Effects of planting date and cultivars of sugar beet on curly top virus infection, and population of leafhopper vectors in Isfahan province

In order to study the effects of planting date and sugar beet cultivars on infection to curly top virus, vector population, damping off, root rot, and sugar yield, an experiment was conducted in Mobarakeh region during 1999-2000 in a split plot design. The main factor was three planting dates and sub factor was six sugar beet cultivars: IC1 as a susceptible cultivar to beet curly top, T41R, 7233, H5505, PP8 and Attila with 4 replications. The results indicated that delaying in planting date until June, caused decrease of leafhopper population density. The populations of vectors (Circulifer tenellus and C. opacippennis) were the same in all sugar beet cultivars but their population in first planting were higher than the other planting dates and showed significant difference with them. The most infection to BCTV was observed in IC1 in first planting date, and showed significant difference with T41R and Attila at p<0.01 and p<0.05 respectively. In second and third planting dates infection to curly top decreased and there were not significant difference among cultivars. Infection of damping off and root rots decreased severely in 2nd and 3rd planting dates, Cultivars 7233 and Attila showed the highest infection to damping off and root rots in first planting date respectively. The least infection to damping off and root rots were observed in T41R. Delaying in planting dates until early July caused decrease of root and sugar yields, and significant differences were observed between third and other planting dates. T41R with 36.95 T/h had the highest root yield among cultivars and showed significant difference with Attila and 7233 at P<0.01 and P<0.05 respectively.