Efficacy of a volatile formulation of hydroprene (Pointsource™) to control Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae)

Three- and 4-week-old Tribolium castaneum (Herbst), the red flour beetle, and Tribolium confusum (du Val), the confused flour beetle, were exposed at five different temperature-relative humidity (r.h.) combinations to a volatile formulation of the insect growth regulator (IGR) hydroprene (called Pointsource™). Typical effects associated with IGR exposure, such as arrested larval growth, morphological deformities in adults, twisted and deformed wings, and incomplete adult emergence were produced in both species. Tribolium castaneum and T. confusum were susceptible to Pointsource™, but T. castaneum appeared to be the more susceptible species. More 3-week-old larvae of both species were arrested in that stage compared to the 4-week-old larvae. Nearly all of the 3- and 4-week-old T. castaneum larvae that were able to complete development to the adult stage quickly died after they emerged and were grossly morphologically deformed. In contrast, some emerged adult T. confusum remained alive after they emerged and were not deformed in any manner or had only twisted and incomplete wings. A greater percentage of larvae of both species were arrested in the larval stage and more adults died after they emerged in exposure studies conducted at 32°C, 75% r.h. as compared with 32°C, 30% r.h., but the reverse was true for exposures conducted at 27°C. Pointsource™ appears to have excellent potential for use in controlling Tribolium species within indoor facilities.     

Impact of physical and biological factors on susceptibility of Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae) to new formulations of hydroprene

Three separate experiments were conducted to: (1) evaluate two new commercial formulations (202-080 and 202-084) of the insect growth regulator hydroprene, (2) determine residual efficacy of hydroprene-treated concrete stored at different environmental conditions, and (3) assess the impact of accumulated flour on residual efficacy. In the first test, late instars of Tribolium castaneum (Herbst), the red flour beetle, and Tribolium confusum (du Val), the confused flour beetle, were exposed on concrete treated with hydroprene. At 40% relative humidity (r.h.), there was no difference between species regarding the percentage of individuals that stopped development in the larval stage (arrested larvae), but at 75% r.h. there were more arrested T. castaneum than T. confusum in all treatments except the low rate of formulation 202-084. No adult T. castaneum lived after emergence (live adults) at either relative humidity, but the percentage of live adult T. confusum ranged from 1.0% to 41.0%, depending on treatment. In the second test, late instars of T. confusum were exposed at 6 and 12 weeks post-treatment on concrete treated with the two experimental formulations and stored under different environmental conditions. At 6 weeks there was no difference between formulations. At 12 weeks, fewer live adults and more dead emerged adults with gross morphological deformities were found on concrete treated with formulation 202-084 and stored at 32°C, 75% r.h. compared to other treatment combinations. In the final experiment, wheat flour was added to treated concrete for 5 weeks before the bioassays were conducted with late-instar T. confusum. There were few live adults produced in the initial bioassays, and dead adults with gross morphological deformities ranged from 83.1% to 97.6%. However, in bioassays conducted with late-instar larvae at 6 weeks, most adults eventually emerged with few deformities. The presence of the flour apparently compromised residual control and the hydroprene was no longer effective. In summary, the new hydroprene formulations were equivalent to the registered product Gentrol^®. Tribolium confusum was less susceptible than T. castaneum, and residual control of T. confusum on a clean surface without flour lasted about 6-12 weeks.     

Initial and delayed mortality of late-instar larvae, pupae, and adults of Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae) exposed at variable temperatures and time intervals

Late-instar larvae, pupae, and adults of Tribolium castaneum (Herbst), the red flour beetle, or Tribolium confusum (DuVal), the confused flour beetle, were exposed for variable durations at 36-54 °C. Beetles were placed in laboratory ovens set at a baseline of 27 °C, the temperature was increased by 0.1 °C per minute until the target temperature was achieved, and beetles were then held for specified exposure durations. There was no mortality after initial exposure or after a 1-week holding period of any life stage of T. castaneum or T. confusum exposed for 32 h to 36, 39, or 42 °C. At 45 °C, there was no initial mortality of either species exposed for different time intervals except for those exposed for 28 h. However, there was a significant increase in mortality after the 1-week holding period of those beetles exposed initially for at least 16 h to 45 °C. There was a sharp increase in mortality after the initial exposures of 4 h at 48 °C; mortality of T. confusum larvae was 90.0±5.7% but was only 10.0±10.0% for larvae of T. castaneum, and no pupae of either species were dead. All life stages of both species were killed after the initial exposure of 12 h, and 1-week mortality of beetles exposed for 4 and 8 h was generally greater than initial mortality. At 51 and 54 °C, 2- and 1-h exposures, respectively, killed all life stages of each species. Mortality in conditions of gradual temperature increase was less than previous studies with sudden temperature increases.     

