Virulence Of LdNPV Mixture Agent And Effects On Activities Of Glutahione S-transferases Of Gypsy Moth Larvae

The gypsy moth larvae?Lymantria dispar L.?is one of the most destructive defoliator of wide species of trees,shrubs and plants,especially of broad-leaf and conifer trees.The Lymantria dispar Nuclear Polyhedrosis Virus?LdNPV?is a pathogenic microorganism that has been used as a pesticide against gypsy moths.Our research has proved that selected suitable fluorescent whitening agents and other synergistic substances could improve the pathogenicity and lethality of LdNPV to the larvae of the gypsy moth and achieved the purpose of using virus to control the insect pests.In our experiment,the effect of different concentrations of fluorescence whitening agent and zinc chloride on nucleotide polyhedral virus was compared by orthogonal experimental method,and the optimal proportion was selected.The LC₅₀ and LT₅₀ of LdNPV agents the second instar larvel of gypsy moth were determined by bioassay,and the sublethal effect of complex mixture on gypsy moth was analyzed.In order to study the principle of this synergistic effect,after the fourth instar larvae were fed with seven kinds of different treated diets including fluorescence whitening,and zinc chloride?ZnCl₂?,activites of glutathione s-transferase in hemoLymph and midguts of larvae were measured.The results were as follows:1.By using 1%concentration of fluorescent whitening agent?VBL?and 0.1%zinc chloride?ZnCl₂?,and exposed 6 hours under ultraviolet light,the mortality of gypsy moth larva caused by the LdNPV mixtured agent was three times higher than that of normal LdNPV,and the mortality rate was 67.7%.It was indicated that the synergistic substances can significantly improve the lethal effect of LdNPV on the larvae of gypsy moth.2.The lethal effect of the LdNPV mixtured agent?1%of the fluorescence whitening agent VBL,the LdNPV,and 0.1%chloride?ZnCl₂??was positively correlated with concentration of the virus.When the virus concentration was increased,the lethal effect was also increased.In addition,the median lethal concentration(LC₅₀)of the LdNPV mixtured agent to the 2^nd instar larvae was 106.4 OBs/?l,and LC₉₀ was 6457.4 OBs/?l.LT₅₀0 of the larvae was 13.12 days when the dose of the virus used was 39 OBs/?l,and it was reduced to 9.37 days when the virus concentration was 3900 OBs/?l.3.LdNPV mixtured agent?1%of the fluorescence whitening agent VBL,the LdNPV,and0.1%chloride?ZnCl₂??a sublethal effect on the larvae of the gypsy moth.After feeding.Male larvae fed on LdNPV mixtured agen diet had the duration 2 to 5 days shorter than that of the control.The numbers of pupae were reduced when virus concentration was increased,and significant reduction in the weight and the egg number were observed as well.4.The activities of GST both in the hemoLymph and midgut of the 4^th instar larval were highest after 72 hours of feeding with LdNPV mixtured agent?1%of the fluorescence whitening agent VBL,the LdNPV,and 0.1%chloride?ZnCl₂??to the 4^th instar larvae.In the hemoLymph,GST activity showed an increase after 72 hrs.of feeding,and it was 72times higher than that of after 24 hrs.,which was 3.7-fold.The increases in the activity of GSP in the larval midgut were observed after 48 hrs.and 72 hrs.,which were 2.4 and4.6-fold higher than that of after 24 hrs.of feeding.