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Tribolium castaneum (Herbst), the red flour beetle, is a cosmopolitan stored product insect that infests a variety of raw grains and processed grain products. Although this pest is prevalent in rice mills, there is a comparative lack of data on growth and development on rice by-products and fractions compared to other grains. In this study, ten mixed-sex adults were exposed on 200 g of either rice flour or brown rice, and populations were assessed after 2, 4, 6, 8, and 10 months at 22, 27, or 32 °C. At 22 °C, the number of adults, pupae and larvae on rice flour and brown rice remained low throughout the 12-month storage period. At 27 °C, the number of adults on rice flour increased to a maximum at 8 months, while adult populations on brown rice remained relatively constant from 2 to 10 months, with few pupae or larvae in the samples. At 32 °C, adult populations on rice flour and brown rice were constant after month 2, with low numbers of pupae and larvae. Adult predation could have accounted for low numbers of pupae and larvae. Using the original 10-month data, populations were projected for an additional 14 months to predict population patterns. Adult numbers showed an increase over time at all temperatures on rice flour and brown rice at 22 °C but numbers seemed to stabilize at 27 and 32 °C. For both diets at 27 and 32 °C, projected pupae and larvae numbers remained steady but low compared to adults. However, populations would not be expected to increase indefinitely because at some point the resources would become limited and populations would crash or decline. Results show T. castaneum can deplete fixed resources such as bags of rice flour or brown rice when temperatures equal or exceed 27 °C.

The Solar Biomass Hybrid Dryer (SBHD) is a new technology developed in Ghana for grain drying and utilizes biomass (agro-residues, timber scraps, etc.) along with solar drying, and is especially useful for drying during rainy periods of the year when solar drying cannot be relied on. This study assessed the effectiveness of a 5.0-MT SBHD comprising a solar tent and a furnace for thermal drying and disinfestation of maize. Mortalities of adults of Sitophilus zeamais (Motschulsky), Tribolium castaneum (Herbst) and Cryptolestes ferrugineus Stephens were assessed. Additionally, mortalities of immatures of these three species were assessed. Internal and cage temperatures (°C) in the SBHD, sun drying (SD) and laboratory (control) were monitored, as were moisture content (MC) and thermally (stress) damaged kernels (TDK) (%). During the 7-h experiment, mean internal temperatures in the SBHD, SD and laboratory were 52.3 ± 1.0 °C, 41.4 ± 0.8 °C and 30.3 ± 0.2 °C, respectively. Similarly, temperatures in cages in the SBHD (49.5 ± 1.0 °C) were higher than those for cages in the laboratory (29.9 ± 0.2 °C) and SD (38.2 ± 0.6 °C). Reduction in the moisture content of maize dried using SBHD, SD and under laboratory conditions were 7.7, 5.2 and 2.9%, respectively. This corresponded to grain MC reduction rates of 1.1%, 0.74% and 0.4% per hour. There was 100% mortality of S. zeamais and C. ferrugineus adults achieved in only the SBHD; some immatures of all three species survived in all three treatments. However, survival of immatures was highest in the laboratory, followed by SD and lowest in the SBHD for all three species. Percent TDK was higher in the SBHD (6.7 ± 0.9) than SD (3.3 ± 0.3) and laboratory (2.7 ± 0.3). These data show that the SBHD is effective for both drying and disinfestation of grain.

The insecticidal effect of an aerosol formulation that contained a 100: 1 mixture of pyrethrin and methoprene (by volume), was evaluated for control of nymphs of four stored-product psocid species, Liposcelis bostrychophila, L. decolor, L. entomophila and L. paeta. The aerosol was applied at two particle sizes, 2 and 16 μm. The application time of the aerosols was 0 (untreated controls, no aerosol), 5, 10, 20 and 30 min. Nymphs were examined at 5 days post-treatment. The aerosol was effective on all species tested, with mortality of 100% after 5–20 min, depending on the species. There was a strong interaction between the application time and the particle size. In all cases, the application of the aerosol at 16 μm was more effective than 2 μm for all species. Moreover, the application at 16 μm required less time to reach 100% mortality, suggesting that this particle size may provide a more cost-effective application, as it requires less formulation and a considerably shorter application time. Our results provide the first series of data for the application of aerosols at different particle sizes against stored-product psocids and could be used as a guide for improved management of psocids.

Maize production in Ghana has been increasing steadily but increases in yield are being undermined by post-harvest losses. This study is part of a larger project to characterize post-harvest losses in Ghana at different points in distribution channels. Here we determined factors contributing to losses during on-farm storage in the Northern Region of Ghana. This study was conducted in six communities: Adubiyili, Diari, Pong-Tamale, Savelugu, Toroyili and Zamnayili. Losses were determined for maize on cobs stored in thatched granary structures, shelled maize in polypropylene (PP) bags stored on the floor in farmers’ homes or small storehouses, and shelled maize in PP bags stored in warehouses. Maize moisture content, temperature, percent weight loss, percent insect damaged kernels on numerical basis (IDKnb), insect pest abundance, and mycotoxin (aflatoxin and fumonisin) levels were determined. Moisture content values of maize at pre-harvest and heaping stages in all six communities were below 15% wb. There were no insect pests on maize at the pre-harvest stage and only a few larvae were found in the heaping stage, but Sitophilus spp., Tribolium castaneum and Cryptolestes ferrugineus infested maize during storage, with significantly more found in granary structures than maize in PP bags in homes or storehouses. Warehouses had significantly fewer insects than granaries and homes or storehouses. Percent IDKnb values in all six communities were

