SEASONAL INCIDENCE AND LIFE HISTORY OF TOXOPTERA AURANTII (BOY, DE FONS.) ATTACKING ORANGE, CITRUS RETICULATA BLANCO

Toxoptera aurantii (Boyer de Fonscolombe) is one of the most important aphid species infesting mandarin orange (Citrus reticulata Blanco) in Darjeeling. West Bengal. This aphid pest is widely distributed and is found on the plant throughout the year having one peak population during August and September and very low population of this pest was recorded during cooler months of the year. This pest is capable of completing about 26 generations in a year from January to December, 1994 under laboratory conditions. It passes through four nymphal instars to become adult. The various stages of the life cycle are prolonged during cooler period of the year. The nymphal duration varied from 7 to 28 days and the adult longevity of the apterous morph ranged from 8 to 34 days. The nymph laying capacity by an apterous viviparous female was found to vary from 10 to 46 days.