EPIDEMIC DEVELOPMENT OF PUMPKIN MOSAIC AND ITS RELATIONSHIP WITH ABIOTIC FACTORS AND VECTORS

The prevalence of aphids in pumpkin field was noticed much earlier than the first incidence of mosaic disease (2nd week of March, 2016). The population of aphid/ trap found to be increased initially and reached in peak (average 55 aphids/trap) during 3rd week of February 2016. The incidence of mosaic disease was increased at a faster rate during the initial period and reached at maximum level of 19.20% during the period from 15th March to 21st March, 2016. A negative correlation was obtained in between aphid population/ trap and periodical increment in percentage disease incidence of common mosaic disease of pumpkin. During the period of 3rd week of February, when average aphid population was maximum (55/trap), the average maximum temperature was 28.36°C. Statistical analysis showed significant negative correlation between minimum temperature and aphid population. The population of aphids was declined in every week irrespective of fluctuation in maximum relative humidity. A range of maximum temperature 34.4 -39.4°C, minimum temperature 17.04 – 23.45° C, maximum relative humidity 78.57 – 87.42°C and wind speed from 2.53 -5.31 km/hour was found to be suitable for the epidemic development of the disease. Significant positive relationship (0.685*) was observed between average aphid population / trap and average rainfall recorded. High R2 value (+0.939) indicated about 93.9% contribution of all meteorological factors in population buildup of aphid in pumpkin field during the season 2015-2016.While, Value of multiple correlation coefficients (R2) +0.681 expressed the non-significant relationship among all meteorological factors and aphid population with periodical increment in disease %. However, the above factors contributed about 68.1 % in developing the common mosaic symptoms in pumpkin field.