Insect pests and fungal pathogens can cause extensive product losses and pose health risks in sub-Saharan Africa. In this experiment, maize stored as de-husked cobs or shelled maize in a ventilated crib and a metal bin, and in bags in warehouses, was monitored monthly in Ghana from October of 2015 to December of 2015 (the major season) and from January to April of 2016 (the minor season). Temperature, moisture content, insect pests, and associated damage were assessed monthly, and samples were taken in October, December, January, and April for mycotoxin analyses. Moisture content, which ranged from 9 to 15% during the year was occasionally greater in the bin and warehouse compared to the crib, and greater in months associated with the major season compared to other months. Temperatures varied with season but were generally warmer in the bin compared to the warehouse and crib. The predominant insect collected was Sitophilus zeamais (Motschulsky), with the lowest populations in the crib, but in each structure the populations were about 10x greater in the major season compared to the minor season. Sitotroga cerealella (Olivier) was the second most-prevalent species, but populations of this species were greater in the crib compared to the bin or warehouse. Scattered populations of other stored product insects were collected from the maize samples and in pheromone traps. Percentage insect damaged kernels (IDK) and weight loss were also greater in samples from months where S. zeamais was present. Aflatoxin was above 10 ppb only in the warehouse in December, while fumonisin levels in all the storage structures were

Contact toxicity of filter cake and Triplex powders from Ethiopia were evaluated against the rice weevil, Sitophilus oryzae (Linnaeus). The study was aimed at determining the lethal and effective concentrations and times for both powders against S. oryzae. The lethal concentrations for 50 and 99% mortality (LC50 and LC99) of filter cake and Triplex against S. oryzae were determined at 14 d after exposing 10 adults for 12 h to concrete arenas inside Petri dishes treated with filter cake concentrations of 0.5–8 g/m2 and Triplex concentrations of 1–9 g/m2. Lethal times for 50 and 99% mortality (LT50 and LT99) were determined at 14 d after exposing adults for 1–24 h to 3 g/m2 of filter cake and 9 g/m2 of Triplex. Effective concentrations (EC50 and EC99) and times (ET50 and ET99) for 50 and 99% reduction of adult progeny production were determined from reduction in adult progeny production relative to production in control treatments at 42 d after exposure to filter cake and Triplex. LC50 and LC99 values for S. oryzae adults were 0.70 and 8.49 g/m2, respectively, when exposed to filter cake and 2.27 and 21.38 g/m2, respectively, when exposed to Triplex. The corresponding LT50 and LT99 values were 3.13 and 27.21 h, respectively, for filter cake and 4.72 and 38.60 h, respectively, for Triplex. EC50 and EC99 values for progeny reduction were 0.57 and 7.95 g/m2, respectively, for filter cake and 2.77 and 18.82 g/m2, respectively, for Triplex. The corresponding ET50 and ET99 values were 2.57 and 17.73 h, respectively for filter cake and 3.39 and 24.74 h, respectively, for Triplex. S. oryzae exposed to filter cake produced significantly less number of insect damaged kernels and grain weight loss than those exposed to Triplex. Filter cake was more efficacious against S. oryzae than Triplex.

Development of Tribolium castaneum (Herbst), the red flour beetle, was assessed on different rice components and their various by-products (i.e., diets) commonly found in rice mills, in two separate experiments. In the first experiment, eggs did not develop through to the adult stage on rough rice hulls, paddy rice dust, and milled rice dust, while eggs developed to the adult stage to some extent on rice flour, milled whole kernels, brown rice, milled broken kernels, and bran. For the diets where development occurred, the lowest percentage was on brown rice, and adults that emerged on brown rice had smaller elytra compared to adults emerging on the other diets. In the second experiment, 1–2-day old neonates were exposed on the diets listed above and held at 22, 27, 32, and 37 °C. At all temperatures, development to the pupal and adult stages was slowest on rice flour. At 22 °C, development to those stages took about twice as long compared to development at 27 °C. As temperature increased developmental times were reduced. Even though neonates developed slowest on rice flour adult emergence rates were not affected. Predictive models were used to estimate potential population development on the diets. At 22 and 27 °C, adult size as measured by elytra length was greatest when they developed on bran, while body weight was generally lowest for adults that developed on brown rice. Results show that T. castaneum can utilize rice components and by-products produced during the rice milling process, although not all components or by-products were optimal for development, and emphasis should be placed on cleaning and sanitation to remove food sources to limit infestations. Mill managers can use these results to show the importance of sanitation, and potentially improve overall pest management programs inside the mill.

Reliable quantitative data on maize post-harvest losses and factors that cause them in northern Ghana are limited. In this study we assessed maize at six markets in the Northern Region of Ghana, in and around Tamale, during the harvest and storage period of October 2015–June 2016. Across all the markets and sampling periods grain temperature was 32.6 ± 0.2 °C and equilibrium moisture content (EMC) was 9.5 ± 0.2%. EMC tended to decrease to a low in January and February and then increased again, while mean maize temperature was above 30 °C in all months. The primary stored product insects collected from the samples were Tribolium castaneum (Herbst), Sitophilus spp., Rhyzopertha dominica (Fauvel), and Cryptolestes ferrugineus (Stephens). Using all the market and sampling month data, there was a significant correlation between EMC and total number of insects recovered, but not between total number of insects and temperature. The average percentage of insect-damaged kernels (IDK) in the maize sampled across all the markets and sampling periods was 2.7 ± 0.2%, with a range between 0 and 21.4%. Using all the market and sampling month data, levels of insect damage tended to be positively correlated with maize moisture, but not temperature, and levels of insect damage increased with number of stored product insects recovered. The action threshold for aflatoxin in maize in Ghana is 15 ppb, but overall mean aflatoxin level was 19.8 ± 1.5 ppb and aflatoxin levels ranged from 0.3 to 132.2 ppb, with 53% of the samples having levels above 15 ppb. The mean fumonisin level was 1.2 ± 0.0 ppm, which is below the 4.0 ppm action threshold for Ghana. Our results show that aflatoxin levels were high in the market maize in Northern Region of Ghana and insects were prevalent, even though grain moisture tended to be relatively low, especially compared to the Middle Belt of Ghana.

