Efficacy of Liquid Smoke to Mitigate Infestations of the Storage Mite, Tyrophagus putrescentiae, in a Model Semi-Moist Pet Food.

The storage mite Tyrophagus putrescentiae infests a wide range of food products including pet food. Control of this mite depends on chemical methods such as fumigation and spraying with insecticides. Methyl bromide was used as a fumigant for high-value stored products, especially to control mite infestation in dry-cured hams and cheeses, but it is now banned for most uses in many countries because of its atmospheric ozone-depleting effects. Effective alternatives to methyl bromide are needed to develop integrated pest management programs for this pest. Liquid smoke is a naturally derived flavoring and preservative with known antimicrobial properties. The objective of this study was to investigate the efficacy of liquid smoke preparations, with varying phenol and carbonyl concentrations and pH, on the survivability and orientation behavior of T. putrescentiae in a model semi-moist pet food. The mite survivability assays using liquid smoke-treated and untreated semi-moist pet food samples indicated that there was no difference among treatments (p > 0.05) for mite infestation and survival. Two-choice behavioral assays using semi-moist pet food cubes dipped in varying concentrations (0%, 0.3%, 1%, 5%, 10%, 25%, 50%, or 100% v/v) of liquid smoke preparations found that some of the liquid smoke preparations containing medium to high carbonyl content repelled the mites. In conclusion, liquid smoke did not kill or inhibit the mite population growth in semi-moist pet food. However, some liquid smoke fractions containing medium to high carbonyl content were repellent to mites and may retard mite infestation in stored semi-moist foods.

Efficacy of the Fumigants Propylene Oxide and Ethyl Formate to Control Two Pest Species of Dry-Cured Hams.

The ham mite Tyrophagus putrescentiae and the red-legged ham beetle Necrobia rufipes are harmful pests to several high-valued stored products. The regulatory phase-out of the fumigant methyl bromide necessitates the search for alternative fumigants. Propylene oxide (PPO) and ethyl formate (EF) were therefore evaluated in the laboratory for controlling these pests of dry-cured hams. Concentration-mortality studies at 25 °C of PPO and EF found that the mobile stages of the mites were very susceptible to low concentrations of 10 mg/L and less of each gas, while mite eggs were very tolerant and required 20 mg/L for PPO and 80 mg/L of EF for 100% mortality. Mixed life stage cultures of mites and beetles were treated for 24 h with either PPO or EF at 1× and 2× the estimated 99% lethal doses and confirmed effectiveness for controlling simulated pest populations. The sorptive properties of each gas in chambers with ham pieces, dog food kibbles, or fish meal were minimal for a reduction in mite toxicity when compared to treatments in empty chambers. There was no evidence that any desorbed gas occurred at a level toxic to mite eggs in any of the fumigated commodities. These fumigation studies with ham pests support further work with PPO and EF on any changes in the sensory quality of dry-cured hams for human taste and for commercial-scale fumigations toward regulatory approval.

Using liquid smoke to control infestations of the ham mite, Tyrophagus putrescentiae, on dry-cured hams during aging.

Eight treatments of edible coatings and nets including liquid smoke (SP and 24P) and xanthan gum (XG) were used to evaluate their effectiveness at controlling mite growth on dry-cured hams. Mite growth was controlled (P < 0.05) in both coating and netting treatments of 1% SP + 1% XG. Increasing SP concentration from 1% to 2% in the SP only treatments without XG did not control mite growth (P > 0.05) in the coating but controlled mite growth (P < 0.05) when infused in the nets. Both coating and netting treatments with 2% 24P + 1% XG controlled mite growth (P < 0.05), and ham cubes with 1% and 2% 24P in infused nets had mite numbers of 4.6 and 9.4, respectively. SP did not impact the sensory attributes of the ham. Results indicate that liquid smoke can potentially be added in coatings or ham nets to control mites and used in an integrated pest management program for dry-cured hams.

The Effect of Residual Pesticide Application on Microbiomes of the Storage Mite Tyrophagus putrescentiae.

