Lethal and sub-lethal effects from short-term exposure of Rhyzopertha dominica on wheat treated with Storicide II®

Abstract

Hard red winter wheat was treated at 0 (untreated control), 25, 50, 75, and 100% of the label rate of the insecticide Storicide II Ò , which is chlorpyrifosmethyl and deltamethrin applied at label rates of 3 and 0.5 ppm, respectively. Paired male and female Rhyzopertha dominica F., the lesser grain borer, were exposed at 27°C and 60% RH on wheat treated at each of the five rates above for 2, 4, 8, 16, or 32 h, and then transferred to untreated wheat and held for 1 week at the same environmental conditions. After this 1-week holding period, the parental adults were removed, mortality was assessed, and the wheat was then held for 7 weeks at the same environmental conditions to determine progeny production. As the concentration and exposure interval increased, mortality of both sexes approached 100%, but at the intermediate concentration-time combinations male mortality was greater than female mortality. Progeny production also decreased with increasing concentration of Storicide II Ò as the exposure time increased, with non-linear patterns of decrease at the lower concentrations and time combinations and linear decline at the higher levels of concentration and time. Results seem to indicate greater susceptibility of males to Storicide II Ò , and also show delayed parental mortality from the insecticide exposure and sub-lethal effects of reduced progeny production.

Insecticide susceptibility of the green plant bug, Apolygus lucorum Meyer-Dür (Homoptera: Miridae) and two predatory arthropods

“…In comparison with female A. lucorum, males were sensitive to all of the insecticides tested, and there were differences in their sensitivity to different insecticides (Table 3). Previous studies with different insecticides also showed differential susceptibility between the sexes of tested insects (López et al 2008;Arthur 2012). It was suggested by Zhang (1988) that females were less sensitive to organophosphates and carbamates than males owing to the lower quantity of acetylcholinesterase in females.…”

Efficacies of Spinosad and a Combination of Chlorpyrifos-Methyl and Deltamethrin Against Phosphine-Resistant <I>Rhyzopertha dominica</I> (Coleoptera: Bostrichidae) and <I>Tribolium castaneum</I> (Coleoptera: Tenebrionidae) on Wheat

“…A study conducted by Arthur (2012) where R. dominica adults were exposed to wheat treated at 0, 25, 50, 75, and 100% of the label rate of a mixture of chlorpyrifos-methyl (3 ppm) and deltamethrin (0.5 ppm) for 2, 4, 8, 16, or 32 h showed that parental adult mortality increased as the concentration and exposure interval increased. Similarly, for progeny production that was assessed after 7 wk, it decreased with increasing concentration of chlorpyrifos-methyl ϩ deltamethrin mixture and increasing exposure time.…”

Using a Lethality Index to Assess Susceptibility of Tribolium confusum and Oryzaephilus surinamensis to Insecticides

“…It remains unclear, however, if the insects that have been exposed for short periods to chlorfenapyr will die even after their removal from the treated substrate, or a continuous contact with the treated surface is needed to obtain high levels of mortality. It is not clear if the absence of knockdown with non-neurotoxic insecticides also leads to increased survival [ 4 , 21 , 26 ]. Additional experimentation is needed with chlorfenapyr, but also with other non-neurotoxic insecticides, to examine if short exposures without knockdown leads to delayed mortality after the removal from the treated substrate.…”

“…However, the authors noted that seven days after the removal of the exposed individuals from the treated grains, adults began to recover from knockdown. Similarly, Arthur [ 4 ] conducted studies by exposing adults of R . dominica on wheat treated with a mixture of chlorpyriphos-methyl and deltamethrin, and noted increased survival and recovery after the removal of the exposed adults from the treated commodity.…”