The distribution of aerosol applications of pyrethrin + methoprene, generated from a mechanical fogger, and pyrethrin + pyriproxyfen, dispensed from a pressurized cylinder, were characterized inside a pilot-scale flour mill using measurements of particle size and concentration and effects on adult confused flour beetles, Tribolium confusum Jacqueline duVal, in bioassay arenas. Particle measurements were made using TSI Aerodynamic Particle Sizer (APS) units placed in an open straight line at distances of 4.3, 8.9, and 13.5 m from the aerosol release point (open configuration). Measurements were also made using a second configuration (termed obstructed), which was done by moving the APS unit at 8.9 m underneath a piece of equipment, and moving the APS unit at 13.5 m behind a support beam. Actual concentration and calculated deposition were about 4× greater for the pyrethrin + methoprene aerosol compared to the pyrethrin + pyriproxyfen aerosol. However, efficacy was similar since bioassays using adult T. confusum showed no difference in recovery after exposure to either insecticide. Concentration and calculated deposition of both aerosols decreased with increasing distance from the spray release point and when the APS units were in the obstructed configuration, and recovery of bioassay insects after exposure increased with increasing distance from the spray release point. Results from this field trial show how efficacy of aerosol applications is impacted by distance and obstacles, and how use of equipment that measures droplet size and concentration can help quantify the dispersion and spread of insecticidal aerosols. Results also provide guidance to develop relationships between aerosol deposition and efficacy and thus improve pest management programs for structural management of stored product insects.

This study focused on assessing maize post-harvest losses in three maize markets in the Middle Belt of Ghana during the storage periods after the harvest of major and minor cropping seasons, September to December and January to April, respectively. The major and minor cropping seasons in the Middle Belt occur during the periods April to August and September to December, respectively. Storage temperature of bagged maize, grain moisture content (MC), and relative humidity (r.h.) were monitored monthly, along with insect infestations, percentage weight loss of kernels (% WL), the percentage of insect damaged kernels (% IDK), and percentage of discolored grains (% DG). Aflatoxin and fumonisin levels were assessed at the beginning and end of the major and minor crop storage seasons. Cryptolestes ferrugineus (Stephens), Cathartus quadricollis (Guerin-Meneville), Carpophilus dimidiatus (F.), Sitotroga cerealella (Olivier), Tribolium castaneum (Herbst), and Sitophilus zeamais (Motschulsky) were found in all markets. Mean insect infestation levels varied throughout the sampling period and were generally similar in the three markets, but were not correlated with temperature, MC, or r.h. (P ≥ 0.05). Mean % WL, % IDK, and % DG peaked in November and December and were usually correlated with total insect populations (P

Grain moisture content (MC), insect pest infestation and mycotoxin contamination of maize are challenges to food safety and security, especially in the tropics where maize is a staple grain. However, very little documentation is available on the impact of these factors on maize in Ghana. This study focused on post-harvest losses of maize and assessed grain MC, insect pests and mycotoxin (aflatoxin and fumonisin) levels on-farm at three stages, during the major and minor seasons (primary and secondary harvest seasons, respectively). Grain MC decreased significantly from the field stage (17.2–19.0%) to the post-drying stage (12.4–14.2%). The mean grain MC was significantly greater in the major season (20.4%) than in the minor season (12.5%). Maize weevil, Sitophilus zeamais Motschulsky, Angoumois grain moth, Sitotroga cerealella Olivier, square-neck grain beetle, Cathartus quadricollis Guerin-Meneville, and corn sap beetle, Carpophilus dimidiatus Fabricius were the dominant insect species that attacked maize on-farm. Mean numbers of each species were generally significantly greater in the minor season than in the major season, but in both seasons, greater numbers were detected at the heaping stage compared to field and post-drying stages. Percentage insect damaged kernels and weight loss were significantly lower at the field stage than at both the heaped and post-drying stages; statistically similar levels were observed in the latter two stages. Mean aflatoxin (ppb) and fumonisin (ppm) levels were significantly higher in the major season (29.1 ppb, 1.6 ppm) than in the minor season (3.5 ppb, 1.0 ppm). Results showed variation between locations sampled, but in general more insect damage and quality deterioration occurred during the major season compared to the minor season. Farmers should dry immediately after harvest to reduce risk of damage from insect pests and mycotoxins.

Spatial and temporal dynamics of pest populations are an important aspect of effective pest management. However, absolute sampling of some pest populations such as the ham mite, Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae), a serious pest of dry-cured ham, can be difficult. In this study sampling methods were compared and sampling plans were developed for the ham mite. In one experiment, the number of food-baited traps was maintained at four and the number of mites varied from 500 to 10,000 individuals in environmentally-controlled 18-m 2 rooms. The number of mites captured in traps increased linearly as the number of mites released increased. Experiments conducted in simulated ham aging rooms suggested that mites preferred the proximal (closer to the pig's body) to the distal side of the ham. The number of mites captured in traps also varied with trap location relative to hams hung from shelves. There were varying degrees of relationships between the number of mites captured in traps and the sampling methods used, such as counts of mites from the storage rack, vacuum sampling of the floor, and ham sampling. Relationships between absolute counts of mites and the number of mites captured in traps or on specific areas of ham were both moderately strong and significant. Two sampling plans were developed for the mite, and it was determined that an economic threshold close to 1 mite per sample unit on the ham can be estimated with 21 and 40 samples at precision levels of 0.35 and 0.25, respectively, or with 10 ham samples when classifying the mite's infestation level as being above or below an action threshold of 0.43. These sampling plans for the ham mite can facilitate the development and evaluation of cost-effective integrated pest management interventions.

