Efficacy of two formulations of pirimiphos-methyl as surface treatment against Sitophilus granarius,Rhyzopertha dominica,and Tribolium confusum

In the present work, the insecticidal effect of two pirimiphos-methyl formulations [emulsifiable concentrate (EC) and capsule suspension (CS)] as surface treatment on concrete, plywood, galvanized metal, plastic, and ceramic tile was evaluated in laboratory bioassays against Sitophilus granarius (L.), Rhyzopertha dominica (F.), and Tribolium confusum Jacquelin du Val. Pirimiphos-methyl was applied at two-dose-rates, 0.01 and 0.1 mg/cm², and insect mortality was assessed after 1, 2, 3, 4, 5, 6, and 7 days of exposure. After the final mortality count, alive individuals were transferred to untreated dishes, and delayed mortality was evaluated after an additional period of 7 days. In another series of laboratory bioassays, the residual efficacy of these two pirimiphos-methyl formulations on concrete was evaluated against S. granarius, R. dominica, and T. confusum. Pirimiphos-methyl was applied at two-dose-rates, 0.01 and 0.1 mg/cm², on concrete dishes which were either kept in continuous darkness or exposed to light. A bioassay was initiated at the day of storage and every 4 weeks for 4 consecutive months (5 bioassays in total). Mortality of the exposed adult beetles was measured after 3 and 7 days of exposure. Both formulations were highly effective, with S. granarius being the most susceptible species. In general, mortality of the exposed beetles was not significantly affected by the surface type, with the exception of the significantly lower mortality counts of S. granarius adults on ceramic tile. CS appeared to be much more persistent on concrete than EC for all three species tested. Moreover, CS was not affected by light. In contrast, in some of the combinations tested, EC performance was poor in dishes that were exposed to light, in comparison with dishes that were in continuous darkness. We conclude that the surface type does not significantly and consistently affect S. granarius, R. dominica, and T. confusum mortality after surface application of the two pirimiphos-methyl formulations tested. Furthermore, CS can provide long-term protection when applied on concrete surfaces.     

Dosage rate, temperature, and food source provisioning affect susceptibility of Tribolium castaneum and Tribolium confusum to chlorfenapyr

A series of experiments were conducted to evaluate residual efficacy of the insecticidal pyrrolle chlorfenapyr (Phantom^®) on treated concrete for control of Tribolium castaneum (Herbst), assess development of progeny from exposed parental adults, and to determine if starvation before exposure with or without a flour food source increased susceptibility of adult T. castaneum and adult Tribolium confusum Jacqueline du Val to chlorfenapyr. No adults survived exposure on concrete treated with chlorfenapyr at the maximum label rate of 1.1 g active ingredient (AI)/m², and no progeny were produced in bioassays conducted at 0–8 weeks posttreatment. In the second test, application rates were reduced, and bioassays were conducted at 27 and 32 °C. Adult survival and progeny production decreased as the application rate increased from 28 to 225 mg AI/m², and survival and progeny production were generally lower at 32 °C than at 27 °C, but at higher rates survival was <1 %, and no progeny were produced. In the final test, adult T. castaneum and adult T. confusum were starved for 1–7 days and then exposed either with or without flour on concrete treated with 3.9 and 27.5 mg AI chlorfenapyr/m². Mortality generally increased with starvation time, the presence of a food source led to decreased mortality at both application rates, and T. confusum was the more susceptible of the two species. Results show that chlorfenapyr could effectively control both species, but precise dosage levels need to be determined. Also, the presence of a food source greatly compromises adult control.     

