Residual Activity of Organophosphorus and Pyrethroid Insecticides Applied to Wheat Stored Under Simulated Western Canadian Conditions

Abstract

Wheat treated with 2,4, or 8 ppm of insecticide, on a whole-seed basis, was bioassayed with Tribolium castaneum (Herbst) and Cryptolestes ferrugineus (Stephens) adults at 30 °C and 70% RH after 4 days, 2 weeks, and then at eleven 1-month intervals. Malathion was more toxic to C. ferrugineus than to T. castaneum whereas the reverse was true for pirimiphos-methyl; malathion showed little effectiveness after 2 weeks. The pyrethroids, cypermethrin and permethrin, were more toxic to T. castaneum than to C. ferrugineus. For malathion and pirimiphos-methyl, percentage knockdown of the insects following exposure for 24 h was similar to percentage mortality after a 3-day recovery period; for cypermethrin and permethrin under the same conditions, knockdown was consistently greater than mortality. Cypermethrin at 8 ppm on wheat gave 90% knockdown of T. castaneum after 1 year of storage. Pirimiphos-methyl gave nearly 100% control of both species for 9 months at 4 ppm and 11 months at 8 ppm, and of the grain mite Acarus siro (L.) for at least 4 weeks at 8 ppm. Seed germination did not change during 1 year of storage; the levels of Penicillium spp. infection observed were much greater (about 60%) on wheat treated with pirimiphos-methyl (2, 4, 8 ppm) or cypermethrin (2 ppm) than with malathion or permethrin.

Toxicity and efficacy of selected pesticides and new acaricides to stored product mites (Acari: Acaridida)

“…In particular, A. siro was very diYcult to control, which is consistent with previous studies Table 2 1 C with this species (Thind and Muggleton 1998). Except for the combination permethrin/benzyl-benzoate/pyriproxifen, the Wtted lethal doses (rC 0 ) are much higher than could be used for practical application (White 1984;White and Leesch 1996).…”

Management of five stored‐product insects in wheat with pirimiphos‐methyl and pirimiphos‐methyl plus synergized pyrethrins

“…The complete suppression of progeny production and kernel damage can be attributed to the high susceptibility of neonate larvae to pirimiphos‐methyl. Reduced susceptibility of R dominica adults to pirimiphos‐methyl, relative to other stored‐product insects, has also been reported from the United Kingdom,22, 28 Australia16–29 and the USA 14, 15…”

“…Pirimiphos‐methyl has lower mammalian toxicity than chlorpyrifos‐methyl 12. Laboratory and field data from past studies in the USA13–15 and other countries12–23 showed pirimiphos‐methyl to be effective on wheat against several stored‐product insects. The reasons for not considering pirimiphos‐methyl as a stored‐wheat protectant in the USA, despite favorable field results, are unclear.…”

Analysis of Permethrin (Cis- andTrans-Isomers) and Esfenvalerate on Almond Twigs and Effects of Residues on the Predator MiteGalendromus occidentalis(Acari: Phytoseiidae)

“…White (1984) showed that cypermethrin at 8 ppm on stored wheat gave 90% knockdown of the beetle Tribolium castaneum (Herbst) after 1 yr of storage. Adesuyi (1982) found that permethrin dust applied at 5 ppm to stored maize provided 8 mo of protection from insect damage.…”