Fitness traits of the tea defoliator, Hyposidra talaca (Walker 1860) (Lepidoptera: Geometridae) on natural and artificial diets in relation to gut enzymes and nutritional efficiencies

Abstract

Summary. The looper pest Hyposidra talaca (Walker 1860) is known to cause heavy damage to tea plantations in North-East India, including Darjeeling Terai-Dooars, by defoliating the bushes. Laboratory rearing of this looper species resulted in production of a healthy population under controlled conditions (aseptic) for three consecutive generations on a newly formulated artificial diet. The performance and fitness traits of the looper species were compared on natural (tea-leaf) and artificial diets along with the quantity of its hydrolytic (amylase, protease, lipase) and detoxifying enzymes [general esterase (GE), glutathione S-transferase (GST)] when reared on these two diets. Activity of protease on the artificial diet was significantly higher than that on the natural diet; however, lipase showed only marginally increased activity on the former diet. When detoxifying enzymes such as general esterase (GE) and glutathione S-transferase (GST) were observed, they were found to be significantly higher on the natural diet. Such variations in the hydrolytic enzymes and detoxifying enzymes indicated a better capacity of the looper to utilize the artificial diet than the tea-leaf diet. The finding was further corroborated by the higher efficiencies (ECI and ECD) and production index (PI) that were recorded on the artificial diet, compared to higher maintenance cost on the tea-leaf diet. The artificial diet also supported a high survival rate of H. talaca in all generations along with higher adult emergence and fecundity. The newly designed artificial diet is a viable alternative for mass rearing and efficient production of control populations of H. talaca under sterile conditions.