Division of Entomology and Hematology, Indian Institute of Horticultural Research, Hesseraghatta Lake, Bangalore-560 089, Karnataka, India.
The ash whitefly Siphoninus phyllireae Haliday has become a serious pest of pomegranate (Punica granatum L.) in peninsular India in recent years. Field studies were conducted for two years from April 1997 to March 1999 to obtain quantitative data on S phyllireae in relation to abiotic and biotic factors chiefly the aphelinid parasitoid Encarsia azimi Hayat. The population of the ash whitefly was found to be high (40.4 to 70.9/leaf) during February-May and very low (0.0 to 18.7/leaf) from June to December. The activity of the parasitoid started along with the appearance of the whitefly in January. The number of parasitoids emerged/leaf ranged from 37.3 in January to 73.8 in April. Although temperature, humidity, rainfall and the parasitoid (E. azimi) were correlated with the population of the ash whitefly, the regression coefficient of the parasitoid was alone found to be significant. The multiple regression equation fitted with the parasitoid and weather parameters to predict the whitefly population (Y) was Y = 51.43 -21.348 x1 + 7.540 x2 - 0.955 x3- 2.474 x4-0.981 x5+ 0.103 x6 with R2= 0.732, where x1, x2, x3 x4, x5 and x6 denotes the parasitoid (£. azimi), maximum temperature, minimum temperature, morning humidity, evening humidity and rainfall, respectively. Since E. azimi had highly significant relationship with the population of whitefly, the regression coefficient of the parasitoid alone was found to be significant, and as high as 94.7% of the whitefly nymphs were parasitised in June, the decline in the population of pomegranate ash whitefly from June onwards could be mainly attributed to the activity of E. azimi in the present study.
Encarsia azimi, ash whitefly, Siphoninus phyllireae, pomegranate, regulation, parasitoid
