Study on varietal preference and nutritional indices of tea looper Hyposidra talaca (Lepidoptera: Geometridae) on ten selected tea varieties

Abstract

To find out the varietal preference of H. talaca larvae, leaves of ten selected tea cultivars were provided separately to II, III, IV, and V instars. The food consumption by different larval instars was the maximum on TV20 followed by TV1 > K1/1 > TV22 > TV26 > TV16 > SNT8 > TS520 > HP12 > B157. The nutritional indices showed the highest ECD and ECI values on TV20 followed by other cultivars. However, AD values were inversely proportional to the ECI and ECD. Biochemical analysis of the host leaves indicated higher carbohydrate and lipid concentrations in TV20 which was positively correlated (r = 0.6351) with the mean food consumption, whereas, the lowest carbohydrate and lipid concentration was observed in TS520. The levels of secondary metabolites such as alkaloids (r = -0.6137) and flavonoids (r = -0.7403) showed a negative correlation with larval food consumption. Results of HPLC analysis showed the presence of different types of catechins like, EGC, Catechin, EC, EGCG, ECG, and caffeine in variable quantity in all cultivars that were positively correlated with larval feeding except the Gallic acid which showed a negative correlation (r = -0.5610). Based on the larval food consumption, the susceptible index of cultivars were categorized as ‘highly susceptible’ (TV20, TV1, K1/1, TV22, TV26, TV16, and SNT8), ‘susceptible’ (TS520 and HP12), and ‘moderately susceptible’ (B157). Based on cluster analysis A1 grouped (TS520 and HP12), A2 indicated B157 whereas sub-branches B1 grouped (TV22, TV16, TV26, and SNT8) and B2 grouped (TV1, TV20, and K1/1).