Occurrence of Bemisia tabaci (Hemiptera: Aleyrodidae) and Aphis gossypii (Hemiptera: Aphididae) on Okra Plants in a Semi-Arid Region of Brazil, with Notes on their Vertical Distribution and the Impact of Deltamethrin

Abstract

The expansion of agriculture in the semi-arid region of northeastern Brazil has been associated to an increase in the number of insect pests and the indiscriminate use of agrochemicals. We performed a field survey of two major okra pests, Aphis gossypii and Bemisia tabaci, taking into consideration their within-plant vertical distribution. We also investigated the presence of parasitized insects and the short-time effect of the application of deltamethrin. Throughout the experiment, 59,787 phytophagous insects were collected, which were categorized in four groups: healthy nymphs/adults of Aphis gossypii (N = 31,767), A. gossypii parasitized by Hymenoptera (N = 4189), Bemisia tabaci eggs (N = 2507) and B. tabaci nymphs (N = 21,324). The abundance of A. gossypii was higher than that of B. tabaci at both, the control and the insecticide-treated area. The frequency of parasitism of A. gossypii by Hymenoptera was higher in the areas that did not receive deltamethrin. Higher numbers of A. gossypii occurred in the middle part of the plants and B. tabaci populations were lower in apical leaves.