Occurrence and biocontrol potential of parasitoids on lychee cecid pest, Litchiomyia chinensis (Diptera: Cecidomyiidae)

Lychee is an economically important fruit tree in sub-tropical area. The lychee pest, Litchiomyia chinensis Yang and Luo, induces blister-galls on the leaves of lychee crop and causes yield losses. Although chemical control may effectively suppress the pest population, insecticide resistance and environmental impact should be considered. It is preferable to develop more eco-friendly tactics using Integrated Pest Management (IPM) on lychee gall midges. The distribution and occurrence of parasitic wasps on L. chinensis in Taiwan were investigated to understand their biocontrol potential. As a result, 11 parasitoids were found, and five species of them were confirmed as parasitic natural enemy of the pest cecid: Aprostocetus sp., Bracon sp., Derostenus sp., and two known Quadrastichus spp. Host and biology of the remaining six parasitoids (Aphanogmus sp., Cirrospilus sp., two Eupelmus spp., Gonatocerus sp. and Quadrastichus sp.) are uncertain, although they were also found inside gall. Besides, Q. johnlasallei is considered as the best biocontrol agent as it displays the highest parasitism in all five sampling localities and commonly found in the other five randomly collected localities of Taiwan. Noncorrelation between parasitism of Q. johnlasallei and two abiotic factors (temperature and rainfall) suggested its high adaptability in various environment. Fundamental biological and distribution information of five parasitic natural enemies of L. chinensis reported herein will be helpful for further developing its biocontrol programme.