Evaluation of spinetoram and spinosad for control of Prostephanus truncatus,Rhyzopertha dominica,Sitophilus oryzae,and Tribolium confusum on stored grains under laboratory tests

Spinetoram and spinosad have been evaluated against certain stored-product insect pests with success but there are no data available on the comparison of the efficacy of these two novel compounds in stored grains. Thus, laboratory bioassays were conducted to compare spinetoram and spinosad as grain protectants against Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) adults, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) adults, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) adults, and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) adults and larvae. Factors such as treatment (1 ppm spinetoram, 1 ppm spinosad, 0.1 ppm spinetoram + 0.9 ppm spinosad, 0.5 ppm spinetoram + 0.5 ppm spinosad, and 0.9 ppm spinetoram + 0.1 ppm spinosad), exposure interval (1, 2, 7, and 14 days), temperature (20, 25, and 30 °C), and commodity (barley, maize, rye, and wheat) were evaluated. Progeny production was assessed after 60 days of exposure. Concerning temperatures, for P. truncatus adults, after 14 days of exposure, all adults were dead in treatments except of the case of spinosad alone at 20 °C. Offspring emergence was completely suppressed in all treatments at 20 and 25 °C. For R. dominica adults, after 7 days of exposure, the overall mortality ranged from 92.8 to 100 %. After 14 days of exposure, all adults were dead in all treatments of the combined use of spinetoram and spinosad at 25 and 30 °C. Progeny production was completely suppressed in all treatments at 30 °C. For S. oryzae adults, after 7 days of exposure, all S. oryzae were died at 25 and 30 °C in all treatments except in the case of spinosad alone. Offspring emergence was very low in all treatments and temperatures except in the case of spinosad alone at 30 °C. For T. confusum adults, after 1, 2, and 7 days of exposure, the overall mortality was low in all treatments and temperatures. Concerning commodities, for R. dominica adults, after 7 and 14 days of exposure, the overall mortality was >97 %. Offspring emergence was very low in all commodities. For S. oryzae adults, after 7 and 14 days of exposure, the overall mortality was increased exceeding 91 % except in the case of spinosad alone 7 days after exposure in barley. Progeny production was high in barley and rye in all treatments. For T. confusum adults, after 7 and 14 days, the overall mortality was low in barley, rye, and wheat. No offspring emergence was recorded in all treatments and commodities. For T. confusum larvae, after 14 days of exposure mortality was further increased, but did not reach 100 % for any of the combinations tested. The results of the present study suggest that the simultaneous application of spinetoram and spinosad was generally equally effective with the use of either spinosad or spinetoram alone. Furthermore, the increase of dose of either compound resulted in the same mortality levels. Thus, no benefits were achieved when spinetoram and spinosad were used simultaneously on grains, regardless of the proportion of each ingredient. These issues should be seriously considered when control measures against stored-product insects are designed.     

Isolation and identification of entomopathogenic fungi and their evaluation against Tribolium confusum, Sitophilus zeamais, and Rhyzopertha dominica in stored maize

The objective of this study was to isolate and identify native entomopathogenic fungi from different components of maize agroecosystem, and evaluate their virulence against Tribolium confusum, Rhyzopertha dominica, and Sitophilus zeamais, three insect pest vectors of aflatoxigenic fungi. Paecilomyces and Metarhizium were the most abundant genera isolated from the soil. Identification of fungal cultures by DNA extraction, amplification, and sequencing showed that all isolates macro- and micromorphological identified as P. lilacinus were Purpureocillium lilacinum. The isolate JQ926223 showed the lowest LT₅₀ for T. confusum (4, 66 days) and R. dominica (9, 38 days), and the isolate JQ926212 demonstrated similar LT₅₀ for the three insects evaluated between the range of 11, 7 to 14, 95 days. Maximum mortality rate was observed for the isolate JQ926223. The isolates of Purpureocillium lilacinum JQ926223 and JQ926212 may be considered good candidates for biologic control in the ecosystem of stored maize.     

