Selection of Trichogramma strains and determination of number of parasitoids to be released to control Gymnandrosoma aurantianum Lima (Lepidoptera, Tortricidae).

Selection of Trichogramma strains and determination of number of parasitoids to be released to control Gymnandrosoma aurantianum Lima (Lepidoptera, Tortricidae). In order to select Trichogramma strains to control G aurantianum, the biological characteristics of 13 Trichogramma species/strains were evaluated. After selection, the ideal number of T. pretiosum (G18 strain) to be released per G aurantianum egg was determined in greenhouse tests. The selection test for species/strains was carried out in an incubator adjusted to 25 +/- 1 degrees C, RH 70 +/- 10%, and a 14 h photophase. The ideal number of parasitoids was estimated in cages covered with a piece of voile-type fabric. The cycle duration for the 13 Trichogramma species/strains varied from 10.2 to 11.9 days. The Atp strain (T. atopovirilia) showed greater parasitism capacity, with an average of 23.3 parasitized eggs and 77.5% parasitism in 24 hours. The G18 strain (T pretiosum) came next, with an average of 16.8 parasitized eggs and 56.1% parasitism during the same time interval. The emergency, longevity of males, and sex ratio for the 13 species/strains were similar. The number of adults emerged per egg was 1.8 for strains G11 (T. pretiosum) and Br10 (T. bruni), which were different from the G3 strain (T. pretiosum) only, with 1.3 adults per egg. With regard to female longevity, distinct values were observed only between T pretiosum strains Tp and L2, with 6.3 and 9.3 days, respectively. Under greenhouse conditions, the estimated ratio of 36 T pretiosum parasitoids per G aurantianum egg allowed the highest percentage of parasitism (89%). Therefore, Trichogramma spp. has a potential to control G. aurantianum, as long as a large number of parasitoids is released per unit area.