Determination of Additional Parameters for Screening of Different Tea Cultivars against Shot Hole Borer: Comparative Assessment on Relationship of Plant Growth Parameters with Galleries in the Stem

Abstract

Shot whole borer (Xyleborusfornicatus Eichh.) (SHB) is considered as the most serious and economically important pest in tea plantations in Sri Lanka. Present study was done to determine the parameters for screening of different tea cultivars against SHB. Prune time assessments on plant growth parameters of plant breeding trials were used to correlate data on galleries per 30cm in the laboratory bioassay to determine their relationship on SHB infestation in tea. A set of new tea cultivars with known tolerant and susceptible cultivars were used in the study. The regression analysis indicated that the intermodal length, mean number of prune cuts and mean prune weight had a significant positive relationship (P<0.05) with SHB infestation and those could be considered as valid parameters for cultivar screening against SHB in tea. Formulated multiple regression model [ 30cm units= (−8.27)+(0.1183 1)+(1.987 2), where; X1-mean number of prune cuts, X2-internodal length], was significant (P=0.007) and it explained 56.05% variation of galleries per 30cm (R2=56.05%). Mean number of galleries per 10cm stem had a significant (P<0.05) positive relationship (0.65) and the model explained 41.62% variation of galleries per foot (R2=41.62%).