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Oviposition preference of Diaphania indica (Lepidoptera: Pyralidae) in response to volatiles of intact and infested cucurbitaceous host plants
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عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
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چکیده
The cucumber caterpillar, Diaphania indica (Saunders) (Lepidoptera: Pyralidae), is a major lepidopteran pest of cucurbitaceous plants. A wind tunnel was used to study the preference of D. indica toward different cucurbitaceous plants (including: cucumber, squash, melon and watermelon) in laboratory conditions (27±1°C, 60–80% RH, 16:8 h (L:D) photoperiod and a constant airflow of 0.5 m/s). Infested plants, were infested by conspecific larvae, whitefly (Bemisia tabaci) and two-spotted spider mite (Tetranychus urticae) separately. Oviposition preference experiments were done with 4-5-d-old mated females during the 8-hour dark period, with release of 5 females. Eight tests were performed using different treatments including, four intact host plants, four host plants infested with conspecific larvae, four host plants infested with whitefly, four host plants infested with two-spotted spider mite, cucumber plants in four different status (including: intact, infested with conspecific larvae, infested with whitefly and infested with two-spotted spider mite), squash plants in four different status, melon plants in four different status and watermelon plants in four different status, were evaluated. Each treatment was replicated 20 times. The results revealed that on intact plants D. indica laid an average of 15.85±0.53, 13.95±0.43 and 11.60±0.39 eggs per plant on cucumber, squash and melon, respectively. However, this pest did not lay any egg on watermelon, and D. indica females significantly preferred cucumber over squash, melon and watermelon (F3,76 = 278.20, P < 0.001). Infestation by the conspecific larvae, whitefly and mite, significantly reduced egg laying (F3,316=60.19, p< 0.001) and this pest laid average 3.42±0.26, 4.85±0.31 and 4.17±0.29 eggs per plant on plants infected by the conspecific larvae, the whitefly and the mite, respectively. When the host plants were evaluated separately in different status, the results revealed that D. indica females significantly preferred intact plants over plants infested with conspecific larvae, whitefly and mite, for cucumber (F3,76= 6.00, p= 0.001), melon (F3,76=278.20, p< 0.001) and squash plants (F3,76=3.38, p= 0.022). For watermelon plants, this pest did not show any preference between treatments in four different status (F3,76=0.20, p= 0.89,). Results revealed that different host plant volatiles with different status, elicit a different oviposition response in D. indica. This is an initial study on the effects of plant volatiles on attraction and oviposition behavior of D. indica. Further studies on the identification and synthesis of volatile compounds may be useful for the improvement in the monitoring and management strategies of D. indica in field.
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