Survival and reproduction of Tribolium castaneum (Herbst), Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) following periods of starvation

This study determined the starvation tolerance of Tribolium castaneum (Herbst), Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) in terms of both adult survival and reproduction, the impact of starvation on reproduction not having been studied before. Experiments were conducted at 30 °C and 55% or 70% r.h. using a laboratory strain and a field strain of each species. The number of progeny was a better indicator of the impact of starvation on a species than adult survival. Tribolium castaneum was the most tolerant species, requiring up to 35 d starvation before no progeny were produced. Rhyzopertha dominica and S. oryzae required up to 8 d starvation before no progeny were produced. The results suggest that hygiene will have a greater impact on populations of S. oryzae and R. dominica than T. castaneum.     

Distribution of the Medea factor M in populations of Tribolium castaneum (Herbst) in the United States

The distribution of the maternally acting, selfish gene Medea⁴ (M⁴) was determined in populations of the red flour beetle, Tribolium castaneum (Herbst), collected in the southern and midwestern United States. We found clear evidence for the existence of two major regional subpopulations, with a boundary that roughly corresponds to 33°N latitude. All 26 strains collected in 10 states north of this latitude were homozygous for the M⁴ allele, while only two of 29 strains collected in six states south of this latitude were homozygous for the allele. Of the remaining 27 southern strains, 21 lacked the M⁴ allele entirely, while six contained a mixture of M⁴ and non-M⁴ alleles. This is the first evidence of either the existence of biotypes or the presence of major barriers to gene flow in wild populations of this ubiquitous insect species.     

Effect of suboptimal temperatures and sublethal CO2 levels on multiplication of Tribolium castaneum (Coleoptera: Tenebrionidae), alone or competing with Cryptolestes ferrugineus (Coleoptera: Cucujidae)

Groups of adults of Tribolium castaneum alone, or in combination with adults of Cryptolestes ferrugineus, were exposed to suboptimal temperatures (15°C, 20°C, and 25°C) and sublethal CO₂ levels (2%, 5%, and 10%) in dry (12%, wet mass basis) and damp (15%, wet mass basis) stored wheat in the laboratory, to investigate effects on population size. The mean adult numbers in single- and mixed-species tests were positively correlated with higher temperature and moisture content and negatively correlated with higher CO₂ levels. Adult numbers in single- and mixed-species tests were lower at sublethal CO₂ levels compared to ambient CO₂ levels at all the test temperatures and decreased in dry grain compared to damp grain. Although, a specific trend was not observed in population inhibition between mixed-species and single-species tests, overall the adult populations of T. castaneum were reduced in the presence of C. ferrugineus. A mathematical model was derived to predict the size of adult populations of T. castaneum alone, or in the presence of C. ferrugineus considering all the variables in this study. The model had an R² value of 0.72 but needs to be validated and refined with field data.     

Effectiveness of spinosad dust against different European populations of the confused flour beetle, Tribolium confusum Jacquelin du Val

Six populations of the confused flour beetle, Tribolium confusum, obtained from Greece, Italy, Portugal, Denmark, Germany and France were tested for their susceptibility to a spinosad dust formulation, containing 0.125% spinosad. For this purpose, adults and larvae of T. confusum were exposed on wheat treated with two dose rates of the dust formulation, 0.06 and 0.19 ppm of a.i. corresponding to 50 and 150 ppm of the formulation, at 25 °C and 65% r.h. Mortality of the exposed individuals was assessed after 7, 14 and 21 days of exposure on the treated substrate. The increase of dose and exposure interval increased mortality, while adults were more tolerant to spinosad than larvae. Significant differences were noted among populations, for both adults and larvae. The most tolerant to spinosad was the strain from Greece, while the least tolerant were the strains from Germany and Denmark. After 7 days of exposure, on wheat treated with 50 ppm, mortalities of adults of the Greek, German and Danish strains were 2%, 25% and 62% respectively, while the respective figures for 150 ppm were 1%, 31% and 81% respectively. In the case of larvae, of the same strains, mortality at 50 ppm was 6%, 27% and 28% and at 150 ppm 11%, 23% and 40%, respectively. The results of the present study suggest that different strains and stages of T. confusum differ widely in their susceptibility to spinosad-treated wheat.     

