Prostephanus Truncatus Research Articles

DETERMINANTS OF FARMER’S PERCEPTION OF PROSTEPHANUS TRUNCATUS (HORN) DAMAGES AND LOSSES ON STORED MAIZE IN TOGO AND BENIN (WEST AFRICA)

Prostephanus truncatus is one of the most damaging post-harvest pests of stored maize in Africa. Research Institutions disseminated Various control strategies during the 1990s in West Africa with significant results. What is farmers’ perception of this pest in decades after those control strategies? This study aimed to assess determinants of farmers’ perception of current damages and losses caused by Prostephanus truncatus on stored maize in southern of the two countries (Benin and Togo). 300 maize farmers (150 from Togo and 150 from Benin) were randomly selected from 10 villages per country. Descriptive statistics were used in addition to Logit and Tobit regression analysis. The results showed that 38% of farmers (35% in Togo and 41% in Benin) still perceive Prostephanus truncatus as the most damaging pest of stored maize. Logit's results showed that factors influencing farmers’ perception of Prostephanus truncatus were group membership, contact with extension agents, and period of maize harvesting. The results from the Tobit regression model showed that factors such as the maize variety, the form of maize storage (with husk), and the storage period influence the extent of damage and loss caused by Prostephanus truncatus. Farmers still perceive Prostephanus truncatus as the main post-harvest pest causing high damage and losses on maize. It is recommended that further dissemination of maize storage technology to reduce postharvest losses.

Insect pests of dried yam (Dioscorea sp.) chips and the perception of processors and marketers on their control

This survey was aimed at understanding the perception of Dried yam chips (DYC) Processors and Marketers on insect pests' infestation of DYC and their damage through the use of structured questionnaires. Data on socio-economic characteristics and technical information were analyzed using descriptive statistics such as frequency distribution, percentages, and means. Data on the perception of insect pests and measures of pest control were placed on a 3-point Likert Rating Scale (LRS). Analysis of variance (ANOVA) was done on the population density of the identified insects and significant mean values were compared using Fisher's Least Significant Difference. Seven insect pests; Prostephanus truncatus, Rhyzopertha dominica, Tribolium castaneum, Stegobium paniceum, Heterobostrychus aequalis, Sitophilus zeamais, Areacerus fasciculatus, and one natural enemy; Peregrinator biannulipes were associated with DYC. However, P. truncatus, R. dominica, and A. fasciculatus were the most prevalent insect pests, causing significant damage to DYC. Approximately, 49% of processors reportedly control insect infestation in DYC using conventional insecticides, 23% by re-drying, 14% by botanicals, and the others by removing affected DYC. These findings provide useful information for extension workers involved in community education, and intervention programs by government or non-governmental organizations including public health experts and researchers.

Insecticidal Properties of Curcuma longa on the Growth of Prostephanus truncates

Prostephanus truncatus, a devastating pest, causes significant damage to stored grains. Synthetic insecticides pose environmental and health risks, necessitating eco-friendly alternatives. Curcuma longa, a medicinal plant, exhibits insecticidal properties. This study investigates the effect of Curcuma longa on the growth of Prostephanus truncatus. Results show that Curcuma longa extracts significantly inhibit the growth and development of Prostephanus truncatus, offering a promising natural insecticide.

Graphene powders as new contact nanopesticides: Revealing key parameters on their insecticidal activity for stored product insects

The overuse and reliance on pesticides has caused insects to develop resistance with global concerns. To address this problem extensive research is directed to find new and sustainable alternatives using chemical-free and resistance-free solutions for pest control. This paper presents a comprehensive investigation of the insecticidal properties of several types of industrially produced graphene powder materials such as graphene and graphene oxide (GO) with micro- and nano size and different structural and chemical properties as new contact nanopesticides against three major stored grain insects: the rice weevil Sitophilus oryzae (L.), the lesser grain borer, Rhyzopertha dominica (F.)˙ and the larger grain borer, Prostephanus truncatus Horn. Bioassays were performed using different concentrations, i.e., 0, 100, 500 and 1000 ppm of graphene powders on the mortality of selected adult insects recorded after 3, 7, 14, and 21 days of exposure and progeny production after 65 days. Results showed that graphene oxide (GO) has no insecticidal efficacy while graphene powders with nano-size particles showed significantly enhanced insecticidal performance compared to micron-size graphene powders. The observed insecticidal effects are explained by the higher probability that nano-sized graphene particles adhere on the insect body compared to large particles. The mortality is proposed as the result of physical mode of action of attached graphene nanoparticles causing stronger interruption of the protective cuticle layer, gas respiratory functions and faster mortality. The findings of this study revealed that it is important to select graphene materials with optimal structural and interfacial properties to achieve the highest insecticidal performance in potential development of a new generation of sustainable insecticides.

