EFFECT OF THE HELIOTHIS NUCLEAR POLYHEDROSIS VIRUS INFECTION ON FOOD CONSUMPTION BY HELIOTHIS ZEA1,2

Abstract

Frass production by Heliothis zea (Boddie) larvae infected at varying mortality levels with Heliothis nuclear polyhedrosis virus (NPV) was determined and used to estimate the effect of the virus on larval food consumption. Treatment in the early stages was essential to substantially reduce food consumption. Reduction in food consumption was also directly related to NPV dosage. Food consumption by larvae surviving NPV treatment was not significantly different from the untreated larvae. Field tests indicated that NPV applications must be timed against 1st- or 2nd-stage larvae to achieve an appreciable mortality level and prevent infected larvae from reaching the damaging late developmental stages. Preliminary maximum treatment levels for use of Heliothis NPV for suppression of H. zea on soybean are presented.