Insecticidal effect of Steinernema feltiae (Filipjev) (Nematoda: Steinernematidae) against Tribolium confusum du Val (Coleoptera: Tenebrionidae) and Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) in stored wheat

The confused flour beetle, Tribolium confusum, and the Mediterranean flour moth, Ephestia kuehniella, are important pests of stored grain products. The insecticidal effect of three strains (UK 76 [=Nemasys], USA/SC, and Hawaii) of the entomopathogenic nematode Steinernema feltiae was determined in the laboratory, in wheat, against these pests. The nematodes were applied at three dose rates: 100, 300 and 900 nematodes/insect individual. The Hawaii strain was most virulent against T. confusum adults and larvae, with a significant dose effect in the case of the larvae. Larval mortality of this species reached 79% and 100% after 7 and 14 d of exposure to the nematodes, respectively, at the highest dose applied. On the other hand, adult mortality of T. confusum did not exceed 66%. In the case of E. kuehniella larvae, USA/SC performed best causing 52% and 69% mortality after 7 and 14 d exposure, respectively, at the highest dose tested. Since very few data are available on the effect of entomopathogenic nematodes against these pests, it is concluded that the Hawaii and USA/SC strains of S. feltiae should be further investigated as promising biological control agents for T. confusum and E. kuehniella.     

Fecundity of wild Tribolium castaneum (Herbst) from southeast Queensland, Australia

Fecundity was investigated in wild Tribolium castaneum (Herbst) from southeast Queensland, Australia. Although the fecundity of T. castaneum has been investigated in laboratory studies, the reproductive potential of wild females may be less than that of females reared and tested under favourable laboratory conditions. Adult T. castaneum were trapped using corrugated cardboard traps baited with whole wheat flour on four occasions during May-July 1997 in a grain-growing area of southeast Queensland. After each trapping period, fecundity of individual wild females was assessed on whole wheat flour at 30°C and 55% erh. In addition, F₁ adults were pooled, a sample was taken and fecundity of individual females was assessed similarly. Almost 90% of the adults were trapped on four of the 10 grain storage sites, and these sites yielded females on all four trapping occasions. There was no systematic effect of trapping period on fecundity of wild females, and in three of these four sites there was no effect at all. There were no significant differences between numbers of progeny produced by F₁ females derived from different trapping periods, so the data were pooled for comparison with the results from wild females. Generally, fecundity of wild females was high relative to that of F₁ females which had been reared under uniformly favourable conditions in the laboratory. Despite the trapping occurring during some of the coldest months of the year, females were clearly active and capable of reproducing, demonstrating the importance of maintaining high levels of grain hygiene throughout the year.     

Grain loss caused by Tribolium castaneum, Sitophilus oryzae and Acanthoscelides obtectus in stored durum wheat and beans treated with Beauveria bassiana

The effect of the fungal entomopathogen Beauveria bassiana (Balsamo) Vuillemin (Hyphomycete) on the losses caused to durum wheat and beans by storage insects was investigated. Grains were infested with Tribolium castaneum (Herbst), Sitophilus oryzae (L.) and Acanthoscelides obtectus (Say). Beauveria bassiana was produced in inoculated autoclaved rice. The spore formulation (ground rice and B. bassiana) was applied to grain (wheat or bean) and shaken to evenly cover the grain. Adults of T. castaneum or S. oryzae were added to wheat and adults of A. obtectus to bean. Five replicates were set up for each treatment and controls (milled rice but no conidia). The insecticidal effect of B. bassiana was tested by measuring the fresh weight and weight loss of grains after four months of storage. Wheat grains infested with S. oryzae without the conidia was significantly more damaged by weevils than grains treated with B. bassiana. The mean fresh weight of grains with the conidia was significantly greater (18.4%) than the corresponding mean without the fungus when S. oryzae were present. Percentage weight loss decreased by 81.5% and was significantly smaller than the loss from the untreated grain. Significant differences were not found in the fresh weight of seed infested with T. castaneum or A. obtectus in treated or untreated grain nor in the percentage weight loss of grains infested with these insects, with and without B. bassiana.     

