Development of leaf curl levels on four cassava varieties infested by pink mealybug, Phenacoccus manihoti Matile-Ferre

Abstract

The pink mealybug, Phenacoccus manihoti is one of the most serious pest of cassava. When this insect feeds on cassava, it causes leaf curl symptom which categorize into 5 level (0-4). The infestation level and amount of the mealybug population differ among cassava varieties. The objective of this study was to compare the development of leaf curl level (LCL) and the number of pink mealybug at each level in 4 cassava varieties : Rayong 72, Rayong 9, Huaybong 60, and Kasetsart 50. The experiments were conducted under net house condition during November 2016 - February 2017. One adult female of pink mealybug was transferred to the 2 months old cassava shoot. There were 5 replications per varieties with Completely Randomized Design (CRD). The developmental period of leaf curl level and the number of pink mealybug were observed daily.The fastest development of the LCL1-LCL4 were found in Rayong 72 during day 7 - day 51 and the slowest was Kasetsart 50, day 13.4 – day 68. The longest appearance period of all leaf curl level was found in Kasetsart 50 and Rayong 9 with 12.4 to 33 days and 13.2 to 31.60 days, respectively. The highest population of the pink mealybug was presented in LCL2 with two time from LCL1 in the three variation excepted Kasetsart 50 of which Rayong 72 showed more population than others. There was no statistical different of mealybug population from LCL2 – LCL4 in Kasetsart 50 and Kasetsart50 showed the increasing number of the mealybug relation to the leaf curl level (1 – 4 ).