From lethality to mortality: exploring the “grey area” of knockdown as an efficacy indicator of different insecticides against major storage insects using a lethality index

In the present work, a lethality index was applied for the evaluation of three insecticides with different modes of action, i.e., thiamethoxam, chlorfenapyr and lambda-cyhalothrin, as surface treatment against adults of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.) and Tribolium confusum Jacquelin du Val, in laboratory bioassays. The insecticides were applied at their highest label dose, while insect knockdown and mortality were evaluated after 1, 3, 5 and 7 days of exposure to the treated surfaces according to the Standardized Lethality Index, by ranking each insect from “0” to “4,” with “0” corresponding to insects moving normally and “4” corresponding to dead individuals. After the end of the exposure, the surviving insects were transferred to clean, untreated dishes and delayed mortality was assessed after an additional period of 1, 3, 5 and 7 days. Based on the results, initial knockdown was high for S. oryzae after exposure to thiamethoxam and lambda-cyhalothrin even after 1 day of exposure, whereas for longer exposures high mortality levels were recorded. In contrast, in the case of chlorfenapyr knockdown was low after 1 day of exposure; however, high mortality levels were noted after 3 and 5 days of exposure. Similar results were noted for O. surinamensis, which was highly susceptible to all three insecticides tested. The most tolerant insect species to the tested insecticides was T. confusum, since a noticeable number of T. confusum adults were still active at the end of the exposure (7 days). Our results indicate that knockdown is most likely to lead to mortality than to recovery, but there were important differences among the three insecticides tested.     

Methodology for determining susceptibility of rough rice to Rhyzopertha dominica and Sitotroga cerealella

Varieties of rough rice, Oryzae sativa (L.), were obtained from different sources in the south-central United States and evaluated for susceptibility to the lesser grain borer, Rhyzopertha dominica (Fab.), and the Angoumois grain moth, Sitotroga cerealella (Olivier), in laboratory studies. Adult R. dominica were fed on the rice varieties for 2 weeks, removed, and assessed for progeny production after an additional 6 weeks. Sitotroga cerealella susceptibility was evaluated by exposing two mating pairs of moths on a particular variety until the adults died. Rhyzopertha dominica parental survival, progeny production, and feeding damage by parental and progeny adults were variable, with survival ranging from 19.4 to 95 %. Rhyzopertha dominica parental feeding damage, progeny production, and progeny feeding damage were all correlated (r = 0.35–0.97, P < 0.001). Parental feeding of R. dominica provided access for neonate larvae to infest the rice hull. All rice varieties supported development of S. cerealella, and the variety Vista, which did not support growth of R. dominica, was one of the most susceptible varieties to S. cerealella. Progeny production of both species was generally correlated, but we observed only two instances of specific correlation for any rice variety. Results show that differences in variety susceptibility to stored product insects and differential susceptibility among species are important factors to consider when developing insect pest management programs for stored rice.     

Susceptibility of different life stages of Tribolium confusum to pyrethrin aerosol: effects of a flour food source on insecticidal efficacy

Accumulated grain dust and flour residues in flour mills can potentially decrease the efficacy of contact surface treatments and aerosol insecticides used for control of adult and immature stages of stored product insects. A study was conducted to evaluate the effects of flour residues on the efficacy of piperonyl butoxide-synergized pyrethrin aerosol against different life stages of the confused flour beetle, Tribolium confusum Jacquelin du Val. Twenty individual adults, pupae, or larvae of T. confusum, confined in Petri dishes containing 0, 0.1, 1, 5, or 10 g of wheat flour, were exposed separately inside an empty shed to the label rate of the aerosol. The formulation contained 1 % active ingredient pyrethrin and the label application rate was 1.04 ml/m³. After 2 h of exposure, all dishes were removed from the shed and placed in an incubator set at 27 °C and 60 % RH. Mortality of T. confusum adults decreased with increasing amount of flour. Recovery of moribund adults 15 days after exposure was greater in the 5 and 10 g flour dishes (15 and 46 %) compared to the 0.1 or 1 g flour dishes (0.7 and 5 %). As the flour amounts increased, more larvae and pupae were able to emerge as adults. Results show accumulated flour residues during aerosol application can compromise aerosol efficacy, and also suggest the flour impaired penetration ability of the aerosol. These results also emphasize the importance of sanitation and cleaning to remove spillage and extraneous material prior to an aerosol application.     