Arthropods can host well-developed microbial communities, and such microbes can degrade pesticides and confer tolerance to most types of pests. Two cultures of the stored-product mite Tyrophagus putrescentiae, one with a symbiotic microbiome containing Wolbachia and the other without Wolbachia, were compared on pesticide residue (organophosphate: pirimiphos-methyl and pyrethroid: deltamethrin, deltamethrin + piperonyl butoxide)-containing diets. The microbiomes from mite bodies, mite feces and debris from the spent mite diet were analyzed using barcode sequencing. Pesticide tolerance was different among mite cultures and organophosphate and pyrethroid pesticides. The pesticide residues influenced the microbiome composition in both cultures but without any remarkable trend for mite cultures with and without Wolbachia. The most influenced bacterial taxa were Bartonella-like and Bacillus for both cultures and Wolbachia for the culture containing this symbiont. However, there was no direct evidence of any effect of Wolbachia on pesticide tolerance. The high pesticide concentration residues in diets reduced Wolbachia, Bartonella-like and Bacillus in mites of the symbiotic culture. This effect was low for Bartonella-like and Bacillus in the asymbiotic microbiome culture. The results showed that the microbiomes of mites are affected by pesticide residues in the diets, but the effect is not systemic. No actual detoxification effect by the microbiome was observed for the tested pesticides.

Pesticide residue exposure provides different responses of the microbiomes of distinct cultures of the stored product pest mite Acarus siro.

BACKGROUND: The contribution of the microbiome to pesticide breakdown in agricultural pests remains unclear. We analyzed the effect of pirimiphos-methyl (PM) on four geographically different cultures of the stored product pest mite Acarus siro (6 L, 6Tu, 6Tk and 6Z) under laboratory experiments. The effect of PM on mite mortality in the impregnated filter paper test was compared. RESULTS: The mite sensitivity to PM decreased in the order of 6 L, 6Tu, 6Tk, and 6Z. Then, the mites were cultured on PM residues (0.0125 and 1.25 µg·g-1), and population growth was compared to the control after 21 days of exposure. The comparison showed two situations: (i) increasing population growth for the most sensitive cultures (6 L and 6Tu), and (ii) no effect on mite population growth for tolerant cultures (6Z and 6Tk). The microbiome of mites was analyzed by quantification of 16S DNA copies based on quantitative polymerase chain reaction (qPCR) and by barcode sequencing of the V4 fragment of 16S DNA on samples of 30 individuals from the control and PM residues. The microbiome comprised primarily Solitalea-like organisms in all cultures, except for 6Z, followed by Bacillus, Staphylococcus, and Lactobacillus. The microbiomes of mite cultures did not change with increasing population density. The microbiome of cultures without any differences in population density showed differences in the microbiome composition. A Sodalis-like symbiont replaced Solitalea in the 1.25 µg·g-1 PM in the 6Tk culture. Sodalis and Bacillus prevailed in the microbiomes of PM-treated mites of 6Z culture, while Solitalea was almost absent. CONCLUSION: The results showed that the microbiome of A. siro differs in composition and in response to PM residues in the diet. The results indicate that Sodalis-like symbionts can help recover mites from pesticide-induced stress.

Synergism of deltamethrin with a mixture of short chain fatty acids for toxicity against pyrethroid-resistant and susceptible strains of Tribolium castaneum (Coleoptera: Tenebrionidae).