Evaluation of kaolinite-based particle films to control Tribolium species (Coleoptera: Tenebrionidae)

Adults of Tribolium castaneum (Herbst), the red flour beetle, and Tribolium confusum (du Val), the confused flour beetle, were exposed to kaolinite-based particle film dusts. When beetles were continuously exposed to the hydrophobic particle film M-96-018 at the rate of 0.1-0.5 mg/cm², all the T. castaneum at 0.1 mg/cm² were dead after 3 days, but 40±13.8% of the exposed T. confusum were still alive after 7 days. At higher concentrations, all the T. castaneum were dead after 2 days, but 5-6 days of exposure were needed to kill all T. confusum. In a subsequent test, adults of both species were exposed for 8-72 h to 0.5 mg/cm² of the particle film M-96-018, removed, then held without food for 1 week. No T. castaneum survived, while survival of the T. confusum ranged from 0 to 55±17.3%, depending on the exposure interval. In a test conducted at controlled conditions of 40%, 57% and 75% r.h., 27°C, T. confusum were exposed for 8-72 h to the particle film M-96-018 and a hydrophilic particle film M-97-009 at the rate of 0.5 mg/cm², then removed and held either with or without wheat flour for 1 week. All the T. confusum exposed to the particle film M-97-009 usually survived, while survival of the T. confusum exposed to the particle film M-97-018 after the 1-week holding period increased with increasing relative humidity and with the presence of food. The particle film M-96-018 was effective against both the Tribolium species, and appears to have a potential for use in management programs to control beetles within storage facilities.     

Comparison of the mitochondrial proteomes of phosphine-susceptible and -resistant Tribolium castaneum

Various lines of evidence suggest that mitochondria might be the site of constitutive differences between coleopteran pests of stored products with and without resistance to the fumigant phosphine. In this study two-dimensional polyacrylamide gel electrophoresis with Differential In-Gel Electrophoresis (DIGE) was used to compare soluble proteins from the mitochondria of phosphine-susceptible and -resistant Tribolium castaneum. Eighty-five spots were aligned across all nine gels and a further 111 across all but one gel. Each gel displayed the proteome from a susceptible strain, a resistant strain and a standard made by mixing aliquots from all experimental samples. No significant differences were observed between resistant strains and strains susceptible to phosphine. However, proteins of lower abundance and membrane proteins were not detected so important resistance-associated differences might yet be detected by more exhaustive techniques.     

Screening of Chinese medicinal herbs for bioactivity against Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst)

Extracts of 40 species of Chinese medicinal herb from 32 different botanical families were screened for contact, fumigant and feeding-deterrent activities against the two stored-grain insects Sitophilus zeamais and Tribolium castaneum. Thirty Chinese medicinal herbs exhibited insecticidal or feeding-deterrent activities against the two species of insects. Extracts of Artemisia argyi, Dictamnus dasycarpus, Evodia rutaecarpa, Litsea cubeba, Narcissus tazetta var. chinensis, Polygonum aviculare, Rhododendron molle, Sophora flavescens, Stemona sessilifolia, Tripterygium wilfordii, and Torreya grandis were most active.     

Calorimetric evaluation of responses of Sitophilus oryzae and Tribolium confusum to elevated temperatures and controlled atmospheres

Metabolic heat rates, determined by microcalorimetry, were used to measure the effect of controlled atmospheres (CAs) and elevated temperatures on the stored-product insects Sitophilus oryzae (rice weevil) and Tribolium confusum (confused flour beetle). Results for larval and adult stages in air, and in a range of low O₂ and/or high CO₂ CAs, at temperatures from 15 to 45 °C, showed the general effectiveness of such atmospheres in lowering the lethal temperatures relative to those in air. Effects on adult S. oryzae at 25 °C were explored in more detail in experiments using the following conditions: exposure to anoxic CAs for extended times; exposure to hypoxic CAs; and simulated hermetic storage. A simple scanning calorimetric method was developed for determining lethal temperatures and a combined thermo-gravimetric and differential thermal-analysis method was used to interpret the thermal events, due to loss of water, occurring at and above these temperatures.     

