Biological Control of Tea Flush Worm, Laspeyresia bipunctata Using An Entomopathogenic Nematode, Heterorhabditis indica

Laboratory assay was made to evaluate the efficacy of entomopathogenic nematodes viz., Steinernema carpocapsae, S. glaseri, S. tami, S. abbasi, S. siamkayai and Heterorhahditis indica against tea flush worm, Laspeyresia hipunctata. Probit analysis indicated that H. indica (LC₅₀ value of 4.35 IJs and LT₅₀ value of 8.42 h) was more virulent and faster in killing L. bipunctata larvae followed by S. glaseri in terms of LC₅₀ value (6.29) and S. carpocapsae in terms of LT₅₀ value (11.38). The results of field experiments revealed that the application of H. indica at @ 3 billion IJs/ha was highly significant in causing mortality of L. bipunctata larvae (72, 128 and 162 dead larvae recovered respectively after 1, 2 and 3 months of application) compared to the chemical endosulfon and untreated control. This treatment was on par with 2 billion IJs/ha for the number of dead larvae recovered after 3 months though was significant for the dead larvae recovered after 1 and 2 months of application. Application of 3 billion IJs/ha recorded more leaf yield at 3 months (2.50 kg/plot) which was also on par with application of 2 billion IJs/ha suggesting that application of H. indica @ 2 billion IS/ha could be economical for the management of L. bipunctata.