Influence of Abiotic and Biotic Factors on the Spatial Distribution of Dialeurodes citri (Ashmead)

The studies conducted during 2000 and 2001 revealed that Dialellrodes citri had two peaks of maximum infestation i.e. April-May and September-October when the mean temperature and relative humidity ranged hom 26–30°C and 65–70%, respectively. The population was maximum (48.7± 6.3 nymphs/25 leaves) at upper canopy (181–270 cm) as compared to middle (91–180 cm) part (39.1 ± 3.7) or lower (0–90 cm) part (16.2 ± 2.0). Temperature (r=0.84) and sunshine hrs/days (r=0.36) had the positive effects on build up of population while relative humidity, wind velocity, total rainfall and total number of rainy days had negative effect. The overall impact of different abiotic factors at lower (R² = 0.89), middle (R² = 0.90) and upper (R² = 0.91) parts was significant. Five coccinellids namely Coccinella septempunctatai, C. repanda. Cheilomenes (Menochillls) sexmaclliata and Brumoides suturalis were the main predators of nymphs of whitefly with their respective populations as 75. 6, 13 and 6%. Chrysopid was also found to predate on the nymphs of whitefly.