The Effect Of Optical Brightener, Host Plants And Geographic Strains Of LdNPV On The Phenoloxidase And Midgut Esterase Activity Of Gypsy Moth Larvae

The 5th instar larvae of gypsy moth fed with three host plants, green poplar (P. cathayana Rehd.), larch (L. principis-rupprechtii Mayr.) and Siberia apricot (A. sibirica Linn.), were treated with optical brightener Tinopal LPW, 3 virus strains (LdNPV-D, LdNPV-H, LdNPV-J)and their mixture with Tinopal LPW repectively. Totally there were 6 treatments and 2 controls (distilled water and Tinopal LPW). The activity of Phenoloxidase (PO) in haemolymph and midgut esterase of larvae was measured at 12h, 24h, 48h, 72h and 96h after the treatment. The experiment was replicated three times.The results showed that the effects of host plants, virus strains and optical brightener on the PO activity of the 5th instar gypsy moth larvae was significant. The PO activity increased after the larva were infected by pure virus 12h post treatment, and then decreased from 24h comparing with both distilled water and Tinopal LPW controls. The 5th instar larvae treated with mixture of Tinopal LPW with D-strain, H-strain and J-strain separately, the Phenoloxidase activity of gypsy moth related to the host plants. Larvae fed on Siberia apricot,their PO activity were lower than that of larvae treated with pure virus strain or both controls. Larvae fed on populer and larch, their PO activity were low than that of larvae treated with pure D-strain, or H-strain, or controls. But there was no difference comparing with J-strain and its Tinopal LPW mixture. Tinopal LPW could low the PO activity comparing with distilled water.The midgut esterase activity of gypsy moth larvae fed with green poplar, larch and siberia apricot showed similar changes, and it reaches the maximum after 72h. The effect of host plants on the midgut esterase activity of gypsy moth larvae was significant. The midgut esterase activity of gypsy moth larvae fed on larch was higher than that fed on siberia apricot, and the midgut esterase activity of gypsy moth larvae fed on green poplar was the lowest. The midgut esterase activity of gypsy moth larvae fed with different host plants were higher than distilled water after 12h and 24h. The midgut esterase activity of gypsy moth larvae fed on green poplar and larch infected by pure virus were higher than distilled water after 48h, but those infected by the mixture were lower than distilled water. The midgut esterase activity of gypsy moth larvae fed on siberia apricot infected by all the treatments was lower than distilled water. The midgut esterase activity of gypsy moth larvae fed with different host plants infected by all the treatments were lower than distilled water after 72h, and decreased gradually with time. There are no differences between Tinopal LPW and distilled water. The inhibition of the mixture of Tinopal LPW and pure virus is above the pure virus.