Efficacy of aerosol applications of pyrethrin + methoprene was assessed through emergence of morphologically-normal adults exposed as larvae and through a developmental index. Concrete arenas were treated with aerosol droplets (particles) averaging 2 μm or 16 μm, food material was placed on the arenas at 1–8 weeks post-treatment, and 3-4-week-old larvae of one of four stored product insect species placed on the arenas at the same time. No exposed Lasioderma serricorne (F.) larvae reached the adult stage at either particle size, though they developed further when exposed to residual deposits of the 2 μm aerosol particles compared to residual deposits of 16 μm particles. No exposed larvae of either Tribolium confusum Jacqueline duVal or Trogoderma variabile (Ballion) reached the adult stage when exposed to residues of the 16 μm particles, but most of the larvae exposed to the 2 μm residues completed development. Exposed Dermestes maculatus (DeGeer) larvae completed development to the adult stage after exposure to both particle sizes, indicating low susceptibility to methoprene residues. When food material in the arenas was also treated with the two particle sizes and bioassays conducted using only larvae of L. serricorne, T. confusum, and T. variabile, results were similar to those described above. In a final experiment, only the 16 μm particle size aerosol was used to treat arenas with or without food, with arenas without food having it added one day after treatment. At 1–8 weeks post-treatment, the food was transferred to new untreated arenas and food was replaced in the arenas originally treated with aerosol. Bioassays were conducted using only larvae of T. confusum and T. variabile. The food material blocked deposition of the aerosol on the arenas or absorbed some of the residues, indicating transference of the methoprene residues from the treated surfaces onto the food.

Electronic nose (E-nose) technology has a potential to be used for detecting insects in stored rice. It may provide a new method to detect the insect activity by providing smell prints for the headspace volatiles in rice mass. The objective of this research was to study the feasibility of using E-nose to detect infested rice during the storage process. An E-nose instrument (Cyranose 320) consisting of 32 sensors for detecting the volatile components produced in infested rice was used for this study. Storage rice with moisture content of 11.8 ± 0.3% was used for conducting the tests. The rice samples were infested with different numbers of adult insects, including rice weevil (Sitophilus oryzae), lesser grain borer (Rhyzopertha dominica) and red flour beetle (Tribolium castaneum), in containers containing 1 kg of rice. The samples were stored at temperatures of 15 °C and 30 °C for four weeks. Air samples in the containers were taken for measurements every five days. The data were analyzed using the principal component analysis (PCA) method. The results revealed that the E-nose was not able to distinguish the clean rice and infested rice with lesser grain borer. While the E-nose had high response ability to the volatile components produced by rice weevil and red flour beetle after four weeks of storage. Consequently, the E-nose could discriminate the clean and infested rice with above insects after four weeks of storage at temperature of 30 °C. Additionally, under the aforementioned conditions, the E-nose could not distinguish the clean and infested rice during the first, second and third weeks of storage. The classification accuracy of E-nose for clean and infested rice was low at storage temperature of 15 °C for the tested insets. It can be concluded that the E-nose has the capability to detect infested rice after four weeks of storage.

Within integrated pest management options, fumigation of stored products is one method to help control post-harvest insect infestations in our food and agricultural products. Fumigant gas concentration monitoring is important to confirm that the treatment was adequate to achieve the desired insect control, but monitoring can be relatively expensive and labor intensive. This study evaluated how accurately dosimeter tubes could monitor phosphine fumigation treatments. The dosimeter tube is designed to continuously react with phosphine gas during the fumigation period and yields a measurement in terms of concentration ∗ time product or CT, which can be interpreted as cumulative exposure. Two models of dosimeter tubes were evaluated (high range and low range). The reference method for these trials were wireless phosphine monitoring sensors, which recorded gas concentrations at hourly intervals during an exposure, and from this a CT product was also calculated. Model LPG-1, high-range dosimeter tube, measured within ± 25% of the phosphine monitoring sensors for CT dosages less the 70,000 ppm∗hr. Model LPG-2, low-range tube, tended to significantly over-estimate phosphine CT dosage by 50%–100% of the phosphine monitoring sensor references. Secondly, bioassays of fumigant efficacy were performed using susceptible and resistant adult Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), lesser grain borers, and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), red flour beetle, for estimating insect control at the varied fumigation CT treatments. For the susceptible strains, CT dosages ∼5000 ppm∗hr controlled both species. However, the insect control varied from 60% to 100% for resistant adults at CT dosages of ∼20,000 ppm∗hr. The dosimeter tubes function in these ranges of dosages where each insect species are controlled and the dosimeter tube model LPG-1 provides reasonable estimates of the fumigation dosage for a given treatment level.

To detect popcorn kernels infested by the internal feeding stored-product insect pest Sitophilus zeamais , maize weevil, a laboratory roller mill was modified so that the electrical conductivity of the grain is measured while the kernels are milled between the rolls. When a kernel with a S. zeamais larvae inside is milled, the moisture from the crushed insect abruptly changes the conductivity of the test circuit. The objective of this study was to determine the potential of the modified conductance mill to detect popcorn infested with different developmental stages. Two laboratory milling units were tested that had differing sharpness, which affected the feed-rate through the rolls. One mill averaged 135 s to feed 1 kg of popcorn while the second mill with sharper teeth averaged 100 s to feed 1 kg of popcorn. Four popcorn varieties were evaluated, with their average kernel weight ranging from 12.5 g to 18.5 g per 100 kernels. Known numbers of infested popcorn kernels were added to 1 kg samples of popcorn. The slower feeding mill detected 81% of the pupae, 91% of the medium larvae, and 47% of the small larvae. The faster feeding mill detected 75% of the pupae, 80% of the medium larvae, and 43% of the small larvae. Our results indicate that the conductance mill is a good method for quickly evaluating popcorn samples for kernels infested with late stage larvae and pupae.

The occurrence of horizontal transfer of the insect growth regulator (IGR) methoprene on confined populations of Tribolium castaneum (Herbst), either with or without hidden refugia, was determined through a series of experiments. Multiple applications were made with the IGR alone or combined with synergized pyrethrin, and compared to untreated controls which received no insecticide applications or were treated with the carrier Isopar M that was a component of the pyrethrin formulation. The total number of living beetles from test colonies inoculated with adults that were treated with Isopar M or with no adults (control) was significantly greater than those colonies that were inoculated with adults treated with either synergized pyrethrin or methoprene (P

