Annona crassiflora Mart. (Annonaceae): effect of crude extract of seeds on larvae of soybean looper Chrysodeixis includens (Lepidoptera: Noctuidae)

摘要

The effect of a crude extract of Annona crassiflora was evaluated on larvae of the soybean looper, Chrysodeixis includens (Lepidoptera: Noctuidae) in different stages of larval development. The extract was prepared with seeds of A. crassiflora fruits collected in the state of Mato Grosso, Brazil. The extract was diluted in water and solubilizer agent at the concentrations of 0.5, 1.0, 2.0, 4.0, and 8.0%; it was tested by ingestion of treated leaves and contact. The mortality rate of topically treated caterpillars of first, third, and fifth instars was significantly higher than that of the control group. For first instar caterpillars, mortality was observed within the first 24 h after application, while, for the remaining instars, it was significant after 72 h. For caterpillars fed treated leaves, no differences in mortality rates were observed within the first 120 h. These caterpillars were monitored until the end of the larval stage, during which mortality rates increased for first and third instar caterpillars. The mortality rate of fifth instar larvae was not significantly different between treatments. The treatment by ingestion was not efficient over a short period of time, but reduced the number of caterpillars that completed their development, decreasing the number of insects in the following generation. We concluded that the crude extract of A. crassiflora affected the development of C. includens and is a promising compound for the control of this pest.