Prostephanus Truncatus Research Articles

Reproductive performance of the larger grain borer Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on three different food hosts

The reproductive performance, damage and weight loss of the Larger Grain Borer (LGB), Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on three food hosts namely cassava (TMS 30572, TME 419 and TMS98/0505), maize (SUWAN-1-SR-Y, BR 9943-DMR-SR and 2009 TZEWDT STR) and wood (Albizia glaberrima, Gmelina arborea and Tectona grandis) were investigated. Samples of 100g of the food host were weighed in four replicates into 250ml Kilner® jar and infested with 10 pairs of 1-5 day old LGB. The developmental period of LGB on each of the food host was noted and recorded. Similarly, weight loss and weight of damaged grains was determined as basis for determining the susceptibility of the food hosts to LGB infestation. Proximate composition of infested and un- infested food hosts of LGB were determined following the analytical procedures. Maize was the most preferred host, followed by cassava as indicated by the high number of adult LGB and grain damage recorded on them. The development of LGB was completed on all maize and cassava varieties but not on any of the wood species examined. Percent damage, weight loss, and percent dust were significantly (P<0.05) different among the food hosts. The mean percent damage (79.0), percent weight loss (57.0) and percent dust (25.0) recorded in cassava variety-TMS30572 was significantly (p<0.05) higher than on other food hosts. No weight loss was recorded on T. grandis. This study revealed the ability of P. truncatus to breed and feed on the maize and cassava varieties with no evidence of breeding on the three wood species. Carbohydrate contents were higher in the most preferred food host, maize (70.91) and less preferred food, cassava (82.02) than non-preferred wood species (13.56), indicating that carbohydrate was an essential component in most preferred food. Infestation of LGB caused significant reduction (P<0.05) in the nutritional component of the food hosts. This study showed that LGB still remains an economically important insect pest of maize and cassava. Considering the importance of these two crops to the livelihood of smallholder farmers, appropriate monitoring and control measures should therefore be put in place to safe guard maize and cassava from the ravages of this pest for the attendant enhancement of food security in Nigeria.

Interspecific Competition and Grain-Hosts Selection of Maize Weevil, <i>Sitophilus zeamais</i> (Motsch.) (Coleoptera; Dryophtoridae) and Larger Grain Borer, <i>Prostephanus truncatus</i> (Horn) (Coleoptera; Bostrichidae)

Laboratory interspecific competition and grain-hosts selection experiments involving maize weevil (MW), Sitophilus zeamais (Motsch.) and larger grain borer (LGB), Prostephanus truncatus (Horn) were performed under ambient temperature and relative humidity (25°C - 35°C and 70% - 80% relative humidity) in their major host cereal, maize grains. The species reproductive rate and grain-hosts preference were evaluated by a number of emerged adults. In combined infestation, both species competed intensively by simultaneously increasing their individuals’ emergence, 9-fold or greater than when reared alone. Even though both species simultaneously increased their progeny, S. zeamais was the dominant competitor and had a significant suppressant effect on P. truncatus. The selection result of grain-hosts showed that P. truncatus placed in the environment containing both uninfested maize grains and grains previously infested by S. zeamais, the insect prefers uninfested grains. Indeed, P. truncatus individuals’ emergences were significantly more important to uninfested grains than to infested grains. The weevil-infested grains seemed to have deterrent and detrimental effects on P. truncatus. Conversely, S. zeamais selection of grain-hosts was significantly (P = 0.0001) more attracted by P. truncatus infested grains than to uninfested grains. Sitophilus zeamais individuals’ emergences were significantly (P = 0.0008) more important to infested grains than to uninfested grains. The S. zeamais preference on grains previously infested would be stimulated by P. truncatus larval vibrations in grain.

