Distribution and Spreading Pattern of Sugarcane Woolly Aphid, Ceratovacuna lanigera Zehntner in Sugarcane Fields

Sugarcane woolly aphid (SWA), Ceratovacuna lanigera Zehntner (Hemiptera: Aphididae) has been recorded as serious pest in the sugarcane growing belts of Tamil Nadu. Distribution pattern and mode of spread of woolly aphid and its natural enemies showed that initial influx of SWA on sugarcane commenced on 105 days after planting. The predator, Dipha aphidivora appeared on 119 days after planting. Maximum temperature and sunshine hours were positively correlated with the spread of the aphid, while relative humidity (%) (evening) and rainfall showed negative correlation. Colonization of the aphid was intense between September'05 and January'06 except in October'05 in which, number of D. aphidivora was noticed thus proving the efficiency of the predator against aphid. The occurrence of another predator, M. igorotus followed the same trend at a lower level of population. The abundance of the predators was found to be independent of weather factors, thus can act against SWA efficiently at various environmental conditions. The spread of the aphid within the field was in a spiral manner. Initially, the aphid colonization was influenced more by certain abiotic factors and when colonies had established, the spread was influenced mostly by biotic forces, particularly D. aphidivora. SWA and its natural enemies preferred the top leaves of the canopy followed by middle and bottom leaves.