ABSTRACT

Yerba mate ampoule, Gyropsylla spegazziniana (Lizer and Trelles, 1919) is one of the main pests of yerba mate crops. This insect attacks sprouts leading to gall formation and defoliation. The nymph’s habit of living inside galls makes them difficult to access with chemical insecticides, hampering the effectiveness of chemical control. This study aimed to evaluate the systemic and contact activity of the azadirachtin-based product (via irrigation and spraying) on nymph and adult stages of the ampoule, both in laboratory and field conditions. In vitro interaction of the product with the fungus Beauveria bassiana (Balls.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) was also evaluated. After the exposure of nymphs to plants treated with azadirachtin, a reduction in adult emergence was recorded (65–99% depending on the concentration applied). It was observed 80% of adult mortality in plants previously treated with the product (residual effect) and 90% of mortality after direct pulverization of the product on the insects. The product did not affect B. bassiana fungal growth, conidial viability, and conidial production on culture media. A synergistic interaction was observed between the azadirachtin insecticide and the fungus in laboratory. In the field trial, after three applications by irrigation of azadirachtin, 67.9% reduction in the number of galls was achieved five weeks after the first application. No phytotoxic effect was observed on yerba mate plants treated with the product. The results of our study demonstrate that the azadirachtin-based product and its association with the fungus B. bassiana have potential in controlling G. spegazziniana.

Keywords
Yerba mate ampoule; Alternative control; Botanical insecticide; Compatibility