Evaluation of alternatives to synthetic pesticides under small-scale farmer-managed grain storage conditions

Reducing farm-level grain storage losses for small-scale rural farmers is important for sustainable household food security in Africa. Farmer-managed trials were conducted over two 32-week grain storage seasons in Zimbabwe to evaluate the effectiveness of diatomaceous earths (DEs); Protect-It® and Chemutsi (raw local DE), enhanced with low doses of deltamethrin or spinosad as protectants of stored maize grain for control of major storage pests: Sitophilus zeamais, Prostephanus truncatus, Tribolium castaneum and Sitotroga cerealella. Five combinations of DE-spinosad and DE-deltamethrin were compared against a commercial insecticide mixture of pirimiphos-methyl + deltamethrin and an untreated control. Treatment effects on insect numbers, grain damage and weight loss, and grain moisture content were assessed at 8-week intervals. Protect-It® 0.1% + deltamethrin 0.0005% w/w, Protect-It® 0.05% + spinosad 0.005% w/w, and Chemutsi 0.1% + spinosad 0.0075% w/w were the most effective (P < 0.001) treatments when all efficacy parameters were considered. These low-dose DE-based combinations have potential to replace organophosphate-based commercial grain protectants currently used in small-scale grain storage systems and thus contribute towards improved household food security and safety in Africa.

Residual toxicity of a commercial cypermethrin formulation on grains against four major storage beetles

In the present study, we investigated the residual insecticidal efficacy of a commercial cypermethrin formulation applied on grains (wheat, maize) against adults of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.) and Prostephanus truncatus (Horn) in laboratory bioassays. The insecticide was applied in its label dose on the grains and a bioassay was initiated at the day of application and every month for four consecutive months (5 bioassays in total). In each bioassay, adult mortality levels were determined after exposure for 7, 14 and 21 d. After the final evaluation, all beetles (dead and alive) were removed and the number of offspring was assessed after an additional interval of 65 d. Based on our results, the application of the tested cypermethrin formulation as a grain protectant provided long-term protection against R. dominica and P. truncatus adults, as in most cases complete control was achieved for these two species, even after four months of storage of the treated commodities. In the case of S. oryzae and O. surinamensis, adult mortality did not reach 100% in any of the cases, moreover, a gradual decline of mortality levels was recorded over the 4-month period of storage. Finally, for S. oryzae and P. truncatus progeny production was notably suppressed by cypermethrin. Results show that the cypermethrin formulation tested could be a valuable tool for stored grain protection, however, factors such as the target species and the storage interval should be taken into consideration.

Physical factors in the hermetic SuperGrainBag® and effect on the larger grain borer [Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)] and aflatoxin production by Aspergillus flavus during the storage of ‘Obatanpa’ maize (Zea mays L.) variety

Controlling invasive pests and aflatoxin production by moulds in stored grains is a global challenge to food security and public health, particularly in Africa. Food storage systems are designed to provide constraints to spoilage organisms by presenting mechanical barrier or unfavourable atmospheric conditions to their growth and productivity. This study examined the physical factors generated in hermetic SuperGrainBags® during the storage of ‘Obatanpa’ variety of maize (Zea mays L.) and the effect on growth of the larger grain borer Prostephanus truncatus (Horn) and aflatoxin contamination by Aspergillus flavus. Cultured P. truncatus or A. flavus was introduced into 1.5 kg of the dried maize and stored in either hermetic SuperGrainBags® or non-hermetic polypropylene bags. The hermetic conditions elicited an increase in the interstitial temperature (ca. 27 °C) but a decrease in the relative humidity (<70%), oxygen concentration (<6.4%) and the grain moisture content (<13.7%), the combined effects of which inhibited growth of the insects and aflatoxin production by the moulds. Total mortality of P. truncatus occurred after 52 d of storage in the SuperGrainBags® while aflatoxins concentration remained within safe limits for human consumption. In contrast, there was proliferous growth of P. truncatus and significant increase in aflatoxin concentration to lethargic levels within the polypropylene bags where temperature, relative humidity and grain moisture increased significantly. Accordingly, grain damage and weight loss percentages were significantly high in the polypropylene bags while that in the SuperGrainBags® were negligible. Altogether, the SuperGrainBags® better preserved the maize grain quality and safeguarded it against health risks than the polypropylene bags.

