Functional response of Phytoseiulus macropilis under different Tetranychus urticae (Acari: Phytoseiidae, Tetranychidae) population density in laboratory

Abstract

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

Biology of Neoseiulus californicus feeding on two-spotted spider mite

“…Tetranychus urticae (Koch) has a large number of hosts to which it causes significant damages (MORAES; FLECHTMANN, 2008). In strawberry plants, this mite attacks mainly the underside of leaves, causing the formation of bleached spots, abundant web, and significant production loss (FERLA et al, 2007). Its populations are larger and more frequent within the fructification period.…”

“…In the state of Rio Grande do Sul, Brazil, two species of predatory mites stand out as natural enemies of T. urticae on strawberry plants: N. californicus and Phytoseiulus macropilis Banks (FERLA et al, 2007). These species have shown potential for control, but Ferla et al (2011) point out that P. macropilis present a low functional response in the presence of low populations of prey. Thus, this predator has a difficulty for remaining in the environment for long periods, due to fluctuations of prey population.…”

Toxicidade de espiromesifeno e acaricidas naturais para Tetranychus urticae koch e compatibilidade com Phytoseiulus macropilis (Banks)

“…Em morangueiro, este predador é capaz de extinguir uma colônia de T. urticae em 20 dias na proporção de 1 predador para 100 fitófagos (OLIVEIRA et al, 2009). Adicionalmente, a quantidade de ovos produzidos por fêmea de P. macropilis é diretamente proporcional ao número de T. urticae consumidos (FERLA et al, 2011).…”

Acarofauna associated to papaya orchards in Veracruz, Mexico

“…These predatory mites are widely distributed in the Americas, including the Antilles, but E. hibisci has been found in Angola, India and Madeira Island (Moraes et al 2004), and P. macropilis is present in many sites around the world, as a result of its massive propagation and use as a biological control agent (Ferla et al 2011). The distribution of all three species includes localities North and South of the study area, so they are considered part of the native fauna or at least have been present there for a long time.…”