Effects of spinosad on the heat tolerance and cold tolerance of Sitophilus oryzae L. (Coleoptera: Curculionidae) and Rhyzopertha dominica F. (Coleoptera: Bostrichidae)

Sitophilus oryzae and Rhyzopertha dominica are serious insect pests of stored products in Sri Lanka. Currently pirimiphos methyl and phosphine fumigation are used as control measures but grain handlers seek for alternatives. Exposure to high or low temperature is popular in stored-product insect pest management but is expensive. Spinosad is effective against certain stored-product insects but has not yet been tested for its synergy with heat or cold. This experiment was conducted to evaluate the effect of spinosad on the heat tolerance and cold tolerance of S. oryzae and R. dominica adults. The experiment was a two-factor factorial, complete randomized design with four replicates. The spinosad concentration and exposure period were changed. Adults of S. oryzae and R. dominica were first exposed to a series of spinosad concentrations. Later they were held at higher (40 °C) or lower (6–11 °C) temperatures than room temperature for different durations.Pre exposure of S. oryzae adults to Spinosad at 18 ppm or above synergized the adult mortality at high or low temperature showing a dose response. Pre-exposure of R. dominica adults to spinosad concentrations 12.5 ppm or higher synergized the mortality at high temperature whereas the spinosad synergized the mortality of R. dominica at low temperature when exposed to 6.25 ppm or higher concentrations; the effects followed a dose response. This study shows that heat and cold tolerance of S. oryzae and R. dominica adults are reduced by pre-exposure to spinosad. Therefore, spinosad is a potential grain protectant at high or low temperatures against these two insect species.     

Insect population dynamics in commercial grain elevators

Data were collected in 1998-2002 from wheat stored in commercial grain elevators in south-central Kansas. Bins at these elevators had concrete walls and were typically 6-9 m in diameter and 30-35 m tall. A vacuum-probe sampler was used to collect grain samples in the top 12 m of the wheat in each bin. The primary insect species found in the wheat samples were: Cryptolestes ferrugineus, Rhyzopertha dominica, and Tribolium castaneum. In the top 3.7 m of grain, R. dominica, C. ferrugineus, T. castaneum and Sitophilus oryzae made up 44, 36, 19 and 1% of the insects found in the samples, respectively. From 3.8 to 12.2 m, R. dominica, C. ferrugineus, T. castaneum and S. oryzae were present at 84, 8, 8, and 1%, respectively. The most prevalent species also changed over time. In June, the start of wheat harvesting and storage in Kansas, insect density was low in the bins. At this time, C. ferrugineus was the most common insect, and it was found mostly in the top grain sample (0-1.2 m). In September through November, C. ferrugineus and R. dominica were at similar densities; however, from February to March, R. dominica was more common.Generally, insect density was greatest at the top and decreased with grain depth. Very few insects were found in samples collected from greater than 12 m (most of the bins contained grain to depths of 24-36 m). Insect density for all species increased rapidly from June through October. During this period less than 20% of the bins had economically significant insect densities (>2 insects/kg). From October until February, the average insect density remained fairly constant but it was greatly reduced in April, May, and June. Bins that had insect densities >2 insects/kg tended to be located adjacent to other heavily infested bins.     

LABORATORY EXPERIMENTS TO COMPARE THE DEVELOPMENT OF POPULATIONS OF FIVE SPECIES OF INSECT DURING DORMANCY BREAK AND SUBSEQUENT COOL STORAGE OF MALTING BARLEY

The increase off five beetle species on 50 g of barley was investigated in the laboratory, under conditions simulating grain dormancy break between 20 and 40°C at 5°C increments, followed by cooling to 15, 10 and 5°C and culminating with approximately four months storage at 5°C. The species of storage beetles used were Trogoderme granerlum Everts, Oryzaephilus surinamensis (L.), Cryptolestes ferrugineus (Stephens), Rhyzopertha dominica (Fabricius), and Sitophilua granarius (L.) . At 40°C, only small numbers of T. granarium larvae developed but at 35°C, this species produced very large populations of larvae. At 30°C, O. surinamenals, R. dominica and S. granarius increased moderately while at 25°C the small numbers of O. surinamensis detected were eclipsed by the very large increases in S. granarius which also increased vigorously at 20°C. No adult insects survived in any experiment after four months at 5°C . These results indicate that the best strategy to break dormancy and discourage infestation would be to break dormancy at just above 40°C, followed by rapid cooling .     

