Trichogramma pretiosumparasitism and dispersal capacity: a basis for developing biological control programs for soybean caterpillars

Abstract

AbstractIn order to succeed in biological control programs, not only is it crucial to understand the number of natural enemies to be released but also on how many sites per area this releasing must be performed. These variables might differ deeply among egg parasitoid species and crops worked. Therefore, these trials were carried out to evaluate the parasitism (%) in eggs ofAnticarsia gemmatalisandPseudoplusia includensafter the release of different densities of the egg parasitoidTrichogramma pretiosum. Field dispersal was also studied, in order to determine appropriate recommendations for the release of this parasitoid in soybean fields. The regression analysis between parasitism (%) and densities of the parasitoid indicated a quadratic effect for bothA. gemmatalisandP. includens. The maximum parasitism within 24 h after the release was reached with densities of 25.6 and 51.2 parasitoids per host egg, respectively, for the two pests. Parasitism ofT. pretiosumin eggs ofP. includensdecreased linearly as the distance of the pest eggs from the parasitoid release sites increased. ForP. includens, the mean radius ofT. pretiosumaction and the area of parasitoid dispersal in the soybean crop were 8.01 m and 85.18 m2, respectively. We conclude that for a successful biological control program of lepidopteran pests usingT. pretiosumin soybean fields, a density of 25.6 parasitoids per host egg, divided into 117 sites per hectare, should be used.