Influence of Weather Factors on the Incidence of Sissoo Defoliator, Plecoptera reflexa Guenee on Dalbergia sissoo Seedlings

The activity of P. reflexa initiated in 25th SMW with 2.62 per cent incidence and 1.74 mean larval population in 1999-2000. It reached to its peak in the SMW 33rd with the incidence and mean larval population being, respectively, 27.78 per cent and 17.18. It remained active till 43rd SMW. During 2000-01, activity of this pest initiated in 25th SMW with 1.68 per cent incidence and 0.99 mean larval population. It reached to its peak in the SMW 33rd with the incidence being 32.85 per cent with 26.21 mean larvae per quadrate. It remained active till 43rd SMW. The correlation coefficient of the incidence and population vs maximum temperature of the corresponding period showed significant negative correlation. During both the years mean value of the correlation coefficient of maximum temperature, respectively for incidence and population was calculated to be -0.5944 and -0.6113. The data indicated that the correlation of incidence and population with that of relative humidity was also significantly positive.