Population ecology of carob moth and relative importance of bottom-up and top-down forces in a tritrophic system
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
Carob moth, Apomyelois ceratoniae Zeller (Lepidoptera, Pyralidae), is the most important pest of pomegranate in Iran. This insect causes a great quantitative and qualitative injury on pomegranate fruits. The current pest management strategies, however, have not achieved asufficient control for thispest. In addition, food safety and sustainable agriculture require more researches on ecological strategies of pest management and basic phenomena of insect population ecology. In the present study, the effects of bottom-up and top-down forces in regulation of carob moth populations were investigated. Factorial experiments were performed using two different factors, including a bottom-up force (at 2 levels: with and without the application of nutrients) and a top-down force (at 2 levels: with and without the release of Trichogramma brassicae). Treatments were replicated four time in a complete block design in a pomegranate orchard in Ruran village of Isfahan county (Isfahan, central Iran) during 2014 and 2015 growth seasons. The number and weight of intact and infested fruits, the number of A. ceratoniaelarvae in fruits and the nutrient elements in intact fruits were recorded at the end of growth season. The results showed that there was a significant difference between treatments for mean fruit infestation. The treatment "top-down plus bottom-up (TDBU)" showed the least infestation (12.5%), but the treatments "top-down (TD)" and "control (C)" indicated the greatest infestation (22.8% and 26.9%, respectively). In addition, the mean population abundance of A. ceratoniae larvae were significantly different between treatments. Such that, the lowest population abundance was observed on the treatment TDBU (5.1 larvae per tree), while the highest population abundances wereseen on the treatments "bottom-up (BU)" and C (11.0 and 16.4 larvae per tree, respectively). Furthermore, the mean population abundance in treatment TD (8.8 larvae per tree) was fewer than that in treatment C.There was no significant difference between treatments for the mean weight of intact fruits. The nutrient quantities in intact fruits varied significantly between treatments; the nutrient amounts in treatments TDBU and BU were greater than that in treatments TD and C. Here, top-down or bottom-up forces separately lowered pest population size or increased fruit quality, respectively. However, when these forces were combined there was a synergistic effect, resulting in decreasing fruit infestation, reducing pest population and increasing fruit quality. These findings indicated that sustainable management of carob moth populations can be achieved by combining bottom-up and top-down forces.
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