The dispersal of aerosol insecticides within a flour mill may be hampered by barriers created from machinery and other equipment that block dispersion. Additionally, seasonal temperature variations may influence aerosol dispersion and subsequent effectiveness against stored product insects. The influence of barriers and temperatures on the efficacy of synergized pyrethrin aerosol against adults and pupae of the confused flour beetle, Tribolium confusum (Jacquelin du Val), was evaluated in experimental sheds. Insects were exposed to the aerosol at target temperatures of 22, 27, and 32 °C. Wooden boxes 1 m in length, 20 cm in width, and 5, 10, or 20 cm in height were used for creating different open and concealed areas for exposing insects. Results showed that exposing adults of T. confusum in open areas produced more moribund adults (those knocked down and unable to move except for reflex twitching or unable to respond when touched with a probe) at all temperatures, while survival increased with increasing distance from the front to the back of the boxes. Given the decreased survival, it would appear that more aerosol dispersed under the box height of 20 cm compared to 5 and 10 cm box heights because survival was generally less under the 20 cm box compared to the other two. Less than 2% of the pupae exposed in the open emerged as adults, but as the distance increased from the front to the back of the box adult emergence from these exposed pupae increased. Synergized pyrethrin aerosol can provide good control of T. confusum pupae and adults and may not be affected by seasonal temperature variations, but aerosol dispersion into obstructed or concealed areas may affect control.

Psocids can cause considerable economic losses to stored products by direct feeding, and they have become global pests during the last two decades. We studied the distribution of Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae), Liposcelis entomophila (Enderlein), and Liposcelis brunnea Motschulsky in different moisture gradients (11–12–13%, 11–13–15%, and 13–14–15%) and a control (13–13–13%) in wheat using a circular metal arena, which has a removable metal divider that partitioned it into three rings (outer, middle and inner). Lipsocelis bostrychophila and L. entomophila preferred grain with the highest moisture content in the different gradients evaluated. In general, populations of Liposcelis brunnea equally preferred grain with moisture contents greater than or equal to 13%. These results showed the moisture contents preferred for three of the main psocid pests of stored grains, and this could help in making better pest management decisions.

Experiments were performed to determine the relative impact of different mechanisms of methoprene horizontal transfer between Tribolium castaneum (Herbst) individuals. Larvae provided during later development with only dead methoprene-treated developmental stages (late-stage larvae, pupae, or adults) resulted in no survival to adulthood. This suggests that transfer through cuticle contact could be involved, but some cannibalization also occurred. The average level of cannibalization was not different between methoprene and control treatments, but the distribution of the amount of feeding did appear to be shifted to greater consumption by larvae exposed to methoprene-treated individuals compared to water-treated. The potential impact of cannibalism on horizontal transfer was further evaluated by scoring the level of feeding by untreated larvae on either water or methoprene-treated pupa and then comparing larval development and survival after different levels of cannibalization. In this experiment, the level of feeding on methoprene-treated individuals did not affect the percentage of normal surviving adults (insects which emerged as adults, exhibited no external morphological malformations, and were alive at the end of the observational period), suggesting that consumption of treated individuals was not contributing significantly to horizontal transfer. Short-term confinement of a methoprene or water treated adult with an untreated late-stage larva did not effect larval development and survival compared to the controls, indicating that brief contact between individuals was not sufficient for detectable negative effects. Transfer of methoprene from treated individuals to a flour substrate and then to an untreated individual through contact with and/or feeding on the flour was evaluated. Exposure of larvae to methoprene-contaminated flour during development resulted in a significantly lower number of normal surviving adults compared to controls. These results suggest that horizontal transfer of methoprene is probably due to prolonged contact with methoprene-treated individuals or methoprene-contaminated flour.

In food facilities the majority of insect populations typically occur within hidden locations with limited direct exposure to insecticides, but there is potential for dispersing insects to transport insecticides into hidden areas and transfer insecticide to other individuals (i.e., horizontal transfer). In a series of laboratory experiments, the potential for transfer of the insect growth regulator methoprene between treated and untreated Tribolium castaneum (Herbst) and Tribolium confusum (Jacquelin du Val) individuals was evaluated. In the first experiment, late-instar larvae were exposed to methoprene or water treated individuals in flour and their ability to develop successfully was determined. For T. castaneum , survival time for individuals exposed to methoprene treated individuals was shorter than those exposed to control individuals, but the difference was not significant for T. confusum . For both T. castaneum and T. confusum , the number of individuals that were able to successfully survive exposure and complete development without externally visible deformities was significantly reduced for individuals exposed to methoprene treated pupae or larvae relative to controls, but not when exposed to methoprene treated adults. In the second experiment, early-stage larvae, late-stage larvae, and pupae were similar in susceptibility to horizontal transfer of methoprene, even though they were exposed as immatures for different lengths of time. In a third experiment, the potential for sublethal effects due to horizontal transfer of methoprene was evaluated, but no difference in reproduction and oviposition was found for normal appearing adults that developed when exposed to methoprene treated or and control individuals. This is the first report indicating that methoprene can be transferred between stored-product insects and further research is needed to determine the impact this potentially has on pest populations.

The red flour beetle (Tribolium castaneum Herbst) and the confused flour beetle (Tribolium confusum Jacquelin du Val) are among the most commonly encountered insects infesting stored food, but their susceptibilities to different insecticides often differ significantly, which complicates efforts to manage populations in milling and processing facilities. In this study, the susceptibilities of T. castaneum and T. confusum late-stage larvae to five selected insecticides, esfenvalerate, pyrethrins, dichlorvos, methoprene and pyriproxyfen, were assessed with and without synergists using topical applications. In four-day bioassays (without flour) with dichlorvos, esfenvalerate and pyrethrins, T. castaneum larvae were less susceptible (low larval mortality) to dichlorvos and esfenvalerate than T. confusum, whereas the reverse was true for treatment with pyrethrins. Pre-treatment with one of three synergists, piperonyl butoxide (PBO, cytochrome P450 monooxygenase inhibitor), S,S,S-tributyl phosphorotrithioate (DEF, esterase inhibitor), or diethyl maleate (DEM, glutathione S-transferase inhibitor), suggested involvement of esterases in the detoxification of dichlorvos and pyrethrins, and cytochrome P450 monooxygenases in the detoxification of esfenvalerate in both species. Interestingly, pre-treatment with some synergists increased the toxicity of insecticides in only one species: DEM and DEF increased the toxicity of dichlorvos to T. castaneum, whereas only DEF increased dichlorvos toxicity to T. confusum. In 28-day bioassays with larvae treated with each of two insect growth regulators (IGRs), methoprene and pyriproxifen, T. confusum was the more tolerant species. All T. castaneum died in either the larval or pupal stages with either IGR. In contrast, only pyriproxyfen caused complete mortality in T. confusum larvae, and even the highest dose of methoprene allowed nearly 70% of T. confusum larvae to pupate, and 4.5% of adults to emerge. Our results show that although these two species are closely related, they display very different susceptibilities to different insecticides, and different metabolic detoxification mechanisms may contribute to their differential insecticide susceptibilities.

