Generating knowledge about the Dracaena marginata pest complex to improve management strategies for crops exported from Costa Rica

Abstract

This study aimed to develop knowledge on the population dynamics of the pest complex found in D. marginata and the actual relationship between plant size and pest incidence. It looked at the role of weed cover on insect abundance and fluctuations of the populations through time to try and detect windows of opportunity to maximize the effectiveness of control measures. The relationship between pest abundance in the field and the interception rate of export shipments at the ports of entry in the United States was also studied. Specific studies were also carried out on the dynamics of the leafhopper Empoasca sp. and the efficacy of chemical insecticides for its control. This cicadellid species was considered particularly important at the interception level because its eggs are abundant on the plant leaves but undetectable during ordinary inspection. An effective staining procedure (Neergaard 1997) was selected for detecting and quantifying Empoasca eggs on D. marginata leaves. This tool allowed for the determination of fluctuations on the abundance of Empoasca eggs under different weed cover compositions. The absence of weed cover induced a high oviposition of Empoasca on Dracaena, possible due to decreased host availability. D. marginata plants growing with the covercrop Drymaria had higher egg densities whereas plants growing with weed cover composed by Rubiaceae, grasses, and weedy cover showed lower pest incidence.