Population growth of two strains of the larger grain borer, Prostephanus truncatus on three maize hybrids grown in Europe

The larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae), continues to threaten maize worldwide, with an endemic range in Mexico, Central and Northern South America, and an exotic range in Sub-Saharan Africa. There was a targeted effort beginning in the 1990s to create maize hybrids in the hope of controlling P. truncatus. Through those efforts, several resistant maize hybrids were developed, which were able to reduce progeny production by P. truncatus. However, where P. truncatus has yet to fully establish, including parts of Europe such as Italy and Greece, existing maize hybrids developed for production in Europe have not been investigated for resistance against P. truncatus. In this study, we sought to compare the fitness of two different strains of P. truncatus, one from the native range in Mexico and the other from the invaded range in Ghana, by investigating the progeny production, number of damaged kernels, and frass production of both strains on three maize hybrids (Pico 1, Hamilton 2, and AGN 672) developed for use in Greece and wider Europe to evaluate susceptibility and/or tolerance to P. truncatus. The Mexico strain of P. truncatus produced more progeny on the Pico 1 than the AGN 672 hybrid, while the Ghana strain did not significantly differ in progeny production among hybrids. All hybrids were susceptible to both strains of P. truncatus. There were no real differences in damaged kernels or frass production between the two strains and across the three maize hybrids. Overall, this study provides a foundation for exploring maize resistance in European cultivars to P. truncatus as a possible new tool.

Predicted range expansion of Prostephanus truncatus (Coleoptera: Bostrichidae) under projected climate change scenarios.

The larger grain borer (Prostephanus truncatus [Horn] [Coleoptera: Bostrichidae]) is a wood-boring insect native to Central America and adapted to stored maize and cassava. It was accidentally introduced to Tanzania and became a pest across central Africa. Unlike many grain pests, P. truncatus populations can establish and move within forests. Consequently, novel infestations can occur without human influence. The objectives of our study were to (i) develop an updated current suitability projection for P. truncatus, (ii) assess its potential future distribution under different climate change scenarios, and (iii) identify climate variables that best inform the model. We used WALLACE and MaxEnt to predict potential global distribution by incorporating bioclimatic variables and occurrence records. Future models were projected for 2050 and 2070 with Representative Concentration Pathways (RCPs) 2.6 (low change) and 8.5 (high change). Distribution was most limited by high precipitation and cold temperatures. Globally, highly suitable areas (> 75%) primarily occurred along coastal and equatorial regions with novel areas in northern South America, India, southeastern Asia, Indonesia, and the Philippines, totaling 7% under current conditions. Highly suitable areas at RCPs 2.6 and 8.5 are estimated to increase to 12% and 15%, respectively, by 2050 and increase to 19% in 2070 under RCP 8.5. Centroids of highly suitable areas show distribution centers moving more inshore and away from the equator. Notably, the result is a range expansion, not a shift. Results can be used to decrease biosecurity risks through more spatially explicit and timely surveillance programs for targeting the exclusion of this pest.

Trait‐dependent plasticity erodes rapidly with repeated intergenerational acclimation in an invasive agricultural pest

AbstractClimate change is associated with increased mean temperatures and amplitudes manifesting both acutely and chronically, triggering organism stress responses that confer fitness costs and/or benefits. The larger grain borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) is an invasive postharvest agricultural pest. While host shift is its well‐known potential invasive mechanism, how repeated intergenerational stress environments may influence offspring phenotypes is largely unknown. We thus evaluated physiological and ecological performance of LGB following repeated intergenerational acute heat acclimation to insinuate its likely responses to projected increased bouts of heat stress associated with climate change. Parental colonies were acutely heat‐acclimated separately at 35°C and 38°C; 80% RH for 2 h in climate chambers and released onto sterilized maize grain at optimal conditions (32°C, 80% RH). The F1 progenies were, respectively, acclimated at the same conditions and incubated to F2 generation. We then evaluated physiological and ecological performance under optimal conditions across parental, F1 and F2 generations. Our results showed that plasticity was highly trait dependent, and that acclimation did not affect F1 and F2 critical thermal maxima, but did improve critical thermal minima. However, while acclimation improved heat knockdown time at F1, repeated acclimation significantly reduced heat knockdown times at F2, suggesting plasticity erosion with generational repeated acclimations. Acute acclimation negatively affected ecological performance of F1 generations although this was restored with repeated acclimation in F2 populations. Our results suggest that the LGB may inflict more economic damage with repeated heat stress due to generational adaptation to temperature stress. The results contribute to knowledge on pest forecasting modelling under changing climates and provides a framework for phytosanitary adjustments in heat treatment protocols for international grain trade.

