&lt;b&gt;Lethal and sublethal effects of neem on &lt;i&gt;Aphis gossypii&lt;/i&gt; and &lt;i&gt;Cycloneda sanguinea&lt;/i&gt; in watermelon

Cíntia Ribeiro Souza,Madelaine Venzon,Gil Rodrigues Dos Santos,Paulo Henrique Tschoeke,Marcela Cristina Agustini C Da Silveira,Renato Almeida Sarmento

doi:10.4025/actasciagron.v37i2.19517

Abstract

The objective of this study was to evaluate the impact of oil extract of neem, Azadirachta indica, on the watermelon aphid Aphis gossypii and its natural enemy Cycloneda sanguinea. Toxicity bioassays were conducted with the commercial product DalNeem (1,475 g L-1 azadirachtin) at 0.0037 µg a.i. mL-1, 0.0074 µg a.i. mL-1 and 0.0148 µg a.i. mL-1, Malathion at 1 µg a.i. mL-1 and distilled water as a control treatment. The products were sprayed to watermelon leaf discs, and the insects were exposed to the product residues. The instantaneous population growth rate of A. gossypii and the survival of C. sanguinea larvae exposed to the different treatments were calculated. A decrease in the instantaneous population growth rate of A. gossypii with increasing concentrations of neem was observed, and the aphids did not reproduce on the leaf discs treated with malathion during the first 24 hours of exposure due to its rapid lethal effect on adult insects. The larvae of the predator C. sanguinea exposed to malathion survived only for 24 hours. The survival of the predator exposed to different concentrations of neem was also significantly reduced compared to the predators exposed only to water. However, laboratory experiments may overestimate the effect of neem on predators because the individuals cannot employ escape behavior caused by neem repellency.

Highlights

Watermelon is a crop adapted to different growth and climate conditions in Brazil, including soil type, high temperatures, photo-oxidation, and water availability via irrigation
With the objective of assessing the feasibility of using neem to control one of the main pests of watermelon, the aphid A. gossypii, we evaluated the lethal and sublethal toxicity of oil extract of neem, Azadirachta indica Juss., on this pest and on one of the natural enemies frequently found in association with this aphid, the predator C. sanguinea
The instantaneous rate of population growth of A. gossypii decreased with increasing concentrations of neem and reached negative values at a concentration of 0.0148 μg a.i. mL-1 (Figure 1)

Summary

Introduction

Watermelon is a crop adapted to different growth and climate conditions in Brazil, including soil type, high temperatures, photo-oxidation, and water availability via irrigation. Watermelon production is limited by the occurrence of disease and by the attack of insect pests that damage watermelon crops, leading to economic losses, such as the aphid. Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) (BALDIN et al, 2009; PINTO et al, 2008). This insect causes direct damage by sucking the sap, which causes deformities of the leaves, twigs, branches and reduces the photosynthetic capacity of the attacked plants, as well as facilitating transmission of viruses of the Potyvirus genus (PINTO et al, 2008). 233-239, Apr.-June, 2015 the control of A. gossypii has been performed exclusively by the application of synthetic insecticides, the majority with a broad spectrum of action (MOREIRA et al, 2000). Non-target organisms may be negatively affected by the overuse of synthetic insecticides (AKTAR et al, 2009)

Objectives

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Results