A Method for Mass-rearing Aphidius gifuensis(Hymenoptera: Aphidiidae)

[Objective] This study presents a method for mass rearing of Aphidius gifuensis, a dominant endoparasitoid of Myzus persicae on tobacco in Southwest China. [Method] The tobacco cultivar Honghuadajinyuan(Nicotiana tabacum) was used as the host plant and M. persicae was the host insect. In a greenhouse, tobacco seedlings were reared in plastic trays. The seedlings at three-true-leaf stage were inoculated with two to three aphids per plant using aphid source with a parasitism rate of 47% ±3.9%. [Result] By this inoculation method, the aphids and parasites were simultaneously inoculated on host plants. After approximately 25 d of rearing, we were able to produce 82.5±5.17 aphid mummies per tobacco seedling. A total of 445 500 aphid mummies were produced in one greenhouse(36 rearing trays per greenhouse) during an approximately 50-day rearing period. The emergence rate was 93.4% ±2.76%, and 54% of the mummies were females. [Conclusion] The demonstrated technological feasibility of using tobacco seedlings for the mass rearing of A. gifuensis increases the potential for the biological control of M. persicae.

Prevention and Control Effects of Aphidius gifuensis against Myzus persicae in Shuicheng

The prevention and control effects of Aphidius gifuensis against Myzus persicae in four major tobacco planting villages and towns in Shuicheng County were investigated from 2015 to 2016. The results showed that the parasitic rate of M. persicae before A. gifuensis release was 0. 85% in field,and that at 20 d after A. gifuensis release was 59. 49%. The incidence rate of aphid-transmitted virus disease was controlled at 0. 62%. The release of A. gifuensis increased its natural population quantity in field,and had obvious direct control effects against M. persicae. Meantime,it indirectly controlled the occurrence of aphid-transmitted virus disease to some extent.

Olfactory responses of Aphidius gifuensis to odors of host plants and aphid-plant complexes

The olfactory responses ofAphidius gifuensis to odors from two host plants （Nicotiana tabacum and Brassica napus ssp.） and their complexes with different infestation levels of two host aphids （Myzuspersicae and Lipaphis erysimi） were respectively examined in an olfactometer. The results showed that female A. gifuensis did not respond to odors of undamaged or mechanically damaged host plants, but significantly responded to odors of aphid/plant complexes. Moreover, A. gifuensis responded significantly to odors of both M. persicae and L. erysimi/plant complexes when host plants were infested by high levels of aphids, suggesting that quantity of aphid-induced volatiles could be important for attracting A. gifuensis. When tested between aphid/plant complexes, .4. gifuensis did not show its preference for either complex. The efficiency of.4. gifuensis against aphids in open fields potentially could be improved by using its olfactory response to aphid/plant complexes.

Two farnesyl pyrophosphate synthases,GhFPS1–2,in Gossypium hirsutum are involved in the biosynthesis of farnesol to attract parasitoid wasps

Sesquiterpenoids play an import role in the direct or indirect defense of plants.Farnesyl pyrophosphate synthases(FPSs)catalyze the biosynthesis of farnesyl pyrophosphate,which is a key precursor of farnesol and(E)-β-farnesene.In the current study,two FPS genes in Gossypium hirsutum,GhFPS1 and GhFPS2,were heterologously cloned and functionally characterized in a greenhouse setting.The open reading frames for full-length GhFPS1 and GhFPS2 were each 1029 nucleotides,and encoded two proteins of 342 amino acids with molecular weights of 39.4 kDa.The deduced amino acid sequences of GhFPS1–2 showed high identity to FPSs of other plants.Quantitative real-time PCR analysis revealed that GhFPS1 and GhFPS2 were highly expressed in G.hirsutum leaves,and were upregulated in methyl jasmonate(MeJA)-,methyl salicylate(MeSA)-and aphid infestation-treated cotton plants.The recombinant proteins of either GhFPS1 or GhFPS2 plus calf intestinal alkaline phosphatase could convert geranyl diphosphate(GPP)or isopentenyl diphosphate(IPP)to one major product,farnesol.Moreover,in electrophysiological response and Y-tube olfactometer assays,farnesol showed obvious attractiveness to female Aphidius gifuensis,which is an important parasitic wasp of aphids.Our findings suggest that two GhFPSs are involved in farnesol biosynthesis and they play a crucial role in indirect defense of cotton against aphid infestation.

Effects of mummy consumption on fitness and oviposition site selection on Harmonia axyridis

Intraguild predation(IGP)has been commonly reported between predators and parasitoids used as biological control agents as predators consuming parasitoids within their hosts.However,the effect of parasitoid-mummy consumption on the fitness of the predator and subsequent oviposition site selection have not been well studied.In our study,we conducted two laboratory experiments to examine the influence of Aphidius gifuen-sis Ashmead(Hymenoptera:Braconidae)mummies as prey on fitness and subsequently oviposition site selection of Harmonia axyridis(Pallas)(Coleoptera:Coccnellidae).Re-sults indicate that when H.aryridis was reared on A.gifiuensis mummies only,its larval development was prolonged,and body weight of the 4th instar larvae and newly emerged adults,and fecundity decreased.Moreover,H.axyridis did not exhibit oviposition pref-erence on plants infested with unparasitized aphids or aphids parasitized for shorter than 9 days.However,compared with plants with mummies(parasitized≥9 days),H.axryridis laid more eggs on plants with unparasitized aphids.In contrast,H.axryridis previously fed with A.gifuensis mummies did not show a significant oviposition preference between plants with unparasitized aphids and those with mummies(parasitized≥9 days).Overall,our results suggest that mummy consumption reduced the fitness of H.axyridis.Although H.axyridis avoided laying eggs on plants with A.gifuensis mummies,prior feeding ex-perience on A.gifuensis mummies could alter the oviposition site preference.Thus,in biological control practice,prior feeding experience of H.axyridis should be carflly considered for reduction of IGP and increase of fitness of H.axyridis on A.gifuensis.