The Fall Armyworm and Larger Grain Borer Pest Invasions in Africa: Drivers, Impacts and Implications for Food Systems.

Invasive alien species (IAS) are a major biosecurity threat affecting globalisation and the international trade of agricultural products and natural ecosystems. In recent decades, for example, field crop and postharvest grain insect pests have independently accounted for a significant decline in food quantity and quality. Nevertheless, how their interaction and cumulative effects along the ever-evolving field production to postharvest continuum contribute towards food insecurity remain scant in the literature. To address this within the context of Africa, we focus on the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), and the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), two of the most important field and postharvest IAS, respectively, that have invaded Africa. Both insect pests have shown high invasion success, managing to establish themselves in >50% of the African continent within a decade post-introduction. The successive and summative nature of field and postharvest damage by invasive insect pests on the same crop along its value chain results in exacerbated food losses. This systematic review assesses the drivers, impacts and management of the fall armyworm and larger grain borer and their effects on food systems in Africa. Interrogating these issues is important in early warning systems, holistic management of IAS, maintenance of integral food systems in Africa and the development of effective management strategies.

Strain effect of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) in population growth studies on different temperatures

The population growth of different strains of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae), a key pest of stored maize, was evaluated at a range of temperatures. Three different strains of P. truncatus with different geographic origins (USA, Mexico and Tanzania) were left for 45 or 70 d to develop and reproduce under six temperatures (25, 30, 32, 35, 38 and 40 °C). Progeny production and maize-infestation indicators (frass, damaged maize kernels) were examined to estimate possible differences between the strains in terms of development performance and optimal thermal requirements. Population growth of the species appeared to be affected by the combination of temperature and/or developmental period. The optimum temperature range for fast development and serious infestations was found to be 25–32 °C, which resulted in newly-emerged adults after 45 days. Differences were observed between the strains, both in terms of their growth rate and the damage they caused on the kernels over time. The present study aims to highlight how the strain is a factor of significance for P. truncatus based on the different thermal responses. These data can support more accurate prediction or elimination of future infestations, targeting immediate and early detection of the pest in areas where it is likely to establish.

Being exposed to Acmella oleracea-based insecticide extract reduces mobility and mating success in Prostephanus truncatus, the major pest of maize in storages

The evaluation of sublethal effects of botanical insecticides is a key tool to develop new strategies in pest management programs, since they potentially affect insect physiology and behavior. Acmella oleracea (L.) R.K. Jansen (Asteraceae) is a medicinal food plant widely used on an industrial level and with recognized efficacy against various arthropod pests and vectors. In this study, the sublethal effects of an A. oleracea hexane extract (HE) on the mobility, mating, and behavior of Prostephanus truncatus were investigated. The concentrations that killed 10, 30 and 50% of the exposed adults were 7.01, 19.5, and 39.5 mg/mL, respectively. The walking behavioral traits, i.e., duration and number of stops, and upside down (i.e., the time spent by the beetle on its back), were significantly higher in the adults exposed to LC30 than LC10 and control ones. The highest velocity was recorded for control beetles (21.5 mm/s), followed by LC10- (20.7 mm/s) and LC30-treated ones (21.2 mm/s). Concerning lateralization, P. truncatus males were right biased during the mating sequence. Sublethal concentrations negatively affected the mating success of LC10- and LC30-exposed males in comparison with control ones. Overall, our findings outlined that the exposure of P. truncatus adults to A. oleracea HE LC10 and LC30 deeply affected their walking and mating behavior, a fact that should be considered further when optimizing pest management tactics in storages.

