Comparison on infestation levels of Pink mealybug, Phenacoccus manihoti (Homoptera: Pseudococcidae) on four cassava varieties

บทคัดย่อ

Four cassava varieties (Kasetsart 50, Huaybong 60, Rayong 9 and Rayong 72) were used in the experiment to compare the levels of infestation by pink mealybugs (Phenacoccus manihoti). The trial was conducted in a greenhouse at the National Biological Control Research Center (Altitude: 367m, 16º 42’ 97” N, 102º 51’ 109” E), Khon Kaen University, from September to October 2012. Five adult pink mealybugs were released on 2.5-month-old cassava. Five replications were done for each variety. The mealybug population and leaf curl symptoms were investigated every day. After 4.4±0.9 days, the Rayong 72 variety showed leaf curl level 1, followed by Rayong 9, Kasetsart 50 and Huaybong 60 at 6.2±0.8 days, 6.4±0.5 days and 6.8±0.8 days, respectively. Rayong 72 took the shortest period to the appearance of all leaf curl levels while Huaybong 60 took the longest. Obviously, Huaybong 60 was more tolerant to pink mealybug damage than Kasetsart 50, Rayong 9 and Rayong 72 varieties, respectively.