Produtos comerciais a base de Neem sobre ovos e ninfas de Diceraeus sp. (Hemiptera: Pentatomidae)

Abstract

The green belly stink bug, Diceraeus spp., has been shown to be a pest with great potential for damage to soybean, wheat and corn crops, both in conventional and organic planting systems. The damage that these insects cause in these plantations occurs from pre-germination to the end of the cycle. In organic systems there are several alternatives to control these bugs and minimize damage, one of which is the use of natural plant-based insecticides such as Neem, Azadirachta indica, A. Juss (Meliaceae). Due to the scarcity of studies with this type of product in relation to bed bugs, especially of the genus Diceraeus spp., this study becomes important and aims to contribute to the existing literature. Thus, the objective of this work was to evaluate the effect of commercial neem-based products on eggs, nymphs and adults of Diceraeusspp. (Hemiptera: Pentatomidae) under laboratory conditions. Commercial products based on neem, Neenmax®, Orignal Neem®, Neem Vitaplan®, BaseNim® were used. As a positive control, the synthetic chemical insecticide Galil® was used, at the recommended concentrations (CR) by the manufacturer and also twice this (2CR), as a negative control, distilled water was used. For the test with eggs, the application was performed using the technique of immersion in 5μl of the solution, using four repetitions (groups of 15 eggs of up to 72 hours), in Petri dishes. For the nymph test, a volume of 3μL of the solutions was applied to the scutellum of each insect, with the aid of a micropipettor. Four replicates were used (Petri dishes), containing 20 insects per dish. The experiments were placed in a climate-controlled environment at a temperature of 27 ± 2°C, relative humidity 60 ± 10% and a photoperiod of 12 hours. For the bioassay with eggs, the evaluation was carried out daily until the fifth day, recording the number of hatched nymphs and the subsequent mortality due to the residual effect of the treatments. In the bioassay with nymphs, the evaluation was carried out daily, quantifying the number of dead insects until the tenth day. No ovicidal effect caused by commercial neem-based products on eggs of Diceraeus spp. For 3rd instar nymphs of Diceraeus spp., the positive control Galil® showed a Knockdown effect (100% mortality) within 1-3 days. Among the neem-based products, at the end of the 10 days of evaluation, the Original Neem® product showed an insecticidal effect at the recommended concentration (76.25% mortality), differing from the negative control distilled water (55% mortality). It was also observed the greatest accumulation of mortality in the period of 1 to 3 days in both concentrations used. In the other periods, mortality was reduced, and from 4 to 7 days, a maximum of 15% of mortality caused by Neenmax® was obtained in CR and 15% for Original Neem® in 2CR. Since the period 8 to 10 days, the highest mortality was 20%, caused by the CR Basenim® and 13.75% in Neenmax® caused by 2CR. Aiming to contribute to pest control practices, both in agroecological and conventional production systems, new studies with other products and new dosages are necessary.