Efecto de franjas marginales de Brassica campestris L. en repollo sobre Plutella xylostella (Lepidoptera: Plutellidae) y sus enemigos naturales

Abstract

The effectiveness of plant diversity in agricultural systems is considered as an important resource in wildlife conservation charity, by providing prey or hosts, shelters, and alternative food sources such as nectar and pollen, but for many authors positive effect have yet to be evidenced. Plutella xylostella is an insect oligophagous, multivoltine and cosmopolitan, considered key pest of most crops of the Brassicaceae family, to whose control is allocated annually, worldwide, nearly 1 billion dollars. In recent years, the flaws in the control of this pest have been due to cross and multiple resistance to insecticides of different mode of action, including Bacillus thuringiensis, which is why it is necessary to implement alternatives of control tactics such as the establishment and increase of natural enemies in agricultural systems. The aim of this study was to determine the effect of marginal strips of B. campestris in cabbage crops on the pest and its major summer transplants a marginal strip B. campestris. Lot settler in the four treatments, with marginal fringe, with and without application of agrochemicals, without marginal fringe agrochemical applications and a witness,without marginal fringe without sprays. Of each were monitored weekly larvae and pupae stage of P. xylostella, in five cabbage plants. The immature larvae were ranked small, medium, large, and pupae were reared in the laboratory to determine the lepidopteran adult emergence or emergence of parasitoids. It was determined that: the main parasitoids was Cotesia plutellae in small and medium larvae and Oomyzus sokolowskii in large larvae and pupae; spring transplants have less pest attack due to less favorable weather conditions, the marginal strips were not effect on the pest attack, in the amount of parasitoids and reproductive parameters.

La diversidad vegetal en los sistemas agrícolas es considerada como un recurso importante para la conservación de la fauna benéfica. Para muchos autores su efecto positivo todavía no ha podido ser evidenciado. Plutella xylostella es un insecto oligófago, multivoltino y cosmopolita, considerada plaga clave de la mayoría de los cultivos de la familia Brassicaceae. En los últimos años, las fallas en los controles de esta plaga se han debido a la resistencia cruzada y múltiple a insecticidas de distintos grupos, incluso al Bacillus thuringiensis. El objetivo del presente trabajo, fue determinar el efecto de franjas marginales de Brassica campestris en cultivos de repollo sobre la abundancia de la plaga y sus principales parasitoides en el cinturón hortícola santafesino. Semanalmente se monitorearon los estados de larvas y pupas de P. xylostella, en cinco planta de repollo, para tres distancias con respecto al borde donde se localizaba la franja de B. campestris. Los estados inmaduros fueron clasificados en larvas chicas, medianas y grandes, y pupas, que fueron criadas en laboratorio para determinar la emergencia del adulto del lepidóptero o la de sus parasitoides. Se determinó que: los principales parasitoides fueron Cotesia plutellae, en larvas chicas y medianas, y Oomyzus sokolowskii en larvas grandes y pupas. Los transplantes de primavera tuvieron menor ataque de la plaga. Las franjas marginales no tuvieron efecto significativo en el ataque de la plaga, en la cantidad de los parasitoides ni en los parámetros reproductivos, peso y diámetro de las cabezas del repollo