Insecticidal efficacy of diatomaceous earth against Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Tribolium confusum du Val (Coleoptera: Tenebrionidae) on stored wheat: influence of dose rate, temperature and exposure interval

Laboratory experiments were conducted in order to assess the insecticidal effect of a diatomaceous earth formulation (Silicosec^®, Biofa GmbH, Germany) against Sitophilus oryzae and Tribolium confusum on stored wheat. Adults of the two species were exposed on wheat treated with diatomaceous earth at four dose rates: 0.25, 0.5, 1 and 1.5 g/kg of wheat, respectively. For each dose rate, the treated wheat was placed at 22°C, 25°C, 27°C, 30°C and 32°C. Dead adults were counted after 24 and 48 h, 7 and 14 d of exposure. After the 14-d interval, the live adults were removed and placed for 7 d in untreated wheat (in the case of S. oryzae) or untreated flour (in the case of T. confusum), and the production of F₁ was recorded. For both species, dose rate, temperature and exposure interval significantly affected mortality (P<0.001). Mortality was higher at longer exposure intervals. The efficacy of SilicoSec against S. oryzae increased with temperature, but for T. confusum mortality was lower at 32°C, compared to 30°C, for 24 and 48 h exposure intervals. Tribolium confusum proved less susceptible to SilicoSec than S. oryzae. In general, the rates of 1 and 1.5 g/kg of wheat provided a satisfactory level of protection against the two species examined. For S. oryzae, F₁ emerged only at 22°C, in wheat treated with 0.25 or 0.5 g/kg. However, for T. confusum, F₁ were recorded at 22°C for 0.5 g/kg and at 22°C, 25°C, 27°C and 30°C for 0.25 g/kg.     

Response and genetic analysis of malathion-specific resistant Tribolium castaneum (Herbst) in relation to population density

Extensive use of malathion for pest control on stored cereals has resulted in worldwide resistance in red flour beetles, Tribolium castaneum. In this paper we investigate population density effects on the malathion-specific resistance in PRm, a strain from the Philippines, in an integrated resistance management framework. Two populations of malathion-specific resistant (PRm) and a malathion-susceptible strain of T. castaneum were bred at different densities: low (4 adults/g) and high (12 adults/g) density on wheat plus brewer's yeast in the laboratory. After eight generations, slopes of probit regression lines and LC₅₀ values were used to monitor the effect of insect rearing density on the progression of malathion-specific resistance. The LC₅₀ of the malathion-susceptible strain (Asm) did not change significantly during selection while LC₅₀s varied for both the high-density and low-density lines of PRm, the LC₅₀ of malathion ranged from 27.51 to 34.06 and from 21.14 to 29.39 μg malathion cm⁻² for high and low density, respectively.More than 33 generations were required to achieve a 10-fold increase of resistance for the low-density line compared to only 17 generations for the high-density line. Calculations from published formulae suggested that the malathion-specific resistance of both high- and low-density lines was under monofactorial control, with complete dominance.The data showed that environmental factors such as population density differences in insect rearing and development may influence the heritability of resistance. Furthermore, the variability in results published worldwide on resistance emphasises the need to standardize test conditions across laboratories.     

Impact of high temperatures on efficacy of cyfluthrin and hydroprene applied to concrete to control Tribolium castaneum (Herbst)

In laboratory trials, concrete was treated with cyfluthrin wettable powder (WP) at 40 mg active ingredient [AI] cyfluthrin WP/m², then heated for 4, 8, or 16 h at either 45°C or 55°C, or treated but not heated (seven treatment combinations). Bioassays were conducted by exposing adult Tribolium castaneum (Herbst) for 0.5, 1, and 2 h. Survival of T. castaneum was generally greater on unheated concrete compared with the heating treatments, and survival appeared to decrease as heating time increased at both 45°C and 55°C. In a second laboratory trial, concrete was treated with hydroprene (Gentrol) at the label rate of 1.9×10⁻³ mg [AI]/cm², and bioassayed by exposing late-instar T. castaneum larvae on the treated surface. There were significant differences between untreated controls and the heat treatment regimes (P<0.05) with respect to the percentage of live emerged adults, the percentage of those adults with deformities, and the percentage of dead adults, but heating did not reduce efficacy of hydroprene. In a field trial, concrete was treated with cyfluthrin at 2 mg [AI] cyfluthrin WP/m², and placed in a flour mill undergoing an experimental heat treatment and in an unheated office. Treated concrete was bioassayed by continually exposing adult T. castaneum for 0.5-120 h. The effect of heating time on insect mortality was not significant (P?0.05). Except for T. castaneum exposed for 0.5 h, the percentage of beetle survival on unheated concrete was greater (P<0.05) than survival on concrete that had been heated in the mill, indicating a possible beneficial effect on cyfluthrin toxicity due to heating. Results of these studies show that short-term exposures to high temperatures may have no appreciable effect on efficacy of either cyfluthrin WP or hydroprene, and combination treatments of heat plus either of these insecticides may be effective alternatives to methyl bromide for disinfesting milling facilities.     

