Effects Of Colony-dependent Diamondback Moth Plutella Xylostella On The Biology And Fitness Of Oomyzus Sokolowskii

The diamondback moth, Plutella xylostella (L.), is a notorious pest worldwide, and causestremendously economic losses on cruciferous vegetables annually. Chemical control has been theprincipal weapon used for management of P. xylostella, but the extensive use of insecticidescauses environmental pollution, human health problem and insecticide resistance. Therefore,exploring alternative management method for this pest is extremely urgent. Oomyzus.sokolowskii (Kurdjumov) is a gregarious larval endoparasitoid of P. xylostella, and is suitable forcontrolling P. xylostella in tropical lowland regions. In our experiment, we compared thebiological parameters of Chinese cabbage-, pakchoi-, cabbage-, cauliflower-, andbroccoli-dependent O. sokolowskii, and the fitness of O. sokolowskii parasitizing on the fiveplant-dependent fourth instar P. xylostella larvae. We concluded that cauliflower was the mostsuitable host plant for O. sokolowskii mass-rearing. The main findings are shown below:Longevity of the five host-plants dependent adult O. sokolowskii. The results showedthat the male longevity of Chinese cabbage-dependent O. sokolowskii was the longest (10.6d)among the five host-plants dependent O. sokolowskii. The longevity of the females without hostof broccoli-and Chinese cabbage-dependent O. sokolowskii was24.7d and22.3d, respectively,which was significantly longer than that of cabbage-and cauliflower-dependent O. sokolowskii,which was17.5d and15.0d, respectively. The longest and the shortest longevity of the femalewith host was from broccoli-and pakchoi-dependent O. sokolowskii, which was5.8d and4.6d,respectively. The longevity of the females without host was2-3times longer than that of femaleswith host.Biological parameters of the five host-plants dependent O. sokolowskii. Thecauliflower-dependent O. sokolowskii performed the best among the five host-plants dependentO. sokolowskii, with the greatest net reproductive rate (Ro=0.196), intrinsic rate of increase (rm=1.217), offspring emerged per host larva (9.0±0.6), percentage of parasitized host larvae withadults emerged (67.6±6.9%), adults produced per female (43.6±7.6), and the shortestdevelopmental time from egg to adult (15.8±0.3d). The numbers of host larvae parasitized per female and percentage of female offspring among the treatments were not significantly different.The fitness of the five host-plants dependent O. sokolowskii on Chinese cabbage-,pakchoi-, cabbage-, cauliflower-, and broccoli-dependent four instar P. xylostella larvae.The results showed that the parameters of the developmental time from egg to adult emergenceand percentage of female offspring were relatively stable and maintained at approximately15dand80%, respectively; the number of host larvae parasitized per female and the offspringemerged per host larva ranged from6to10and from5to9, respectively; Chinese cabbage-,pakchoi-, and cabbage-dependent O. sokolowskii had the highest number of adults produced perfemale when parasitizing cauliflower-dependent P. xylostella larvae, and cauliflower-dependentO. sokolowskii all had approximately40adults produced per female when parasitizing pakchoi-,cabbage-, cauliflower-, and broccoli-dependent P. xylostella larvae; Chinese cabbage-, pakchoi-,cabbage-, cauliflower-, and broccoli-dependent O. sokolowskii performed the best in percentageof parasitized host larvae with adults emerged when parasitizing on cauliflower-, cabbage-andcauliflower-, cauliflower-, pakchoi-and cauliflower-, and cabbage-dependent P. xylostella larvae,respectively.