Biochemical characteristics of hyphantria cunea nuclear polyhedrosis virus

Abstract

The fall webworm, $\underline{Hyphantria}$ $\underline{cunea}$ Drury, an occasional pest on fruit and deciduous trees is one of the major forest pests in Korea. The fall webworm is susceptible to both a granulosis virus and a nuclear polyhedrosis virus. In view points of development for a viral insecticide of the fall webworm, the characteristics of H. cunea nuclear polyhedrosis virus should be available, that is meaningful criteria for identification and monitoring can be selected. Nevertheless, little is known about the molecular properties of this fall webworm pathogenic nuclear polyhedrosis virus. Using virus of $\underline{H.}$ $\underline{cunea}$ was isolated from in our laboratories, the biochemical characteristics were investigated. The early sign of nuclear polyhedrosis virus infection of fall webworm was behavioral changes. The infected larvae refused to eat and became sluggish. Later, infected larval integument changed color from yellow-green to brown and skin became fragile and flaccid. Larvae at the advanced stage of the disease tended to clime to the top of plant or the container. They formed a kind of inverted V shape. In general, the younger instar larvae were more susceptible than the older ones. A dosage of $10^6$ PIB/ml caused 83% mortality to second instar larvae and 67% mortality to third instar larvae. The $LT_{50}$ values of second and third instar insects for the dosage of $10^5$ PIB/ml were 6.85 and 15 days, respectively. Concerning species specificity, no pathogenic effect of this $\underline{H.}$ $\underline{cunea}$ nuclear polyhedrosis virus was observed to larvae of silkworm, Bombyx mori and pine caterpillar, $\underline{Dendrolimus}$ $\underline{spectabilis}$. The isolated nuclear polyhedrosis virus of fall webworm replicated successfully in an established cell line of Trichoplusiani (TN-368), and serially passaged in this cell cultures. Hypertrophy of the nucleus was observed in a few cells as early as 6 h postinfection. Within...