Behavioral aspects of Helicoverpa armigera in the cotton vegetative phase1

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.

Ethological aspects of Helicoverpa armigera in the reproductive phase of cotton

“…Therefore, it can be inferred that the caterpillars are more exposed to the action of natural enemies and this exposure can be used for insecticides to reach them. These results coincide with those of RODRIGUES et al (2019) who observed caterpillars of the first three instars crawling more frequently on the adaxial face of cotton leaves in the vegetative phase.…”

“…As they crawl more in the morning, this is a good indication that a good time to spray to reduce their population is in the morning. A similar result was obtained by RODRIGUES et al (2019) when they studied the behavior of up to third instar H. armigera on cotton in the vegetative phase. Therefore, spraying to control H. armigera in the vegetative and reproductive phases of cotton should be done in the morning.…”

“…It appears that the two most frequent behaviors in all instars were eating and resting, followed by crawling. JOHNSON; ZALUCKI (2005;2007) and RODRIGUES et al (2019) obtained similar results when they studied the behavior of H. armigera in the vegetative stage of mung bean (Vigna radiata L.) and cotton in the vegetative period (Gossypium hirsutum L.), respectively.…”

“…Plants that were between B2 and B3 according to the MARUR scale (MARUR; RUANO, 2001) were used to evaluate the behavior in the reproductive phase. The experiment was conducted following the methodology of RODRIGUES et al (2019) who studied the behavior of H. armigera in the cotton vegetative phase.…”

“…Heliothinae moths prefer to feed and lay eggs on plants that are flowering and have nectar (CUNNINGHAM; ZALUCKI, 2014). Their attack in cotton can occur in the vegetative (PASCUA; PASCUA, 2002;RODRIGUES et al, 2019) and reproductive (LUONG et al, 2016;GOMES et al, 2017) phases. The movement of H. armigera caterpillars on the plant is influenced by several factors such as microclimate, odors, wax, trichomes and the presence of flowers (CRIBB et al, 2010;PERKINS et al, 2010).…”