Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/1998
Publication Date: N/A
Interpretive Summary: It is difficult to control insects in crops with insecticides without having natural insect predators. Granular malathion incorporated into corn flour provided control of chewing corn ear pests, and indirect control of ear mold, without harming insect predators or leaving residues at much lower levels of actual malathion compared to conventional spray formulations. This formulation should be useful for safer, more selective insect control in many different crops.
Technical Abstract: Malathion was formulated with pregelatinized flour as adherent granular product and tested in the laboratory and field against chewing insect pests of corn ears. Granules containing malathion at 1000 ppm killed more than 95% of neonate Helicoverpa zea, Ostrinia nubilalis larvae and adult Carpophilus lugubris, Diabrotica virgifera virgifera and Sitophilus zeamais within 24 hrs. These insects did not distinguish between granules with and without malathion, and showed no preference between malathion granules and pollen (C. lugubris) or silks (H. zea). In a two year small plot field study, when malathion was applied at a rate of 0.01 lb per acre (0.011 kg/h) in 10 lbs (4.5 kg) of granules, the control of C. lugubris and H. zea was significantly better than untreated plots, and generally equivalent to control when malathion was applied in 5 sprays at a rate of 1 lb a.i. per acre (1.1 kg/h). The incidence of potentially mycotoxigenic Fusarium fungi was also significantly reduced by application of granules compared to control plots, and approximately equal to plots receiving 5 sprays of malathion. With a threshold of detection of 80 ppb, no residues of malathion were detected in ears collected at harvest. These granules should provide more selective and environmentally acceptable control of chewing insects in field corn compared to conventional malathion sprays. Also these granules should reduce the incidence of mycotoxigenic fungi by controlling the insects that contribute to spread and establishment of these fungi.