Deltamethrin is one of the most effective pyrethroid compounds used in stored product protection to control a wide range of pests. However, the development of resistance to deltamethrin in many pest species has been reported and useful research to overcome this problem is required. The present study investigated the possible synergistic effect of a commercial formulation of a mixture of the short chain fatty acids, octanoic, nonanoic and decanoic acid, in a formulation called "C8910" on the lethal activity of deltamethrin against susceptible (Lab-S) and relatively pyrethroid-resistant (Pyr-R) strains of T. castaneum. The possible mechanisms of synergism were studied by investigating the inhibitory effect of C8910 on the activity of detoxification enzymes including cytochrome P450s, esterases, and glutathione S-transferases (GST). In addition, the possible role of C8910 in enhancement of cuticular penetration of deltamethrin through insect cuticle was studied using GC analysis. The results showed that C8910 enhanced the toxicity of deltamethrin at mixing ratios of 1:5 and 1:10 against the Lab-S strain after 24 and 48 h of exposure, and synergistic factors (SF) ranged between 5.69 and 13.59. C8910 also showed greater synergism on the deltamethrin toxicity against the resistant strain than the susceptible one after 24 and 48 h of treatment at 1:5 and 1:10 ratios with SF values ranging from 22.82 and 47.16. C8910 showed strong inhibition of cytochrome P450 of rat microsomal fraction with IC50 value of 6.24 mM. Meanwhile, C8910 inhibited the activity of general esterases in Lab-S and Pyr-R strains with IC50 values of 26.22 and 51.73 mM, respectively. However, weak inhibition of GST activity was observed with inhibition of 52.0 and 22.6% at concentration of 100 mM of C8910 for Lab-S and Pyr-R, respectively. In addition, the results showed no significant difference between the unpenetrated amounts of deltamethrin when insects were treated with deltamethrin alone or with deltamethrin+C8910 (1:20) through the insect cuticle. Results suggested that the synergism between C8910 and deltamethrin could be related to the ability of C8910 to inhibit the detoxification enzymes such as cytochrome P450 and esterases. Therefore, C8910 could be a promising synergist to enhance deltamethrin toxicity and to be a possible natural alternative for conventional synergists such as piperonyl butoxide.

Nitric Oxide Fumigation for Control of Ham Mite, Tyrophagus putrescentiae (Sarcoptiformes: Acaridae).

The ham mite, Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae), is a common pest infesting several stored products, particularly the aged hams. In this study, we reported the efficacy of nitric oxide (NO) fumigation, a recently discovered fumigation treatment under the ultra-low oxygen environment, at various concentrations and time under the laboratory conditions at 25°C against different mite stages on both dietary media and ham meat. Our results showed that NO fumigation was effective against all mite stages and 100% control was achieved. Generally, the egg was the most tolerant stage and required 48-, 24-, 16-, and 8-h treatments to achieve 100% mortality at 0.5, 1, 1.5, and 2% NO concentration on dietary media, respectively. Tyrophagus putrescentiae mobile immatures and adult stages were less tolerant, and 100% mortality was achieved after 16-, 8-, 8-, and 4-h treatment at 0.5, 1, 1.5, and 2% NO, respectively. The median lethal concentration (LC50) of NO on egg was 0.86, 0.68, and 0.32% for 8-, 16-, and 24-h treatments. In addition, a confirmatory test was conducted on ham meat at 0.5 and 1.0% of NO and similar efficacy was found. Complete control of egg was achieved after 48- and 24-h treatment at 0.5 and 1.0% of NO, respectively, and larvae and adult mites were 100% controlled after 16 and 8 h at 0.5 and 1.0% of NO, respectively. Our results demonstrated that NO fumigation was effective against T. putrescentiae and can be a potential alternative treatment to methyl bromide for cured-ham pest control.

Effects of Diet and Temperature on the Life History of the Redlegged Ham Beetle (Coleoptera: Cleridae).

We investigated the effects of various foods and different rearing temperatures on the survival and development of the redlegged ham beetle Necrobia rufipes (De Geer) (Coleoptera: Cleridae), a serious pest of dry-cured hams. The diets tested were dried pet food, finely shredded copra, shredded cheese, dry-cured ham, ground fish meal, and mature larvae of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). As indicated by the growth index and k-values, N. rufipes populations grew fastest on the pet food and slowest on the copra. On the other hand, N. rufipes fed both ham and T. castaneum larvae produced significantly heavier larvae. The adult beetles lived significantly longer on cheese compared to other foods. Studies conducted to determine the developmental rates of N. rufipes fed pet food at temperatures of 22, 25, 28, and 31°C showed that the total developmental time and longevity of N. rufipes significantly varied at different temperatures tested. The shortest developmental time (93.32 d) was observed at 28°C. Oviposition rate was highest for females reared at 25°C while lowest at 22°C. Based on the development, reproduction, and thermal requirements, the most suitable temperature for N. rufipes was between 28 and 31°C. The results also revealed that larval cannibalism prevailed among adult beetles.