Food source provisioning and susceptibility of immature and adult<Emphasis Type="Italic"> Tribolium castaneum</Emphasis> on concrete partially treated with chlorfenapyr (Phantom<Superscript>®</Superscript>)

A series of experiments were conducted in which adults, pupae, and 4-week-old larvae of Tribolium castaneum (Herbst), the red flour beetle, were exposed separately on concrete arenas partially treated (14.4% of the total area) with the insecticide chlorfenapyr (Phantom^®) at 1.1 g of active ingredient/m². A flour food source (patch) was also provided in the untreated portions of the arenas. In the first trial, adult mortality averaged 60.0 ± 10.6%, but progeny production occurred in the provided food patches. Pupal mortality was only 8.3 ± 3.1%, indicating that when adult emergence occurred, those adults were able to escape exposure, and there was no difference in progeny production from that in untreated controls (P = 0.27). In the second trial, few larvae exposed in choice and no-choice arenas were able to emerge as normal adults. In a final trial, residual efficacy declined during a 3-week period, with larvae being more susceptible than adults. Results show mobility of life stage may be a determining factor when assessing susceptibility of T. castaneum to contact insecticides.     

Colorimetric and vibrational spectroscopic characterization of weathered surfaces of wood and rigid polyvinyl chloride–wood flour composite lumber

Rigid polyvinyl chloride–wood flour composite lumber containing either pine or maple wood flour and pine and maple lumber was subjected to accelerated weathering according to the ASTM Standard G 53 protocol. Non-weathered and weathered surfaces of all specimens were analyzed using colorimetric methods, reflectance infrared Fourier transform and Raman spectroscopic techniques. In the FT-IR spectra, conjugated ketones (1,744 cm^?1) of lignin as evidenced by their skeletal vibrations (1,560–1,500 cm^?1) and stretching (1,440–1,500 cm^?1) were reduced in weathered specimens. Cellulose was largely unaffected by weathering. C–O bending vibrations at 1,040 cm^?1 from holocellulose in pine specimens and intensity bands at 1,125–1,090 and 1,360 cm^?1 (C–O stretching and O–H bending from cellulose) in the maple and wood–plastic composite (WPC)-maple specimens were unaffected. A band at 1,650 cm^?1 became prominent after weathering of both pine and maple WPC specimens which is due to C=C–C=C stretching vibration of weathered PVC portion of the specimen. Raman shifts at 530 and 840–900 cm^?1 are attributed to C–O and C–C–O stretching in cellulose (remain unchanged). The role of extractives in weathering of pine is shown by the disappearance of Raman shifts at 392 and 434 cm^?1 (C=C deformations in pine extractives) in weathered pine. One-Way ANOVA, between-group designs showed significant effect on brightness (L*), redness (a*) and yellowness (b*) for all treatments.     

Untersuchungen über die Invasion von Eilarven von vorratsschädlichen Insekten durch verschieden große Poren des Verpackungsmaterials

The diameter of head capsules of egg-larvae of the stored product insect species was measured with an ocular micrometer. The average diameter of head capsules of the egg-larvae in μm:Lasioderma serricorne=142±8,Oryzaephilus surinamensis=257±9,Rhizopertha dominica=126±3,Stegobium paniceum=141±7,Tenebroides mauritanicus=232±9,Tribolium castaneum=151±2,Tribolium confusum=177±4,Plodia interpunctella=177±4. Moreover, the invasion of the egg-larvae ofL. serricorne, O. surinamensis, Rh. dominica, T. castaneum andP. interpunctella through the different sizes of Pores of a cellophane foil (40 μm) was investigated: 100, 125, 150, 175, 275, 200, 225, 250, 275 and 300 μm. These results revealed that the egg-larvae were not able to invade through the pores which were smaller than the diameter of head capsules of the larvae.     

