Multiacreage evaluation of aerially applied adherent malathion granules for selective insect control and indirect reduction of mycotoxigenic fungi in specialty corn.

Aerially applied adherent corn flour granules containing 1% malathion were more often as, or more, effective than 15% chlorpyrifos (Lorsban 15G) granules in controlling caterpillars and sap beetles in high amylose corn in 1997 than 1996. Use of malathion granules corresponding closely in size to chlorpyrifos granules in the second year of the study apparently increased relative efficacy. Significantly less corn borer damage occurred on plants (1996) or ears (1997) within 2 wk of application for both types of insecticide granules compared with untreated plots. In 1997, there were sixfold fewer milk stage ears with more than 20 kernels damaged per ear in the malathion-treated plots compared with chlorpyrifos-treated plots, and severity of caterpillar damage was also less in malathion versus chlorpyrifos-treated plots at harvest. Control of beetles (corn rootworm adults and sap beetles) for both treatments was less effective compared with caterpillars. Significant corn rootworm adult control was noted for both chlorpyrifos and malathion in 1996 and significant sap beetle control was noted for the malathion granules in 1997. Significantly fewer live lady beetles, and more dead lady beetles were present in chlorpyrifos-treated plots compared with malathion-treated or untreated plots in 1996. The incidence and severity of Fusarium mold on ears at harvest was often indirectly reduced by both malathion treatments and chlorpyrifos treatments, with the malathion treatment significantly better than the chlorpyrifos treatment in one case.