Studies on host plants of Scirtothrips dorsalis in the Palm House at Kew Gardens (United Kingdom)
In December 2007, an outbreak of Scirtothrips dorsalis (Thysanoptera: Thripidae – EPPO A2 List) was detected in the Palm House collections at Kew Gardens, Southern England (United Kingdom). This infestation within plant collections presented a unique opportunity to study the potential host status of a great variety of plants. The objectives of this study were to identify plants that are susceptible to S. dorsalis and which had not been previously documented as breeding hosts, as well as to demonstrate how botanic collections of taxonomically verified plants could be used to gather new information on the host range of invasive pests. A survey was thus conducted in June 2010 (3 years after the initial infestation was discovered). Young leaves and buds were collected from 181 plant species (67 families). All life stages of S. dorsalis were recorded as present or absent on the foliage of sampled plants and the numbers of adults and immature stages were recorded. These observations were also compared to a list of host plants compiled from the literature. By 2012, eradication measures were taken under the supervision of NPPO in the Palm House (i.e. movements of plants from the glasshouse were prohibited and chemical treatments were applied). Monitoring of the glasshouse is continuing, and biological control agents are used to manage pests. Currently, there is no evidence of the presence of S. dorsalis in the Palm House.
Out of the 181 plant species studied, 73 (belonging to 38 families) were found to harbour S. dorsalis in their young leaves and leaf buds (i.e. 40% of the studied plant species – which also means that 60% of the other plants did not harbour the pest). It was observed that 44 species infested by S. dorsalis contained immature life stages, indicating that these plants were providing suitable oviposition sites and sufficient nutrients to sustain developing immature stages. The highest numbers of S. dorsalis specimens (adults and immature stages) were observed in 2 species native to tropical Africa (Ehretia cymosa var. cymosa and Oncoba spinosa) which showed some thrips damage. The full list of plant species found to be susceptible to S. dorsalis in the Palm House collections is available on the Internet: https://static-content.springer.com/esm/art%3A10.1007%2Fs10340-017-0916-2/MediaObjects/10340_2017_916_MOESM1_ESM.doc
It is acknowledged that the collections in the Palm House are more representative of the wild flora or crop relatives than of agronomically important plants. However, it is noted that 23 (out of 38) plant families contain species that have been previously recorded in the literature as hosts of S. dorsalis (or with host associations) based on field observations; and that 15 of the plant families harbouring S. dorsalis had not been previously recorded in association with the pest. The authors concluded that botanic gardens can provide useful information in identifying which plant species are at risk from invasive pests.
Scott-Brown AS, Hodgetts J, Hall J, Simmonds MJS, Collins DW (2018) Potential role of botanic garden collections in predicting hosts at risk globally from invasive pests: a case study using Scirtothrips dorsalis. Journal of Pest Science 91(2), 601-611.