Combination Insecticide Treatments with Methoprene and Pyrethrin for Control of Khapra Beetle Larvae on Different Commodities.

Trogoderma granarium Everts, the khapra beetle, is a serious pest of stored products throughout the world. Larvae pose a significant threat to stored products because they feed on >100 different commodities, possess the ability to enter facultative diapause, and are difficult to detect. Control methods for T. granarium include fumigation, contact insecticides, trapping, and insecticide-incorporated packaging. The objective of this study was to determine the residual efficacy of two insecticide formulations (methoprene + deltamethrin + piperonyl butoxide synergist Gravista® and methoprene + deltamethrin, DiaconIGR®Plus). These insecticides were evaluated on three stored product commodities, corn, wheat, and brown rice, by exposing T. granarium larvae during a 12-month testing period. Both formulations significantly reduced adult emergence on corn and wheat for 12 months and on brown rice for up to 6 months. Adult emergence was highest at month 12 for corn (8.41%), and brown rice (85.88%), and month 9 for wheat (39.52%), treated with DiaconIGR®Plus or Gravista®, respectively. A biological index used to measure the development of exposed larvae on the treated grain from the larval stage (low values) to adult emergence (high values) was lower (fewer adults) on corn and wheat compared to controls. Despite differences in formulations, each of these grain protectants could be utilized by stored commodity managers to protect commodities during storage and transportation for T. granarium when and if this pest is detected at USA ports of entry.

Aerosolized Insecticide Spray Distributions and Relationships to Efficacy against Stored Product Pests.

Aerosol insecticides are widely used in stored product insect management programs in food facilities. Previous research has shown spatial variation in aerosol efficacy within facilities, but information on how spatial patterns of aerosol droplet concentration, size distribution, dispersal, and deposition contribute to this variation in efficacy is limited. This study involved two aerosol application systems: a high-pressure cylinder containing TurboCide Py-75® with pyriproxyfen IGR (ChemTech Ltd., Des Moines, IA, USA) and a hand-held fogger containing Pyrocide 100® (MGK, Minneapolis, MN, USA) with Diacon II which contains methoprene IGR (Wellmark, Schaumburg, IL, USA). These systems were used at single or multiple application locations. The spray trials were conducted in a small-scale flour mill, Hall Ross Flour Mill (Kansas State University, Manhattan, KS, USA). The droplet size distributions were monitored at multiple positions within the room using nine aerodynamic particle sizing (APS, TSI Incorp, Shoreview, MN, USA) instruments. The APS data collected over the treatment period were summarized into a mass concentration index (MCI), which ranged from 155 to 2549 mg/m3 for Turbocide and 235-5658 mg/m3 for Pyrocide. A second parameter called the Deposition Index (Dep.Idx) was derived to estimate potential insecticide depositions on the floor and has units of g/m2. The Dep.Idx was below 5.3 g/m2 for most Turbocide applications, while the Dep.Idx was below 8.4 g/m2 for most Pyrocide applications. The MCI and Dep.Idx values varied with APS position and spray application location, with proximity to the aerosol application location and degree of obstruction between the release point and APS position contributing to this variation. We assessed the relationship between aerosol droplet parameters and insect efficacy using Tribolium confusum Jacqueline DuVal, the confused flour beetle. The adults were treated directly, while the larvae were treated two weeks later during the residual test (previously published). For Turbocide, efficacy against adults increased with MCI and Dep.Idx values, but for residual efficacy of the IGR, efficacy was high at all aerosol droplet values, so no relationship was apparent. In contrast, the relationship between Pyrocide deposition and adult insect efficacy was highly variable. But with larval insect efficacy, residual larvae control was directly related to increases in Pyrocide MCI and Dep.Idx. Contour plots of Dep.Idx values were developed, which could be used to predict areas of the mill that are not receiving an adequate application rate, and this could be used to develop more effective application strategies for aerosol insecticides in food facilities.

