Inviabilização de ovos de Spodoptera frugiperda (Lepidoptera: Noctuidae) com radiação UV visando estudos com Trichogramma spp. (Hymenoptera: Trichogrammatidae)

Abstract

Parasitoids of eggs Trichogramma spp. (Hymenoptera: Trichogrammatidae) have been related as agents of biological control of several lepidoptera-pest. These parasitoids are commonly bred in unviable eggs of an alternative host such as Anagasta kuehniella (Lepidoptera: Pyralidae). This unfeasibility occurs by exposing the eggs to the radiation produced by a germicidal lamp. However, for research purposes and even for mass creation, the possibility of using other hosts must be constantly studied. The objective of this study was to evaluate different times of non-viability using germicidal lamps with two use times over the parasitism and the emergence of T. pretiosum on eggs Spodoptera frugiperda (Lepidoptera: Noctuidae). Eggs of S. frugiperda were exposed to UV radiation produced by lamps with 280 or 380 hours for one, two and three hours. After each exposure period, groups of 20 eggs were glued in celestial blue cardboards and inserted into glass tubes (2.5 x 8.5 cm) containing one female of the T. pretiosum parasitoid, where they remained for 24 hours. After this period, the females were removed from the tubes and they remained under controlled conditions (25 ± 3ºC, 70 ± 10% RH and 12h photophase). After 15 days, parasitism (%) and emergence (%) were evaluated. The experimental design was completely randomized, with 15 replicates, each repetition being a batch containing 20 eggs. Data were submitted to analysis of variance and the means were compared by the Duncan test at the 5% probability level. It was observed that the parasitism of S. frugiperda eggs by T. pretiosum decreases with increasing the exposure time of eggs to UV radiation when using lamps with 280 hours of life. However, the parasitism of eggs of S. frugiperda with lamp with 380 hours of use was superior in the longer time of exposure. For the emergency, no significant difference was observed, obtaining indices above 70% of adults' emergence of the parasitoid regardless of the exposure time or lamp life. Thus, the optimal time to prevent eggs from S. frugiperda to the germicidal light has a direct relationship with the period of use of the lamp, necessitating longer exposure times for longer lamp usage.