Abstract

R. K. Arora, R. K. Gupta* and K. Bali

Population dynamics of leaf curling aphid, Brachycaudus helichrysi (Kalt.) and natural enemies associated with the pest were studied. The initial occurence of the alate forms of B. helichyrsi on peach was noticed as the first alates (1.33/10 leaves) in the 3rd week of October, 2004. In the aphid colonies, alates appeared (2.33 alates/10 leaves) in the 3 rd week of February and their percent population increased gradually in proportions. However, the winged aphids totally disappeared from 2nd week of December to 2nd week of February. There was a decline in the aphid population from 3rd week of April (12.62%) and onwards both apterous and alate forms disappeared from the host plants. During 1 st week of February, the overwintering nymphs developed into apterous adults. There was a rapid increase in aphid population (170.67/10 leaves) and peak population (592.00/10 leaves) was recorded in 3rd week of March when the mean atmospheric temperature and relative humidity were 16.2°C and 74.44% respectively. A positive correlation was observed between the population build up of the pest and combined effect of atmospheric temperature and relative humidity (R1.23 = 0.7051). The independent effect of humidity (r13.2 = 0.7741) and atmospheric temperature (r12.3 = 0.5551) was also found positively correlated with population build up of the pest. Overwintering stage of the pest from December - January revealed that nymphs produced in the last week of November overwintered in the axils and bases of dormant buds of peach tree. The population of overwintering nymphs was more in January (3.0/10 buds) than in December (0.67/10 buds). Coccinella septempunctata L., Leis dimidiata F., Coelophora sauzeti Muls., Ischiodon scutellaris (F.), Paragus (Paragus) serratus (Fabr.) and Paragus (Pandasyophthalmus) tibialis (Fallen) were recorded as aphidophagous predators and Diaeretiella rapae M’Intosh and Aphidius sp. as parasitoids of the pest.