Competition of Rhyzopertha dominica and Sitophilus oryzae on six sorghum varieties.

We tested the effect of simultaneous infestation by adults of the lesser grain borer, Rhyzopertha dominica (F.) and the rice weevil, Sitophilus oryzae (L.) on six sorghum varieties. For this purpose, vials containing sorghum and either each species alone or both species were placed at 30 °C and 65% relative humidity. After ten days, all parental adults were removed and the vials were returned to the same conditions. Five weeks later the vials were emptied, to record adult emergence, the percentage of insect damaged kernels (IDK), and frass weight. Our results indicated that progeny production capacity for both species was not affected by the simultaneous presence of R. dominica and S. oryzae, and that adult emergence was more of a variety- mediated parameter. Both species had previously shown similar preferences towards specific sorghum varieties. IDK and frass were higher in vials containing R. dominica alone rather than S. oryzae alone, but these indicators were not always related to progeny production. Specifically, the most and the least frass production was noted on Sumac and PE sorghum varieties for both species, respectively. When the two species were placed together in the same vial, the most frass production was noted in the Non-Waxy Burgundy and Sumac varieties. Our results suggest that varietal resistance in sorghum could be utilized to help reduce post-harvest infestations by S. oryzae and R. dominica.

Development and Immature Mortality of the Sawtoothed Grain Beetle (Coleoptera: Silvanidae), on Different Sorghum Fractions and Different Temperatures.

Developmental ability of Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) was examined on six different sorghum milling fractions: Bran, Shorts, Cgrits, Fgrits, Red dogs, Flour, and also on a standard diet of Oat Flakes. For this purpose, a 1-day-old egg was placed in a vial containing 1 g of one of the sorghum fractions and exposed to three temperatures: 25, 30, or 32°C. All vials were checked daily for pupal and adult emergence and mortality of immatures. The developmental time was significantly affected by the type of sorghum fraction. After two weeks, for most of the temperatures examined, the longest developmental times in most cases for both pupation and adult emergence were observed in Flour and Oat flakes. Increasing the temperature from 25 to 30 accelerated the development, while adult emergence time did not differ between 30 and 32°C for all fractions except Flour. Egg mortality ranged from 11 to 78%, while larval and pupal mortality ranged from 0 to 22 and 0 to 45%, respectively for all sorghum fractions and different temperatures tested. Moreover, the mean overall immature mortality occurred at 30°C was 49.2, 39.7, and 65.1% at 25, 30, and 32°C for all the diets examined. The findings of the present work show that O. surinamensis can develop and survive in sorghum milling fractions and that the optimal temperatures for growth enhancement are 30 and 32°C. The temperatures within sorghum milling facilities could support O. surinamensis development on milling fractions if they are not addressed through phytosanitary measures.

Immediate and delayed movement of resistant and susceptible adults of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) after short exposures to phosphine.

BACKGROUND: During the last decade, the evaluation of certain behavioral attributes has been utilized as an indicator of resistance to phosphine. In this context, an underappreciated challenge may be the development of behavioral traits that are related with resistance to phosphine such as the movement to refugia and recovery of stored product insects after short exposures. Thus, the aim of the current study was to track the movement of phosphine-resistant and -susceptible adults of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), which is a major pest of stored products, after brief exposures to phosphine. Exposures were followed for extended intervals to assess the recovery patterns and how those patterns are related to known resistance to phosphine. A video-tracking procedure coupled with Ethovision software was used to assess movement after exposure. RESULTS: Overall, we found baseline movement was less for phosphine-resistant T. castaneum, suggesting resistance comes at a considerable fitness cost. In the presence of phosphine (1000 or 3000 ppm), there was a much greater reduction in movement for phosphine-susceptible than phosphine-resistant T. castaneum adults immediately after brief 5-min exposures. Twenty-four hours later, these effects were more variable and less apparent, regardless of the susceptibility level. CONCLUSIONS: The initial knockdown associated with successful fumigation may just be a temporary state whereafter insects shortly resume movement and may be able to seek out refugia from phosphine, thereby promoting the development of resistance. Our results strengthen a growing consensus that it is the speed to knockdown that truly matters, with quick knockdown indicating slow recovery and a reduced likelihood for the occurrence of resistance. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

A Combination Sulfuryl Fluoride and Propylene Oxide Treatment for Trogoderma granarium (Coleoptera: Dermestidae).