Toxicity of coumaran to stored products beetles

The fumigant activity of coumaran was tested against mixed-age cultures of the rice weevil (Sitophilus oryzae L.), the lesser grain borer (Rhyzopertha dominica F.), the rust-red flour beetle (Tribolium castaneum Herbst), saw-toothed grain beetle (Oryzaephilus surinamensis L.) and flat grain beetle (Cryptolestes ferrugineus Stephens). T. castaneum was tolerant to coumaran, for total population extinction was achieved in 72 h exposure at 50 μg/L dose only. In contrast all developmental stages of O. surinamensis, C. ferrugineus and R. dominica were quite susceptible 100% mortality was attained at < 50 μg/L doses in 24 or 72 h exposure. Further results showed that T. castaneum, generally tolerant pest to fumigants and R. dominica, a predominant stored grain pest in India, could be controlled by coumaran. The findings indicate that, coumaran is good source for alternate to methylbromide for effective control of stored grain insect pests.     

Efficacy of Beauveria bassiana in combination with an electrostatically charged dust for the control of major stored-product beetle species on concrete

Laboratory bioassays were carried out to determine the insecticidal efficacy of a Beauveria bassiana formulation (Bb38, Exosect Ltd, UK), which is based on the combined use of the fungus with the electrostatically charged dust Entostat. The efficacy of Bb38 was conducted on concrete surfaces against adults of the lesser grain borer, Rhyzopertha dominica, the rice weevil, Sitophilus oryzae, the confused flour beetle, Tribolium confusum and the rusty grain beetle, Cryptolestes ferrugineus, in two series of bioassays. In the first series, adults of the above species were exposed on concrete surfaces treated with Bb38 and mortality was recorded after 7 and 14 days of exposure (immediate mortality). These tests were carried out in all combinations of two temperatures, i.e. 25 and 30° C and two levels of relative humidity (r.h.), i.e. 55 and 75%. In the second series of bioassays, adults of the above species were exposed to Bb38 for 7 days, and after this interval, the surviving individuals were transferred in untreated concrete, where mortality was recorded again 7 and 14 days later (delayed mortality). From the species tested, R. dominica was by far the most susceptible, given that mortality reached 100% in almost all temperatures and r.h. levels. From the other species, S. oryzae and C. ferrugineus were moderately susceptible, while Bb38 was less effective for T. confusum. In the second series, immediate mortality for R. dominica was much higher than that of the other species. Moreover, delayed mortality of R. dominica reached 100% in contrast with the other species, where delayed mortality was low. Based on the results of the present work, we found that the insecticidal effect of Bb38 is not affected much by temperature and r.h., for the vast majority of the species and conditions tested. Moreover, in some cases, there was some post-exposure delayed activity of the formulation. This is one of the few studies that examine commercial formulations of fungal-based insecticides against stored product insects, which are expected to provide solutions in stored product protection, where traditional insecticides cannot be applied, as in the case of organic products.     

The influence of some biological and physical factors on the heat tolerance relationships for Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) (Coleoptera: Bostrychidae and Curculionidae)

The influence of several biological and physical factors on the exposure time required to obtain a given level of mortality of immature Rhyzopertha dominica and Sitophilus oryzae exposed to air at 70 or 80°C in a fluidized bed of wheat was determined.The tolerances of five Australian populations of R. dominica differed little. In this species, median tolerance and variance increased as the age span of the exposed insects widened from 0–7 to 0–35 days. Acclimation of R. dominica at 22 or 32°C and S. oryzae at 15 or 30°C before exposure had no appreciable influence on heat tolerance.Changing the initial grain temperature from 32 to 22°C did not alter LT values for R. dominica. However, the LT_99.9s for both warm and cold acclimated S. oryzae in 15°C grain were greater than those in 30°C grain. The LT_99.9s for R. dominica in wheat of 14% m.c. exceeded those in 11.3% m.c. wheat. Heating curves showed that the time taken for cold or moist grain to reach a given high temperature was extended.     