The use of Beauveria bassiana for the control of the larger grain borer, Prostephanus truncatus, in stored maize: Semi-field trials in Ghana

Laboratory research in Ghana demonstrated the effectiveness of an isolate of Beauveria bassiana (IMI 389521) from the United Kingdom against the larger grain borer Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), a major pest of stored maize. The minimum effective concentration, following artificial infestation trials on maize, was between 109 and 1010 cfu/kg maize. Before moving out to village-level control, a major requirement was to determine if the product could effect control in artificially infested maize held under real environmental conditions in several locations in Ghana. Therefore, this study investigated the efficacy of formulated conidia of B. bassiana, IMI 389521, at two concentrations (1 × 109 and 3.16 × 109 cfu/kg maize) to control P. truncatus on stored maize kernels under semi-field conditions in Ghana. Maize (‘Obatanpa’ cultivar) kernels were treated with the formulated B. bassiana product and stored in polypropylene woven bags in cribs in Southern Ghana. After 24 h, one hundred adults of P. truncatus were placed into each bag containing the treated maize. Mortality and the percent of weight loss of kernels were assessed every two weeks for three months. The semi-field trials revealed the possibility of successfully controlling adult P. truncatus on maize kernels treated with B. bassiana at 3.16 × 109 cfu/kg maize. However, due to the minimal protection of kernels after four weeks, re-treating maize kernels after this period is recommended to ensure maximum protection during prolonged storage.

Efficacy of Contact Insecticides for the Control of the Larger Grain Borer, Prostephanus truncatus (Horn), on Stored Maize

One of the most destructive insect species for stored maize is the larger grain borer, Prostephanus truncatus. Its control is challenging, as it seems to have a natural tolerance to active ingredients that are effective for other stored-product insect species that cause infestations in maize. The objective of the present study was to comparatively evaluate a wide range of insecticides that are currently in use in stored product protection for the control of P. truncatus. Specifically, three inert dusts—namely, a kaolin, a zeolite and a diatomaceous earth formulation—and three residual insecticides—i.e., the pyrethroid deltamethrin, the bacterial insecticide spinosad and the juvenile hormone analogue S-Methoprene—were evaluated against adults of P. truncatus. Adult mortality was assessed after 7, 14, 21 and 28 d of exposure, whereas progeny production was measured after an additional interval of 28 d for inert dusts and 65 d for the contact insecticides. Moreover, the number and weight of infested and uninfested kernels per vial was measured. Low mortality levels were recorded for the three inert dusts even for the highest application rate and after 28 d of exposure. Moreover, the inert dusts tested failed to suppress the progeny production of P. truncatus. In contrast, high mortality levels were recorded for deltamethrin and spinosad that exceeded 95% already after 7 d of exposure at the lowest application rate (0.5 ppm). The application of S-Methoprene did not result in high adult mortality rates, irrespective of the application rate and the evaluation interval. Deltamethrin, spinosad and S-Methoprene significantly suppressed progeny production of the species at the doses tested.

Effect of Nitrogen on Stored-Product Insect Control at Industrial Scale.

In this study, we evaluated the insecticidal effect of nitrogen against Sitophilus granarius (L.), Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Prostephanus truncatus (Horn), Tribolium confusum Jacquelin du Val, and Oryzaephilus surinamensis (L.). Four trials were conducted in chambers containing flour in bags or sacks with >99% nitrogen level. Adults of all the above species, as well as immature life stages (eggs, larvae, and pupae) of T. confusum were used in the trials. Our results showed that nitrogen caused high mortality for all species and life stages tested. Some survival was recorded for R. dominica and T. confusum pupae. Low progeny production was recorded for S. granarius, S. oryzae, and R. dominica. In conclusion, our trials indicated that a high nitrogen environment can provide satisfactory control of various primary and secondary stored-product insect species.

Efficacy of deltamethrin and pirimiphos-methyl in proportionally layer-treated maize against the larger grain borer and the maize weevil.

Two insecticides (deltamethrin and pirimiphos-methyl) were evaluated in laboratory assays as grain protectants when applied as a total percentage of a maize mass to control adult Prostephanus truncatus and Sitophilus zeamais. All experiments were conducted at the University of Thessaly in Greece at 30°C and 65% RH under continuous darkness. Either insecticide was applied to 20 g of maize placed in a vial or to the upper one half, one fourth, or one-eighth layer of the maize, then insects were either added to the vials before or after the maize in a completely randomized block design CRBD with n = 9 replicates. Mortality, progeny production, and insect damaged kernels (IDK) were then evaluated for each vial. Insect introduction method (before or after) did not have any impact on any of the variables. Mortality was nearly 100% for all treatments for both insecticides for P. truncatus. Subsequently, progeny production and the number of insect damaged kernels were very low or zero for P. truncatus. Mortality of S. zeamais remained low across layer treatments for deltamethrin. However, S. zeamais was easily controlled by pirimiphos-methyl. The results of this laboratory study show that while deltamethrin and pirimiphos-methyl have some effectiveness as a layer treatment on a column of maize, efficacy will be dependent on the target species, and the depth of the treated layer, as well as the location on which the insects are present.