The khapra beetle, Trogoderma granarium, is an important quarantine pest of stored-products. While it is not established in the North America, frequent interceptions highlight the need for treatments to eradicate isolated populations if they occur. Methyl bromide has long been the standard fumigant used for this purpose; however, increasing restrictions on its use necessitate the development of new treatment options. Here we evaluate a treatment for khapra beetle using a combination of sulfuryl fluoride (SF) and propylene oxide (PPO). Experiments were conducted to determine the most tolerant stages and the effective rates for each compound. Combination treatments using both products were then evaluated at several temperatures to determine effective doses for quarantine level control. The egg stage was by far the most tolerant to SF, requiring concentration × time (CT) products roughly 10-fold greater than the next most tolerant stage, diapausing larvae. Diapausing larvae were significantly more tolerant to SF than non-diapausing larvae in a recently collected 'field' strain, but not in a more than 30-yr-old 'laboratory' culture. PPO treatments were shown to completely control the egg stage at CTs greater than 155 hr-mgL-1 at both 10 and 20°C. Resulting combination treatments with initial dose rates of 96 and 40 mgL-1 at 10°C and 80 and 40 mgL-1 at 20°C are proposed for SF and PPO, respectively. These combination treatments utilize SF's efficacy against the larval stage along with PPO's superior ovicidal properties to provide enhanced treatment efficacy over each product alone against all life stages of khapra beetle.

Effects of Dehumidification on the Survivorship of Four Psocid Species.

Psocids are damaging stored-product pests. In this study, eggs and early-instar nymphs, adults, and all life stages of Liposcelis entomophila, L. decolor, L. bostrychophila, and L. paeta were subjected to 43, 50, or 75% (Control) relative humidity (RH) for 2, 4, 6, 8, 10, 12, 14, or 16 d at 30.0°C. All adults of these species died within 8 d at both 43 and 50% RH, except for L. bostrychophila, which required 12 d at 50% RH for 100% mortality to occur. For all life stages and eggs and early-instar nymphs, maximum survival times (times to 100% mortality) at 43 or 50% RH for L. entomophila, L. decolor, L. bostrychophila, and L. paeta, were 8 and 10 d, 8 and 12 d, 12 and 14 d, and 12 and 16 d, respectively. During this study, numbers of nymphs and adults of all species 14 d after the RH treatments increased within the 75% RH Control arenas. Different species and life stages responded differently to 43 and 50% RH, as time to kill all stages of the four psocid species was 8-12 and 10-16 d, respectively. Results indicate that using a specific RH environment may be effective in psocid management.

Susceptibility of Four Different Sorghum Varieties to Infestation by the Khapra Beetle.

In this study, we evaluated the susceptibility of four different sorghum varieties to infestation by the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), as compared with wheat, which served as a 'control' commodity. In population growth assays, there was preference for population development on wheat compared to the different sorghum varieties. In contrast, there were no significant differences in total population development among the four varieties of sorghum. However, the proportion of immature stages (larvae, pupae) in relation to the adult stage varied significantly among the different varieties. Moreover, significant differences were noted among the commodities tested regarding the final weight decrease, as well as the amount of frass and kernel damage. Our study clearly demonstrates noticeable differences in the susceptibility of the varieties to T. granarium infestation. These results show that this species can develop on different varieties of sorghum, and variety selection should be further considered in a host-plant resistance-based management program for T. granarium.