Effect of radio frequency heating on the mortality of Rhizopertha dominica (F.) and its impact on grain quality

The use of radio frequency (RF) heating to reach temperatures lethal to stored product pests has significant potential. We examined the lethal effects of RF on the stored grain pest, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), under four different RFs, three types of grain, and different moisture contents of rice. The quality of two rice cultivars, after RF heating, was also tested. When heated to 58 °C by RF, R. dominica adult mortality reached 100%. The mortality of R. dominica adults reached 100%. The fastest mortality rate occurred at 50–52 °C. With an increase in RF, the time needed to attain a lethal temperature decreased. The heating time to reach 100% mortality differed among the three types of grain; for example, the heating time of wheat was faster than corn or rice. Kernel size and chemical composition was the main factor influencing the RF lethal rate in the different types of grain under the same experimental conditions. There was a significant linear relationship between moisture content (m.c.) and heating time (Y = −38.05 X + 15.501, R = 0.9803) in rice. RF heating of rice to 58 °C did not significantly affect milling quality, storage quality, or seed quality. Thus, heating time, types of grain, and the m.c. of the grains are three important factors that should be considered in RF heating to control stored product pests. These results indicate that RF heating could be an effective physical method for killing stored grain pests.     

Dosage-mortality relationships for Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) exposed to heat in a fluidized bed

Batches of wheat containing immature Rhyzopertha dominica were heated in a fluidized bed to examine the influence of air inlet temperature, bed depth and grain temperature on the exposure time needed for a given level of mortality.With a bed depth of 160 mm, raising inlet temperature from 60 to 80°C decreased the LT_99.9 for R. dominica from 16.1 to 3.25 min: corresponding values for 20 mm beds were 1.92 and 0.54 min.For a given bed depth, $\text{1}\text{LT}{}_{99.9}$ was linearly related to inlet temperature. With inlet temperatures of 80 to 90°C, LT values were linearly related to bed depth over 40 to 160 mm. By contrast, LT value and bed depth were not linearly related at lower temperatures.With beds of 40 to 160 mm, the grain temperature asociated with 99.9% mortality ranged from 57.1 to 64.0°C and varied with inlet temperature but not, generally, with bed depth. Heating grain to 56–57°C and allowing it to soak, unfluidized, before cooling increased mortality from about 50 to > 99%.Four other species of stored product beetle suffered complete mortality when subjected to a treatment expected to yield 99.9% mortality of R. dominica.The experimental results are discussed in terms of heating strategies, heat recovery and the choice of optimal bed depth.     

Delayed mortality responses of Rhyzopertha dominica (F.) adults subjected to short exposures on spinosad-treated wheat

Laboratory studies were conducted to characterize post-exposure (delayed) mortality responses of adults of the lesser grain borer, Rhyzopertha dominica (F.), following brief exposures to wheat treated with dry and liquid spinosad formulations at the labeled rate of 1 mg (a.i.) kg⁻¹ of grain. Exposure of R. dominica adults to a dry spinosad formulation at the labeled rate for 4 h resulted in 16–34% mortality. When these adults were placed on untreated wheat, post-exposure mortality continued to increase in a non-linear fashion, with 100% mortality observed at 60 h. Similarly, when R. dominica adults were exposed to wheat treated with a liquid spinosad formulation at the labeled rate for 0.5–48 h, 100% post-exposure mortality on untreated wheat occurred within 24–168 h. Exposure for 72 h resulted in 100% mortality on spinosad-treated wheat itself. There was an inverse relationship between exposure of adults to spinosad-treated wheat and time to 100% mortality on untreated wheat. These results suggested that short exposures (0.5–48 h) of R. dominica adults to wheat treated with the labeled rate of spinosad will ensure its complete control even after removal from treated grain. Adults of R. dominica which disperse to untreated grain after brief exposures to spinosad-treated wheat may eventually die because of delayed toxicity effects of spinosad against this economically important insect species.     

Movement of Rhyzopertha dominica in response to temperature gradients in stored wheat

The movement and temperature preference of Rhyzopertha dominica was determined in a 56 cm diameter cylinder with 9 cm high sides containing 19.9 kg of hard red winter wheat. Two temperature gradients were tested over a 24 h period: 42 to 20 °C and 24 to 20 °C with the cooler temperature being on the periphery of the cylinder. No preference existed when there was no temperature gradient. Beetles preferred the moderate temperature region of the cylinder in the 42 to 20 °C gradient, but avoided the highest temperature region. In the 24 to 20 °C gradient, insects did not move very much during the 24 h period. When a longer duration was used (96 h) for the 24 to 20 °C gradient, there were significantly more insects in the warmest center region of the gradient compared to the middle or outer regions. Compared to other stored grain Coleoptera, such as Cryptolestes ferrugineus, R. dominica appears to move more slowly through the grain into preferred temperature regions.     