Efficacy of phosphine and insect penetration ability in ZeroFly® bags

The deltamethrin incorporated woven polypropylene ZeroFly® storage bag is a promising novel technology for grain storage. However, if grain stored in ZeroFly bags gets infested and has to be fumigated using phosphine (PH3), data on the effectiveness of such treatments are needed. Additionally, obtaining field data on ability of stored-product insect pests to breach ZeroFly bags would facilitate insect management. Therefore, efficacy of PH3 in immature and adult Sitophilus zeamais (Motschulsky), Prostephanus truncatus (Horn), Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst) in experimental cages in maize stored in 100-kg polypropylene (PP), jute and ZeroFly bags was investigated. Post-fumigation mortality of adults was recorded after 7 d, and after 7 wk for immatures. The ability of either S. zeamais or P. truncatus to penetrate fabric of PP, jute and ZeroFly bags was assessed. Phosphine efficacy was good in all the three types of bags and resulted in complete mortality of adults and immatures of the four species tested. Sitophilus zeamais and P. truncatus were more successful in penetrating the PP bag fabric and on average made 84 and 780 holes per bag over a 4 mo-period, respectively; this was followed by jute with 37 and 614 holes. The ZeroFly bag was harder to breach and ≤3 holes per bag were made for both species. This study shows that PH3 is highly efficacious in insects that infest maize stored in ZeroFly bags, and that these bags are not easily penetrated by stored product insect pests. Hitherto, ZeroFly bags are a good technology for storing grain that is not infested, and fumigation using PH3 can be effectively conducted if infestation occurs. Therefore, ZeroFly bags can be incorporated in integrated stored product insect management (IPM) programs for bagged grains.

Modeling the potential range expansion of larger grain borer, Prostephanus truncatus (Coleoptera: Bostrichidae)

Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), is a beetle that is a member of a family that is primarily comprised of wood-boring insects, including forest insect pests. It is native to Mexico and Central America, where it has adapted to become a pest of stored maize. It was accidentally introduced into Africa in late 1970s, where it quickly spread throughout the sub-Saharan region, perhaps aided by adaptation to alternate hosts and the ability to persist in non-agricultural habitats. We used the correlative modelling algorithm, MaxEnt, to identify global areas of potential high suitability based on the climate locations with documented populations. Predictions using a model trained in Mexico + Central America showed potential high climatic suitability extending north into the southern United States and southward into South America, including parts of Argentina, but predictions using a model built from African occurrences did not include those areas as highly suitable. However, there was general agreement in both models that large areas of the tropics in the Western Hemisphere and in Asia have climatic conditions that could support P. truncatus if it were to become established. The models also showed consistency in capturing potential suitability at sites not used to build a given model. Results can be used as an initial guide to establish surveillance programs to monitor for this insect in high risk areas where it is not currently found, and to proactively mitigate the biosecurity risk from P. truncatus.

Acoustic, Pitfall Trap, and Visual Surveys of Stored Product Insect Pests in Kenyan Warehouses.

Grain production is an important component of food security in Kenya but due to environmental conditions that favor rapid growth of insect populations, farmers and other agricultural stakeholders face ongoing and novel challenges from crop and stored product pest insects. To assist development of methods to reduce economic losses from stored product insect pests in Kenya, acoustic, visual, and pitfall trap surveys were conducted in five grain storage warehouses. Two commercially available acoustic systems successfully detected the pests of greatest economic importance, Sitophilus zeamais (Motschulsky) and Prostephanus truncatus (Horn). Other insects of lesser economic importance also were observed in the visual surveys, including Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), and Tribolium castaneum (Herbst). This study demonstrated that the use of acoustic technology with visual surveys and pitfall traps can help managers to identify and target infestations within their warehouses, enabling them to reduce postharvest losses. With most warehouses being located in relatively noisy urban or peri-urban areas, background noise considerations are being incorporated into the design of future acoustic detectors for stored pest infestations. Kenya must import grain yearly to meet consumption needs; however, if the current yearly postharvest losses of 20–30% in warehouses decreased, import costs could be reduced considerably.

