Impacts of Dichlorvos and Spiromesifen Effects on Aphis gossypii (Hem.: Aphididae)
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
Aphis gossypii Glover (melon aphid) is one of the most important pests of crops, greenhouse, and ornamental plants that causes considerable damage annually. Unfortunately, repeated application of insecticides against this pest caused many problems including resistance to insecticides. Therefore, studying pesticides with a novel mode of action against this pest is necessary. This study was conducted to evaluate the toxicity of dichlorvos (DDVP® EC 50%) and spiromesifen (Oberon® SC 24%) on the melon aphid. Dichlorvos is a commonly used insecticide to control melon aphid and spiromesifen, a tetronic acids compound, is recommended against immature stages of whiteflies and mites. In this study, contact toxicity of dichlorvos and spiromesifen against third instar nymphs of A. gossypii and rate of reproduction in adult tested by using the topical method. Aphid melon was collected in summer 2015 from cucumber plants in the greenhouse in Karaj and after transferring to the laboratory, aphids grew up on cucumber variety Negin. Experiments were carried out at 25±1°C, 65±5% RH and under a photoperiod of 16L:8D in a growth chamber. Third instar nymphs were treated with different concentrations of dichlorvos (ranging from 35.39 to 58.91 mg a.i/L) and spiromesifen (ranging from 71.046 to 154.71 mg a.i/L). Acetone was used as the solvent for dichlorvos and water-methanol (10:90 v/v) was used as the solvent for spiromesifen. 15 third instar nymphs of melon aphid were used for each concentration. Experiments were performed in three replicates and five concentrations and dead insects were counted 24 h post treatment for dichlorvos and 48 h post treatment for spiromesifen. LD50 values were estimated by using the Polo-Plus software. Survived insects in the test of bioassay, kept in separate Petri dishes containing leaf disc and were evaluated to determine the rate of reproduction. Results showed that A. gossypii was significantly more susceptible to dichlorvos than spiromesifen. LD50 values of dichlorvos and spiromesifen were 46.26 and 106.63 mg a.i/L, respectively and survived insects showed decrease in reproduction compared to the control. However, no significant difference was observed between the two pesticides on the rate of reproduction of melon aphid. Although one of the recommended pesticides in greenhouse to control the whitefly is spiromesifen and according to the results obtained in this study, these pesticides can also affect the cotton aphid. It seems that using spiromesifen could be useful for managing resistance of aphid melon in IPM programs.
کلیدواژه ها