Persistency evaluation of two insecticides on tomato plants to determine releasing time of Habrobracon hebetor (Say)Hymenoptera: Braconidae
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عنوان دوره: سومین کنگره بین المللی حشره شناسی ایران
نویسندگان
1Plant Protection Department, University of Agricultural Sciences and Natural Resources, Gorgan, Iran, ati.khosroabadi@gmail.com, afshari@gau.ac.ir, vahidrahiminejad@gau.ac.ir
2Plant Protection Department, University of Agricultural Sciences and Natural Resources, Gorgan, Iran,
چکیده
Habrobracon hebetor (Say) (Hym.: Braconidae) is a well known cosmopolitan ectoparasitoid that attacks larvae of lepidopteran pests including tomato fruit worm, Helicoverpa armigera (Hübner), the most destructive pest of tomato (Lycopersicon esculentum) in northern Iran. One of the major purposes of Integrated Pest Management (IPM) strategies is to combine the safe and sustainable use of pesticides with biological control agents. Therefore, using reduced-risk chemicals is a principal tool to reach this goal. The safe time interval between tomato field spraying and H. hebetor releasing is an important question that is often asked by tomato producers. International Organization of Biological Control (IOBC) has recommended a standard method for assessing the duration of harmful activity (persistence) of pesticides against natural enemies and identifying selective pesticides for use in integrated control programs. Therefore, this study was carried out to determine persistence of two insecticides, Proclaim Fit (as a newly registered insecticide) and Thiodicarb (as a conventional insecticide) on tomato plants and their residues lethal and sublethal effects on the parasitoid under laboratory conditions (25 ± 1 °C, 65 ± 5% RH, and 16:8 h L: D). Field recommended concentration of insecticides was sprayed on tomato plants. Then, tomato leaves were removed at one-day intervals and exposed to 30 females of H. hebetor in a container. The mortality and fecundity of parasitoid were assessed every day until insecticide toxicity reach to harmless category, according to IOBC standards. Our results showed that, Proclaim Fit was a non-persistent insecticide and its residues on tomato plants caused only 14.1% mortality (harmless category) in parasitoid population one day after treatment. Moreover, Proclaim Fit residues had no sublethal effect on parasitoid fecundity in the first seven days after treatment. In contrast, Thiodicarb was a more persistent insecticide compared to that of Proclaim Fit, however, its mortality and fecundity reduction effects reached to harmless category 7 and 14 days after treatment, respectively. In conclusion, H. hebetor can be recommended to release about one day after Proclaim Fit spraying, whereas at least a 14-days interval should be considered between thiodicarb spraying and H. hebetor releasing in tomato fields
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