Geostatistical analysis of adult Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) in wheat stored at constant temperatures

Insect monitoring and sampling programmes are used in the stored grains industry for the detection and estimation of insect pests. At the low pest densities dictated by economic and commercial requirements, the accuracy of both detection and abundance estimates can be influenced by variations in the spatial structure of pest populations over short distances. Geostatistical analysis of Rhyzopertha dominica populations in 2-dimensions showed that, in both the horizontal and vertical directions and at all temperatures examined, insect numbers were positively correlated over short (0–5 cm) distances, and negatively correlated over longer (≥10 cm) distances. Analysis in 3 dimensions showed a similar pattern, with positive correlations over short distances and negative correlations at longer distances. At 35 °C, insects were located significantly further from the grain surface than at 25 and 30 °C. Dispersion metrics showed statistically significant aggregation in all cases. This is the first research using small sample units, high sampling intensities, and a range of temperatures, to show spatial structuring of R. dominica populations over short distances. This research will have significant implications for sampling in the stored grains industry.     

Interspecific associations among stored-grain beetles

Recent increases in prices of raw grain, including wheat, will reduce action thresholds for insect damage and therefore justify more research into management practices and understanding of pest ecology in stored grain. Compared to most other habitats, natural or man-made, a filled grain silo constitutes a unique and fairly homogeneous habitat in which food availability for many grain-feeding insects is unlimited. A fundamental aspect of stored-grain insect ecology is a better understanding of associations among common beetle species. We analyzed the densities of three important stored-grain beetle species, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae), and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in wheat samples collected in 1999–2001 from 129 grain silos in Kansas. The beetles studied here are highly mobile, and the number of insects in each grain sample is a result of the beetles' preference for favorable micro-environmental conditions and possibly of intra- and interspecific associations. In general, the number of T. castaneum in a grain sample increased as the number of R. dominica increased, but the number of C. ferrugineus was not correlated with the number of R. dominica. The densities of both T. castaneum and R. dominica decreased as the number of C. ferrugineus increased. Cryptolestes ferrugineus and T. castaneum can be predators and the species composition of insects in a grain sample may be modified by predation. As T. castaneum populations increased, so did R. dominica but not C. ferrugineus. Our analysis of the species composition in grain samples is discussed in an ecological context.     

Growth performance and digestive enzymes activity of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) feeding on six rice cultivars

The lesser grain borer, Rhyzopertha dominica (F.), is one of the major insect pests of stored-grains such as wheat and rice. Due to various difficulties associated with synthetic pesticides, more environmentally friendly alternative methods are greatly appreciated for controlling pests. In the present study, development, growth index, reproductive success of the females and the amylolytic and proteolytic activities of R. dominica were investigated on six rice cultivars. The experiments were carried out under laboratory conditions inside a growth chamber, which was set at 28 °C, 70% R.H. Our results showed that cultivar Hashemi was the more suitable host for R. domininica because the highest larval and pupal survival rate, longevity of adults, fecundity, hatchability of females, food consumption, maximal growth index, as well as the highest amylolytic and proteolytic activities. In contrast, cultivar Gohvar showed the most suitable suite of traits to reduce potential aspects of feeding by R. domininica because the lowest larval and pupal survival rate, adult longevity, fecundity, hatchability, and lower adult weight and food consumption. Results suggested that cultivar Govhar cultivar as an unsuitable host for R. domininica could be considered in the integrated management of this pest.     