A comparative study of monoterpenoids and phenylpropanoids from essential oils against stored grain insects: acute toxins or feeding deterrents

The relationship between the acute toxicity and feeding deterrent activity of ten compounds occurring commonly in essential oils was explored in order to determine whether they are acute toxins or antifeedants against stored-grain pests. Simultaneously, the objective was also to demonstrate the comparative efficacy against three post-harvest stored-grain pests. Thymol, carvacrol, eugenol and trans-anethole were specifically toxic, and linalool was a generalist feeding deterrent against all three species studied. Thymol was most toxic to Tribolium castaneum and Rhyzopertha dominica compared to carvacrol and eugenol but was least toxic to Sitophilus oryzae. Similarly, linalool deterred feeding of S. oryzae (FI₅₀ = 0.025 mg/g of the wafer diet), T. castaneum (FI₅₀ = 0.207 mg/g of the wafer diet) and R. dominica (FI₅₀ = 0.482 mg/g of the wafer diet) at different concentrations; R. dominica beetles required about 20 times the concentration to deter feeding compared to S. oryzae and more than twice compared to T. castaneum. Comparison of toxicity and deterrent activity with respective artificial blends as binary mixtures revealed that synergism was not a generalized phenomenon, and the variations were both species as well as blend specific. Individual compound efficacy correlations were not ascertained, which suggests that artificial blends could be prepared to obtain potential mixtures for substantial control of stored-grain insect pests. The present study also implies that the compounds are mostly acute toxins, and whatever inhibition in feeding was obtained could be due to physiological toxicity rather than any interaction with gustatory receptors.     

MA-chitosan nanogel loaded with Cuminum cyminum essential oil for efficient management of two stored product beetle pests

Natural essential oils have received increased attention as alternatives to synthetic pesticides for pest management of foodstuffs. Recently, microencapsulation and other controlled release techniques are used to increase insecticidal efficiency and persistence of essential oils with slow and controlled release. In this study, the possibility of improving the insecticidal activity of plant essential oils was investigated for effective management of two stored product beetle pests. Self-assembly technique was used to prepare nanogels of myristic acid-chitosan loaded by essential oil extracted from cumin, Cuminum cyminum L. Fumigant toxicity of C. cyminum oil and oil-loaded nanogels (OLNs) were investigated at 4, 7, 10, 13, and 16 µL/L air against the granary weevil Sitophilus granarius L. and 8, 11, 14, 17, and 20 µL/L air for confused flour beetle Tribolium confusum Jacquelin du Val. Experiments were conducted at 27 ± 1 °C and 55 ± 5 % relative humidity in continuous darkness. Insecticidal bioassay revealed that OLNs were more toxic than C. cyminum oil against tested beetle pests. The persistence of the oil and OLNs was also evaluated against two tested species. Results indicated that C. cyminum oil completely lost its insecticidal activity after 12 days, whereas at the same period, the OLNs lost about 60 % of its activity when applied against S. granarius and 15% for T. confusum. Therefore, it could be concluded that encapsulation improved the persistence of the oil.     

Chemical composition,insecticidal and repellence activities of essential oils of three Achillea species against the Khapra beetle (Coleoptera: Dermestidae)

