ABSTRACT
The horizontal transmission of the entomopathogenic fungus Beauveria bassiana Unioeste 76 strain among adults of Euschistus heros was evaluated in the laboratory and greenhouse using sporulated cadavers and live insects contaminated as a source of inoculate. Adult insects in the laboratory bioassay either received treatments with dry conidia or were sprayed with an oily dispersion formulation, and the treatments were comprised of 10, 30, or 50% of contaminated insects. For the greenhouse bioassay, nylon cages were prepared, with soybean plants grown in pots. A total of 20 healthy brown stink bugs were released along with one or three sporulated cadavers of brown stink bugs, attached to the plant stem. In the bioassay with live insects, 20 stink bugs were released, and the treatments were comprised of 10, 30, or 50% contaminated insects (2:18, 6:14, and 10:10, fungus-treated insects : healthy insects). In all experiments, the control group was comprised only of healthy insects. Dead stink bugs were daily disinfested and transferred to a wet chamber for confirmation of death by fungus. Confirmed mortality was observed, which shows the occurrence of horizontal transmission. Mortality was higher when more contaminated insects were used in the population, in most treatments. The occurrence of transmission in the laboratory and the greenhouse emphasizes the potential of the Unioeste 76 strain as mortality agent and as an agent for maintaining the inoculum potential for the brown stink bug.
Keywords
auto-dissemination; biological control; microbial control; entomopathogen; soybeans