Potential of four Turkish isolates of entomopathogenic nematodes against three major stored products insect pests

The insecticidal effect of native entomopathogenic nematode (EPN) isolates (Steinernema feltiae UTP-5 isolate, Heterorhabditis bacteriophora UMK-7 isolate, S. feltiae DDKY-11 isolate and H. bacteriophora AVB-15 isolate) recovered from the Cappadocia Region of Turkey were investigated on the adults of S. granarius and R. dominica and the larvae of E. kuehniella at different temperatures (15 °C, 20 °C and 25 °C) and concentrations (250, 500 and 1000 IJs/adult for S. granarius and R. dominica; 10, 50 and 100 IJs/larvae for E. kuehniella) under controlled conditions. Insect mortality was recorded after 4th, 6th and 8th day of exposure time for S. granarius and R. dominica, and 2nd and 4th day for E. kuehniella. The results showed that the efficacy of the isolates at 25 °C was generally higher than the ones at 15 °C and 20 °C. Steinernema feltiae DDKB-17 isolate caused the highest mortality (86%) against S. granarius adults at all temperatures tested. The virulence of the tested isolates on R. dominica adults did not exceed 44% at all temperatures and concentrations tested. UMK-7 and AVB-15 isolates were the most virulent isolates against E. kuehniella larvae with a mortality rate of 100%. Based on the results obtained from the laboratory tests, it appeared that the isolates tested have a good potential for the management of S. granarius, R. dominica and E. kuehniella.     

An evaluation of fluidized-bed heating as a means of disinfesting wheat

Wheat of 14% m.c. containing all immature stages of Sitophilus oryzae (L.), Rhyzopertha dominica (F.) and Sitotroga cerealella (Oliv.) was exposed to air temperatures of 60, 70 or 80°C in a 10 kg capacity fluidized-bed operated with an airflow of 14.51 ls^?1 kg^?1 at 1.6 m s^?1. Exposures of 12, 6 and 4 min respectively produced grain surface temperatures of 59, 62 and 65°C and gave almost complete disinfestation. The required minimum exposure was determined by the heat tolerance of R. dominica which exceeded that of the other species. The moisture content of treated wheat was not changed appreciably and its baking quality was not impaired. Experiments with S. oryzae and R. dominica showed that the adults were also controlled by such exposures. The cost of fluidized-bed heating is discussed and appears to be comparable to that of recirculatory fumigation with methyl bromide.     

Efficacy of methoprene for multi-year protection of stored wheat,brown rice,rough rice and corn

Hard red winter wheat, brown rice, rough rice, and corn were treated with the insect growth regulator (IGR) methoprene at rates of 1.25 and 2.5 ppm, held for 24 months at ambient conditions in buckets on the floor of a grain bin, and sampled every two months. Bioassays were done by exposing 10 mixed-sex adults of Rhyzopertha dominica (F.), the lesser grain borer, and Tribolium castaneum (Herbst), the red flour beetle, on wheat, R. dominica and Sitotroga cerealella (Oliver), the Angoumois grain moth, on brown rice and rough rice, and T. castaneum and S. cerealella on corn. Sample size for all commodities was about 80 g, and these samples were held for 3 months at 27°C-60% r.h. Both rates of the IGR completely suppressed adult progeny development of R. dominica with little resulting feeding damage, sample weight loss, or insect damaged kernels (IDK). Some adult progeny production of S. cerealella and resulting IDK occurred at both rates on rough rice, brown rice, and corn, but was far less than in untreated controls. There was little adult progeny production but some feeding damage caused by larval T. castaneum in the treated wheat and corn but again far less than in untreated control. Allowing continual exposure of parental adults on grains treated with an IGR, rather than exposing those parental adults for a short time period, may give more accurate evaluations of residual efficacy. Results show that methoprene used as a grain protectant will give residual control of stored product beetles for 24 months, but complete control of S. cerealella may require inclusion of a contact insecticide.     

Impact of Rhyzopertha dominica (F.) on quality parameters of milled rice

The impact of Rhyzopertha dominica, the lesser grain borer, on milling quality of Francis and Wells cultivars of rough rice was assessed for the 2007 and 2008 crop years by infesting 200-g rough rice samples harvested at moderate and low moisture contents with 0, 10, 25, 50, and 100 parental adult insects, which were removed after one week. The samples were incubated for seven weeks at either 27 or 32 °C and 60% relative humidity to determine progeny production and feeding damage (insect frass), and subsequently the milled rice yield (MRY) and head rice yield (HRY). Progeny production from each parental density level varied with variety and temperature. The number of progeny produced by the parental adults was positively correlated with feeding damage, and the feeding damage caused by the progeny was in turn negatively correlated with MRY and HRY. For both years, more progeny production and feeding damage occurred in Francis versus Wells for each of the harvest moisture contents. Results show differential susceptibility of Francis and Wells cultivars to R. dominica, and also provide new methodologies for evaluating effects of infestation on rice milling quality.     

