Pathogenic virus and insect tissues: an effective way of pest control

When different doses, i.e. 0.1, 0.25 0.5 and 0.75 ml of 2 X 10(9) polyhedra per ml of SINPV were used against fourth instar larvae of Spodoptera litura (Fab) and observations were taken after 24, 48 and 96 h, F-value in CRD ANOVA was highly significant for doses as well as time period. Per cent mortality increased from 5.43 to 78.91 as the dose was increased from 0.1 to 0.75 nil of 2 x 10(9) polyhedra per ml solution. Various viral pathological symptoms such as flaccid and swollen body, stumpy legs, shrinkage of body segments at midgut area and extremely moist droppings were observed. Histopathological studies of fourth instar treated with highest dose, i.e. 0.75 nil, revealed the effect of the virus on various midgut cells, fat bodies, connective tissues and also on the integument. These tissues either lost their identity or became highly disorganized. The virions were found scattered in different tissues and deposited heavily on the body wall, suggesting the spread of infection in almost all the tissues of the larvae.