Rating knockdown of flour beetles after exposure to two insecticides as an indicator of mortality.

Knockdown and mortality of adults of the red flour beetle, Tribolium castaneum (Herbst) and the confused flour beetle, Tribolium confusum Jacquelin du Val, were assessed after exposure to two contact insecticides, chlorfenapyr and cyfluthrin, on a concrete surface. Individuals were rated on a scale for knockdown of exposed adults according to their mobility from 1, representing immobilized adults to 5, representing normally moving (similar to the controls). Only cyfluthrin gave immediate knockdown. Adults were rated at 1, 3 and 7 days post-exposure. After the final assessment, adults were discarded and the same procedure was repeated for 5 consecutive weeks with new adults exposed on the same treated surfaces. Despite initial knockdown, many individuals did not eventually die after exposure to cyfluthrin. In contrast, adults exposed to chlorfenapyr were not initially knocked down after exposure but most died after 7 days. These trends were similar during the entire 5-week residual testing period. The storage of the treated dishes in illuminated or non-illuminated conditions did not affect the insecticidal effect of either insecticide. The results of the present study can be further implemented towards the design of a "lethality index" that can serve as a quick indicator of knockdown and mortality rates caused after exposure to insecticides.

Characterizing and predicting sublethal shifts in mobility by multiple stored product insects over time to an old and novel contact insecticide in three key stored commodities.

BACKGROUND: There has been a push to diversify integrated pest management (IPM) programs away from exclusive fumigant use in food facilities. Residual insecticides increasingly have been included among plans. In stored products, sublethal toxicity has been neglected in favor of evaluating direct mortality. Here, we evaluated the movement of Tribolium castaneum, Rhyzopertha dominica, Sitophilus oryzae and Sitophilus zeamais in response to aged residues of an existing (Diacon IGR+® with 11.4% methoprene + 4.75% deltamethrin) and novel (Gravista® with 2.85% methoprene + 1.2% deltamethrin + 33.3% piperonyl butoxide synergist) residual insecticide. RESULTS: Using the maximum labeled rate and two exposure times for each species, we assessed distance moved and velocity on wheat, rice and corn. Assessments were made from commodity residues aged between 0 and 12 months (at 3-month intervals). We found that after exposure, movement was reduced by 50-88% and equally by adults exposed to each insecticide formulation compared to untreated controls. After initial application, predicted distance moved increased from 4 to 14 m then 28 m in a 24 h period at 3 and 12 months post-application, respectively. Effectiveness of each insecticide at suppressing movement generally declined by 9-12 month post-application. CONCLUSIONS: Given the quick and dramatic increases in sublethal movement after initial application, our results suggest that sanitation programs in post-harvest environments are extremely important and it may be beneficial to pair chemical control with monitoring to prevent dispersal of affected insects to new areas of a facility. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Sublethal exposure of Trogoderma granarium everts (Coleoptera: Dermestidae) to insecticide-treated netting alters thigmotactic arrestment and olfactory-mediated anemotaxis.

Long-lasting insecticide treated netting (LLIN) has a number of potential uses for the control of insect pests. Using such netting, stored products may be protected from insects including the khapra beetle (Trogoderma granarium Everts, Coleoptera: Dermestidae) a widespread pest of many agricultural commodities. Here we first examined whether brief exposures of larvae to LLIN, for less than 30 min, decreased the chance of eventual adult emergence compared to larvae exposed on untreated netting. Next, we observed the responses of larvae that were either not exposed to any netting, exposed to untreated netting, or exposed to LLIN for 10 min and then placed in a wind tunnel and monitored for movement toward a stimulus. The wind-tunnel assay was performed either with or without a lure containing kairomones and pheromones known to be attractive to larvae of this species. There was little effect of the LLIN on adult emergence of exposed larvae. However, there were interacting effects of untreated netting and LLIN relating to thigmotaxis and anemotaxis. Larvae not exposed to netting showed increased likelihood of walking upwind if the semiochemical lure was provided, as expected. A similar pattern was observed when the untreated netting was used, but the larvae became more likely to remain stationary in the assay after acclimating to the net. When LLIN was used, the larvae became more likely to move and there was a baseline increase in the likelihood of moving upwind. However, upwind walking was no longer related to semiochemical presentation. These observations suggest that particular care should be used in relation to the airflow patterns and semiochemical landscape of the warehouse settings in which LLIN is deployed.