Suitability of Wild Host Plants and Firewood as Hosts of Prostephanus truncatus (Coleoptera: Bostrichidae) in Mozambique.

Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) populations are maintained in wild host plants such as trees that act as pest reservoirs from where beetle infestation of maize granaries take place. In this study, we assessed the suitability of plant species sold and transported as firewood as well as other plant species in Mozambique as hosts for P. truncatus. Prostephanus truncatus was only recorded from three tree species, which are sold as firewood, i.e., Brachystegia spiciformis, Strychnos spinosa, and Colophospermum mopane. The pest survived and bred in 13 tree and 7 grass species. Dry wood of several tree species and the grasses Acroceras macrum and Hyparrhenia hirta were suitable hosts for pest development. Sale and transport of certain firewood species may be an important driver of the spread of this pest. The importance of dry maize stalks and several grass species in sustaining pest populations is described for the first time. Several grass species are used as thatch or fencing material and, together with maize crop residues close to small-scale granaries, may provide significant sources of beetle infestation.

Occurrence and Control of Prostephanus truncatus (Coleoptera: Bostrichidae) on Stored Dried Cassava Chips in Southwestern, Nigeria

Occurrence and Control of Prostephanus truncatus (Coleoptera: Bostrichidae) on Stored Dried Cassava Chips in Southwestern, Nigeria

Insecticidal efficacy of a binary combination of cyphenothrin and prallethrin, applied as surface treatment against four major stored-product insects

In the present study, we investigated the insecticidal efficacy of a commercial binary combination of two pyrethroids, cyphenothrin and prallethrin, as structural treatment against adults of Sitophilus oryzae (L.), Oryzaephilus surinamensis (L.), Tribolium confusum Jacquelin du Val and Prostephanus truncatus (Horn) in laboratory bioassays. In a first series of bioassays, the insecticide was applied at its label dose on concrete and metal surfaces, whereas mortality and knockdown levels were recorded after 1, 3, 7 and 14 d of exposure. In a second series of bioassays, the residual efficacy of the insecticide was evaluated on concrete for a period of four months, stored either in continuous darkness or exposed to light. In these bioassays, mortality and knockdown of the exposed insects was measured after 3, 7 and 14 d of exposure. Finally, in a third series of bioassays, we investigated the immediate and delayed effect of the tested formulation on adults of the four insect species after exposure for 1, 3 and 7 d. Based on our results, the application of the tested insecticide as surface treatment can provide efficient control against adults of all four species tested. The surface type did not significantly affect the insecticidal efficacy of the tested formulation, at least for the surfaces tested. Moreover, exposure to light negatively affected the residual activity of the insecticide, as for all insect species tested, mortality was significantly lower on dishes exposed to light than on the ones stored in the dark for storage intervals equal or longer than two months. Finally, reduced delayed mortality was observed for all exposure intervals, as knocked down individuals remained, in most cases, knocked down even 7 d after their removal from the treated dishes.

Evaluation of the suitability and optimal use of postharvest storage bag technologies and a combination thereof for maize storage in Nigeria.

The severity of postharvest losses varies considerably depending on storage method and prevalence of storage insect pests known to bore into storage bags. Polypropylene (PP) bags used by smallholder farmers in Nigeria do not provide effective protection for stored produce due to insect boring activities. Deltamethrin incorporated polypropylene, ZeroFly® (ZF) and ZeroFly® Hermetic Storage Bags are technologies with potential to improve protection of stored food commodities against insect attack. Therefore, a 12-month study was conducted in Ibadan, Nigeria to determine the suitability and potential of combined postharvest bag technologies involving ZeroFly® (hermetic and non-hermetic) bags for smallholder farmers when exposed to Sitophilus zeamais and Prostephanus truncatus infestation pressure. Cleaned but un-fumigated 50-kg lots of maize were used to fill bags in each of the following 8 treatments — PP and ZF bags alone, diatomaceous earth-treated maize in PP and ZF bags, single and double hermetic liners in ZF bags, single hermetic liner in PP bags and lastly PICS bags. Results obtained over a 12-month period showed infestation by S. zeamais, Tribolium castaneum, Cryptolestes ferrugineus and Liposcelis spp. and abundance of insect increased with storage period in PP and ZF bags without liner. The percentages of insect damaged kernels by number (IDK) were higher in PP and ZF bags without liner and were 5.4 and 16.9%, respectively; in ZeroFly bags with hermetic liners, these values were ~ 0.5%. The PP and ZF bags without liner also had higher weight loss values of 1.4 and 6.7%, respectively compared with ZeroFly bags with hermetic liners and PICS bags which had a relatively lower weight loss of =0.2%. These results indicate that the ZeroFly Hermetic bag mitigates insect infestations, thereby offering a suitable alternative towards achieving significant reduction in postharvest losses during storage.