Essential oils of Achillea biebersteinii, Achillea santolina and Achillea mellifolium were obtained by hydrodistillation and analyzed using gas chromatography/mass spectrometry. The plant oils were tested for their toxic and repellent activities against the Khapra beetle, Trogoderma granarium (Everts) (Coleoptera: Dermestidae). T. granarium was sensitive to the oils via topical application, contact and fumigation bioassays, where A. biebersteinii oil was the most toxic regardless of the technique used. Using topical application, a dosage of 15 μg/mg insect of A. biebersteinii oil was sufficient to kill 100 and 83.2.0 % after 7 days exposure of adults and 2nd instar larvae, respectively. Meanwhile, twice this concentration of A. santolina and A. mellifolium oils caused 90.4 (72.5 %) and 73.8 (60.1 %) adult and larval mortality after 7 days, respectively. Using fumigation and 7 days exposure, a concentration of 50.0 μl/l air of A. biebersteinii oil displayed the strongest activity (percentage adult and larval mortalities of 100.0 and 88.0 %), respectively, while A. santolina and A. mellifolium oils at the same concentration caused 92.5 (76.8 %) and 76.1 (61.3 %) adult and larval mortality, respectively. The three oils were strongly repellent to the larvae and adults of T. granarium. The repellent activity was time and concentration-dependent, where A. biebersteinii oil was the most effective, even though at low concentrations (percentage repellency of 100 and 81.0 % were recorded against adults and larvae after 6 h exposure to a concentration of 0.22 μl/cm², respectively). Results suggested the potential use of Achillea oils as natural grain protectants against T. granarium.     

Laboratory evaluation of five novel pyrrole derivatives as grain protectants against <Emphasis Type="Italic">Tribolium confusum</Emphasis> and <Emphasis Type="Italic">Ephestia kuehniella</Emphasis> larvae

Several naturally discovered or laboratory-synthesized pyrrole compounds have insecticidal, acaricidal and microbial properties. The novel sulfanyl 5H-dihydro-pyrrole derivatives exhibit certain antioxidant activities. However, there is a knowledge gap whether these substances are potent grain protectants against stored-product insect pest species. In this context, we evaluated the insecticidal activity of five novel pyrrole derivatives (under the trivial names 3a, 3g, 3l, 3m, 3h), against larvae of Tribolium confusum Jaquelin du Val and Ephestia kuehniella Zeller at different doses (0.1, 1 and 10 ppm), exposure intervals (7, 14 and 21 days or 1, 2, 7, 14, 21 days), temperatures (20, 25 and 30 °C), relative humidity (RH) (55 and 75 %) levels and commodities (wheat, maize, barley). The pyrrole derivative 3a exhibited the highest insecticidal activity, while 3g, 3l, 3m and 3h caused similar mortality against larvae of T. confusum. Apart of the level of efficacy, all tested pyrrole derivatives performed similarly according temperature. We found that increase in temperature increased mortality in the majority of the tested combinations. Generally, the pyrrole derivatives caused the highest mortality levels at 30 °C. The pyrrole derivatives 3a, 3g, 3l and 3m were affected by relative humidity at almost all combinations tested. The 75 % level of RH moderated the efficacy of the pyrrole derivatives, while the 55 % enhanced it. Mortality of T. confusum and E. kuehniella on maize was much lower on treated maize than barley or wheat. However, 100 % control of both species was recorded only on treated barley. The results of the present study indicate that the pyrrole derivatives tested could serve as grain protectants against noxious stored-product insects under certain biotic and abiotic conditions.     

Bioinsecticidal effect of the flavonoids pinocembrin and quercetin against <Emphasis Type="Italic">Spodoptera frugiperda</Emphasis>

Flavonoids function in many aspects of plant–insect interactions, but the responses of insects to these compounds vary greatly. In this study, we determined the effects of two widely distributed flavonoids, pinocembrin and quercetin, on the feeding behavior, survival, and development of the fall armyworm Spodoptera frugiperda J.E. (Smith) (Lepidoptera: Noctuidae). In a choice test, S. frugiperda larvae strongly rejected leaves treated with pinocembrin at concentrations of 10, 50, or 100 μg/cm². Larvae fed normally on leaves treated with quercetin at 10 and 50 μg/cm², but showed 57 % deterrence when fed on leaves treated with 100 μg/cm² quercetin. At concentrations of 0.01–1 µg/cm², pinocembrin and quercetin functioned as phagostimulants for S. frugiperda. In a multiple-choice experiment, S. frugiperda larvae preferred to consume untreated leaves or those treated with 0.1 µg/cm² pinocembrin, but rejected leaves treated with 5–50 µg/cm² pinocembrin. In a no-choice feeding experiment, larvae fed on leaves treated with 5 and 50 μg/cm² pinocembrin consumed less than those fed on leaves treated with 0.1 and 1 μg/cm² pinocembrin or untreated leaves. Pinocembrin at 1–50 μg/cm² negatively affected larval weight and survival, thus showing a toxic effect. In contrast, leaf consumption and larval weight were not significantly affected by quercetin at 0.1, 1, 5, and 50 μg/cm², and mortality rates only slightly increased. Because of its dual activity, pinocembrin could be used for insect control in a stimulo-deterrent diversionary strategy: the same compound could promote both stimulate (low doses) and deter insect activity (high doses).     