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.

Trapping Tribolium castaneum (Coleoptera: Tenebrionidae) and Other Beetles in Flourmills: Evaluating Fumigation Efficacy and Estimating Population Density.

This paper reports beetle pests common to flourmills targeted during a series of trapping studies over a two-year period in flourmill 1 and a one year period in flourmill 2. Objectives were (1) use pheromone-baited traps to detect T. castaneum (Herbst) and other pest species present for their distribution over space and time, (2) monitor T. castaneum activity before and after fumigations to assess efficacy of the treatment, and (3) correlate counts of T. castaneum via trap capture against direct T. castaneum counts from samples of the milled flour to assess the value of trap data to estimate relative size of the pest population. Traps were deployed in two different flourmills over two consecutive years. T. castaneum was the most commonly trapped beetle during both years in mill 1. In mill 2, Typhaea stercorea (L.) and Cryptolestes ferrugineus (Stephens) were both captured in higher numbers than T. castaneum. In mill 1, trap capture was higher overall during Year 2 for most of the species compared with capture during Year 1, likely due to a dust cover modification made for the pitfall trap used in Year 2. Trap capture was also evaluated by location within the mills and a significant difference was found in the capture of T. stercorea during both years in mill 1. T. castaneum captures were significantly reduced following most fumigations, which used methyl bromide in milling areas and phosphine in bulk-stored finished flour. However, in most cases trap catches showed that beetle populations were not eliminated. Trap captures after fumigation suggest either that the fumigations were not entirely effective, or that full grown adult beetles were entering the mill soon after fumigation. When captures of T. castaneum from traps in two spaces of mill 1 during Year 2 were compared with counts of beetles from samples of siftings collected in the finished flour, the correlation coefficients were nearly significant for both sets of traps.

Responses of Red Flour Beetle Adults, Tribolium castaneum (Coleoptera: Tenebrionidae), and Other Stored Product Beetles to Different Pheromone Trap Designs.

A series of laboratory and field experiments were performed to assess the responses of Tribolium castaneum (Herbst) and other stored-product beetles to pheromone-baited traps and trap components. A commercial Tribolium pitfall trap called the Flit-Trak M2, the predecessor to the Dome trap, was superior in both laboratory and field experiments over the other floor trap designs assessed at capturing walking T. castaneum. In field experiments, Typhaea stercorea (L.) and Ahasverus advena (Stephens) both preferred a sticky trap to the pitfall trap. Although the covered trap is effective at capturing several other species of stored product beetles, the synthetic Tribolium aggregation pheromone lure is critical for the pitfall trap's efficacy for T. castaneum. Although the food-based trapping oil used in the pitfall trap was not found to be attractive to T. castaneum when assayed alone, it had value as an enhancer of the pheromone bait when the two were used together in the trap. A dust cover modification made to go over the pitfall trap was effective in protecting the trap from dust, although the trap was still vulnerable to dust contamination from sanitation techniques that used compressed air to blow down the mill floors. Capture of T. castaneum in the modified trap performed as well as the standard trap design in a non-dusty area of a flour mill, and was significantly superior over the standard trap in a dusty area. T. castaneum responded in flight outside a flourmill preferentially to multiple funnel traps with pheromone lures compared to traps without pheromone.

Efficacy of Sulfuryl Fluoride Against Fourth-Instar Pecan Weevil (Coleoptera: Curculionidae) in Pecans for Quarantine Security.

