Resumo
ABSTRACT Aiming to the red mite Oligonychus yothersi control in yerba-mate, the systemic action of an azadirachtin-based product (12 g of azadirachtin.L-1) was evaluated in the laboratory. To assess the activity on oviposition and mortality of the mite (1), three weekly applications of the product in an aqueous solution (30, 48, and 66 mg i.a..L-1) were performed. The applications were carried out in the soil, next to the base of yerba mate seedlings. After seven days of each application, leaves were removed for infestation with 15 adult mite females. To evaluate the activity in the development, survival, and reproduction of the progeny (2), yerba mate seedlings were irrigated with azadirachtin solution of 30 mg i.a..L-1 (recommended concentration). After seven days, leaves were removed and infested with adult females for oviposition and observation of the progeny. Reduction in fecundity (from 23.7 to 44.2%), fertility (27.4 to 48.1%), and an increase in mortality from 14.6 to 47.5% were observed in females fed on azadirachtin-treated plants. Continuous feeding on plants treated with azadirachtin solution significantly reduced oviposition, pre-oviposition period, and longevity of males. In addition, the viability of the egg-adult, and the duration of the egg-adult period increased. The potential of azadirachtin for the control of O. yothersi and its action from the irrigation of yerba mate plants was confirmed.
Resumo
Aiming to increase the activity of the fungus Beauveria bassiana (Unioeste 44) against adults of Gyropsylla spegazziniana, the combination of the fungus with adjuvants Aureo® and Assist® was evaluated for application. The bioassays were carried out in direct and residual contact with insects on yerba mate seedlings. The effects on some biological parameters of the fungus were also evaluated in vitro. The combination of the fungus and the adjuvants in direct contact resulted in mortality rates of 65 and 75% (Aureo® and Assist®, respectively), with no difference between them; however, the mortality rate was greater than that obtained with the fungus alone (47 %) (P < 0.05). Mortality from residual contact was lower, but the association with adjuvant Assist® (48%) compared to Aureo® (16%) was still advantageous. Conidiogenesis in cadavers was not affected by adjuvants in the treatment by direct contact. However, in residual contact, conidiogenesis increased with the Assist® addition. Despite affecting the germination and growth of the fungus, the adjuvants were considered compatible. In addition to the efficiency of their combination, neither adjuvant caused phytotoxicity to yerba mate seedlings, representing advantages of its use in G. spegazziniana population management.
Visando incrementar a atividade do fungo Beauveria bassiana Unioeste 44 contra adultos da ampola-da-erva-mate (Gyropsylla spegazziniana), avaliou-se a associação do fungo com adjuvantes Aureo® e Assist®, para calda de aplicação. Os bioensaios foram relizados em contato direto e residual sobre insetos. Foram também avaliados in vitro os efeitos sobre alguns parâmetros biológicos do fungo. A associação fungo + adjuvantes resultou em mortalidade de 65 e 75%, sem diferença entre eles, porém, significativamente maior que a obtida com o fungo isoladamente. A mortalidade no contato residual foi menor, mas também houve vantagem na associação com adjuvantes, principalmente Assist® (48%), em relação ao Áureo® (16%). A conidiogênese nos cadáveres não foi afetada pelos adjuvantes no tratamento de contato direto. Contudo, houve incremento na conidiogênese no tratamento de associação com Assist® no contato residual. Apesar de afetarem a germinação e o crescimento do fungo, os adjuvantes foram considerados compatíveis com o fungo. Além da eficiência da associação, ambos adjuvantes não causaram fitotoxidade para a erva-mate, representando vantagens do seu uso no manejo da ampola.