The dispersal ability of the invasive larger grain borer and the cosmopolitan maize weevil after brief exposure to a newer insecticide formulation

The larger grain borer (Prostephanus truncatus) and the maize weevil (Sitophilus zeamais) are major pests of stored maize. Given the threat of these insects to our maize supply, the increasing insecticide resistance to currently used chemical control tactics such as phosphine, and the removal of effective chemistries from the market (methyl-bromide), there is a need for alternative integrated pest management tools. Here, we present a more realistic test of the effectiveness of a novel insecticide formulation (methoprene + deltamethrin + piperonyl butoxide, PBO; tradename, Gravista ®) in comparison to past conventional insecticide evaluations at reducing the horizontal dispersal capacity to food patches of both stored product species in comparison to an older formulation (methoprene + deltamethrin; tradename, Diacon IGR+®). For these experiments, we used a dispersal apparatus (consisting of 30 or 70 cm PVC pipe modified with a baited pitfall trap at one end) where we introduced cohorts of adults after exposure on concrete arenas at labeled rates and gave them 48 h to disperse to a novel food source consisting of 15 g of maize. The dispersal capacity for P. truncatus, measured as the percentage of adults dispersing to the novel food source, was significantly reduced by 90–97% after exposure to Gravista or Diacon IGR+ compared to the control. By contrast, the dispersal capacity for S. zeamais was only reduced by 5–25% after exposure to either insecticide formulation compared to the control. Both formulations performed equally well for each individual species, but dispersal of S. zeamais was not strongly impacted. Overall, our study highlights the importance of using realistic behavioral assays in comprehensive insecticide testing to provide a full picture of insecticide efficacy.

Sub-Lethal Effects of Pirimiphos-Methyl Are Expressed to Different Levels in Wings of Three Stored-Product Coleopterans: A Geometric Morphometrics Investigation

Tenebrio molitor L. (Coleoptera: Tenebrionidae), Prostephanus truncatus (Horn), and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) are noxious insect pests of grains in storages. Pirimiphos-methyl is widely used to protect grains at the post-harvest stage. However, the sub-lethal impact of this active ingredient on the offspring of all three coleopterans remains unknown. Thus, mated females of each species were exposed separately to pirimiphos-methyl at short exposures (30 min, 3, 5, 8, 16, 24, and 36 h), where the elytra and hindwings of the adult progeny were analyzed with the geometric morphometrics method. Males and females of all species were incorporated into the analysis. The results revealed variability among species. Tenebrio molitor was the most sensitive among three species, displaying significant deformations in the elytra and hindwings. Males had more conspicuous morphological changes than females. Prostephanus truncatus hindwings exhibited deformities after 36 h of exposure to pirimiphos-methyl. In contrast, R. dominica offspring were not affected by pirimiphos-methyl. In light of our findings, organophosphorus insecticides may cause variable sub-lethal effects to stored-product insects. This issue may lead to different insecticidal treatments according to the targeted stored-product species.

Population growth of Prostephanus truncatus and Sitophilus zeamais and infestation patterns in three maize hybrids

Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) cause significant damage to stored maize (Zea mays L.). In this study, we evaluated the progeny production and damage of these species in three maize hybrids (‘AGN 717’, ‘AGN 672’, and ‘AGN 794’) obtained from three locations in Northern Greece. The trials were conducted under laboratory conditions, and the progeny production, number of damaged kernels (NDK), weight of damaged kernels (WDK), and frass were evaluated after 65 days. The hybrids had a significant effect on the progeny production of both beetle species, with the highest number of progeny being produced in the hybrid ‘AGN 672’. The percentage of dead adults was affected by planting location of hybrids in both species, but no significant differences were found among the tested hybrids and species. The effect of location on frass production was only observed in S. zeamais, but hybrids did not affect the production of the frass in either species. NDK and WDK were found to be significantly different among the hybrids in S. zeamais, but only WDK was different in P. truncatus. These parameters did not differ among the locations for either species. The results showed that different hybrids and cropping locations had a significant effect on the progeny production and damage of S. zeamais and P. truncatus in maize. Therefore, planting locations and hybrids should be taken into account when growing maize or specified in maize susceptibility studies to P. truncatus and S. zeamais.