The efficacy of sulfuryl fluoride was evaluated for control of fourth-instar pecan weevil, Curculio caryae (Horn), at 25°C for a 24-h exposure. Larvae, collected as they naturally emerged from pecans, were used to artificially infest pecan nuts. Infested nuts were fumigated with six concentration by time (CT) treatment dosages of sulfuryl fluoride (0-750 g-h/m3) within air-tight, glass containers. The sulfuryl fluoride concentration in each fumigation container was analyzed 30 min after sulfuryl fluoride introduction and just prior to termination of the experiment. Mean sulfuryl fluoride CT dosages were calculated from sulfuryl fluoride measurements and were used for probit analysis. The lethal accumulated dosage (LAD99) of sulfuryl fluoride for pecan weevil was 1052.0 g-h/m3 with a 95% C.I. of 683.21-2,573.0 g-h/m3. For the confirmatory trial, we used two sulfuryl fluoride CT dosage treatments, 1,100 and 1,300 g-h/m3, and a nonfumigated control. All larvae were dead in both fumigation treatments by 14-d postfumigation. Due to higher mortality in the nonfumigated control in the confirmatory trial compared to that of the dose-response trial, 1300 g-h/m3 was selected as the sulfuryl fluoride CT dosage for a proposed quarantine treatment schedule. Fumigating pecans with sulfuryl fluoride can control larval pecan weevil infestations in commercially traded nuts and maintain compliance with quarantine regulations both within and outside the United States.

Ethanedinitrile as a Fumigant for Lasioderma serricorne (Coleoptera: Anobiidae), and Rhyzopertha dominica (Coleoptera: Bostrichidae): Toxicity and Mode of Action.

This study evaluated the fumigant ethanedinitrile (EDN) against the cigarette beetle, Lasioderma serricorne, and phosphine-resistant and susceptible lesser grain borer, Rhyzopertha dominica, life stages under laboratory conditions. Eggs of both species were the most susceptible stage to EDN. EDN is, therefore, a promising alternative because eggs are generally tolerant to most common fumigants. Lasioderma serricorne eggs were the most susceptible with an LC50 estimated of 50.4 ppm, followed by adults, pupae and larvae with LC50 values of 160.2, 192.5, and 446.6 ppm, respectively, after 24-h exposure at 25°C. Eggs of phosphine-susceptible (LC50 = 11.2 ppm) and resistant (LC50 = 12.0 ppm) R. dominica strains were more susceptible to EDN than were adults of both strains, with LC50 values of 27.7 and 36.0 ppm, respectively. Lasioderma serricorne mixed life stage cultures were completely controlled at concentrations ≥2,000 ppm at 24 h. Fumigation with 600 ppm was enough to suppress adult emergence in the case of the phosphine-susceptible R. dominica strain (USDA), while an average of only 4.0 adults emerged from the phosphine-resistant R. dominica strain (Belle Glade) compared with 514.3 adults in the control. Lasioderma serricorne was more tolerant to EDN than both R. dominica strains. EDN caused 61.8 and 68.2 % inhibition of R. dominica (USDA) cytochrome c oxidase activity at concentrations of 0.0038 and 0.0076 mM in vitro, respectively, and it did not inhibit its activity in the case of an in vivo assay. These results suggest that cytochrome c oxidase may not be the main target for EDN toxicity.

Comparison of Methyl Bromide and Phosphine for Fumigation of Necrobia rufipes (Coleoptera: Cleridae) and Tyrophagus putrescentiae (Sarcoptiformes: Acaridae), Pests of High-Value Stored Products.

Fumigation with methyl bromide has been a long established and effective method for controlling many pests of stored products, including the key major pests that infest dry-cured hams, aged cheese, and other value-added durable stored products. Methyl bromide had been widely used for the disinfestation of dry-cured ham facilities in the United States, but is now phased out of use since it is an ozone-depleting substance. This paper reports laboratory studies to evaluate the efficacies of methyl bromide and phosphine for controlling two of the key arthropod pests of dry-cured hams and aged cheeses. Larvae of the red-legged ham beetle, Necrobia rufipes (Fabricius), were the most tolerant life stages when treated with either phosphine or methyl bromide for 48 h exposure at 23°C, whereas eggs of the mold mite, Tyrophagus putrescentiae (Schrank), were slightly more tolerant than mobile stages for both compounds. Under laboratory conditions, complete control was achieved for the both species with concentrations of 0.85 and 4.0 g/m3 of phosphine and methyl bromide, respectively, at 48 h exposure. The results give new information for judicious use of the existing stocks of methyl bromide, whether for pest mitigation or to help in developing a quarantine treatment schedule with that gas. Phosphine shows good potential as an effective alternative to methyl bromide, but if it was to be adopted as a fumigant in the dry-cured ham industry, methods to prevent metal corrosion would need to be designed and effectively implemented.

