بررسي اثرات كشنده و زيركشنده حشره كش هاي تيوديكارب و هگزافلومورون بر زنبور پارازيتوييد تخم، Trichogramma brassicae Bezde. در شرايط آزمايشگاهي

Lethal and sublethal effects of thiodicarb and hexaflumuron on egg parasitoid, Trichogramma brassicae Bezdenko under laboratory conditions

در اين پژوهش اثرات كشنده و زيركشنده فرمولاسيون هاي تجاري دو حشره كش تيوديكارب و هگزافلومورون بر زنبورTrichogramma brassicae Bezde بررسي شد. هر دو حشره كش موجب بروز تلفات معني دار و كاهش طول عمر و قدرت پارازيتيسم زنبور شدند، اما شدت تاثير تيوديكارب از هگزافلومورون بيشتر بود. غلظت هاي مختلف تيوديكارب در هر دو روش خوراكي و تماسي موجب بروز صد درصد تلفات در جمعيت زنبورهاي نر و ماده شدند و فرو بردن تخم هاي پارازيته شده ميزبان درون غلظت توصيه شده اين حشره كش موجب مرگ و مير 87/3 درصد پيش شفيره هاي زنبور گرديد. در مقابل، غلظت توصيه شده هگزافلومورون در روشهاي خوراكي و تماسي به ترتيب موجب بروز 38/1 و 24/3 درصد تلفات در جمعيت زنبورهاي ماده شد و فرو بردن تخم هاي پارازيته شده ميزبان درون غلظت توصيه شده اين حشره كش موجب 62/9 درصد تلفات در پيش شفيره ها گرديد. فرو بردن تخم هاي سالم ميزبان درون غلظت هاي توصيه شده تيوديكارب و هگزافلومورون درصد پارازيتيسم آنها را به ترتيب 55/8 و 43/6 درصد كاهش داد. بر اساس استانداردهاي سازمان بين المللي كنترل بيولوژيك، حشرهكش تيوديكارب در هر دو روش خوراكي و تماسي در گروه حشره كش هاي مضر و هگزافلومورون در گروه حشره كش هاي كم ضرر طبقه بندي گرديد. بنابراين، هگزافلومورون به دليل اثرات منفي كمتر روي زنبور T. brassicae، براي استفاده در برنامه هاي كنترل تلفيقي آفات بال پولكدار به ويژه كرم غوزه پنبه در شمال ايران مناسب تر از تيوديكارب مي باشد.

Background and Objectives Conservation of the natural enemies is an important approach to develop a biological control program. Knowledge of the side-effects of insecticides on parasitoids and using reduced-risk chemicals is a principal tool for integrating biological and chemical methods to pest management in agricultural ecosystems. Because of the important role of Trichogramma brassicae in lepidopteran pests control in agricultural ecosystems of Iran, this study was carried out to investigate lethal and sublethal effects of three concentrations of two insecticides, thiodicarb and hexaflumuron on this parasitoid under laboratory conditions. Materials and Methods Thiodicarb was prepared at three concentrations of 250, 500 and 1000 ppm and hexaflumuron was prepared at concentrations of 250, 500 and 750 ppm, and their effects were assessed through three exposure methods, including contaminating adult’s food (honey solution 10%) with insecticides, adult’s residual contact, and dipping parasitized (in prepupa stage of parasitoid) and unparasitized host eggs into insecticide solutions. Lethal effects on adult and immature stages of parasitoid and some sublethal effects such as male and female longevity and mean of daily oviposition were assessed for each insecticide/concentration. Results Thiodicarb at all three concentrations and in both oral and contact exposure method caused 100% mortality in both male and female adults. Dipping parasitized host eggs in 1000 ppm concentration of thiodicarb caused 87.3% mortality in wasp prepupa population. In contrast, 750 ppm hexaflumuron in oral and contact exposure methods caused 30.2 and 30.54% mortality in adult female population, respectively and 60.55% mortality in wasp prepupa. Dipping unparasitized host eggs in highest concentration of thiodicarb and hexaflumuron resulted in 55.8 and 43.6% reductions in parasitism rate, respectively. Dipping unparasitized host eggs into both insecticide solutions reduced their parasitism significantly. Hexaflumuron in both oral and contact bioassay tests reduced significantly male and female longevity and mean of oviposition, but there was no significant difference among three concentrations of this insecticide. Discussion According to the "total effect" and IOBC categories of toxicity, thiodicarb was found to be a "harmful" insecticide in both oral and contact exposure methods. Therefore, its application is not recommended in fields. Lethal effect of hexaflumuron was significantly lower than thiodicarb, categorized as a "slightly harmful" and "moderately harmful" insecticide in oral and contact exposure methods, respectively. However, because of high total effect of hexaflumuron on T. brassicae, using other less-toxic insecticides is recommended in IMP programs of lepidopteran pests, especially cotton boll worm.