Pathogenicity of Serratia marcescens to hazelnut weevil(Curculio dieckmanni)

The hazelnut weevil(Curculio dieckmanni Faust.)is a major pest of Asian hazel(Corylus heterophylla Fisch.)in China.Dead hazelnut weevil larvae were examined and the associated pathogenic bacterium was identifi ed as Serratia marcescens Bizio.This signifi cantly shortened the lifespan of hazelnut weevil.Larval weight was reduced as a function of S.marcescens concentration and exposure time.The structure of infected midgut cells was altered,with necrosis of the wall tissues and many cells becoming dislodged,creating cavities.The S.marcencens strain inhibited digestive enzyme activity and protective enzymes in the midgut of adult hazelnut weevil.Inhibition on S.marcencens strain increased with treatment time.S.marcescens directly destroyed the midgut cells and interfered with digestive and protective enzymes.This decreased the food intake and increased mortality of hazelnut weevil.S.marcescens appears to be an eff ective bacterium for the control of hazelnut weevil but requires further study,including biological formulation development and fi eld application.

Molecular characterization and functional analysis of USP-1 by RNA interference in the Asian gypsy moth Lymantria dispar

Ecdysteroids play an important role in regulating diverse physiological processes in arthropods,such as molting,metamorphosis,reproduction and diapause.Ecdysteroids mediate the response by binding to a heterodimeric complex of two nuclear receptors:the ecdysone receptor and the ultraspiracle(USP).To investigate the role of USP in development of the Asian gypsy moth(Lymantria dispar),a USP cDNA was obtained from the transcriptome of L.dispar and verified by PCR.In-depth profiling of transcript levels of L.dispar USP-1(LdUSP-1)at different developmental stages and over time in thirdinstar larvae and different tissues isolated during the thirdinstar stage of L.dispar was then carried out.Transcript levels of LdUSP-1 were relatively high before 72 h in the third-instar larvae after ecdysis and in the adult male.The function of LdUSP-1 in molting was analyzed by knockdown of LdUSP-1 in third instar larvae using RNA interference.Silencing of LdUSP-1 significantly downregulated the transcript level of E75,an ecdysone-inducible gene,and of Sad,a Halloween gene.In addition,the duration of the third-instar stage was slightly shortened and larval mortality increased after the LdUSP-1 knockdown.