اثر غلظت‌های کشنده و زیرکشنده سه حشره‌کش روی برخی فرآسنجه های رشدی زنبور پارازیتوئید habrobracon hebetor به روش تماسی و میزبان مسموم

تعیین اثرات غلظت‌های کشنده و زیرکشنده‌ی حشره‌کش‌ها بر فرآسنجه های رشدی دشمنان طبیعی زنده مانده یکی از نیازهای تحقیقاتی در برنامه‌های مدیریت آفات می‌باشد. هرچه این اثرات کمتر باشد حشره‌کش انتخابی‌تر عمل کرده و در برنامه کنترل آفات از جایگاه بهتری برخوردار می‌باشد. زنبور پارازیتوئید habrobracon hebetor say به‌عنوان یک دشمن طبیعی موثر نیز از این قاعده مستثنی نیست. در این تحقیق اثر کشنده و زیرکشنده‌ی حشره‌کش‌های رایج آبامکتین® و پروتئوس® و سیرینول® به دو روش تماسی و میزبان مسموم بر خصوصیات رشدی این زنبور بررسی گردید. آزمایش‌های زیست‌سنجی در شرایط آزمایشگاهی (دمای 2±25 درجه سلسیوس، رطوبت نسبی 5±60 درصد و روشنایی 8d:16l) در پنج تکرار و هر تکرار با 30 زنبور در روش تماسی و هر تکرار با 15 لارو میزبان آزمایشگاهی (شب‌پره آرد، ephestia kuhniella zeller) در روش میزبان مسموم انجام شد. غلظت کشنده این تیمارها در روش تماسی روی این زنبور پارازیتوئید به ترتیب 1.38، 0.037 و 6.621 میلی‌لیتر بر لیتر و روی لارو میزبان آزمایشگاهی برای این زنبور به ترتیب 0.490، 2.155 و 0.138 میلی لیتر بر لیتر بدست آمد. نتایج نشان داد که بیشترین کل طول دوره‌ی رشدی این زنبور پس از تیمار شاهد (0.79± 25.95 روز) مربوط به تیمار سیرینول در روش میزبان مسموم با غلظت زیرکشنده (0.86 ± 23.42 روز) بود. بیشترین طول عمر حشرات ماده زنبور مربوط به تیمار سیرینول در کاربرد غلظت زیرکشنده به صورت تماسی (0.17± 30.31 روز) و بیشترین طول عمر حشرات نر مربوط به کاربرد تیمار سیرینول در غلظت زیرکشنده در روش میزبان مسموم (0.15± 22.02 روز) بود. بیشترین میزان تخم گذاشته‌شده در تیمار سیرینول در غلظت زیرکشنده به صورت کاربرد تماسی (1.48 ± 177.01 عدد) مشاهده شد. نتایج نشان داد که تیمار سیرینول به صورت کاربرد تماسی کمترین اثر سوء را روی زنبور پارازیتوئید داشت.

Effect of Lethal and Sublethal Concentrations of Three Insecticides on Some Growth Parameters of Parasitoid Wasp, Habrobracon hebetor by Contact and Poisonoushost Method

Introduction: Population growth and the high food demand have led to more efforts to increase agricultural production. With making chemical pesticides, farmers were encouraged to use much chemicals, but their destructive effects on the environment, human and other organisms have been later revealed. Parasitoids are important natural enemies of crop pests. Most of them belong to order hymenoptera and superfamily Ichneumonoidea. The Braconidae is a family of parasitoid wasps and one of the richest families of insects. Nowadays, parasitoid wasp, Habrobracon hebetor Say has been widely used against lepidopteran larvae. Habrobracon hebetor is a wellknown gregarious, idiobiont, ectoparasitoid of the larvae of a wide range of economically important moths infesting stored grains, nuts, and fruits as well as field crops worldwide. Due to overuse of chemical pesticides for larvae controlling, determining the side effects of insecticides on the biocontrol agents such as parasitoids is required.;Materials and Methods: In the present study, we investigated the side effects of three insecticides on H. hebetor by direct (contact) and indirect (poisonoushost) methods. After rearing this parasitoid on the laboratory host, Ephestia kuhniella Zeller (Lep.; Pyralidae), the lethal and sublethal concentrations of insecticides were evaluated. Bioassay experiments were carried out under laboratory condition (25±2°C, 60±5% RH, 16L: 8D photoperiods) in five replicates and each replication included 30 parasitoids in contact method and 15 flour moth larvae in poisonoushost method. The lethal concentrations of these insecticides in contact method on the parasitoid were determined to be 1.38, 0.037 and 6.621 ml/L and on flour moth larvae were 0.490, 2.155 and 0.138 ml/L, respectively. For contact method, different concentrations of insecticides were applied on all inner sides of transparent plastic cup (4.5×8 cm) and airdried. 15 pairs of 24hours old parasitoids were introduced inside each cup. After 24 hours, one pair of alive parasitoids was introduced into cup with four last instar host larvae to oviposit. The host larvae were replaced daily. The parasitoid characteristics such as longevity and survival rate of different stages, TPOP and Oviday, the number of deposited eggs and sex ratio were then recorded. As to poisonoushost method, whole wheat flour (10 g) was mixed with 3.5 ml of each tested concentration of insecticides per each experimental set. After 72 hours, alive larvae were transferred in a plastic cup with one pair of H. hebetor wasp for 24 hours. Then, each larva was transferred separately in a petri dish with untreated flour. Different growth factors of parasitoids such as longevity and survival rate, TPOP and Oviday, the number of deposited eggs and sex ratio were recorded. Estimated LC30 and LC50 were considered as sublethal and lethal concentrations in all experiments, respectively.;Results and Discussion: In contact method, the highest survival rate of preadult stages and adult female were observed in Sirinol treatment at lethal concentration, after control. In poisonoushost method, the highest survival ratio of the preadult stages belongs to Sirinol and in adult female the highest survival ratio was observed in lethal concentration of Sirinol. The lethal concentration of Proteus reduced preadult longevity of the parasitoid significantly, followed by lethal and sublethal concentration of Sirinol. Lethal and sublethal concentrations of Proteus also exhibited a significant reduction of total longevity. In poisonoushost method, all concentrations of all insecticides generally induced highly significant differences for oviday compared with that of control (17.91 days), as the shortest value was recorded for sublethal dose of Abamection (7.46 days) and the longest period was found for sublethal dose of Sirinol (13.2 days). In poisonoushost method, the longest TPOP was observed in sublethal concentration of Sirinol (16.02 days), followed by sublethal concentration of Abamection (14.63 days), and the shortest period was recorded in sublethal concentration of Proteus (12.3 days), after control (12.19 days). On the other hand, in contact method, the longest oviday and TPOP were observed in sublethal concentration of Sirinol (18.19 days) and lethal concentration of Abamection (13.26 days), respectively. The shortest adult female longevity was observed in lethal concentration of Proteus (27.55 days) in contact method and lethal concentration of Sirinol (22.85 days) in poisonoushost method. In all treatments, the number of deposited eggs was significantly reduced compared with control. The largest reduction in egg deposition was recorded for sublethal concentration of Proteus (71.05 eggs) in contact method and sub lethal concentration of Abamection (36.14 eggs) in poisonoushost method, compared with control (227.47 eggs). It seems that Sirinol is suited to be used as a component of IPM alongside with H. hebetor.