Toxicity of ethyl formate to adult Sitophilus oryzae (L.), Tribolium castaneum (herbst) and Rhyzopertha dominica (F.)

Fumigations were conducted using a continuous flow-through laboratory process to maintain constant concentrations of ethyl formate and low levels (<0.8%) of respiratory carbon dioxide. The procedure minimised the effects of sorption by exposing test insects without media and minimised the effect of carbon dioxide by use of continuous flow. The concentration×time (Ct) products of ethyl formate for adult Sitophilus oryzae, Tribolium castaneum and Rhyzopertha dominica at 25 °C and 70% relative humidity for the 6 h exposure were, respectively: (1) LD₅₀ 107.8, 108.8 and 72.8 mg h L⁻¹ and (2) LD_99.5 207.4, 167.1 and 122.2 mg h L⁻¹. Endpoint mortality was reached within 24 h of initial exposure.     

Effect of low pressures on the survival of cocoa pests at 18°C

This study forms part of an effort to eliminate the need for fumigation with methyl bromide to control insect infestations in stored cocoa beans, through development of novel alternative vacuum-hermetic technology. In this communication, the effects of low pressures and exposure time were studied on the mortality of insects at a temperature of 18°C, chosen to simulate cocoa bean storage conditions in temperate climates.Three insect species were used, two of which are major pests of cocoa beans in producer countries, Ephestia cautella (Walker), and Tribolium castaneum (Herbst), while the third, Oryzaephilus surinamensis (L.), is a potential storage pest in temperate climates. For T. castaneum and E. cautella the egg stage was the most resistant to 55±10 mm Hg at 18°C, the times needed to obtain 99% egg mortality were 96 and 149 h, respectively. For O. surinamensis, the adult stage was the most resistant with 164 h being required to obtain 99% mortality.     

Protection of stored maize from insect pests using a two-component biological control method consisting of a hymenopteran parasitoid, Theocolax elegans, and transgenic avidin maize powder

The hymenopteran parasitoid, Theocolax elegans (Westwood), and transgenic avidin maize powder were tested to determine if their individual or combined use would protect stored grain from infestation by both internal and external insect pests. Small-scale tests were conducted in plastic jars containing 3 kg of non-transgenic maize. We tested treatments of 0.3% powdered avidin maize, the parasitoid wasp, and the combination of the parasitoid plus 0.3% powdered avidin maize. One pair each of Sitophilus zeamais Motschulsky, Tribolium castaneum (Herbst), and Cryptolestes ferrugineus (Stephens) was added to each jar. After 8 weeks, the entire contents of each jar were examined for adult insects. Control and avidin maize powders had no detrimental effects on the beneficial insect parasitoid T. elegans. The parasitoid suppressed populations of the internal feeder S. zeamais. The avidin maize powder treatment had no effect on S. zeamais because these larvae developed inside the maize kernels where no avidin maize powder was present. For S. zeamais, the combination treatment was not significantly different from the parasitoid treatment. In contrast, populations of the external feeder T. castaneum were not suppressed by the parasitoid but were suppressed by the avidin maize powder treatment. The parasitoid-avidin combination treatment produced the greatest percentage reduction for all three insect species and resulted in 78%, 94%, and 70% reductions in populations of S. zeamais, T. castaneum, and C. ferrugineus, respectively, when compared to the control treatment. The percentage reductions for the parasitoid treatment were 70%, 8%, and 20% for S. zeamais, T. castaneum, and C. ferrugineus, respectively. For the avidin maize powder treatment, populations of S. zeamais, T. castaneum, and C. ferrugineus were reduced by 10%, 85%, and 40%, respectively. The combination treatment of avidin maize powder plus the release of parasitoid wasps was superior to either treatment alone when applied to mixed populations of internal and external feeders.