YIELD LOSSES (simulated damage) CAUSED BY Erinnyis it (1.) AND CRITICAL LEVELS OF POPULATION IN DIFFERENT STAGES OF DEVELOPMENT IN THREE CLONES OF YUCCA

Abstract

Erinnyis ello (L.) is considered one of the most important pests of cassava due to the severity of its damage. The objective of this study was to quantify the losses on root yield, planting material, and percentage of starch in two different ecosystems by means of simulated damage. In some treatments plants were completely defoliated once; in others, plants were completely defoliated twice with the second defoliation one month after the first. Both types of treatments were carried out with plants of different ages. A total of 4 experiments were conducted in Santander de Quilichao (Cauca), a site with poor soils, and a CIAT-Palmi­ra (Valle) a fertile site. The number of fifth instar larvae needed to cause the defoliation estimated from data on leaf area and E. ello consumption rates were determined. Three clones of yuca were used, M Mex 19 CM 305-41 and HMC 2 with wide, intermediate, and narrow leaves respectively. The results showed that yield loss in sites with poor soils can reach 64% when there are two consecutive defoliations and 46°/o after one defoliation. Infertile soil losses reached 47 and 25.5% with two and one defoliation respectively. The greatest losses of planting material resulted when plants were defoliated twice at one and two months of age, and once at one month of age. These losses were 72 and 62% respectively. Decreases in the percentage of starch in the roots occurred when plants 7 months old or older were defoliat­ed.