The present study deals with the impact of different spacing viz., 12.5,18.5, 23.5, 30 and 38.5 cm and abiotic factors (temperature, relative humidity and precipitation) on the population dynamics of sucking insect pests of cotton viz., Bemisia tabaci, Amrasca devastans and Thrips tabaci under unsprayed conditions. The period of abundance of jassid (Amrasca devastans) and thrips showed 1st (1.75, 11.43), 2nd (1.85, 10.44) and 3rd peak (1.66, 12.83) during 3rd, 2nd and 2nd week of July, August and September respectively. Where as peek population of whitefly was observed during 4th weak of August and 1st weak of September. The population of jassid, whitefly and thrips was significantly effected by plant spacing and decreased with the increase in plant spacing. The minimum population of jassid (0.96), thrips (8.45) and whitefly (2.82) was observed in plots laid out at 38cm plant spacing. Simple correlation analysis revealed that the rainfall and temperature showed significant and positive effect on jassid population where as relative humidity showed non-significant effect. Similarly effect of temperature was also significant and positive on the thrips and whitefly population. Relative humidity and rainfall did not show significant effect on thrips population where as significant and positive correlation was found to exist between relative humanity and whitefly population. Rainfall did not show significant correlation with Whitfly population. However R2 value computed through Multivariate Regression Analysis showed that temperature humidity and rainfall collectively showed 53, 36.8 and 66.4% influence on population fluctuation of jassid, thrips and whitefly respectively.
Muhammad Jalal Arif, Muhammad Dildar Gogi , Mansoor Mirza , Khuram Zia and Faisal Hafeez , 2006. Impact of Plant Spacing and Abiotic Factors on Population Dynamics of Sucking Insect Pests of Cotton. Pakistan Journal of Biological Sciences, 9: 1364-1369.