Direct effect of wind stress on the settlement of Aphis nerii and Eurygaster integriceps on host plants
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
Consecutive droughts and blocking water of Kajaki dam leading to dryness of Sistan plain cause heavy sand and dust storm during a period of 120 days (June and September) which are the most important climatic feature of the region. Effect of this phenomenon on the activity of agricultural pests and beneficial organisms (natural enemies and pollinators) is unclear. It was hypothesized that wind exposure might alter the settlement of insects on host plants, which result in population fluctuation. Hence, direct effects of wind stress on the settlement of two pests of this region namely Aphis nerii and Eurygaster integriceps on plants were investigated in a laboratory trial. Young plants of wheat and oleander were prepared by a local greenhouse. Colonies of Aphis and Eurygaster were collected and reared under laboratory conditions. Insects (first instar) were randomly chosen. In each replication 15 Aphis or 5 and Eurygaster were placed on top of the host plants. Plants were individually covered with net cages (35×20×15 cm3) and placed 0.5 m from fan. After 24 hours, the plants were exposed to zero (control), or moderate to high wind speeds (14, 19, and 28 m/s) for 10, 30, 60, 120, and 300 minutes. Then, the settlements of insects on the plants were quantified. The experiments were replicated three times. All statistical analyses (ANOVA, Tukey test) were conducted in SPSS (version 16) to compare the treatment groups with control (p < 0.05, 0.01). The results showed that the effect of increasing wind speed and duration of wind exposure significantly decreased the settlement of both pests on their host plants. By increasing wind speed and duration of wind exposure, the settlement of both pests was significantly impressed. The absence of 100 percent of both pests at the speed of 28 m/s and 300 minutes were observed (p < 0.01). No significant differences were detected between Aphis and Eurygaster activities on the plants after wind exposure. In conclusion, wind as a pervasive abiotic stressor in terrestrial landscapes has enormous potential to affect the foraging behaviors of insects on host plants. Our results showed when plants were exposed to wind, insects dropped from plants and it is suggested spraying insecticides at this time to protect beneficial insects. The dramatic effects of wind on insect settlement on plants reveal the significant potential of wind to influence plant-insect and pest-natural enemy interactions which are suggested to explore in future.
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