Abstract
ABSTRACT Helicoverpa armigera (Hübner) is part of an important complex of insects-pests that attack the cotton crop. This study aimed to identify the preferential plant parts for the oviposition of moths, as well as the movement and feeding behavior of caterpillars, in the vegetative phase of the cotton cultivar BRS 369 RF. Plants emitting floral buds were used to study the oviposition behavior of moths. For this, a completely randomized design, with three treatments (adaxial and abaxial sides of the leaf and floral buds) and twenty replications (plants in pots), was used. In order to evaluate the behavior of the caterpillars in the cotton vegetative phase, another 3 × 5 factorial design, with nine replications, was used. The treatments were three ages (first, second and third instars) combined with five behaviors (walking, resting, waving, eating and drop-off). In this trial, the period of the day when caterpillars are more active was also evaluated. It was observed that H. armigera moths prefer to lay their eggs on the adaxial leaf side and on the last two nodes of the plant, in a descending direction. The adaxial leaf side is also the part of the plant preferred by caterpillars for walking, eating and resting, being this last behavior the most frequent in all instars. In general, the caterpillars walk more in the morning.
Highlights
Brazil is among the largest cotton producers and the planted area in the 2017/2018 crop season was 1,176.1 thousand hectares, with an expected production of 4,947,000 tons of cotton seed and 1,979.4 thousand tons of fiber
Sites with trichomes are probably chosen by H. armigera to oviposite (Zalucki et al 1986, Luong et al 2016) because these structures may hinder the movement of natural enemies when searching for their prey or hosts, resulting in protection for the pests’ progeny (Vendramim 2002)
Olsen & Daly (2000) verified this fact in cotton and Santos et al (2017) in soybean, a behavior found in Chloridea virescens and H. zea Heliothinae (Torres & Ruberson 2006)
Summary
Brazil is among the largest cotton producers and the planted area in the 2017/2018 crop season was 1,176.1 thousand hectares, with an expected production of 4,947,000 tons of cotton seed and 1,979.4 thousand tons of fiber. The Central-West region is responsible for 70.4 % of this production, where the. Mato Grosso state is the largest producer, with 777.8 thousand hectares of cotton, corresponding to 66.1 % of the area planted in the country. The projected cotton seed production for this state is 3,213.9 thousand tons, 27.1 % higher than in the 2016/2017 harvest, with a yield of 4,132 kg ha-1 (Conab 2018). The crop is attacked by a complex of insectspests capable of infesting all the phenological plant.
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