Volatile constituents of tea stems (Camellia sinensis L.O. Kuntze) as semiochemicals to attract low country live wood termite (Glyptotermes dilatatus Bugnion & Popoff), in Sri Lanka

Abstract

Low country live wood termite (LCLWT), Glyptotermes dilatatus Bugnion & Popoff is one of the major insect pests of low grown tea in Sri Lanka. The present study was aimed at investigating the chemical constituents and the attractant effects of tea stem volatiles isolated from different tea cultivars on the behaviour of alates of G. dilatatus. Volatile extracts of decayed and healthy stems of susceptible cultivars (TRI 2023, TRI 4042) and resistant cultivars (TRI 2027, TRI 4049) were collected. The attractant effects of stem extracts on termite alates were evaluated using the olfactometer bioassay. Volatile extracts of decayed stems obtained from the four tea cultivars were more attractive to alates than that of the healthy stems. The responses of alates to volatile extracts from decayed stems of TRI 2023, TRI 2027, TRI 4042 and TRI 4049 were 37 ± 0.04, 34 ± 0.04, 36 ± 0.035 and 32 ± 0.04, respectively whereas the responses of alates to volatile extracts from healthy stems TRI 2023, TRI 2027, TRI 4042 and TRI 4049 were 16 ± 0.03, 13 ± 0.03, 14 ± 0.38 and 16 ± 1.5, respectively. The analysis of volatile extracts from decayed stems using Gas Chromatography-Mass Spectrometry led to the detection of 96 compounds in the four tea cultivars. Among them 15 compounds were common in all four tea cultivars and n-hexadecanoic acid and 9,12-octa decadienoic (Z,Z) acid were identified as the major constituents of decayed tea stems. Compound mono(2-ethylhexyl) phthalate was identified as the major constituent in healthy stem volatiles. Mono(2- ethylhexyl) phthalate and n-hexadecanoic acid were present in both types of tea cultivars and they can be developed as an alternative method to control the test insect.