جستجوی مقالات مرتبط با کلیدواژه "eurygaster integriceps" در نشریات گروه "گیاهپزشکی"

Abstract. Trissolcus grandis Thompson (Hymenoptera: Scelionidae), a native Sunn pest egg parasitoid in Iran, has the potential as a biological control agent for sunn pest, Eurygaster integriceps Puton (Het.: Scutelleridae). However, its ecological characteristics have remained unclear. Thus, this study aimed to develop a parasitism model of T. grandis with sunn pest egg as host. In order to obtain the data for the model, the longevity, survivorship and parasitism capacity of the adult female T. grandis were examined at nine constant temperatures (15, 17.5, 20, 25, 27.5, 30, 32.5, 35, and 37.5±0.5 °C), relative humidity 65 ± 5 % RH, and a photoperiod of 16:8 (L:D) h. Longevity (mean±SE) decreased as temperature increased and was the longest at 15°C (73.18±3.86 days) and the shortest at 35°C (18.98±0.48 days). A modified model of Sharp-DeMichele well described adult developmental rate (1/mean longevity) in the range of studied temperatures (r2 = 0.994) and was used to calculate the physiological age. The mean total host eggs parasitized/female (mean±SE) was greatest at 17.5°C (275.84 ± 3.21 host eggs) and lowest at 15°C (25.06 ± 3.221 host eggs). The temperature-dependent total parasitism, the age-specific cumulative parasitism rate, and the age-specific survival rate were best described by an extreme value function (r2 = 0.934), the two-parameter Weibull function (r2 = 0.967), and a sigmoid function (r2 = 0.979), respectively. I anticipate that the fitted models and parameters may be useful in developing a population model for T. grandis and lead to a better understanding of its parasitism strategy.

Ooencyrtus fecundus Ferriere and Voegele (Hymenoptera: Encyrtidae) is a gregarious egg parasitoid of sunn pest Eurygaster integriceps Puton. Superparasitism enables a female to produce multiple progeny per host and thus reduces the time spent searching for hosts, but results in progressively smaller progeny as more individuals compete for limited resources within hosts. In this study, we tested whether gregarious development would affect the functional response of O. fecundus reared under laboratory condition (26 ± 2 ºC, 50 ± 10% RH and 16: 8 L: D h). Various host densities (1, 2, 4, 8, 16 and 32 eggs) were offered to females that had developed either as single, or as twins, triplets or quadruplets within host eggs. To resolve the functional responses of these females, a total exposure time of five hours was chosen, based on direct observations of handling time and the maximum daily number of host attacks/female. Functional response of the parasitoid was type III in singleton and twin parents, and type II in triplet and quadruplet ones. However, host mortality rate was 100% in host densities ≤ 8, suggesting density independence at lower densities as expected from a type I functional response. In such circumstances, handling time is expected to be zero, but was observed to be 11.4 to 14.3 minutes in different treatments. These results suggest that when enough time was available to find and handle all hosts, a type II functional response resembles Type I one. Searching efficiency increased and handling time decreased with body size of the parasitoid of four categories.