A three-year monitoring study was performed using pitfall traps baited with pheromone lures and food oil to assess seasonal prevalence of selected stored product beetle species inside a large community food storage warehouse located in the Midwestern United States. The four predominant species captured were Tribolium castaneum, Lasioderma serricorne, Oryzaephilus surinamensis, and Trogoderma variable. During the first year, T. castaneum was the dominant species, comprising 79% of all beetles caught in the traps. This species declined the next year to 2% of the total and L. serricorne, O. surinamensis, and T. variable were the dominant species. During the final year total numbers of these three species declined, but they were still the primary species caught in the traps. Few or no beetles of any species were trapped between November and June in any year, most likely because of lower temperatures inside the warehouse during that time. Beetle captures among trap locations varied considerably during the study, probably due to movement of food products into and out of the warehouse, and movement of products and beetle populations within the warehouse. All four primary species were also consistently caught in traps placed in zones within the warehouse where no food products were stored. Specific traps and zones within the warehouse were identified as primary activity sites based on comparisons among trap locations and contour mapping of the yearly and total infestation patterns. Results show how monitoring data could be used to identify those areas within a food storage site that are most vulnerable to insect infestation.

The colonization of food processing plants by stored-product pests and their distribution within a facility depend, in part, on their dispersal ability. In this case study, we relied on self-mark recapture to evaluate the ability of Tribolium castaneum, the red flour beetle, to move among floors within a flour mill and the effects of a heat treatment on insect activity. Marking stations with pheromone and fluorescent powder were placed on each of five floors in the mill, and two techniques were used to recover marked individuals (trapping and direct collection of individuals from the floor). Considering both recovery techniques, T. castaneum was able to move among floors, but the majority of individuals remained on the same floor where they were marked (86%). Most individuals captured on a different floor were captured on a floor below the one they were marked (70%) and adjacent to it (87%). There was a spike in the number of beetles captured during heat treatment, but not an increase in movement of marked beetles between floors. These results suggest that the rate of heating was sufficient to prevent beetles time to move to cooler floors to escape heat. T. castaneum movement among floors needs to be taken into account when identifying sources of infestation and targeting pest management. Published by Elsevier Ltd.

Small-scale field sheds were infested to establish resident populations of the red flour beetle, Tribolium castaneum (Herbst), and either left untreated (control) or treated every two or four weeks with an aerosol spray of esfenvalerate (Conquer®). Prior to treatments, sheds were infested by placing flour (food) patches underneath shelves in the shed, and two trials were done in separate blocks. Aerosol efficacy was assessed using pheromone traps to estimate live adults (indirect sampling) and by collecting dead adults and estimation of eggs, larvae, pupae, and adults in the food patches (direct sampling). Beetle populations readily colonized the food patches, and overall populations of each life stage in the food patches were similar in the controls and in the 2- and 4-week aerosol treatments. However, the proportion of individuals in the egg and larval stages was greater in the control versus the aerosol treatments. There were more live adults trapped in the controls than in the aerosol treatments, with lower adult numbers in the two-week aerosol spray than in the four-week sprays, and more dead adults in the food patches in the control and 4-week spray than in the 2-week spray. Indirect sampling using pheromone traps gave consistent indications of aerosol efficacy, regardless of the extent of food patch colonization; however; the presence of the food patches allowed continued population development, and as a result the frequency of aerosol application had little impact on T. castaneum populations in the food patches.

Populations of Plodia interpunctella (Hubner), the Indianmeal moth, were monitored inside a 105,000 m 3 food warehouse in the central United States for a 3-year period, using pheromone-baited traps for males. A total of 52 traps were placed in the warehouse, which was roughly divided into four main areas. Ten traps were placed in the grounds outside the warehouse. Total inside moth catch was nearly 50,000 for the three-year study, suggesting a large population was present within the warehouse. Moth captures both inside and outside the warehouse generally peaked during the summer months, and few adult males were caught during the cooler months of the year. Within a year, trap locations where greater numbers of moths were captured varied over time within the warehouse. Trap locations in an area where food was not stored consistently captured adults, but this area was connected to the main part of the warehouse that contained the stored food. Inside temperatures were above 15 °C for most of the year, while outside temperatures were consistently above 15 °C from mid-May to mid-October. Economic analyses of conducting a monitoring program were done using estimates for fixed costs of traps and variable costs for labor provided by private industry, calculating labor costs for in-house monitoring versus outside contractor costs, and comparing those estimates with the research costs of conducting the program (three different scenarios). A threshold trap catch level of two males per day was used to describe methodologies for reducing total trap numbers and associated economic costs, with minimal loss of data resolution.

