عنوان مقاله [English]
Curly top disease is one of the important diseases of sugar beet. Spatial pattern and population variation of leafhoppers Circulifer haematoceps, and C. tenellus, vectors of sugar beet curly top virus, were studied in Hamadan province, Iran for three years (2007- 2009). Sampling was carried out at the early stage of the plant growth, in accordance with planting date for 9 weeks, in 7- 10 day intervals. For this purpose, four fields of five hectares each with a distance of approximately one kilometer from each other were selected in Asadabad region, Hamedan province. The insect sweep net was considered as sampling unit. By using the data obtained, the RV (a measure of sampling accuracy) factor for the three years was 12.2, 6.52, and 16.65%, respectively. Because of finding C. haematoceps as a vector of the disease in this region, variance to mean ratio () was used for determination of the spatial pattern of C. haematoceps population. The numerical value of Z for the whole year and total of three years was more than 1.96 which indicates the cumulative spatial distribution of the vector. The proportion of C. haematoceps population to total population of other leafhopper species in 2007, 2008, and 2009 was 5.68, 1.97 and 2.43%, respectively. Average of infected sugar beet plants to curly top disease in 2007, 2008, and 2009 was 5.2, 8.6, and 5%, respectively. In 2007, the number and proportion of leafhopper vector population was higher than total population of other species but owing to late planting, infection percentage was low, while in 2008, due to early planting and slow growth of the plants, vectors had more time for distribution. Despite the low number and proportion of leafhopper vector population to total population of other species in 2008, the average of plants infection (8.6%) was higher than two other years. Also, a linear positive and significant relationship was found between leafhopper vector population frequency and the frequency of plants infection throughout the season. The coefficient of determination (R2) for three years were 96, 90 and 94%, respectively, indicating the existence of a strong relation between the curly top occurrence and the vector population in the field.