ترجيح غذايي كنه شكارگر Amblyseius swirskii روي سفيد بالك گلخانه Trialeurodes vaporariorumتيمار شده و تيمار نشده با قارچ Beauveria bassiana

Prey Preference of Predatory Mite Amblyseius swirskii (Acari: Phytoseiidae) on Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) Treated and Untreated with Beauveria bassiana

كنه شكارگر Amblyseius swirskii و قارچ بيمارگر Beauveria bassiana از دشمنان طبيعي مهم سفيد بالك گلخانه Trialeurodes vaporariorum هستند. در بررسي كارايي و انتخاب دشمنان طبيعي، تعيين ترجيح غذايي آنها، هنگامي كه دشمن طبيعي در برابر ميزبان آلوده يا غير آلوده به عوامل بيمارگر قرار مي گيرد، از اهميت خاصي برخوردار است. در اين تحقيق ترجيح غذايي كنه شكارگر دو روز پس از بالغ شدن در برخورد با پوره سن سوم سفيد بالك گلخانه غير آلوده و تيمار شده با قارچ B. bassiana در دو تيمار زماني ۲۴ و ۴۸ ساعت بعد از آلودگي شكار با استفاده از شاخص بتاي منلي تعيين شد. شكارگرهايي كه ۲۴ ساعت گرسنگي داده شده بودند بر روي ديسك هاي برگي خيار رهاسازي شدند و پس از ۲۴ ساعت تعداد سفيد بالك هاي مصرف شده شمارش شدند. آزمايش درون ظروف پتري تهويه دار و به مدت ۲۴ ساعت انجام شد. براساس نتايج مقدار شاخص در بازه زماني ۲۴ و بازه زماني ۴۸ ساعت پس از تيمار شدن ميزبان به قارچ، به ترتيب ۰/۱۹±۴/۱۵ و ۰/۱۲±۲/۲۳ برآورد شد. نتايج نشان داد، A. swirskii در تغذيه از سفيد بالك هاي غير آلوده در مقابل سفيد بالك هاي تيمار شده با قارچ در بازه زماني ۲۴ ساعت (۰۰۰/۰۰۳۴>P) و ۴۸ ساعت (۰/۰۰۰۱>P) به سمت سفيد بالك هاي غيرآلوده ترجيح نشان مي دهد با توجه به نتايج مي توان گفت كه اين كنه شكارگر با رفتار عدم ترجيح در آزمون دو انتخابي نسبت به ميزان آلوده مي تواند در كنترل بيولوژيك همراه با اين قارچ به كار رود.

Introduction: Tria/eurodes vaporariorum is an economically important pest of various crops in greenhouses. Negative impacts of insecticides such as development of resistance, undesirable effects on nontarget organisms and fostered environmental and human health concerns, have encouraged the development of alternative methods of pest control by biological control agents. Use of several natural enemy species has been promoted, as a strategy to enhance management of pests in greenhouses. Based on this strategy, combinations of two or more species of natural enemies of greenhouse pests (such as aphid, two-spotted spider mite, thrips and whitefly) including predators, parasitoids, and pathogens are added to a pest-crop system. Recently, the phytoseiid Amb/yseius swirskii has received interest as a biological control agent of whiteflies and thrips and has been commercially available since 2005. The application of entomopathogens to control certain pests may be a future alternative for solving problems of chemical resistance and environmental contamination in agroecosystems. Amb/yseius swirskii and entomopathogenic fungus Beauveria bassiana were used as biocontrol agents of Trialeurodes vaporariorum. Determination of the host preference of predators in the fields when receiving signals related to either Beauveria bassiana-treated or -untreated pest is important. In the present study, the host preference of A. swirskii was investigated when the B. bassiana- infected and uninfected whitefly were offered to predatory mite on the leaf. The aim of the study was to understand if the predatory mite would able to detect the presence of an entomopathogenic fungus and avoid feeding on fungus infected prey. Materials and Methods: Tria/eurodes vaporariorum was collected from the cucumber plants ( Cucumeris sativus) in a greenhouse in Karaj City, Alborz Province, Iran. The colony was maintained on cucumber plants in cages in greenhouse for one year. The natural enemy, A. swirskii was purchased from Kopperl Biological systems Inc., the Netherlands. Tyrophagus putrescentiae (Schrank) (Acari: Acaridae) and soybean pollen were supplied twice per week as food for A. swirskii. Beauveria bassiana isolate DEBI008 was originally obtained from a Chorthippus brunneus Thunberg (Orthoptera: Acrididae), that had been stored in the "Pathogen Bank" at the Department of Plant Protection, Faculty of Agriculture, University of Tehran, Karaj, Iran. It was cultured on Sabouraud dextrose agar plus]/. yeast extract (SDAY) at 25 ±l°C, 60-70% RH and in darkness for 10-14 days to obtain conidia. The conidia were harvested from the culture medium by adding 10 ml sterile distilled water containing 0.02 % Tween 80 by scrubbing the surface with a glass bar. The conidia suspension was filtered through moist filter paper (Whatmann® No.I ). The conidial suspension was vortexed for 15 min to produce a homogenous suspension. Spore concentration was calculated using a Neubauer haemacytometer and suspension of I xI 05conidiallml was achieved through dilution in the surfactant Tween 80 (0.02 %). Conidial suspension used for experiment was less than 4 h old and was stored in rerrigerator. The viability of the conidia was determined by inoculating conidial suspension on plates of SDA Y which were then incubated for 18 hat 25 °C. In this research, ·the prey preference of adult female (2 days old) of A. swirskii was determined on untreated and B. bassiana-treated ofT. vaporariorum (Hemiptera: Aleyrodidae) in various treatments base on Manly Index. These difTerent treatments consisted of two time intervals; 24 and 48 h post-inoculation of greenhouse whiteflies with I xI 05 conidia /ml of B. bassiana with 13 replicates. 24-h starved predators were individually added to the leaf discs and then the number of consumed uninfected and B. bassiana-infected T. vaporariorwn in each Petri dish was assessed after 24 h. Results and Discussion: The results revealed that the mean number of consumed B. bassiana-infected T. vaporariorum in following two time intervals; 24 and 48 h after inoculation were 4.15±0.19 and 2.23±0.12, respectively. This investigation showed a significant preference of the predatory mite toward uninfected whitefly at 24 (P< 0.0034) and 48 h. (P