Population Growth and Development of the Khapra Beetle (Coleoptera: Dermestidae), on Different Sorghum Fractions.

A series of tests was performed to examine the development ability of Trogoderma granarium Everts on six different sorghum milling fractions: bran, shorts, coarse grits, fine grits, red dogs, and flour. In the first bioassay, 20 adults and 20 g of each fraction were placed in vials of 60 ml at 30°C and 60% relative humidity for a period of 65 d. In the second part of the experiment, a neonate larva (1-d old) was placed in vials with 1 g of each fraction and exposed at 25, 30, and 32°C until adult emergence. Significantly more live larvae were found in bran compared with flour and to the two grain controls (soft wheat and whole wheat flour), where most dead adults were recorded. The increase in temperature reduced both the time to adult emergence and larval mortality before the appearance of the first adult. Developmental times ranged between 25.5 and 37.5 d, and 23.2 and 29.0 d for 30 and 32°C, respectively. At 25°C, larvae in the milling fractions did not reach 100% adult emergence even after almost 3 mo. However, the first adult appeared in the shorts fraction at all temperatures tested. Our results show that all sorghum milling fractions support the development of T. granarium and that the optimal temperatures for growth and development are 30 and 32°C. These results also have important implications for phytosanitary regulations and international trade, given the quarantine restrictions on this insect.

Effects of Aerosol Insecticide Application Location on the Patterns of Residual Efficacy Against Tribolium confusum (Coleoptera: Tenebrionidae) Larvae.

Aerosol insecticides are one tool that pest management professionals can utilize as a spatial treatment inside food facilities and storage warehouses. Methods of aerosol application can vary significantly and can affect the spatial pattern of efficacy achieved. We investigated how the location from which an aerosol insecticide is applied inside a mill influenced the spatial dispersal of the insecticide. Treatments were performed using two commercial formulations, pyrethrin + pyriproxyfen (insect growth regulator [IGR]) and pyrethrin + methoprene (IGR), applied at one of three static locations or a fourth application comprising of splitting the application among all three locations. Concrete arenas were placed out at different locations within the mill during applications. At 2, 4, and 6 wk post-aerosol application, Tribolium confusum Jacquelin du Val, confused flour beetle, larvae were added to the concrete arenas and monitored for development and efficacy was evaluated based on percent adult emergence and an efficacy index that ranged from 1 (low) to 21 (high). The spatial pattern of aerosol coverage varied between insecticide formulations and the aerosol application location. Areas of the mill near walls, corners, equipment, and farthest away from the application location had larger zones of low efficacy index values among all four application locations. This study illustrated that the aerosol insecticide formulation, application location, and delivery method all significantly influenced residual efficacies of the insecticides. To increase the overall spatial coverage and IGR efficacy, targeting these areas of a mill floor with the aerosol or additional intervention techniques would increase uniform coverages and overall effectiveness.

Mobility of Stored Product Beetles after Exposure to a Combination Insecticide Containing Deltamethrin, Methoprene, and a Piperonyl Butoxide Synergist Depends on Species, Concentration, and Exposure Time.

