and wheat weight loss were determined for all individual and binary treatments. Adult mortality increased with respect to increased exposure interval and application rate. Complete adult mortality (100%) was achieved after 21 days using 0.5 mg/kg of spinosad with all tested doses of DE and with 2.10 × 10⁷ spores/kg of T. harzinum). Progeny production of S. oryzae was significantly reduced at all treatments compared to untreated wheat. No progeny was observed in the wheat treated with the combined treatments (0.5 mg/kg of spinosad + 1000 mg/kg of DE) and (0.5 mg/kg of spinosad + 2.10 × 10⁷ spores/kg of T. harzinum) after 45 and 90 days. Similar trends were noted for wheat weight loss as the combined treatments at highest rates preserved the wheat intact and free from damage caused by S. oryzae for 90 days. Our findings suggest the combinations of spinosad at low rates with DE or T. harzianum can be effectively used for the control S. oryzae and provide long-term protection of stored wheat.     

Efficacy of surface applications with diatomaceous earth to control Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) in stored wheat

Commercial formulations of diatomaceous earth (DE) products labeled for use as grain protectants usually specify on the label the depth for using them as a surface treatment, which is often 30.5 cm. An experiment was conducted at two temperatures (27 and 32 °C) and three exposure intervals (7, 10 and 14 d), at a relative humidity of 57–60% to determine if Rhyzopertha dominica (F.), the lesser grain borer, could penetrate a 30.5-cm layer of wheat treated with the labeled rates of three commercial formulations of DE, and, if so, to measure rates of adult survival and progeny production. When R. dominica adults were introduced to this surface layer of 30.5-cm wheat admixed with DE, they were able to penetrate the DE-treated layer and oviposit in the untreated wheat below. Both adult survival and progeny production were significantly lower in wheat with a surface-layer treatment of Dryacide^® (1000 ppm) as compared to Insecto™ (500 ppm), Protect-It^® (400 ppm) or the untreated control. Temperature and exposure interval had no effect on adult survival or progeny production. The vertical displacement patterns of adults were significantly different among DE treatments, but not for temperature or exposure intervals. More R. dominica traveled a greater distance in the untreated control, followed by Insecto™, Protect-It^®, and then Dryacide^®. Results indicate that R. dominica can penetrate a surface layer of DE-treated wheat and reproduce within and below it, but it is possible that pest suppression is dose dependent, or it may depend on a combination of application rate and specific DE formulation.     

Insecticidal effect of three diatomaceous earth formulations, applied alone or in combination, against three stored-product beetle species on wheat and maize

Laboratory tests were carried out to examine the insecticidal effect of three commercially available diatomaceous earth (DE) formulations on wheat and maize against three major stored-grain beetle species: Rhyzopertha dominica, Sitophilus oryzae, and Tribolium confusum. The three DEs tested were Insecto^®, PyriSec^®, and Protect-It^®. These DEs were applied alone or in all possible combinations (Insecto^®+PyriSec^®, Insecto^®+Protect-It^®, PyriSec^®+Protect-It^®, and all three DEs together), at three (total) dose rates: 0.25, 0.5, and 0.75 g/kg of each commodity. Adults of the above species were exposed to the treated commodities for 7 d at 26 °C, and 65% r.h., and after this interval the mortality was measured. For each species, adult mortality was significantly affected by the type of DE, the commodity, and the dose rate. All DEs were less effective against T. confusum, where mortality did not exceed 67%, in comparison with the other two species, where 100% mortality was achieved in some combinations. For all species tested, all DEs were more effective on wheat than on maize. Generally, the mix of two or three DEs was more effective than the application of one DE, for all species and commodities. The results of the present work clearly indicate that a blending of several DEs together may produce a new DE formulation that is highly effective at low dose rates.     

