نامه انجمن حشرهشناسی ایران (Aug 2019)
Lethal and sublethal effects of propargite, benomyl, haloxyfop etotyl, imidacloprid and chlorpyrifos on life table parameters of egg parasitoid, Trichogramma brassicae (Hym.; Trichogrammatidae)
Abstract
Trichogrammabrassicae Bezdenkois an important egg parasitoid of several lepidopteran insect pests. The parasitism potencial of this parasitoid is affected by insecticides applications. In this study, lethal and sublethal effects of propargite, benomyl, haloxyfop etotyl, imidacloprid and chlorpyrifos were evaluated on different life stages and biological parameters of the insect. Bioassays were carried out by residual contact method on adult stage of the parasitoid at 26±1 , 70±5% RH and a photoperiod of 16: 8 (L: D) h. The LC50 values of propargite, benomyl, haloxyfop etotyl, imidacloprid and chlorpyrifos were 753, 1190, 1731.6, 5.85 and 1.96 mg a.i./L on adult T. brassicae, respectively. The results of bioassays on adult stage showed that chlorpyrifos had the highest toxicity compared to the other tested pesticides. Field recommended rate of the pesticides excluding chlorpyrifos showed lower adverse effects on immature stages of the parasitoid. According to IOBC standards, propargite, benomyl, haloxyfop etotyl and imidacloprid were classified as harmless and chlorpyrifos as slightly harmful at immature stages. The sublethal effect studies revealed that LC30 of chlorpyrifos and propargite negatively affected the fecundity and fertility of the females; but the other pesticides did not. Intrinsic rate of increase (rm) values for propargite, benomyl, haloxyfop etotyl, imidacloprid and chlorpyrifos were 0.344, 0.322, 0.338, 0.337, 0.334 and 0.318 (female offspring/female/day), respectively. Results showed that almost all pesticides excluding chlorpyrifos had less adverse effects on the parasitoid. Therefore, propargite, benomyl, haloxyfop etotyl and imidacloprid can be choose for further evaluation including semifield and field studies. Whether getting suitable results in field studies they would be used in combination with T. brassicae as biological control agent in integrated pest management (IPM) programs.
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