Resumo

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.

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.

Resumo

Neoseiulus HUGHES, 1948 is currently one of the largest genus of Phytoseiidae Berlese. Neoseiulus demitei sp. nov., a new species of phytoseiid mite from Rio Grande do Sul State, Brazil, is illustrated and described based on specimens collected on Tibouchina sp. (Melastomataceae) plants. This new species differs from others by having most of propodossomal setae reaching the base of nearby setae and a constriction of ventrianal shield at level of preanal pores. Nevertheless, this new species is the first of the species subgroup kennetti described from Brazil. A key of Neoseiulus species reported in Brazil is also included.

Resumo

We tested the functional response of the phytoseiid predator Phytoseiulus macropilis (Banks, 1904) to different population densities of Tetranychus urticae Koch, 1836 (the two-spotted spider mite - TSSM) in the laboratory. We evaluated the curve that best fits the data obtained, based on the reduced X². The predators were obtained from leaves of Oso Grande strawberries at the municipality of Bom Princípio, state of Rio Grande do Sul, Brazil. Fifteen seemingly healthy females of P. macropilis were randomly chosen and individualized in each of the arenas with different TSSM densities. The following prey densities were tested: 1, 2, 3, 5, 10, 20, 30, 35, 45, 55, 70 and 125 females. The tests were performed in a germination chamber with photoperiod of 12 hours at 28 ± 1ºC per day and 22 ± 1ºC at night and 80 ± 5% relative humidity. In all tests with up to three prey items, P. macropilis showed low functional response, whereas higher rates were observed when more prey items were offered. There was a strong positive correlation between increased prey numbers and daily prey consumption (r = 0.84 and p = 0.0006). A significant correlation was found between prey consumption and total oviposition (r = 0.70, p = 0.01). The daily oviposition rate was lower when few prey items were offered, increasing significantly with increased prey availability. The results showed a positive correlation between the number of prey items offered to the predator and its oviposition rate (r = 0.66, p = 0.01). Nevertheless, a strong correlation was observed between the daily consumption of prey and eggs/female/day (r = 0.92, p 0.0001). A shorter oviposition period was reported when up to three prey items were offered. The oviposition period and the increase in prey numbers were positively correlated (r = 0.30, p = 0.34), but the difference was not statistically significant. Nevertheless, the longer the egg-laying period, the greater the oviposition rate (r = 0.90, p 0.0001). The curve that best fits the data obtained in each case was also calculated, based on the least square method.