: Adults of Rhyzopertha dominica (F.), the lesser grain borer, Cryptolestes ferrugineus (Stephens), the rusty grain beetle, and Sitophilus oryzae (L.), the rice weevil, were exposed for 1, 24, and 72 h on wheat treated with concentrations of 0% (untreated controls) to 100% of the proposed label rate of an experimental formulation of deltamethrin + Methoprene + piperonyl butoxide synergist. Movement and velocity of movement were assessed after each exposure time using a camera-based monitoring system (Ethovision®). Movement of R. dominica decreased with increasing concentration and exposure time, so that movement had virtually ceased at the 48 and 72 h exposures. Cryptolestes ferrugineus was less susceptible compared to R. dominica, but there was still a general pattern of decreased movement and velocity of movement with increasing concentration and exposure time. Sitophilus oryzae was the least susceptible species, with less differences at the 1 h exposure interval compared to the other two species, but after 24-72 h, the patterns of declining movement and velocity were apparent as the concentration increased. Data were analyzed using curve-fit equations to show the relationship between concentration and exposure time for each species. Results show that the Ethovison system can be used to assess the sub-lethal effects of exposure to grain protectant insecticides and elucidate behavioral variation between different stored product insects.

Cool Down-Warm Up: Differential Responses of Stored Product Insects after Gradual Temperature Changes.

Insect survival after exposure to 0 °C for 7 days was examined in laboratory bioassays for control of adults of six major stored-product beetle species, Oryzaephilus surinamensis (L.), the sawtoothed grain beetle, Cryptolestes ferrugineus, (Stephens), the rusty grain beetle, Dermestes maculatus DeGeer, the hide beetle, Sitophilus oryzae (L.), the rice weevil, Tribolium castaneum (Herbst), the red flour beetle, and T. confusum Jacquelin DuVal, the confused flour beetle In this test there were four different acclimation treatments, insects that had been subjected to a pre-acclimation period to 0 °C, a post-acclimation period, both a pre and post-acclimation period, and adults that were not acclimated. Insect survival for all species except S. oryzae was not affected by the exposure to 0 °C, regardless of the acclimation scenario. In contrast, exposure to 0 °C drastically reduced survival of S. oryzae. Moreover, adults that were exposed to the post-acclimation only and un-acclimated adults had lower survival rates than those that had either exposure to pre-acclimation, or to both pre- and post-acclimation. Results of this experiment show that acclimation played a limited role in adult survival of five of the six tested species, and that exposure of adults to 0 °C for 7 d had no effect in survival of these species as well.

To Acclimate or Not to Acclimate? Simultaneous Positive and Negative Effects of Acclimation on Susceptibility of Tribolium confusum (Coleoptera: Tenebrionidae) and Oryzaephilus surinamensis (Coleoptera: Silvanidae) to Low Temperatures.

Laboratory tests on acclimated and nonacclimated life stages of Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) (adults, pupae, larvae, and eggs) and Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) (adults, larvae, and eggs) were conducted at 0, -5, -10, and -15°C to evaluate effects of acclimation on susceptibility to cold treatment. Acclimation of all tested life stages for 7 d at 15°C affected susceptibility of both species to the cold temperatures. After 1 d exposures for ≥2 h, acclimated adults had a noticeable increase in cold tolerance compared with nonacclimated adults for both tested species. Nonacclimated pupae of T. confusum were equally susceptible to cold compared with acclimated pupae at short exposures to low temperatures. Exposure of nonacclimated life stages of T. confusum, at -10°C for 1 d gave 0% survival. Similarly, almost all (99.6%) nonacclimated individuals of O. surinamensis died at -10°C. At 0°C, nonacclimated larvae were more cold tolerant than acclimated larvae, but this trend was reversed when larvae were exposed to -5°C. Mixed results were obtained for larvae of O. surinamensis because in some of the combinations tested, nonacclimated larvae were more tolerant, even at temperatures that were lower than 0°C. In contrast to O. surinamensis, eggs of T. confusum that had not been exposed to cold were not affected by acclimation, while exposure to cold showed increased cold hardiness in acclimated eggs. Results show that individual stored-product insect species may have mixed susceptibility to cold temperatures, which must be taken into account when using cold treatment as a management strategy.

