Patch time allocated to patches of different qualities in Ooencyrtus telenomicida egg parasitoid of sunn pest, Eurygaster integriceps
Paper ID : 1888-24IPPC (R2)
Authors
1Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz
2Full Professor
Abstract
The egg parasitoids, Ooencyrtus spp. (Hym., Encyrtidae) play role as primary parasitoid of sunn-pest (SP), Eurygaster integriceps Puton (Hem. Scutelleridae) and hyperparasitoid of Trissolcus spp. (Hym., Scelionidae). Considering their late-season activity, they often encounter eggs parasitized by the other species or developed host eggs. Their preference and choice in this situation was unknown, therefor, in this study, seven kinds of hosts of different quality in regards of previous parasitism or level of host embryogenesis was investigated in a Plexiglas container (30 cm diameter, 10 cm height) in five repetitions. Ten female O. telenomicida were introduced into the above mentioned arena including two clutches of each host where separately put in seven petri dishes (6 cm diameter) with random arrangements. The available hosts were newly laid eggs, 2 and 4 d-old eggs, newly parasitized and 3, 7 or 10 d-old parasitized eggs of SP by T. grandis. The time spent by females in each patch was recorded by direct observations in 15 min intervals. At the end of the experiment, the wasps were removed and the parasitized eggs were maintained in laboratory condition to determine the fate of them. Overall, 60% of wasps' time spent out of the patches. From the remaining time, 4.25-22.3 insect-hours were spent at different patches, where 7 and 3 d-old parasitized eggs and 4 d-old eggs were the most occupied ones with above 20 insect-hours of residence, whereas 10 d-old parasitized eggs were the most avoided choice. A significant difference both in allocated time and number of emerged O. telenomicida was observed among patches (χ2=21.13, df=6, P=0.0017, for time and χ2=34.80, df=6, P<0.0001 for emergence). In both cases 10 d-old parasitized eggs caused χ2-values increased. Excluding the recent treatment from the analysis left no reason to reject the null hypothesis of equivalency of treatments with a 99% confidence (χ2=11.67, df=5, P=0.0697, for time and χ2=14.87, df=5, P<0.021 for emergence). In other words, difference among the other treatments was proportional to random deviations. In fact, this parasitoid does not deeply affect by host change, hence parasitism of old or parasitized eggs has been over the new ones.
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