The impact of host storage at low temperature on laboratory performance of Trichogramma brassicae
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
Eggs of hosts may be kept in a refrigerator for up to 30 days without losing their viability as hosts for Trichogrammatidae. However, parasitoids reared on refrigerated eggs may have reduced performance because long exposure to low temperatures reduces host quality. The objective of this study was to evaluate the suitability of Anagasta kuehniella Zeller and Phthorimaea operculella Zeller eggs stored at 4°C for different time periods as a host for Trichogramma brassicae Bezdenko. Hosts eggs subject to 6 storage periods (0, 1, 4, 7, 15 and 30 days in a refrigerator at 4°C and the control no storage) were used. Then, eggs were placed inside a microtube with a single 1-day old parasitoid female at 26±1°C, RH: 65±10% and 16:8h L:D photoperiod separately. After this period, the cards with each hosts eggs were transferred to glass tubes until emergence of T. brassicae adults at the mentioned standard condition. 10 replications were considered for each host. The parasitism rate, adult emergency rate, longevity and sex ratio were analyzed with factorial design using SAS and means were separated at the 5% significance level by using Duncan test. The highest parasitism mean was observed in control treatment of P. operculella (82.76%) followed in control treatment of A. kuehniella (73.33%). The mean of this parameter in 1, 4, 7, 15 and 30 days’ storage of P. operculella eggs were 72.9%, 52.33%, 59%, 55% and 29.67% and for A. kuehniella were 62.67%, 51.33%, 44%, 28.33% and 15.33% respectively that have significant differences between control and 30 days in both hosts. The least adult emergency percentage (31.89%), sex ratio (23.53% female), longevity (4.48 d) were in 30 days’ storage of P. operculella eggs and the least of fecundity (28.7 eggs per female life span) was in 15 days’ storage of A. kuehniella eggs. The mean of adult emergency percentage in 1, 4, 7 and 15 days’ storage of P. operculella eggs were 75.79%, 67.81%, 74.01 and 70.32% and for A. kuehniella were 77.5%, 80.04%, 62.15% and 64.4% and for 30 days’ storage was 48.02% respectively. The mean of fecundity in 1, 4, 7, 15 and 30 days’ storage of P. operculella eggs were 60.24, 65.48, 54.1, 51 and 52.84 eggs per female life span respectively. Due to low adult emergence, parasitism rate and sex ratio after 30 days, suggest that, the hosts has not been storage at low temperature more than 15 days.
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