Evaluation of Residual Efficacy of Pyrethrin + Methoprene Aerosol on Two Dermestids: Impact of Particle Size, Species, and Temperature.

Residual effects of pyrethrin + methoprene aerosol dispensed at 4 and 16-µm particle sizes and an untreated control, was assessed against late-stage larvae of Trogoderma inclusum (LeConte), the larger cabinet beetle, and T. variabile (Ballion), the warehouse beetle. Treated arenas were stored at 25, 30, 35, and 40 °C and bioassays were conducted at 1, 3, or 6 weeks post-treatment. Larval development was monitored through adult emergence to compare the efficacy of treatments by using both the percentage of normal adult emergence and a developmental index as dependent variables. There was no overall effect of temperature on residual activity as measured using either adult emergence or developmental index values. Both the 4 and 16-µm particle sizes resulted in reduced adult emergence and low developmental index values compared to untreated controls. The insecticide was more effective on T. variabile than on T. inclusum. The impact of particle size varied between species, both particle sizes reduced adult emergence and developmental index in T. variabile, but only the 16-µm particle size resulted in reduction of adult emergence of T. inclusum. Furthermore, there was a reduction in activity of methoprene with residual exposure time. The variations in susceptibility of species to methoprene, differences in efficacy of particle sizes, and decrease in residual persistence at smaller particle sizes highlight the need for attaining optimal particle size to improve overall efficacy of aerosol mixtures containing methoprene.

Bioassays and Methodologies for Insecticide Tests with Larvae of Trogoderma granarium (Everts), the Khapra Beetle.

New insecticide treatment options would be beneficial for control programs for Trogoderma granarium Everts, the khapra beetle, in the United States. Two insecticides were evaluated, the Polyzone® formulation of deltamethrin and a formulation of the insect growth regulator methoprene combined with deltamethrin and the synergist piperonyl butoxide. In the test with Polyzone® deltamethrin, concrete arenas were treated with a low and high rate, and held outside, inside a shed, or inside a lab. Compared to storage in the lab, residue degradation increased slightly in the shed, and then further outside, as evidenced by greater larval survival and adult emergence. Across all environmental treatments, the high rate was more effective than the lower rate. For the combination methoprene product, the effect of food contact with treated surfaces was examined. When treating arenas with food and transferring the food to clean dishes, there was no immediate effect on larval survival, but there was a reduction in survival and emergence to the adult stage after one month. For both tests, larvae apparently often went into diapause after they were introduced onto the treatment arenas. Both treatments could be utilized in management programs if T. granarium infestations are detected.

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.

Case Study: A Practical Application of an Aerosol Treatment in a Commercial Mill.

In recent years, there has been an increasing interest and need for alternatives to structural fumigations, and one alternative that has been used across the industry is aerosol insecticides. Previous tests inside a pilot-scale mill demonstrated that aerosol particle size, delivery method, and the spatial configuration of the mill all influenced effectiveness. However, there is no research conducted inside large commercial facilities. The objective of this research was to evaluate a pyrethrin-plus-methoprene aerosol application inside a commercial mill on adult Tribolium confusum Jacquelin duVal, confused flour beetle, directly exposed to the aerosol and residual effects on larvae. Additionally, five aerodynamic particle sizer spectrometers were placed in the facility and recorded instantaneous spray concentration and estimated aerosol deposition. Adult T. confusum exposed nearest to the aerosol application points had the highest percentage of affected adults (>60%). The aerosol also had vertical movement when released at the top of a three-story open room; instantaneous concentrations were recorded on the ground floor. The aerosol residual was highly effective after 6-weeks post aerosol exposure, as 80% of the bioassays did not have any adult emergence from exposed larvae. This research demonstrates a practical use of aerosol insecticides and their potential to be an effective alternative to structural fumigations.