Tribolium castaneum (Herbst), the red flour beetle, is a major pest of food facilities and is typically monitored using traps that capture walking individuals. In flour mills the accumulation of residues of flour on surfaces has the potential to influence beetle movement and response to trap attractants. Different flour residue landscapes of habitat (flour) within a matrix of no flour with the following characteristics were created: low abundance (10% coverage) and fragmented distribution, high abundance (30% coverage) and fragmented distribution, low abundance and clumped distribution, high abundance and clumped distribution, 0% coverage, and 100% coverage. Response of individual beetles to traps placed on top of these landscapes was evaluated; traps were either baited with aggregation pheromone and kairomone or contained no attractants. Encounters with the two types of traps were not significantly different for any of the specific landscapes, but greater numbers tended to encounter traps with attractants on fragmented landscapes and 100% flour landscapes. Combining landscape types, the proportion of beetles encountering pheromone þ kairomone-baited traps (0.61) was not greater than the proportion encountering empty traps (0.50). However, when combining just the fragmented landscapes there was a significantly greater response to traps with attractants (78%) than traps without (50%), but no difference in response on the combined clumped landscapes. Movement pathways, analyzed using video recordings of beetles, showed a general trend for 0% and 100% habitat landscapes to be most different from each other and 10% and 30% habitat landscapes tended to group together, but only for maximum distance traveled in an interval, velocity, and mean turn angle were significant differences observed. Results suggest that fragmented landscapes may have some impact on beetle response to attractants, but a potential mechanism for this needs further evaluation. Published by Elsevier Ltd.

The red flour beetle, Tribolium castaneum (Herbst), is a major pest of food processing facilities and can be monitored using pitfall type traps. To determine how beetles interact with these traps under field situations, the behavior of individual beetles released in the vicinity of traps was observed in a large arena. Specifically, the response of adults to traps baited with combinations of commercially available pheromone and kairomone attractants was measured, as was the influence of beetle sex and strain, airflow presence or absence, and distance from trap. The beetle’s response to traps was strongest (e.g., more encountered trap, more remained in observation zone, more time was spent on treatment side, and decreased speed and increased turn angle) to pheromone/kairomone or pheromone baited traps when there was air movement, while kairomone alone and all attractants under still air conditions generated no significant response by the beetles. Even with the best combination of attractants and with airflow, average number encountering trap was only 40%. With airflow, beetles were successful at locating a pheromone/kairomone baited trap out to 90 cm, the maximum distance tested, but under still air conditions even at 10 cm there was no difference between traps with and without attractants. Since airflow at trap locations within commercial food facilities can vary considerably, these patterns of response to traps could significantly impact insect detection. Published by Elsevier Ltd.

Wheat flour and different packaging surfaces (cardboard, flour bag, muslin bag, paper bag, pallet wrap, plastic overwrap, polyethylene) were exposed to aerosol formulations of either 1% active ingredient (AI) pyrethrin (synergized with piperonyl butoxide)+ 33.6% (AI) methoprene or 3% (AI) pyrethrin + 33.6% AI methoprene. The mixture was formulated as specified on the insecticide labels to give a 100 to 1 ratio of active ingredient pyrethrin to methoprene. Residual bioassays were conducted every two weeks for 16 weeks post-exposure to the aerosol by placing four-week-old larvae of the red flour beetle, Tribolium castaneum (Herbst), or the confused flour beetle, Tribolium confusum (Jacqueline duVal), on treated flour or a treated packaging surface with untreated flour added. T. castaneum was clearly the more susceptible of the two species. Less than 2% of T. castaneum larvae exposed to aerosol-treated flour or packaging surfaces emerged as normal adults, regardless of the pyrethrin concentration. Most of the T. castaneum larvae on treated flour did not advance to the pupal stage because they were either developmentally arrested or died as larvae. They were able to develop further on the treated packaging surfaces, but still could not emerge as adults. T. confusum larvae exposed to aerosol-treated flour or packaging surfaces were able to develop to the pupal or adult stage. Emergence of normal-appearing adults from T. confusum larvae exposed on the packaging surfaces treated with 1% pyrethrin + methoprene gradually increased (range of 29.7 ± 2.9 to 49.0 ± 6.7%, depending on the surface), whereas adult emergence of larvae exposed to treated flour peaked at 10 weeks post-exposure. However, when T. confusum was exposed to 3% pyrethrin + methoprene treated flour or packaging surfaces, adult emergence was reduced. Overall there were few significant differences attributable to the individual packaging surfaces.

Tribolium castaneum and Tribolium confusum can be monitored in food processing facilities using traps baited with pheromones and kairomones, but beetle response to traps might be enhanced by adding visual cues. Against a white background, T. castaneum adults were more likely to visit black pillars than white pillars when presented with a choice (e.g., 73% of beetles visited black and 17% visiting white pillar), and visits to black pillars increased with pillar height. When tested against a black background, beetles did not show a significant preference for either color pillar regardless of height. When comparing beetle’s captures in pheromone/kairomone baited traps placed in front of a white or black panel in a white arena under high, low, or dark light conditions, more beetles were captured in traps in front of black panels under both high and low light conditions, but not under dark conditions. A similar pattern of capture under low light and dark conditions was also found for the closely related species T. confusum .I n a larger scale choice test, the same pattern of greater T. castaneum captures in traps in front of black panels than white panels was obtained, whether traps were placed in corners or along walls. Our results suggest that captures in monitoring traps could be increased by adding dark vertical shapes behind trap locations or placing traps near dark structures. Published by Elsevier Ltd.

Capture of Rhyzopertha dominica in pheromone-baited traps located many kilometers away from grain storage suggests that this species may be exploiting non-grain food sources. To investigate the potential for survival of this species on alternative hosts in the absence of grain, we conducted no-choice feeding assays with twigs and seeds of trees, and seeds of grasses, forbs, and shrubs, commonly encountered on Kansas prairie landscapes where R. dominica has been captured. In addition, R. dominica development and progeny production were assessed on seeds that adults were able to survive on for at least two weeks. Adult survival was poor on grass and forb seeds, although 13.4% of individuals survived on Elymus canadensis, Canada wildrye, seeds after two weeks, compared with 80.3% on Triticum aestivum, wheat, and 0.0% survival in the absence of food. Beetles readily tunneled into twigs from a wide range of tree species, but survival was generally low. A few individuals survived up to four weeks on Gleditsia triacanthos, honey locust. In contrast, bioassays showed that R. dominica could survive and reproduce on damaged seeds (acorns) of six species of oak, but not on undamaged seeds. For example, survival was 95.8% on damaged Quercus muehlenbergii, chinquapin oak. A survey of acorns at the original field collection site showed that the majority of the acorns on the ground had been cracked or bored into by insects and small mammals. Furthermore, we recovered three R. dominica adults from acorns collected in the field and held in sealed containers in the laboratory. These findings suggest that R. dominica populations in Kansas can persist on wild acorns when grain is not available.