Resistance to the Fumigant Phosphine and Its Management in Insect Pests of Stored Products: A Global Perspective.

Development of resistance in major grain insect pest species to the key fumigant phosphine (hydrogen phosphide) across the globe has put the viability and sustainability of phosphine in jeopardy. The resistance problem has been aggravated over the past two decades, due mostly to the lack of suitable alternatives matching the major attributes of phosphine, including its low price, ease of application, proven effectiveness against a broad pest spectrum, compatibility with most storage conditions, and international acceptance as a residue-free treatment. In this review, we critically analyze the published literature in the area of phosphine resistance with special emphasis on the methods available for detection of resistance, the genetic basis of resistance development, key management strategies, and research gaps that need to be addressed.

High-dose strategies for managing phosphine-resistant populations of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae).

BACKGROUND: Rhyzopertha dominica is a serious pest of stored grains and many populations have resistance to the fumigant phosphine. Some populations contain beetles with a 'strong resistance' phenotype. Recent work found the LC50 values for two strong-resistant populations recently studied in North America, Belle Glade and Minneapolis were 100- and 595-fold higher, respectively, compared to LC50 of a lab-susceptible strain. Populations with 'weak-resistant' phenotypes had LC50 values 5- to 10-fold that of a susceptible strain. The work reported below aimed to determine the minimum phosphine concentrations and number of days of exposure needed to effectively control all life stages of representative weak- and strong-resistant strains, and then to recommend the treatment conditions needed to control strongly phosphine-resistant R. dominica in pest populations. RESULTS: A dose-mortality assay estimated that phosphine fumigation over 48 h using 730-870 ppm at 25° C would control adults of both strongly resistant R. dominica populations. Fumigations with mixed life stage cultures found 200 ppm killed all susceptible and weak-resistant beetles in 2 days, but the strong-resistant Minneapolis and Belle Glade strains had substantial survivors at 200 ppm. Furthermore, the Belle Glade strain had beetles that survived 1000 ppm in 2-day fumigations. The strong-resistant Belle Glade strain needed nearly 10 days at over 400 ppm to have acceptable levels of control. CONCLUSION: This study recommends protocols to manage strongly resistant R. dominica populations provided that a minimum phosphine concentration of 400 ppm be maintained at 25° C or higher for up to 10 days. © 2019 Society of Chemical Industry.

Development of a Quick Knockdown Test for Diagnosing Resistance to Phosphine in Sitophilus oryzae (Coleoptera: Curculionidae), a Major Pest of Stored Products.

A key component in the management of resistance to fumigant phosphine in stored products pests is their early detection and implementation of control strategies. Currently, resistance testing involves exposing adults to a specific discriminating concentration over a fixed time period (20-48 h). Although it is widely adopted, this test takes significant time for assay preparation (up to 4 wk) as well as diagnosis (1-2 wk). To address these lacunae, we have established a 'quick knockdown test' using a key grain insect pest, rice weevil, Sitophilus oryzae (L.). Susceptible, weakly and strongly phosphine-resistant reference strains were exposed to a threshold concentration of phosphine over short exposure periods (min to h). The time to knockdown (KT) responses to phosphine were characterized at 2 (1,440 ppm) and 5 mg/liter (3,600 ppm). The time to 99.9% KT (KT99.9) at 2 mg/liter was 12.52 min for the susceptible adults, compared with 167.9 and 1,510 min in the case of weakly and strongly resistant phenotypes, respectively. As anticipated, increasing the concentration of phosphine to 5 mg/liter halved the KT99.9 (81.57 min) to separate weakly and strongly resistant populations than it was required at 2 mg/liter. We validated the KT99.9 value for the 5 mg/liter against field-derived populations of S. oryzae. The results were aligned with the existing Food and Agriculture Organization approach, confirming that the proposed 'quick test' is a reliable tool to rapidly diagnose resistance in this species.

