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
Phytoseiulus macropilis (Banks) (Phytoseiidae) is a natural enemy of Tetranychus urticae Koch (TSSM), a common pest in several cultures, especially in greenhouses. This research aimed to know the biological parameters of a strain of P. macropilis from Vale do Taquari, State of Rio Grande do Sul, feeding on TSSM at different temperatures. The study was initiated with 30 eggs individualized in arenas under the temperature of 20, 25 and 30 ± 1°C and relative humidity of 80 ± 10%. The average length (T) of each generation decreased with the increase of temperature, ranging from 25.71 days at 20°C to 11.14 days at 30°C. The net reproductive rate (Ro) ranged from 45.47 at 20°C to 18.25 at 30°C; the innate capacity for increase (rm) was 0.15 at 20°C, reaching 0.26 at 30°C and the finite increase rate (λ) ranged from 1.41 to 1.82 females day-1 at 20 and 30°C, respectively. In the present study, it was observed that the strain of the evaluated predatory mite from mild climate of South Brazil, might present a good performance to control TSSM when exposed to a temperature range between 20 and 30°C.(AU)
Phytoseiulus macropilis (Banks) (Phytoseiidae) é um inimigo natural de Tetranychus urticae Koch (ácaro rajado), uma praga comum em diversas culturas mantidas em estufas. Esta pesquisa teve o objetivo de conhecer características biológicas de uma linhagem de P. macropilis do Vale do Taquari, Rio Grande do Sul, que se alimenta do ácaro rajado em diferentes temperaturas. O estudo foi iniciado com 30 ovos individualizados em arenas nas temperaturas de 20, 25 e 30 ± 1°C e umidade relativa de 80 ± 10%. A duração média (T) de cada geração diminuiu com o aumento da temperatura, variando de 25,71 dias, a 20°C, e 11,14 dias, a 30°C. A taxa líquida de reprodução (Ro) variou de 45,47, a 20°C, para 18,25, a 30°C; a capacidade inata de crescimento (rm) foi de 0,15, a 20°C, atingindo 0,26, a 30°C, e a taxa de aumento finito (λ) variou 1,41 até 1,82 fêmeas/dia, a 20 e 30°C, respectivamente. No presente estudo, observou-se que a estirpe de predador avaliada, de clima ameno do Sul do Brasil, pode apresentar um bom desempenho para controlar TSSM quando exposta a temperatura entre 20 e 30°C.(AU)