INFLUENCE OF PLANTING DATES AND ORGANIC SOIL AMENDMENTS ON THE INCIDENCE OF STEM BORER, SCROBIPALPA HELIOPA AND LEAF EATING CATERPILLAR, SPODOPTERA UTURA ON BURLEY TOBACCO

摘要

Studies on the effect of planting dates on incidence of Scrobipalpa heliopa and Spodoptera litura showed that among the five dates of planting, the stem borer infestation was significantly high in the month of July and gradually increased from 10 to 40 DAP. The higliest infestation was recorded in plantings done during second week of July. A highly significant and positive correlation was observed between the progressive growth of the crop and stem borer infestation at second week of July (r = 0.96)and first week of August (r = 0.93) planting dates. Negatively skewed distribution of stem borer infestation was observed under different dates of planting and thus control measures are to be initiated from 10 DAP. The caterpillar spodoptera litura was significantly low in second week of July followed by first week of August planting and reached a peak in plantings done during third week of September. A strong positive correlation existed between the planting dates and infestation at 80 DAP (r = 0.96).Regression analysis showed that there was 0.8 per cent increase in caterpillar infestation at every delay in planting of 15 days. Most of the planting dates exhibited positively skewed distribution of infestation indicating initiation of control measuresfrom 40 DAP for caterpillar. The crop planted during third week of August not only exhibited significantly lower stem borer and caterpillar infestation but also recorded maximum yields. Influence of organic soil amendments on these insect pests indicated that supplementing 25 per cent of recommended N in the form of either FYM or neem cake was effective in managing the pest infestation with better cured leaf yields as compared to cent per cent recommended dose in the form of in organic fertilizers.