Assessing repellency,movement, and mortality of three species of stored product insects after exposure to deltamethrin-incorporated long-lasting polyethylene netting

Long-lasting insecticide-treated netting (LLIN) has begun to be used in agricultural product protection. We investigated the effect of a deltamethrin-incorporated LLIN on three stored product insects, red flour beetle, Tribolium castaneum (Herbst), lesser grain borer, Rhyzopertha dominica (F.), and rice weevil, Sitophilus oryzae (L.). Long-distance repellency was assessed in a wind tunnel for adults of each species, but no repellency was observed. Insect movement and behavior was assessed by observing the movement of adult beetles on treated and untreated netting during a 5 min period for distance traveled, velocity, mobility, and time on each netting type. Among all netting combinations, T. castaneum spent the most time highly mobile, higher velocity, and traveled a greater distance. Sitophilus oryzae and R. dominica spent significantly more time immobile and lower velocity. Efficacy of LLIN was tested by exposing adults for 60 min, removing, and holding with or without food, and monitoring for mortality up to 7 d. All S. oryzae and R. dominica were either affected or dead at all post-exposure times. The number of affected and dead adult T. castaneum combined 7 d after exposure was 42% and 95%, with or without food, respectively, and 52% of affected adults were able to recover when food was present. Overall, LLIN had no repellency or negative effect on insect movement, which increases the probability of lethal exposures of adults from walking on the netting. LLIN can be adopted in existing integrated pest management (IPM) programs for food processing facilities to prevent stored product insect infestations.

     

Wirkungsweise amorpher Diatomeenerden auf vorratsschädliche Insekten. Untersuchung der abrasiven sowie sorptiven Effekte

The present study examined the morphological and physiological effects of amorphous diatomaceous earth against the stored product pestsS. granarius, T. molitor andT. confusum. Diatomaceous earth, namely Fossil Shield^® and Dryacide^® increased the mortality rate of this insects. After contact with Fossil Shield^® the individuals ofS. granarius had significant lost of weight and reduced their water content respectively. This showed that silica dusts break the water barrier of the cuticle. However, it increases the transpiration rate of water across the cuticle and the insect died past several times through dehydration. As well, an addition of food affected the effectiveness of dusts against insects. A lot of stored product beetles will be able to produce metabolic water of feed substrates. This ability protects and weaves contrary to the loss of water. Diatomaceous earth’s can be effective primarily through the sorptive properties of the hygroscopic particles. One day after dust treatment a significant weight loss ofT. molitor pupae was recorded. The exposure to the silica dust Fossil Shield^® caused partly an incomplete metamorphosis and death of the individuals. Pupae dipped in Fossil Shield^® or abrasive aluminium dust and rolled for further five minutes, reduced not significant higher their weight as unrolled exuvial stages. The morphological analyses of treated insects under the Scanning Electron Microscope showed, that the dust covered the hole integument. Partly, the silica particles sunk into the cuticle. After application of Fossil Shield^® at the cuticle of adults,T. molitor, did not show any wax layer. Also it could not be found once blocked by stigma of the mealworm. The dust particles accumulated around the respiration openings and they partly overgrew.     

