The Population Dynamics of the Borer, Sesamia grisescens Walker (Lepidoptera: Noctuidae), on Sugarcane in the Ramu Valley of Papua New Guinea.

Abstract

The top borer, Sesamia grisescens, is a serious pest of sugarcane at Ramu, Papua New Guinea. Borer populations were sampled at the Ramu Sugar plantation for 147 weeks, from 1986 to 1989. Populations increased during the North West monsoon and declined during the drier part of the year. Life stages were strongly synchronized during the period of study and this was attributed to nitrogen boost to the population at the start of the North West Monsoon. Additionally, a field trial showed a strong correlation between rates of nitrogen applied and percent stalks bored by S. grisescens. From the available evidence, natural enemies exerted little control over borer populations, however discrete life stages provide scope for augmentative releases of natural enemies in the future.