Influence of morphological and chemical constituents of plant foliage on thrips host selection among the botanical collections in the Temperate House, Royal Botanic Gardens, Kew
Scott Brown AS, Veitch NC, Simmonds MJS
Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK.
Correspondence: a.scott-brown@rbgkew.org.uk
One of the primary aims of the Royal Botanic Gardens (RBG), Kew, is to conserve its unique living collections of 33,000 plant species, many of which are classified as rare and endangered. Thrips have persisted as a threat to plant species contained in the display glasshouses since the introduction of IPM programs at Kew in the early 1990s. The genetic and phenotypic diversity of plants housed together in artificial conditions has lowered the efficiency of biological control predators which have been used successfully to control invasive thrips species on protected crops in the commercial horticultural sector. We have monitored and documented plants among the collections in the Temperate House, RBG Kew, as hosts or non-hosts to two invasive thrips; Heliothrips haemorrhoidalis (Bouch¨¦), and Frankliniella occidentalis (Pergande) and further investigations have highlighted species of host plants where the effectiveness of the predators; Neoseiulus cucumeris (Oudemans), Iphiseius degenerans (Berlese) and Orius laevigatus (Fieber) were significantly reduced. This study aims to highlight the morphological and chemical differences among the foliage of the hosts and non-hosts of H. haemorrhoidalis. Scanning electron microscope techniques were used to describe the morphology of the leaf surface of 19 species in order to help identify which morphological features could play a role in the selection of plant species by thrips from among a diverse botanical collection. The results showed H. haemorrhoidalis had a preference for species with leaves that were coriaceous, with one or both surfaces being smooth. Plants evading these thrips commonly possessed glandular trichomes and waxes present on the surfaces of leaves were observed to be of dense, non-uniform forms, thus potentially disrupting feeding and oviposition of H. haemorrhoidalis. In addition, detailed analysis of the phytochemical profiles of the leaves of non-hosts are in progress to identify which groups of compounds deter thrips, and which compounds present in hosts may result in a decrease in efficiency of the introduced predators. Initial studies have focused on the profiles of two non-hosts of H. haemorrhoidalis and several isolated compounds present in the foliage of these species have shown levels of activity against immature stages of F. occidentalis in controlled bioassay tests. Evaluating the roles of morphological and chemical characteristics of non-host plants in plant-thrips-predator interactions can serve to advance our methods in controlling thrips pests in all sectors of Horticulture.
