Thrips of Sri Lanka have been poorly studied despite their significance to agriculture and horticulture of the country. A survey of thrips and their host plants was conducted in several parts of Sri Lanka during [2005][2006][2007][2008], with a view to record the species present, their distribution, host plant relationships and damage caused. Over 1,000 plant species comprising crops, ornamental plants, weeds, shrubs, and trees were examined for thrips in 22 study sites, representing a range of habitats in nine districts covering 12 agrochemical regions of the country. Damage in plants due to thrips infestations was documented. This paper presents a list of 72 thrips species in 45 genera recorded during the survey from 324 host plant species in 83 plant families. Megalurothrips usitatus, Thrips palmi, and Haplothrips gowdeyi were the most widely distributed species. The grass infesting Haplothrips spp., several species of Thrips, Microcephalothrips abdominalis, M. usitatus and Scirtothrips dorsalis are some of the species with a large number of host records. Thrips simplex in particular was confined to the Upcountry Wet zone, while Thrips flavus was most widespread in this region and was present on almost all the vegetation. The survey identified 24 species of thrips represented in 20 genera that were not recorded previously from Sri Lanka. Majority of the thrips recorded are pest species, cosmopolitan in distribution. The most common damage due to thrips infestations was discolouration, scarring and browning of leaves and flowers, most pronounced in cut flowers. The survey updates the information on the Thysanoptera of Sri Lanka and highlights their importance in agriculture and floriculture.
The responses of the tea shot-hole borer beetle, Xyleborus fornicatus, to conspecific and host plant odours were tested in an olfactometer. Males showed greater attraction to unmated females than to mated females and mated females showed a negative density dependent response with extremely significant repulsion shown when 10 mated females were present. Plants of the susceptible tea cultivar TRI2025 were significantly more attractive to females than those of the less susceptible cultivar TRI2023, although stem extracts of the susceptible cultivar were not found to be attractive to beetles. Beetles were found to be attracted to ethanol and to the known tea volatiles eugenol, hexanol, a-and b-pinene, geraniol, and methyl salicylate. The attraction of the tea volatiles was found to be enhanced when they were mixed with ethanol, indicating that ethanol has a broad synergistic effect. In a study on phagostimulant effects of tea extracts, sugars, and caffeine, the methanol extract of cultivar TRI2025 and the sugars glucose and sucrose were found to be attractive, and caffeine repulsive, to beetles. Pellets containing the extract were found to be preferred over those containing glucose. Beetles were attracted to pellets containing glucose/inositol mixture with glucose:inositol in the 3:1 ratio found in the susceptible cultivar TRI2025, being preferred to the mixture in 5:1 ratio found in stems of the less susceptible cultivar TRI2025. Both volatile and nonvolatile constituents of tea appear to play a role in attracting the female beetle to the plant.
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