Testing the consistency of spatio-temporal patterns of flight activity in the stored grain beetles Tribolium castaneum (Herbst) and Rhyzopertha dominica (F.)

Many studies have been published on the flight activity of stored grain beetles in temperate regions, but few have focussed on tropical and sub-tropical regions. The spatio-temporal patterns of flight activity of Tribolium castaneum (Herbst) and Rhyzopertha dominica (F.) were quantified in a grain growing district on the Tropic of Capricorn in central Queensland, Australia. Nine traps baited with aggregation pheromone lures were monitored at 2-wk intervals (fortnightly) for 1 year along a 28.4 km linear transect that included sites at bulk grain depots and sites away from stored grain. Beetles of both species were trapped every fortnight during the study. The spatio-temporal patterns of flight activity differed greatly across the two species, as predicted from studies elsewhere. Rhyzopertha dominica was widespread across the landscape, as the mean trap catch of this species was equal in depot and non-depot traps. In contrast, T. castaneum was more frequently trapped in depot traps than non-depot traps during the colder months, but was much more widespread across the landscape during the summer months. Tribolium castaneum also showed a clear mid-summer peak in flight activity, whereas R. dominica flight activity was highly variable throughout the study. In general, our results reveal patterns that are consistent with those found for T. castaneum and R. dominica in southern Queensland. The contrasting spatio-temporal patterns of flight activity of R. dominica and T. castaneum show that species-specific approaches may be needed to manage these pests and that the spatio-temporal dynamics of resistance genes may differ across these species.     

Variation in Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) progeny adult emergence in different animal feed stored under ventilated and non-ventilated conditions

In contrast to the traditional practices of using naturally-available food materials for livestock production, multiplicity types of animal feed are currently available at the market. Prolonged storage of animal feed concurrently with human food items is practiced, and niche users experience the deterioration and possible risk of contamination of animal feed by insects. This study was conducted to determine the infestation of eleven types of animal feed commonly used in Sri Lanka by Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), a major granivorous insect species. Twenty adults of one-month-old R. dominica were introduced to 20 g of different animal feed: fish feed, rabbit feed, dog feed, cat feed, chick mash, grower mash, layer mash, broiler starter, broiler finisher, bird feed (Bajiri) and rice polish. Each animal feed was maintained either ventilated or non-ventilated. From each animal feed, four replicates were tested. The parent adults were maintained in animal feed for 21 days under ambient environmental conditions (30 °C, 60% relative humidity, continuous darkness), and then sifted out. The progeny adults emerged in each animal feed were determined at monthly intervals for 5 months. In general, fish feed, rabbit feed, layer mash and bird feed (‘bajiri’) were more infested by R. dominica than other animal feed tested. Furthermore, progeny adults emerged in animal feeds differed with the status of ventilation and the duration of storage. The study reveals that the status of ventilation has mixed effects on the infestation of different animal feeds by R. dominica.     

Disinfestation of stored wheat grain and flour using gamma rays and microwave heating

Samples of wheat grain and flour (20 gm of each) were infested with 20 larvae or 5 pairs of adult insects of Tribolium confusum, Lasioderma serricorne, Corcyra cephalonica or Rhyzopertha dominica. The infested samples were tested as follows : (1) microwave heating at four temperature levels 40, 45,50 and 55 °C, for exposure times from10 to 50 s; (2) gamma irradiation over the dose range of 0.5-4 KGy; (3) gamma irradiation + microwave heating. Complete kill of all stages tested was achieved at 50 °C with an exposure time of 50 s. A dose of 2 KGy induced 100% mortality of R. dominica after three days, but it took up to 7 days for all T. confusum and L. serricorne adults to die after a 4-KGy exposure. All insects died within 24 h when exposed to the combination of 1KGy + 50 °C for 30 s.Biochemical analyses on the samples of wheat grain and flour subjected to those treatments at which high mortality was obtained generally showed no detectable changes in the quality of protein, fat, fiber, carbohydrates or ash. The germination of wheat grain was lowered after treatment with microwave radiation but was not affected by a dose of 1 KGy gamma radiation.