Tests of Oil Sprays for Suppression of Aphid-Borne Maize Dwarf Mosaic Virus in Ohio Sweet Corn1

Abstract

JMS stylet oil was evaluated for maize dwarf mosaic virus (MDMV) control in Ohio sweet corn. In laboratory tests, oil sprays reduced transmission of MDMV by single green bugs, Schizaphis graminum (Rondani), from 33% in untreated controls to 3% when virus source plants were sprayed, 6% when test plants were sprayed, and 0% when both source and test plants were sprayed. Alate corn leaf aphids, Rhopalosiphum maidis (Fitch), took longer to initiate probes on oil-sprayed than on nonsprayed corn leaves. In 1978, oil failed to control MDMV spread in a field experiment with a high inoculum level (33%). In a 1979 field test with a 1% inoculum level, maize dwarf mosaic (MDM) incidence was 3.2% in a plot receiving weekly oil sprays and 57.9% in an unsprayed control. In 1980, also with a 1% inoculum level, plots receiving weekly and biweekly oil sprays had significantly less MDM spread (19.3 and 14.2%, respectively) than did nontreated controls (25.7%). A simulation experiment indicated that rainfall was not the reason for the poor performance of oil in the field. Until formulations or application techniques are improved, oil sprays are unlikely to control the spread of MDMV in Ohio sweet corn.