Understanding how plant compounds influence insect behahiour
Our research into the role plant-derived compounds play in plant-insect interactions aims to increase our understanding of how these compounds influence different stages of insect host selection behaviour, especially feeding and egg-laying. The majority of insects have a narrow host range and use chemical stimuli to select among species of plants. However, it is often difficult to identify the role played by specific compounds in the different stages of behaviour used by insects to discriminate between host and non-host plants. To date, we have concentrated on investigating the role of non- or low volatile metabolites, such as flavonoids, diterpenoids, alkaloids and non-protein amino acids, on insect behaviour and have shown that within each group of compounds small changes in their molecular configuration can result in a loss of activity. A range of insects with different host ranges are used to compare the specificity of compounds. Since 1985, nearly 10,000 species of plants have been tested at Kew for activity in insect bioassays as well as about 2,000 compounds isolated from these species. Some of the most active antifeedant compounds isolated include the limonoids, such as azadirachtin, from the neem tree, (Azadirachta indica), the neo-clerodane diterpenoids from labiates, polyhydroxyalkaloids from legumes and monocots, non-protein amino acids from legumes, and coumarins and flavonoids from species from various plant families.
The information obtained from this project can be used to address specific plant-insect questions. For example, the role played by surface phenolics in the susceptibility of legumes such as pigeon peas in host selection or the factors in oak timbers that influence the behaviour and development of the deathwatch beetle. We are also investigating ways to control deathwatch beetle and furniture beetles that can cause structural damage to wood in buildings and to valuable artifacts. This research is being undertaken in collaboration with English Heritage and the University of Hamburg and involves identifying what compounds in the wood modulate the egg laying behaviour of these insects and are timbers currently been used in the construction industry more susceptible to insect attack than older timbers. This knowledge will be of use in the development of pest control strategies.
Another part of this project relates to the research within the glasshouses at Kew to support the use of integrated pest management strategies. Recently, research has concentrated on studying compounds from the species of the plants (e.g. Plectranthus spp.) in the Temperate House that are resistant to attack by thrips, whereas others are highly susceptible. Species of plants in the glasshouses not only modulate the behaviour of thrips but their respective control agents and this can influence the effectiveness of some of the beneficial organisms that are used to control the thrips.
The major outputs from these projects are presented in scientific publications. The results also contribute to the development of botanical based products that have potential for use in different forms of integrated pest management strategies.
Key publications 2006-2011
- Green, P.W.C., Veitch, N.C., Stevenson, P.C. & Simmonds, M.S.J. (2011). Cardenolides isolated from Gomphocarpus sinaicus and Pergularia tomentosa (Apocynaceae: Asclepiadoideae) deter the feeding of Spodoptera littoralis, Arthropod-Plant Interactions 5: 219–225.
- Scott Brown, A.S., Veitch, N.C. & Simmonds, M.S.J. (2011). Leaf chemistry and foliage avoidance by the thrips Frankliniella occidentalis and Heliothrips haemorrhoidalis in glasshouse collections, Journal of Chemical Ecology 37: 301–310.
- Green, P.W.C. The effects of insect extracts and some insect-derived compounds on the settling behaviour of Liposcelis bostrychophila. Journal of Chemical Ecology 35: 1096-1107.
- Stevenson, P.C., Dayarathna, T.K., Belmain, S.R. & Veitch, N.C. (2009). Bisdesmosidic saponins from Securidaca longepedunculata roots: Evaluation of deterrency and toxicity to Coleopteran storage pests. Journal of Agricultural and Food Chemistry 57: 8860–8867.
- Sharma, H.C. Gowda, C.L.L. Stevenson, P.C. Ridsdill-Smith, T.J. Clement, S.L. Ranga Rao, G.V. Romies, J. Miles, M. & Bouhssini, M. (2007). Host plant resistance and insect pest management in chickpea. In S S Yadav, R Redden, B Sharma. (Eds) Chickpea Breeding and Management. CABI, Oxford, UK.