Development of Bacterial Blight on Cotton in Relallon to Genotypes, Their Age and Weather Under Rainfed Conditions

Development of bacterial blight caused by Xanthomonas campestris pv. malvacea-rum was studied on normal, late and and very late sown L 147, SRT 1, Godavari and H4 cottons during the years 1980, 1981 and 1982. Higher disease intensity was recorded on very late sown crop as compared to late and normal sown crops in both varieties and hybrids. The normal sown crop facilitated inoculum build up and its dissemination to later sown crops. Hence, the disease appeared at early stage and developed fast on these crops. During disease development period, the average maximum temperature ranged between 29.3 to 34.2°C and average Telative humidity remained above 75% which appear to be congenial for initiation of infection, dissemi-nation of inoculum and development of the disease. All the four genotypes showed variation in disease intensity viz. 47.8 per cent in L 147 followed by 41.4, 38.6 and 34.5 per cent in SRT I, Godavari and H4, respectively. At later stage, disease did not progress further even though the maximum temperature regime was favourable for disease development. This may be due to inadequate relative humidity (51.9 to 72.4 per cent).