Insecticide treated packaging for the control of stored product insects

Improper or poor post-harvest handling and storage of stored grains contributes significantly to product loss, and bagged stored grain presents an option for safe storage and handling. Bagged grain is intended to maintain quality and safety, while protecting it from infestations. The objective of this research was to determine the effect of deltamethrin-treated packaging material on adults and larvae of common stored product pests. Adults or larvae of several species of stored product insects were exposed to deltamethrin-treated packaging for time intervals ranging from 1 h to 4 weeks. The percentage of affected Prostephanus truncatus, Callosobruchus maculatus and Rhyzopertha dominica adults was 96% larval death within 1-2 weeks.The major primary stored product insects were highly susceptible to the deltamethrin-treated storage bags, but there was variation in susceptibility between species and life stages tested. The deltamethrin-treated storage bags can offer protection of bagged grains and be used as a preventative measure to reduce infestations during storage.

Maize Grain Stored in Hermetic Bags: Effect of Moisture and Pest Infestation on Grain Quality

Maize (Zea mays) is an important staple food crop produced by the majority of smallholder farmers that provides household food security through direct consumption and income generation. However, postharvest grain losses caused by insect pests during storage pose a major constraint to household food security. Hermetic storage technology is an alternative method that minimises postharvest losses by depleting oxygen and increasing carbon dioxide levels within the storage container through metabolic respiration of the grains, insects, and microorganism. Maize grain was stored for 180 days in hermetic bags or open-weave polypropylene bags to compare quality preservation when subject to initial grain moisture contents of 12, 14, 16, and 18 percent and infestation by Sitophilus zeamais. The moisture content of grain in hermetic bags remained unchanged while in polypropylene bags decreased. Dry grains (12% moisture content) stored well in hermetic bags and suffered 1.2% weight loss while for equivalent grains in polypropylene bags the weight loss was 35.8%. Moist grains (18% moisture content) recorded the lowest insect density (7 adults/kg grain) in hermetic bags while polypropylene bags had the highest (1273 adults/kg grain). Hermetic and polypropylene bags recorded the lowest (0–4 adults/kg grain) and highest (16–41 adults/kg grain) Prostephanus truncatus population, respectively. Discoloured grains were 4, 6, and 12 times more in grains at 14, 16, and 18 than 12 percent moisture content in hermetic bags. Grains at 18% moisture content recorded significantly lower oxygen (10.2%) and higher carbon dioxide (18.9%) levels. Holes made by P. truncatus in the hermetic bags were observed. In conclusion, storage of moist grains (14–18% moisture content) in hermetic bags may pose health risk due to grain discolouration caused by fungal growth that produces mycotoxins if the grains enter the food chain. The study was on only one site which was hot and dry and further investigation under cool, hot, and humid conditions is required.

Do temperature, relative humidity and interspecific competition alter the population size and the damage potential of stored-product insect pests? A hierarchical multilevel modeling approach

The premises of stored agricultural products and food consists of a complex ecosystem in which several pests can seriously affect the quality and quantity of the products. In this study we utilize a 4-level hierarchical linear multilevel model in order to assess the effect of temperature, relative humidity (RH) and interspecific competition on the population size and damage potential of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) and the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). As RH was increased, we observed higher percentage of live insects, while increased levels of temperature significantly decreased the percentage of live insects. The combination of R. dominica and P. truncatus lead to reduction of the percentages of live insects in comparison to single species treatments. However, P. truncatus is more damaging than R. dominica in maize, based on the proportion of damaged kernels which were infested by each insect species. We expect our results to have bearing in the management of these species.

