Chrysoperla externa(Hagen): dietas artificiais na alimentação larval e controle de Bemisia tabaci(Gennadius) na cultura da melancia

Abstract

Green lacewings (Neuroptera: Chrysopidae) have been associated to several agricultural pests in many studies, whether in laboratory or by means of its release in greenhouse or field. Species belonging to the genus Chrysoperla are the most studied and commercialized by companies in North America and Europe. In Brazil, the Chrysoperla externa species is highlighted, with many studies on its biology, laboratory rearing and predatory capacity. However, C. externa larvae are traditionally fed eggs from alternative prey, which present high costs, factor that prevents the use of this predator in biological control programs. Some artificial diets might substitute these alternative prey, reducing the feeding cost. Therefore, the present work tested different artificial diets for larvae of C. externa, evaluating its effects, during seven generations, and testing its performance as biocontrolling agent against the whitefly Bemisia tabaci in watermelon culture. From the three artificial diets tested, we observed that C. externa larvae could be reared in two of them, as long as Anagasta kuehniella eggs be provided to the first instar and the artificial diets only in the second and third instar. The use of the feeding regime proposed here means a reduction of 90% in A. kuehniella eggs. Regarding to the use of C. externa for controlling B. tabaci in watermelon culture, eggs and larvae of the predator were weekly released during three weeks, and the effect of the last release was accompanied by another week. The release of the predator was performed in commercial cultivation, without the interruption of chemical control. At the end of evaluations, it was observed that the release of eggs of C. externa reduced in 80 and 85% the number of eggs and nymphs of the whitefly, respectively, when compared to the exclusive use of chemical control. When releasing larvae, this reduction was of 93 and 98% in the number of whitefly eggs and nymphs, respectively. Therefore, the use of C. externa in the integrated management of B. tabaci was shown to be promising and, using the artificial diet proposed in this work, in its rearing in laboratory, a high reduction in cost might be achieved.