Asymmetry of mating behaviour affects copulation success in two stored-product beetles

Lateralization (i.e. left–right asymmetries in the brain and behaviour) has been documented in all vertebrate classes, while evidences for invertebrates are limited. To the best of our knowledge, there is no information about behavioural asymmetries in the order Coleoptera. In this research, we investigated the lateralization of mating traits in two major pests of stored products: the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae), and the confused flour beetle, Tribolium confusum (Coleoptera: Tenebrionidae). Both T. confusum and S. oryzae males showed population-level left-biased copulation approaches of potential mates. Interestingly, T. confusum and S. oryzae males performing left-biased copulation attempts achieved higher mating success over right-biased males. Furthermore, S. oryzae males periodically exhibited a typical head wagging behaviour, which consists of waving the rostrum laterally across the female thorax and then resting the rostrum on the mid thorax. This behaviour was right-biased, even in the majority of males that previously showed left-biased copulation attempts. The quantification of mating displays could allow comparisons with other strains, in order to evaluate the impact of a given host or of the rearing methods on the mating traits of S. oryzae and T. confusum. Overall, this is the first report of lateralization of mating traits in Coleoptera. Furthermore, this research adds basic knowledge to the reproductive behaviour of S. oryzae and T. confusum.     

Wound occlusion and decay in Picea abies stems

In forest stands, Picea abies is commonly subjected to logging and bark stripping injuries. Most mechanical wounds do not exceed 300 cm², but their pathological consequences are unclear. The aim of the study was to estimate the rate of wound occlusion and the probability of decay in P. abies stems in relation to initial wound size and wounding season. The study included forty-five stems with 1-, 2-, 3-, 4- and 5-cm-wide by 15-cm-long wounds (15–75 cm²), and eighty-three stems with 15-cm-wide by 20-cm-long wounds (300 cm²), made either in January or in August. After 19–21 years, each wound was assessed for occlusion rate and the presence of decay. All 1- to 2-cm-wide wounds were occluded, compared to 58–70% of the 3- to 4-cm-wide wounds, 25% of the 5-cm-wide wounds, and 0% of the 15-cm-wide wounds. On average, it took 3.6, 5.5, 10.4, 12.7 and 14.7 years to occlude wounds ranging in size from 1- to 5-cm-wide, respectively. After 21 years, the observed size of wounds comprising an initial area of 300 cm² ranged between 14 and 481 cm². Wounding season and stem DBH had no impact on wound healing. Wound decay incidence correlated positively with the initial width of injury (r = 0.925; P < 0.05). All 1- to 2-cm-wide wounds lacked any decay, while the proportions of decay among 3-, 4-, 5- and 15-cm-wide wounds were 58.3, 50.0, 83.3 and 100%, respectively. Length of decay comprised 35–225 cm. Consequently, wounds on P. abies stems greater than 5 cm width are unlikely to be occluded and more prone to decay development.     

Effect of botanical insecticide Nimbecidine<Superscript>®</Superscript> on food consumption and egg hatchability of the terrestrial snail <Emphasis Type="Italic">Monacha obstructa</Emphasis>

In the laboratory, a commercial neem-based insecticide—Nimbecidine^®—was evaluated as a potential pest management tool for the terrestrial snail, Monacha obstructa (Pfeiffer, 1842) (Hygromiidae). Effects of different concentrations of the botanical insecticide on food consumption and egg hatchability of the terrestrial snail were studied. Generally, food consumption of immature and adult snails decreased as the concentrations of Nimbecidine^® increased. At the highest concentration (10 ml/l), the snails avoided contacting with food completely. The food intake of immature individuals was significantly (p < 0.05) more affected by the Nimbecidine^® treatment (at 1.25 ml/l) than that of adults. LC₅₀ of Nimbecidine^® for the treated eggs was 2.18 ml/l, and eggs failed to hatch at concentration of 10 ml/l. Nimbecidine^® showed sufficient biological activity against the food consumption and eggs viability of M. obstructa, thus the preparation has a potential to protect field crops from this pest snails.