Population dynamics and influence of weather parameters on the incidence of sucking pests on Bt and Non-Bt cotton (Gossypium spp.)

Abstract

Studies on population dynamics and influence of weather parameters on the incidence of cotton sucking pests were carried out at Regional Agricultural Research Station, Lam, Guntur during kharif 2009 and 2010. The highest leafhopper population of 13.64 in RCH 2 BG II, 6.92 in Mallika BG II and 8.75 in L 604 was recorded in 42nd, 44th and 41st std. week, respectively, while
peak whitefly population was recorded during 52nd std. week (Dec. 24-31) in RCH 2 BG II (6.96 no./top 3 leaves/plant), while it was during 1st std. week (Jan. 1-7) both in Mallika BG II (11.66 no./top 3 leaves/plant) and L 604 (8.36 no./top 3 leaves/plant). Whereas peak incidence (no./top 3 leaves/plant) of aphids and thrips (14.86 and 7.48 in RCH 2 BG II, 29.14 and 15.40 in Mallika BG II and 23.10 and 14.80 in L 604 non-Bt) was recorded during 44th (Oct. 29 - Nov. 4) and 41st (Oct. 8-14) std. week, respectively. Maximum and minimum temperatures, evening relative humidity and rainfall have significant positive influence on aphids, leafhoppers and thrips population while both maximum and minimum temperatures have significant negative influence on whitefly population. Morning relative humidity had significant positive impact on whitefly and significant negative impact on leafhoppers and thrips population. The multiple linear regression analysis indicated that the total influence of all the weather variables accounted for 42.9, 57.2, 69.7 and 27.6 per cent variation in aphid, leafhoppers, thrips and whitefly populations, respectively which are significant (R2=0.429*, 0.572*, 0.697* and 0.276* in aphid, leafhoppers, thrips and whitefly populations, respectively).