Varietal preference and abundance of Amrasca devastans (Dist.) on sunflower crop in relation to temperature

The seeds of eight sunflower varieties namely, HO-1, M-I, M1I, M-III, M-IV, Suncross-42, Record and SF-187 were sown in a four-replicated randomized complete block design. Each sub plot was measuring 3x5 m. Four rows were planted in each sub plot. The distance between rows was maintained 45 cm and plant-to-plant 15 cm. The population of Jassid was recorded by counting adults and nymphs as well at weekly intervals. For recording the population of the pests 15 leaves from each sub plot were examined. The results indicated that the population of Jassid fluctuated through out the season. Initially, very low population of Jassid was appeared on the plants of all varieties. Which were 1.85 plus minus 0.21, 4.42 plus minus 0.85, 5.30 plus minus 0.62, 2.19 plus minus 0.41, 5.60 plus minus 0.81, 5.25 plus minus 0.57, 4.33 plus minus 0.64 and 3.89 plus minus 0.49 per leaf on HO-1, M-I, M- II, M-III, M-IV, Suncross-42, Record and SF-187, respectively. This number of Jassid increased very proportionally to the growth of the plants. Two peaks in the population were recorded on all varieties. The first peak was recorded from 2nd to 3rd weeks of February and the second from last week of March to 1st week of April on all varieties except M-II. The peak in population on M-II was recorded in 2nd week of April. Before the 1st peak this variety had a consistent population for many weeks. However, at first peak the maximum population (8.93 plus minus 1.24) per leaf was recorded on M-II Followed by (7.82 plus minus 1.32) on M-IV, (7.69 plus minus 1.24) on Suncross-42, (7.63 plus minus 1.09) on M-I, (7.57 plus minus 1.41) on M-III, (6.39 plus minus 1.24) on SF-187, (6.18 plus minus 1.30) on Record and minimum population (4.85 plus minus 0.12) on HO-I. Similarly, at second peak maximum population (8.88 plus minus 1.51) was recorded again on Suncross-42 and the minimum population (7.25 plus minus 1.40) was recorded on Sf-187. The overall means showed the abundance of A. devastans on all eight varieties of sunflower. The mean populations 4.38 plus minus 0.60, 4.97 plus minus 0.85, 6.16 plus minus 0.92, 4.98 plus minus 0.82, 5.07 plus minus 0.89, 4.67 plus minus 0.96, 5.21 plus minus 0.85 and 4.70 plus minus 0.82 were recorded on HO-I, M-I, M-II, M-III, M-IV, Suncross-42, Record and SF-187, respectively. According the Jassid populations recorded on these varieties it is concluded that variety M-II was more preferable and HO-I was least preferable to the Jassid. Analysis of variance showed significant difference in population of Jassid between the varieties at one present level of probability. However, L.S.D. showed non-significant difference between the population appeared on Record and M-IV; M-III, M-I, Suncross-42 and SF-187 at P less than 0.05. The population of Jassid showed different correlation with temperature on different varieties. Jassid showed its negative correlation with temperature on all varieties except HO-1. It is concluded that A. devastans attacked all varieties of sunflower from germination unto maturity of crop. Population Jassid fluctuated through out the cropping season; therefore two peaks in the population were recorded. Sunflower variety M-II was the most preferable and HO-I was the least preferable variety to A. devasains as compared to other varieties tested. The population of Jassid was negatively correlated with temperature except M-II.