Consórcio algodão colorido x capim citronela: viabilidade econômica e controle de pragas

Abstract

The objective of this study was to evaluate the viability of growing cotton in a consortium with citronella grass and citronella extracts effect on the behavior of Spodoptera frugiperda. For this three cropping systems were evaluated: colored cotton in monoculture and colored cotton intercropped with citronella grass in arrangements 3x1 and Ixl. The main cotton pests were monitored. The plant height, production of bolls, whole cottonseed and fiber in the cotton plants were evaluated; tussock height, production of fresh and dry mass and essential oil content of citronella grass; the economic viability was evaluated of systems cropping. Samples of the leaves of citronella grass, harvested in two periods, and subjected to the process of extracting the essential oil. There was no reduction in the attack of insect pests in colored cotton and there was a greater occurrence of coccinellids in the consortium systems. In the first harvest of the citronella grass, plants of consortium 1x1 and 3x1, developed and produced in a similar way. After regrowth, citronella grass plants in the consortium system in 1x1 produced more. The citronella grass cultivated in the consortium showed similar essential oil content in two harvests. The colored cotton was more productive in monoculture. The consortium of cotton with citronella grass showed higher rentability than cotton in monoculture. Evaluated the non-preference to feeding and oviposition of S. frugiperda in maize leaves and plants treated with essential il (0.001%, 0.005% and 0.01% (W / v)) and aqueous extract (1%, 2% and 3% (w/ v)) of citronella grass. As control, the distilled water was used. In test with free choice, two leaf sections of maize, a treated and the other not, were placed in a Petri dish, where were liberated 10 larvae at first instar S. frugiperda. For the no-choice bioassay only one section of maize leaf was placed in the Petri dish. In all bioassays, the evaluations were made 30 minutes, 1, 6, 12 and 24 hours after the liberation of the larvae by counting the larvae present in each section of maize leaf. For the free-choice tests of non-preference of oviposition were placed two maize plants in cages, one of the treated plants and the other not. Similarly, the mno-choice test, was placed only a com plant in each cage. In each of the cages “were liberated two couples of S. frugiperda. The postures and number of eggs perposture were quantifying, 24 hours after the liberation of couples. Data were subjected to analysis of variance and Skott Knott or Dunnett's test 5%. Essential oil of citronella grass at 0.001%, 0.005% and 0.010% repelled first instar larvae of S. frugiperda. At concentrations of 0.005% and 0.010% essential oil reduced oviposition of S. fugiperda causing minor postures. Aqueous extracts of citronella grass are not repellents to the first instar larvae of S. frugiperda. Only, the aqueous extracts at 3% showed repellent properties, inhibiting the posture.