غلبه زنبور پارازیتویید Ooencyrtus telenomicida بر Ooencyrtus fecundus در شرایط ازدحام

Two egg parasitoids Ooencyrtus telenomicida and Ooencyrtus fecundus (Hym., Encyrtidae) are co-existing egg parasitoids of sunn-pest, Eurygaster integriceps (Hem., Scutelleridae) in cereal fields of Iran. Negative interactions such as inter-specific competition and multiparasitism between parasitoids may reduce their impact on host. Hence, studying of such interactions is worthwhile, both from theoretical and applied points of view. In this study, multiparasitism of the above species was investigated in different parasitoid per host rates and densities. Densities of 1:1:1, 2:2:2, 5:5:5, 1:2:2, 5: 10:10, 2:1:1 (Host: fecundus, telenomicida respectively), were included in experiments. The host eggs were simultaneously exposed to both species, wasps were removed 24 h later and then host eggs were kept in growth chamber (26±1 °C, 55±5 RH and 16L: 8D photoperiod) to determine their fate. Number of wasps were counted separately for female and male for each one at emergence. The fecundus was a male-less parthenogenetic population, while telenomicida showed 68.5% female progeny as average of all treatments with non-significant difference among them (χ2=10.31, df=9, P=0.326). Moreover, it was known that 94% of progeny in 5:10:10 treatment was telenomicida, while in other treatments it was 68-77% (average 74.2%). Chi square test revealed that difference among treatments was significant (χ2=175.5, df=11, P<0.0001), that excluding of density of 5:10:10 caused to become non-significant (χ2=10.96, df=9, P=0.278). Thus, telenomicida was the dominant species with a 3:1 ratio in multiparasitism condition that crowding caused this ratio increased to 15:1. An average of 1.7 progeny from the two species was emerged from a single host egg, where 1.26 of them was telenomicida and remaining 0.44 was fecundus. In 5:10:10 treatment it was reached to 2.05 with 1.92 telenomicida and 0.13 fecundus per host.