Background

Sunn pest (Eurygaster integriceps Puton) © University of Greenwich

The Sunn pest (Eurygaster integriceps Puton) is a very damaging insect pest of wheat and barley in countries of West Asia, including Afghanistan, Iran, Iraq, Lebanon, Syria and Turkey, as well as in the Central Asian republics (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan), and Bulgaria and Romania. Sunn pest infestations spread over 15 million ha in the affected area. Both nymphs and adults cause damage by feeding on leaves, stems and grains. Yield loss is commonly estimated at 20-30% in barley and 50-90% in wheat. Apart from the direct reduction in yield, the insects also inject chemicals that greatly reduce the baking quality of the dough.
Wheat is the most important food crop in the Central and West Asia region. It provides a substantial component of the human diet: wheat products provide over 40% of the per capita dietary supply of calories and protein in most of the countries mentioned above, and substantially more in some of the Central Asian Republics.
Control of Sunn pest by chemical insecticides is expensive, costing over US$ 40 million annually in the countries concerned, and poses a risk to human health, water quality and the environment as a whole. The present insecticide-based strategies for control of Sunn pest must be replaced with multi-dimensional integrated pest management (IPM) approaches. The proposed research addresses an urgent need of farmers in the West and Central Asian region in their effort to grow an abundance of high-quality grain.

Results
The purpose of the project is to reduce constraints to wheat production caused by Sunn pest in West and Central Asia, through the development and application of appropriate, low-cost and environmentally acceptable IPM approaches.
The project involves assessment of economic thresholds for Sunn pest populations and determination of the role of egg parasitoids in suppressing Sunn pest populations. Entomopathogenic fungi will be evaluated for control of Sunn pest. The role of semiochemicals in host and mate finding by Sunn pest will be established and their use in management of the pest investigated. Sources of resistance to Sunn pest in wheat and its wild relatives will be identified and germplasm will be developed. Appropriate IPM packages will be tested on-farm and disseminated through a farmer participatory approach.
NRI is responsible for the work on semiochemicals. To date, attraction of female bugs by male bugs has been demonstrated in a laboratory bioassay. Males have been confirmed to produce large amounts of a homobisabolene with smaller amounts of bisabolene and vanillin. Ethyl acrylate was not found. The compounds are produced only by the overwintering generation and not by the summer generation, suggesting that they have some role in mate-finding. However, no components were observed to elicit responses in linked GC-EAG analyses. Recordings of characteristic vibrational signals were made from male bugs in the presence of male or female bugs on the same stem. Results indicate these signals are probably important in mate recognition at close-range.

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