Desempenho biológico de Trichogramma spp. (HYM.: Trichogrammatidae) em ovos de Spodoptera cosmioides (LEP.: Noctuidae) criada em eucalipto

Abstract

Trichogramma (Hymenoptera: Trichogrammatidae) is a genus of wasps commonly used for the biological control of agricultural and forestry pests. Recently, the occurrence of Spodoptera cosmioides (Lepidoptera: Noctuidae), a soybean pest, has been observed in eucalyptus plantations. It is known that females of the parasitoid Trichogramma spp. are unable to develop in eggs of the eucalyptus brown looper Thyrinteina arnobia (Lepidoptera: Geometridae), likely due to a toxic compound sequestered by this eucalyptus-feeding lepidopteran. The objective of this study was to compare the biological characteristics (parasitism, emergence, life cycle duration, individuals per egg, sex ratio, and longevity of females and males) of T. pretiosum and T. bruni reared on S. cosmioides eggs obtained from caterpillars fed on artificial diet and eucalyptus leaves. The experiment was conducted using twenty 24-hour-old S. cosmioides eggs, which were glued to sky blue cardboard cards (1.0 cm wide and 7.0 cm long) using 30% arabic gum, and placed individually in glass tubes (1.5 cm in diameter and 10 cm in height) sealed with plastic film and a droplet of honey. Each tube containing a card with 20 glued eggs received a single Trichogramma female up to 24 hours old. Parasitism was allowed for 24 hours in a climate-controlled room at 25 ± 2 ºC, 70 ± 10% RH, and a 14-hour photophase. During the trial, the following characteristics were evaluated: life cycle duration (egg to adult), parasitism percentage, number of parasitized eggs, emergence percentage, number of individuals per egg, sex ratio, and longevity of the offspring. The experimental design was completely randomized (CRD) with two treatments: eggs from S. cosmioides raised on artificial diet (T1) and eggs from S. cosmioides raised on eucalyptus leaves (T2), each with 15 replicates. The experiment showed that both T. pretiosum and T. bruni were able to parasitize S. cosmioides fed on eucalyptus leaves, indicating potential for future use in its biological control. However, it was also demonstrated that T. pretiosum adults that emerged were negatively affected, and in T. bruni, no adult emergence occurred.