The Effect Of Host Plants And Virus Geographical Strains On The Virulence Of LdNPV

Gypsy Moth, Lymantria dispar L., is one of the most important Lepidopteron defoliafor pest over the world. Lymantria dispar L. Nucleopolyhedrovirus (LdNPV) is one of the important factors to gypsy moth population dynamic. It is also an extensive used agent to control gypsy moth. But LdNPV has different geographic strains in nature. Each strain has different virulence to gypsy moth. It is very important to compare the virulence of different geographic strains of LdNPV and select the high virulence strain for use.The toxicity of three geographic strains of LdNPV to the 2nd instar larva of gypsy moth fed on two host plants, Larix principis-rupprechtii Mayr. and Aarmeniaca sibirica Linn. was determined in laboratory. LdNPV-D, collected from Northern American, LdNPV-H, collected from Hei Long Jiang Province of China, LdNPV-J, collected from Japan. The results showed that LD50 of LdNPV-D, LdNPV-H and LdNPV-J to the 2nd instar larva of gypsy moth fed on L. principis-rupprechtii Mayr. were 24 OBs/larva, 30 OBs/larva and 4472 OBs/larva, respectively. LT50 of LdNPV-D, LdNPV-H and LdNPV-J were 9.6d, 20.6d and 20.2d, respectively. LD50 of LdNPV-D, LdNPV-H and LdNPV-J to the 2nd instar larva of gypsy moth fed on A. sibirica Linn. were 9 OBs/larva, 40 OBs/larva and 974 OBs/larva, respectively. LT50 of LdNPV-D, LdNPV-H and LdNPV-J were 12.6d, 13.4d and 16.1d, respectively. LdNPV-D strain had more virulent lethal effect on gypsy moth than the others what ever they fed. LdNPV-J was the weakest strain of the three based on the virulence.The sublethal effects of three geographic strains of LdNPV to the 2nd instar larva of gypsy moth fed on the two host plants were determined in laboratory, too.The results showed that three geographic strains of LdNPV have effects on the developmental period, pupal weight and fecundity of gypsy moth. But the effects had no relation with concentration and strains of virus.The lethal and sublethal effects of LdNPV on gypsy moth fetched on two host plants were significantly different, the larva of gypsy moth fed on A. sibirica Linn. were more easily infected with LdNPV than that fed on L. principis-rupprechtii Mayr..