Foliar Loss Assessments and Economic Decision-Making for the Tobacco Budworm on Maryland Tobacco23

Abstract

During the growing season of 1977, field studies were conducted to determine the damage density relationships resulting from artificial infestations (1 larva/plant) of Heliothis virescens (F.) on Maryland tobacco. It was found that yield and quality reductions were negatively correlated with larval density, while plants were able to compensate for some foliar loss throughout most growth stages. Compensation was highest during growth periods of rapid meristematic activity. Sensitivity to defoliation was most evident during root formation and production of floral parts, although markedly less during the latter. Theoretical economic injury levels (EIL's) for the tobacco budworm were determined by integrating several economic parameters with value-density relationships. EIL’s indicated that throughout most developmental stages of MD. 609 tobacco large populations of budworms can be tolerated without sufficient damage to warrant suppression. Under Maryland conditions, economic thresholds of 25% infestation densities would better approach optimal benefit-cost relations than the current 10% level.