High quality genomic resources for stored product insects

The expansion of genomic resources for stored product insects has largely been hampered by cost, time required for inbreeding, and technical issues that can arise during genome assembly from pooling multiple individuals together for DNA isolation and library preparation. However, newer library methods, such as 10X Chromium libraries, largely overcome these issues in that sufficient DNA can be recovered from a single individual for library prep and allelic variants are assembled as separate phase blocks, eliminating the need for inbreeding. Using 10X Chromium libraries coupled with 150 x 150 bp HiSeqX sequencing to a depth of at least 60X coverage, we are developing high quality draft genome assemblies for eight different stored product insect species, including Dermestidae (Trogoderma variabile, Trogoderma granarium, and Dermestes maculatus), Tenebrionidae (Tribolium confusum), Anobiidae (Lasioderma serricorne and Stegobium paniceum), Bostrichidae (Prostephanus truncatus), and Pyralidae (Plodia interpunctella). Overall, BUSCO (Benchmarking Using Single Copy Orthologs) scores exceeded 95% in all assemblies with few fragmented or duplicated genes, suggesting a high quality assembly of the gene space. Further, scaffold N50s exceeded 1 Mb in many cases and further improvements to these scaffolding metrics will be made using linkage maps and Hi-C libraries. Overall, this approach will yield high quality assemblies for eight different insects and could be used to quickly and efficiently generate draft assemblies of invasive or emerging stored product pests.

Evaluation of AgroZ Hermetic Storage Bag against insect pests on stored maize

A study on AgroZ airtight bag was conducted against two major storage insects under simulated farmers' storage practice. Two (2) lots of 50kg white maize of Pioneer variety were put into AgroZ bag and polypropylene woven bag to serve as a control. Four replications of each bag type were used. In each bag, 50 adults of unsexed larger grain borer, Prostephanus truncatus, and maize weevil, Sitophilus zeamais, each were introduced. AgroZ bag had one liner placed inside polypropylene bag to provide support and handling convenience. Each liner had been tested for air tightness before use. The AgroZ bags were securely tied to ensure airtightness thus leading to a hermetic environment. The bags were then randomly placed in a barn on pallets in a randomised complete design (RCD). Sampling was done every 4 weeks up to 24 weeks. A 500g sample was initially taken using a compartmented long spear probe from each bag for baseline data, and subsequent ones at 4, 8, 12, 20 and 24 weeks. Repeated sampling from the same storage device reflected farmer practices of opening the device at regular intervals to draw grain for use as household food. Gas analysis in AgroZ bags showed oxygen level dropping rapidly to 7% within 4 weeks and later increased gradually to 10% at 12 weeks. Conversely, carbon dioxide level increased sharply to 10% and declined gradually to 9% over the same period. The number of insects and percentage damaged grains between AgroZ bag and polypropylene bag significantly differed from 12th week to 24th week. AgroZ bag outperformed the polypropylene bag commonly used by farmers and conveniently protected maize from insect infestation within the 6-month storage period.

Insect infestation sources in stored maize grain; what is more important resident versus incoming infestation?