Evaluation of Knockdown Bioassay Methods to Assess Phosphine Resistance in the Red Flour Beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae).

Resistance to the fumigant phosphine in Tribolium castaneum occurs worldwide. This study evaluated tests based on adult knockdown time, the time for a beetle to become immobile, when exposed to a high concentration of phosphine. We recorded knockdown times of beetles that remained completely still for 30 s when exposed to 3000 ppm of phosphine in a large, gas-tight glass tube. Beetles were used from 12 populations, of which six were 'susceptible' to phosphine, three were 'weakly resistant', and three were 'strongly resistant'. Knockdown times were determined for single beetles, as well as for groups of ten beetles for which the time to knockdown for either five beetles (KT50) or ten beetles (KT100) were recorded. Similar knockdown times occurred across susceptible and resistant populations. However, the KT100 tests generated conservative times for diagnosing strong vs. weak resistance. The strong resistant populations were all over 100 min with KT100, compared to 60 min or less for susceptible and weak resistant populations. Special tests on single beetles revealed higher knockdown times in insects that were deliberately disturbed compared to those without any disturbances. Work reported here suggests a knockdown test conducted on beetles in a matter of minutes or hours could help classify phosphine resistance status prior to decisions on phosphine fumigation.

Biology and Control of the Khapra Beetle, Trogoderma granarium, a Major Quarantine Threat to Global Food Security.

The khapra beetle, Trogoderma granarium, is a voracious feeder of stored products and is considered one of the most important quarantine pests globally. Its ability to survive for long periods under extreme conditions facilitates its spread through international commerce, which has led to invasions of new geographic regions. The khapra beetle is an important quarantine pest for many countries, including the major wheat-producing countries the United States, Canada, Russia, and Australia, and has been classified as one of the 100 worst invasive species worldwide. This species cannot always be controlled by insecticides and other nonchemical methods that are usually effective against other pests of stored products, particularly owing to its diapausing late larval stage. It can rapidly develop at elevated temperatures and under dry conditions, which are not favorable for many major stored-product insects. We synthesize key published work to draw attention to advances in biology, detection and control of the khapra beetle, and directions to consider for future research.

Evaluation of Light Attraction for the Stored-Product Psocids, Liposcelis entomophila, Liposcelis paeta, and Liposcelis brunnea.

Psocids have become global pests of stored commodities as they can cause considerable economic losses. These insects are difficult to control because they have developed resistance to many chemical insecticides. Therefore, it is crucial to investigate alternative integrated pest management (IPM) approaches, such as the use of light attraction for monitoring and/or controlling psocids. Light attraction has been studied for Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae) but not for other psocid species. In this study, we investigated the response of adults of three psocid species (Psocoptera: Liposcelididae), Liposcelis entomophila (Enderlein), Liposcelis paeta Pearman, and Liposcelis brunnea Motschulsky, to six wavelengths of light from light-emitting diode (LED) in paired-choice pitfall tests. L. entomophila females and males were not attracted to any of the wavelengths tested. L. paeta females responded positively to two ultraviolet (UV) wavelengths (351 and 400 nm) and to green light (527 nm), while males did not respond to any light. L. brunnea females and males responded positively to all six wavelengths evaluated. Most of the LEDs that elicited positive responses to L. paeta females and L. brunnea females and males were also preferred when these lights were presented against brewer's yeast, a food attractant highly preferred by several psocid species. Females of L. paeta and L. brunnea were attracted to white light when compared with a blank, but females of L. entomophila were not attracted to white light compared to a blank.