Colin J. Demianyk

A rapid method to detect Cryptolestes ferrugineus (Coleoptera: Cucujidae) larvae in stored grain

Modifications of three detection methods, based on the heat-gradient principle employed by the Berlese funnel method were investigated to extract larvae of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), developing under the seed coats of infested kernels in grain samples. One-kilogram samples of wheat, barley and corn were artificially infested with rusty grain beetle eggs, resulting in survival rates (to larval stage) of 71.1 ± 14.4, 58.9 ± 14.3, and 24.7 ± 11.8%, respectively. Sets of 10 infested kernels containing different-aged larvae (10 individuals × 4 instars) were added to 1-kg samples of hydrated grain, then heated on screens beneath heat sources (lights) at several heights in three different containers (Berlese funnel, with a 7-cm-deep grain layer, or square and rectangular screened boxes with a grain layer several kernels deep). There were no significantly different extraction rates between the rectangular and square containers for all heating trials. A larval extraction rate of 3...

Population growth of Cryptolestes ferrugineus and C- pusillus (Coleoptera: Cucujidae) alone, or in competition in stored wheat or maize at different temperatures

Cryptolestes ferrugineus (Stephens) and C. pusillus (Schonherr) were reared separately at initial densities of 20 or 40 adults each and together at an initial density of 20 adults/100 g cracked wheat or cracked maize at 35, 30, 25, and 20°C and 70% r.h. for developmental periods of 10, 11, 16, or 40 weeks, respectively. Intraspecific competition in the 40-adult treatments restricted population growth to levels similar to 20-adult treatments for each species; impact was greatest for C. pusillus on maize at 30°, where the population of the 40-adult treatment was less than half that of the 20-adult treatment. Both species produced larger populations on wheat than on maize, except for C. pusillus at 35°C; mortality for both species was high on wheat at 35°C. Interspecific competition resulted in significantly reduced populations relative to single species populations for both C. ferrugineus at 30, 25, and 20°C and C. pusillus at 35, 30, and 25°C on wheat and for C. ferrugineus at 25 and 20°C and C. pusillus at 35, 30, and 25°C on maize. During interspecific competition, C. ferrugineus was more successful in multiplying at 35 and 30°C on wheat and 35°C on maize; both species multiplied equally well at 25°C on wheat or 30 and 25°C on maize; C. pusillus multiplied best at 20°C on both wheat and maize. Cryptolestes pusillus reproduces more effectively alone or in interspecific competition under cool conditions, although C. ferrugineus occurs with much greater frequency in cool Canadian stored grain, probably because of cold-hardiness and winter survival

Degradation and biological impact of chlorpyrifos-methyl on stored wheat and pirimiphos-methyl on stored maize in western Canada

Insecticide degradation and pest survival were monitored in treated stored wheat and maize in southern Manitoba. Wheat stored in two wooden bins each holding 2.4 tonnes of grain was treated with the insecticide chlorpyrifos-methyl at calculated levels of 5 ppm; untreated wheat was placed in two other identical bins in the same granary. Maize was simultaneously stored in four identical bins each holding 2.3 tonnes of grain in another granary and the maize in two of these bins was treated with the insecticide pirimiphos-methyl at calculated levels of 6 ppm. Monthly samples were taken from the top and at 1 m depths of the grain bulks for 18 months. Grain surface temperatures fluctuated with ambient air conditions, but at 1 m depth lagged behind top temperatures. Moisture content of the wheat ranged from 12.2 to 15.1% and the maize from 12.1 to 15.3% over 18 months. Chlorpyrifos-methyl residues on wheat declined 51 and 38% at the top and 1 m depths, respectively. Pirimiphos-methyl residues on maize did not decrease; however, after 8 months, pirimiphos-methyl began to appreciably lose effectiveness against the insect Tribolium castaneum (Herbst) in 24 h laboratory bioassays, and after a year against T. castaneum and the mite Tarsonemus granarius Lindquist within the granaries. Fat acidity values increased in both wheat and maize and insecticide treatments were not directly related to the increases. Under western Canadian conditions chlorpyrifos-methyl applied on wheat degraded with time, but at 4.6 ppm, offered effective insect control (>90%) for 10 months. Pirimiphos-methyl (5.6 ppm) on maize killed > 90% of insects for 8 months. It did not degrade at either the surface or 1 m depth, but became less effective with time, based on short-term exposure of adults, possibly because of translocation into the seed.

Rapid detection of rusty grain beetles (Coleoptera: Cucujidae) from wheat samples passing through a mechanical dockage tester

A dockage tester (Carter dockage tester, Hart-Carter Co., Minneapolis, MN) was set up to clean wheat in accordance to Canadian grain industry guidelines and several running conditions. Under all conditions, 84–91% of adults and 57–81% of larvae of the rusty grain beetle, Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae) were recovered from infested 1-kg samples in the aspirator discharge pan. All immature insects implanted in the germ of wheat kernels remained within the kernels, and were found within the bulk of the cleaned whole wheat. It is therefore possible to monitor the aspirator discharge pan of cleaned wheat samples for rapid detection of most free-living C. ferrugineus to limit infested grain from entering primary elevators. Key words: Cryptolestes, detection, dockage tester, Insecta, rusty grain beetle, wheat

Effects of red versus white wheat bran on rate of growth and feeding of some stored-product beetles.

The red pigment in the seed coat of hard red spring wheat is produced by phenolics. Most of the wheats grown in western Canada are hard red spring varieties; however cultivars with a whiter seed coat are being developed for their better milling and baking attributes. Because phenolics serve to protect some plants against insect attack, we compared the susceptibility of white and red spring wheat to attack by stored-product insects. Tenebrio molitor (Tenebrionidae) larvae reared on red wheat bran gained less weight than larvae reared on white wheat bran but this insect has a long developmental period and does not attack sound grain. Tribolium castaneum (Tenebrionidae) pupal weights were not affected by the type of wheat milled products on which the larvae fed. A feeding bioassay showed that red bran did not act as an antifeedant for T. molitor, T. castaneum, or Sitophilus oryzae (Curculionidae). However, it acted as a feeding stimulant for Rhyzopertha dominica (Bostrichidae), which is related to wood-borin...