O extrato hexânico de frutos e sementes de Ricinus communis é seletivo a Telenomus podisi (Ashmead, 1893) (Hymenoptera: Platygastridae)?

Abstract

The use of plant extracts in agroecossitemas is a growing tool in Brazil, due to the floral diversity and exploration capacity of these by-products, being castor, Ricinus communis, one of the plants that stands out with insecticide potential. The Telenomus podisi egg parasite is an efficient natural enemy for the control of phytophages stink bugs, especially for Euschistus heros. The association of the use of plant extracts and biological control agents, such as T. podisi, is characterized as an innovative and fundamental alternative for the development of agroecosystems, but still poorly understood, since the extract can negatively interfere with biological parameters of the parasitoid. In this context, the objective of this work was to evaluate the selectivity of the hexane extract of Ricinus communis L. (Malpighiales: Euphorbiaceae) at the Parasitoid T. podisi, under laboratory conditions. For this, eggs of E. heros were immersed in different concentrations (0.5, 1.0 and 2.0%) of the hexane extract of R. communis, previously or after parasitism (pre and post-parasitimo) of females of T. podisi, four bioassays: 1) Test with chance of choice; 2) Test with no chance of choice (pre-parasitism) and 3) Test with no chance of choice (post-parasitism). The parameters evaluated were: percentage of parasitism, emergency percentage, sexual ratio, duration of the egg-adult period and longevity. The effect of dry residues of the hexane extract of R. comunnis (2%) on adults of T. podisi was also evaluated at exposure times of 4, 7 and 10 minutes. The different concentrations (0.5, 1.0 and 2.0%) of the hexane extract of R. communis interfered significantly on the variable’s preference of parasitism in the test with chance of choice (bioassay 1) and on the percentage of parasitism (bioassays 2 and 3). The extract, however, did not cause changes in the parameter’s sexual ratio, egg-adult period and longevity. Dry residues of castor bean extract, a concentration of 2.0%, caused significant mortality among adults of T. podisi. Field selectivity tests are important for the validation of laboratory results and development of joint control strategies.