POPULATION FLUCTUATION OF BENEFICIAL INSECTS ASSOCIATED TO COTTON PESTS

ABSTRACT

With the objective of identifying and quantifying the natural enemies associated to cotton pests sampling was made of these arthropods during the 2001/2002 and 2002/2003 crop season in Dourados, MS, Brazil. Evaluation was made of 100 plants in 20,000 m², in a total of 20 samplings from 7 to 140 days after the plants' emergence, making use of the cotton cultivars DeltaOpal and Fibermax 986, in 2001/2002 and 2002/2003, respectively. In 2002/2003 samplings of the beneficial arthropods on the ground in the experimental area were made, through visual evaluations in the spaces between lines of plants in 25 plots of 100 m² and through the utilization of 25 pitfall traps installed in each plot. For species most abundant in the ground the standard analysis was made of their spatial distribution using the Morisita index. In the two crop seasons, the Coccinellidae family was the most abundant of the complex of predators, with population levels following the fluctuation of a cotton aphid Aphis gossypii Glover population (Hemíptera: Aphididae). The suborder Heteroptera (Hemiptera) presented the highest diversity, with insects from 5 families, during the crop season 2001/2002. The pitfall trap method was more efficient than visual evaluation. Amongst the soil predators, the most abundant was Calosoma granulatumwhose standard of spatial distribution was aggregated in the experimental area.

KEY WORDS
Natural enemy; predator; sampling; Gossypium hirsutum