Efficacy of Beauveria bassiana against adults of Prostephanus truncatus (Horn), Sitophilus zeamais Motschulsky and Teretrius nigrescens Lewis in stored maize

The larger grain borer, Prostephanus truncatus (Horn) and the maize weevil, Sitophilus zeamais Motschulsky continue to cause tremendous losses to stored maize. Research in the UK has identified Beauveria bassiana, IMI 389521 as a suitable control agent for grain storage pests in the UK. The pathogenicity of B. bassiana, IMI 389521 was evaluated against adult P. truncatus, S. zeamais and Teretrius nigrescens in Ghana. Fifty adults of each insect species were treated with 0.5 g dry conidia powder of this isolate at 8.65 × 108 conidia/g for 1 minute and mortality recorded daily for 14 days. The results indicated that B. bassiana, is pathogenic against P. truncatus and S. zeamais, inducing over 90% mortality by day 7. Teretrius nigrescens was, however less susceptible to the fungus with 30% mortality. To determine the most effective concentration of B. bassiana for the control of P. truncatus, a laboratory dose response experiment using four concentrations of B. bassiana (108–1011 cfu/kg maize) was also conducted. Maize grains (250 g) in separate jars were treated with the four concentrations of the product. Fifty adults of P. truncatus were placed into the jars containing the treated maize and mortality was assessed weekly for 3 weeks. The most effective dose was 1010 cfu/kg maize, which resulted in 96% and 100% mortality of P. truncatus after 2 and 3 weeks, respectively. This study shows that B. bassiana could effectively be integrated into bio-control programme of these two key pests of maize in Ghana after further field trials.

Etofenprox guarding concrete for six weeks: immediate and delayed mortality of three major stored-product coleopterans

This study addresses the residual efficacy of the pyrethroid insecticide etofenprox sprayed on concrete surfaces for the management of Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) adults, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) adults, and Trogoderma granarium Everts (Coleoptera: Dermestidae) adults and larvae, through a period of six weeks. Three doses of etofenprox (5 μg/cm2, 15 μg/cm2, and 45 μg/cm2) were tested to assess immediate (1, 2, 3, and 7 days of exposure) and delayed (7 days post-exposure) mortality. For P. truncatus, after 7 days of exposure, immediate mortality ranged between 35.6% and 53.3% the first week while the sixth week ranged from 12.2% to 27.8% after a gradual decrease the weeks in-between. Similarly, at the same exposure interval, the tested doses of etofenprox killed 36.7–62.2% of R. dominica the first week while 20.0–41.1% the sixth week. Etofenprox provided the highest mortality rates against T. granarium adults reaching 93.3–97.8% the first week. After a progressive decrease, mortalities ranged from 73.3% to 87.8% the sixth week. Regarding T. granarium larvae, 43.3–63.3% of the exposed individuals died the first week but during the last week mortalities decreased to 13.3–32.2%. Delayed mortality of all tested species/developmental stages was elevated the first week, reaching 100.0% for all tested doses against P. truncatus and T. granarium adults. During the last week, 45 μg/cm2 killed 100.0% of P. truncatus adults, 67.4% of R. dominica adults, and 42.9% and 31.1% of T. granarium adults and larvae respectively. The results indicate that the efficacy of etofenprox on concrete depends on the pest species/developmental stages that are exposed and/or the time that has passed since the application date.

Delayed responses of major stored-product beetle species after exposure to an alpha-cypermethrin-coated net

Carifend® is an alpha-cypermethrin-coated net that has been evaluated with success for the control of insects that infest stored tobacco. More recent data indicate that nets that contain insecticides can be further utilized against a wide range of stored-product insect species in different application scenarios. The aim of the current study was to evaluate Carifend® against adults of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), the granary weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae), the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae), the saw-toothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae), and the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). Adults of these species were exposed to dishes containing Carifend® for 2, 8 and 24 h, and then they were transferred to untreated dishes, where mortality was recorded 7 d later. In most of the cases, the duration of the initial exposure increased mortality, but, in general, mortality was further increased after the termination of the post-exposure interval. Among the species tested, T. confusum was found to be the least susceptible to Carifend®. For instance, the mortality level was 5.5% for T. confusum even 7 d after exposure, while for P. truncatus it was 100%. The results of the present study clearly demonstrate that Carifend® can be an effective tool against a wide range of major stored-product beetle species, even at exposures that last for <24 h.