A field test was conducted whereby adult Tribolium confusum (du Val), the confused flour beetle, were exposed in Petri dishes lined with filter paper and containing 0–2000 mg of flour, to a pyrethrin–CO2 aerosol inside an empty warehouse. Applications were made according to label directions, and beetles were exposed to the aerosol for 2 h. After exposure, knockdown was assessed, and beetles were held for 2 weeks either in the same Petri dishes in which they were exposed or transferred with the flour to new Petri dishes lined with clean filter paper. Resident insect populations inside the test warehouse and outside were assessed through the use of pheromone traps. Virtually all beetles were knocked down at the time of removal from the exposure environment. Recovery from knockdown, or survival, increased with the presence of flour, and varied depending on the position of the exposure dishes inside the warehouse. Survival was also greater for beetles transferred along with the exposed flour to new Petri dishes lined with unexposed filter paper, compared to beetles that were held with the flour and the Petri dish that was exposed to the aerosol. Inside the warehouse, Plodia interpunctella (Hubner), the Indian meal moth, and Trogoderma variabile Ballion, the warehouse beetle, were the major species collected in pheromone traps. Large numbers of T. variabile were captured outside the warehouse, but their numbers declined during the study, while captures of P. interpunctella outside remained relatively constant. The intermittent aerosol treatments did not seem to affect these resident populations.

Adult female lesser grain borers (Rhyzopertha dominica [F.]) were observed in a mono-layer of wheat sandwiched between two layers of glass to determine if movement patterns and survival rates differed in wheat that was admixed with diatomaceous earth (DE) compared with untreated wheat. Observations were also made to determine if responses to DE differed depending on the commercial formulation of DE tested at the labeled rates. Mortality was higher in the DE treatments than in the untreated controls, and also varied according to the DE formulation. In wheat treated with 1000 ppm Dryacide®, 400 ppm Protect-It®, and 500 ppm Insecto™ (labeled rate for the individual products), mean percentage mortality was 100±0, 71.4±10.1, and 57.1±11.1, respectively. Although total distance traveled and the number of turns taken by the beetles was lower in the Dryacide treatment compared to the untreated controls, the movement patterns were not significantly different among the three DE treatments. Observed differences in mortality are likely related to DE products or amount applied rather than to differences in DE exposure resulting from movement behavior.

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

Entomopathogenic nematodes (Nematoda: Heterorhabditidae and Steinernematidae) are commonly used biological control agents of insects in cryptic habitats, but their potential for suppressing stored-product insects in these habitats has not been explored previously. Here, we provide data from the first step in a program to evaluate entomopathogenic nematodes in the genus Steinernema as biological control agents of stored-product pests by determining their pathogenicity to some of the major stored-product pest species. When evaluated against larvae, pupae and adults of six pest species (Plodia interpunctella, Ephestia kuehniella, Oryzaephilus surinamensis, Tenebrio molitor, Tribolium castaneum, and Trogoderma variabile), and the adults of two additional pest species (Sitophilus oryzae and Rhyzopertha dominica), Steinernema riobrave was either the most pathogenic or of similar pathogenicity compared to S. carpocapsae and S. feltiae. A dose of 10 infective juveniles of S. riobrave caused 80% or higher mortality against larvae of P. interpunctella, E. kuehniella, T. castaneum, and O. surinamensis, pupae of T. castaneum and T. molitor, and adults of T. molitor and the two moth species. All stages of Trogoderma variabile exhibited 70% or higher mortality. Adults of S. oryzae and R. dominica exhibited low susceptibility with 15% and 35% mortality, respectively. On the basis of these results, S. riobrave was selected for further evaluation under more field-like conditions.

Stored-product Coleoptera were monitored continuously over 22 months using pitfall traps at an operating food mill and adjacent warehouse in Kansas. Mill management practiced conventional pest management, including monthly crack and crevice applications of a residual insecticide and semi-annual fumigation with methyl bromide in the mill, and application of dichlorvos+pyrethrin (commonly called fogging) in the warehouse. The dynamic temporal changes in insect captures and effect of the global interventions on insect captures were analyzed. Data show that more Trogoderma variabile individuals were captured in the warehouse than any other species, but Tribolium castaneum was captured with greater frequency. Trogoderma variabile captures inside the warehouse tended to mirror outside captures suggesting immigration from the outside. The food mill was infested year round with T. castaneum but developed substantial populations of Typhaea stercorea during the warm months from May through October. Stored-product insects were nearly always captured during the first trapping interval following methyl bromide or dichlorvos+pyrethrin applications, but it was not clear if the insects were surviving inside the structure or if they were rapidly recolonizing after treatment. Population increases immediately following fumigation or fogging occurred only in fungus-feeding species in late spring or summer. The most successful fumigation was conducted late in the autumn when environmental conditions prevented insect activity outside. Information contained in this study provides data that could be used to improve insect management programs for milling and processing facilities.

Stored-product insects often live in an environment of spatially separated food patches that vary considerably in size, quality, and persistence. The movement of individuals among patches of food influences the probability that stored products will become infested and pest populations will persist within storage facilities, thus affecting many aspects of pest management. We examined how a major stored-product pest, the red flour beetle, Tribolium castaneum (Herbst), exploits patches of food. Individuals are often inactive, periods of inactivity are often outside of food patches, males are more likely to be inactive outside of flour patches than females, and there is considerable variation among individuals in the time spent outside of patches. Beetles outside of food patches tend to be observed near edges due to a tendency to be inactive at edges, to move along edges, and to move more slowly when moving along edges. This tendency to move along edges makes beetles more likely to infest flour patches near the edges than patches further from the edge. A better understanding of the influence of landscape on pest behavior, spatial distribution, and population dynamics is needed to develop effective stored-product pest IPM programs.