Biology and prey stage preference of the coccinellid Hyperaspis polita by feeding on the spherical mealybug Nipaecoccus viridis
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
The predatory ladybird Hyperaspis polita Weise is one of the most important natural enemies of Nipaecoccus viridis (Newstead), an important citrus pest in southwestern Iran. Biology of H. polita were evaluated on N. viridis at two constant temperatures, 25 and 30 ± 1°C, 65 ± 5% RH, a photoperiod of 14L:10D and analyzed by TWOSEXMS–Chart program. Prey stage preference of all stages of H. polita were also investigated by their feeding on eggs, 1st, 2nd and 3rd instar nymphs as well as adult females of the mealybug N. viridis in choice and no-choice experiments. Results indicated that the mean duration of egg, 1st, 2nd, 3rd and 4th instar larvae, prepupa and pupa of H. polita at two studied temperatures were significantly different (P<0.05). These values at 25°C were 7.37, 3.40, 4.22, 4.34, 7.53, 3.34, 10.64 and at 30°C were 5.41, 2.61, 2.64, 2.83, 2.83, 2.62 and 8.96 days, respectively. In both temperatures tested, no significant differences between total preadult duration of males and females ladybirds were detected (P<0.05). Preadult mortality of H. polita was %57 and %44 at 25 and 30°C, respectively, and no significant difference was observed. Mean longevity of adult male and female ladybirds were 86.23 and 110.06 at 25°C and 98.00 and 85.03 at 30°C, respectively, with significant difference between sexes. Mean fecundity of females (180.83 at 25°C and 368.65 at 30°C) and their longevity were significantly different at two temperatures. Prey preference experiment in no-choice test revealed that all stages of ladybird fed on all stages of mealybug. But in choice test, in which all stages of prey were simultaneously available to predator, adult male and female ladybirds fed more on eggs than other prey stages, except 2nd nymphal stage which showed no significant difference with egg stage (P<0.05). First, third and fourth larval stages of ladybirds also fed significantly more eggs than any other stages of N. viridis. Second larval stage of ladybird showed least preference to adult female N. viridis, however no significant preference was found among other mealybug stages. Other ladybird stages also showed least preference to adult female N. viridis. According to these results, H. polita was able to complete well its life cycle by feeding on all developmental stages of N. viridis and mealybug eggs were most preferred stage.
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