Population dynamics of aphid, Aphis gossypii Glover infesting isabgul under north Gujarat Agro-climatic conditions

A field experiment was conducted on the population dynamics of Aphis gossypii Glover during rabi 2017-18 at Chimanbhai Patel College of Agriculture, Sardarkrushinagar. The results showed that the aphid infestation was started from 1st week of January (1st Standard Meteorological Week) and gradually increased up to 4th week of February (8th Standard Meteorological Week) with a peak population of 2.40 aphid index. During the peak period, the minimum and maximum temperatures and morning and evening Relative Humidity (R.H.) were recorded 33.6 oC and 13.8 oC and 65.9 and 37.0 per cent, respectively. Among the natural enemies, the lady bird beetle larva was found active between 4th week of January and 3rd week of March. Lady bird beetle adult found active between 4th week of January and 4th week of March, whereas, larval population of syrphid fly was recorded during 1st week of January to 2nd week of March, 2018. The larval population of lady bird beetle and syrphid fly had highly significant positive correlation with aphid, whereas, ladybird beetle adult had significant positive correlation.