Efficacy and adherence ratio of diatomaceous earth and spinosad in three wheat varieties against three stored-product insect pests

Laboratory tests were carried out in order to evaluate the efficacy of three diatomaceous earth (DE) formulations; Protector, SilicoSec, and Insecto, and one spinosad dust formulation in three commercially available wheat (Triticum durum) varieties, Athos, Pontos, Sifnos, originating from Greek cultures. The efficacy of the above formulations was assessed against adults of Rhyzopertha dominica, Sitophilus oryzae and Tribolium confusum. The DE formulations were applied at three dose levels; 250, 500 and 1000 ppm, while spinosad was applied at 100, 500 and 1000 ppm of the formulation, corresponding to 0.125, 0.625 and 1.25 ppm active ingredient (a.i.), respectively. The adherence ratio of the DE and spinosad formulations to the kernels of the wheat varieties was assessed. Bioassays were carried out at 30°C and 60% r.h. Mortality was recorded after 7 and 14 d in the case of R. dominica and S. oryzae, and after 7 d, 14 d and 21 d of exposure in the case of T. confusum, on the treated varieties. Progeny production of the individuals exposed on the treated varieties was also assessed. Even the lowest dose of spinosad was highly effective (>90%) against R. dominica and S. oryzae. In the case of T. confusum a combination of longer exposures with higher doses was required for each formulation to be effective. Generally, the performance of all formulations was greater in Athos or Sifnos compared to the Pontos. Progeny production of S. oryzae and R. dominica was significantly higher in untreated Pontos than in the other varieties. Progeny production was always greater in untreated than treated substrates. Although adherence ratios for the tested DE and spinosad formulations were generally high (>90%), significant variations in adherence levels among the wheat varieties were recorded.     

Movement and behavioral response of stored product insects under stored grain environments - A review

Understanding movement of insects and their behavioral response in stored grain bulks helps in controlling their infestation. Studies have been conducted on insect movement; however, determination of patterns of insect distribution is quite difficult because their behavioral responses vary with species and life stages as well as with external stimuli under different storage conditions. This review discussed insect movement, movement detection and tracing methods. Different experimental setups used for determining insect movement were presented along with their advantages and limitations with special emphasis on factors influencing insect mobility. Various model equations to predict insect movement and their spatial distribution were stated. Further, practical difficulties and challenges associated with studies of insect movement under multiple gradients were discussed. Based on literature analysis, directions for future research were presented with respect to the requirement and applicability of the emerging cost-effective technologies for insect movement detection.     

Insecticidal efficacy of diatomaceous earth against Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Tribolium confusum du Val (Coleoptera: Tenebrionidae) on stored wheat: influence of dose rate, temperature and exposure interval

Laboratory experiments were conducted in order to assess the insecticidal effect of a diatomaceous earth formulation (Silicosec^®, Biofa GmbH, Germany) against Sitophilus oryzae and Tribolium confusum on stored wheat. Adults of the two species were exposed on wheat treated with diatomaceous earth at four dose rates: 0.25, 0.5, 1 and 1.5 g/kg of wheat, respectively. For each dose rate, the treated wheat was placed at 22°C, 25°C, 27°C, 30°C and 32°C. Dead adults were counted after 24 and 48 h, 7 and 14 d of exposure. After the 14-d interval, the live adults were removed and placed for 7 d in untreated wheat (in the case of S. oryzae) or untreated flour (in the case of T. confusum), and the production of F₁ was recorded. For both species, dose rate, temperature and exposure interval significantly affected mortality (P<0.001). Mortality was higher at longer exposure intervals. The efficacy of SilicoSec against S. oryzae increased with temperature, but for T. confusum mortality was lower at 32°C, compared to 30°C, for 24 and 48 h exposure intervals. Tribolium confusum proved less susceptible to SilicoSec than S. oryzae. In general, the rates of 1 and 1.5 g/kg of wheat provided a satisfactory level of protection against the two species examined. For S. oryzae, F₁ emerged only at 22°C, in wheat treated with 0.25 or 0.5 g/kg. However, for T. confusum, F₁ were recorded at 22°C for 0.5 g/kg and at 22°C, 25°C, 27°C and 30°C for 0.25 g/kg.