Relative infestation of Jassid, Amrasca devastans on cotton varieties vis-à-vis the crop age and weather factors

The study revealed that jassid population in 2000 was the highest on varieties Ganganagar Ageti, which was at par with Bikaneri Narma, RST 9 and H 777 followed by RS 875 and the others. The least population was recorded on G–27 and Papui, which were Gossypium arboreum varieties as against the others which were Gossypium hirsutum varieties. In the year 2001, jassid population was the highest on H 777 followed by RST 9, RS 875, Bikaneri Narma and the others. The least population was again found to be on G–27 and Papui. The jassid was active throughout the crop season with higher population in the initial period of the crop i.e. at 30^th day after sowing. Correlation studies showed that almost all the weather factors as well as crop age had effect on the jassid population in one or the other variety and the population of the jassid appeared to be determined by a complex of factors. Based on the present finding, it is suggested that for effective management of the jassid, suitable measures should be adopted by 30^th day of the crop sowing and more attention should be paid on susceptible varieties like H 777, RST 9, RS 875 and Bikaneri Narma.