Most studies targeted pest control inside stores; incognisant of the population dynamics in the store vicinity; leading to product re-infestation. Distinction between storage insect pest source and sink grain patches is important for effective pest management strategies. We examined the role of resident versus incoming insect infestation in phosphine-fumigated closed or open and unfumigated closed or open maize farm stores. Grain quality measurements were recorded over 32 weeks for two storage seasons. Whether open or closed, fumigated grain had significantly lower (p < 0.001) grain damage and lower grain weight loss (p < 0.05) than unfumigated grain. Fumigated open stores had significantly higher (p= 0.004) grain damage and weight loss than closed ones. Grain damage was higher in unfumigated-closed than fumigated-open, evidence that resident infestation inflicted higher food loss than incoming infestation. Prostephanus truncatus, Cryptolestes ferrugineus and Tribolium castaneum had significantly higher populations (p < 0.001, p = 0.018 and p = 0.001; respectively) at bottom levels of unfumigated and fumigated grain (T. castaneum). Sitotroga cerealella and Sitophilus zeamais were significantly higher (p < 0.001) at the top of closed than open unfumigated compartments. Grain suffers less infestation and quality loss when it is a sink patch than when it is a source patch. Population build-up and ‘settling’ to inflict significant food loss takes longer for incoming compared to resident infestation. These results have ecological implications on postharvest IPM.

Competition of three stored-product bostrychids on different temperatures and commodities

We evaluated the competition among three species of stored-product Bostryhidae: Rhyzopertha dominica, Prostephanus truncatus and Dinoderus porcellus. In this context, ten adults of each species were placed in vials, either alone or in all possible combinations of two or three species. The experiments were carried out on wheat and maize, at 25 and 30° C. Sixty-five days later, the adult progeny production in the vials was recorded, as well as the weight of damaged and undamaged kernels, the number of grains with more than 1 hole and the weight of frass. On wheat, when each species was alone, progeny production of R. dominica on wheat was, for both temperatures, higher than that for the other two species. There was practically no progeny production on wheat for P. truncatus, but offspring numbers of D. porcellus were, in some cases, comparable with those for R. dominica. In contract, on maize, P. truncatus progeny production was constantly higher than the other two species, regardless of the species’ combination. In general, R. dominica prevailed on wheat, while P. truncatus in maize. However, the simultaneous presence of D. porcellus had a detrimental effect on progeny production of the other two species, while the presence of the other two species increased D. porcellus progeny production, in some of the combinations tested. On wheat and maize, the number of damaged kernels was higher in the combinations that R. dominica and P. truncatus, respectively, were present. When the species were alone, however, D. porcellus produced the higher amount of frass. Paradoxically, despite the absence of P. truncatus progeny on wheat, some damaged kernels were recorded when this species was alone in this commodity. Temperature had no effect on progeny production of D. porcellus. Our results showed that different species of Bostrychidae can coexist in stored grains, and specific displacement conclusions can be drawn according to the commodities and temperatures.

The Use of Mass Trapping to Suppress Population Numbers ofProstephanus truncatus(Horn) (Coleoptera: Bostrichidae) in Small-Scale Farmer Granaries in Mozambique

This study evaluated the potential of mass trapping to reduce Prostephanus truncatus population numbers in granaries and hence its possible utilisation as pest management tool. Universal moth traps (Uni-traps) were used to trap the pest and its predator, Teretrius nigrescens Lewis (Coleoptera: Histeridae), in granaries of small-scale farmers in three villages of the Gaza Province of Mozambique during the maize storage period of August 2013 to January 2014. Five granaries were selected in each village. Two baited pheromone traps were set up adjacent to each of three of these granaries. The other two granaries were used as controls, without traps. Numbers of both the pest and its predator were monitored in these traps as well as in stored maize ears inside the granaries for a 6-month period. Mean numbers and densities of P. truncatus, the percentage damaged maize kernels and maize kernel weight loss in granaries with and without traps were compared by means of t-tests. The Cohen's standard of effect size was applied to measure the magnitude of differences between studied variables. An average of 1272 individuals of P. truncatus was caught per trap. Mean densities of P. truncatus recorded per maize ear in granaries with traps were lower (27 individuals/ear) than of those without traps (129 individuals/ear). Mean numbers of T. nigrescens per trap followed similar patterns between granaries with and without traps. The percentage of damaged maize kernels was higher (62 %) in granaries without traps than in those with traps (22 %). Highly significant negative correlations were found between mean numbers of P. truncatus caught in traps and mean infestation in maize ears inside granaries. These findings indicate that mass trapping holds potential for control of P. truncatus in granaries of small-scale farmers.