Evaluation of a Baculovirus Bioinsecticide for Small-Scale Maize Growers in Latin America

o t s o 1 Near identical trials conducted concurrently in maize lots in Honduras and Mexico produced similar reults in the pattern of larval mortality of Spodoptera rugiperda following application of a baculovirus or a onventional synthetic insecticide. The highest appliation rates of virus resulted in approximately 40% ortality of S. frugiperda larvae. Virus-induced mortalty decreased with time. Parasitism by wasps and achinids also contributed up to 40% mortality in eld-collected larvae. The application of chlorpyrifos esulted in a resurgence of S. frugiperda. Chlorpyrifos lso reduced a number of important predators in the aize crop which is likely to have been influential in he observed resurgence of this pest. The use of granuated sugar in the viral formulation caused an increase n the population density of several maize-associated nsect species, and in Mexico a transient increase in arasitism was observed in sugar-treated plots. Sugar id not appear to increase the probability of infection y acting as a feeding stimulant in either trial. A reliminary analysis of the cost of viral production nd application indicates that virus was considerably ore costly than conventional control. To be commerially viable, economies of scale both in the cost of raw aterial for the insect diet and in the efficiency of anpower-related activities are needed to substanially reduce the costs of the viral product. Despite igh levels of infestation by S. frugiperda, grain weight/ ob was not significantly improved by the application of he biological or synthetic insecticide. Natural mortality actors both biotic and abiotic appear to have a large mpact on larval S. frugiperda populations. For improveents in yield, the impact of control measures against . frugiperda may be dependent on plant growth stage. rials on timing and frequency of virus application are n progress to test this idea. r 1999 Academic Press