ARABLE: Field evaluation of synthetic blends of semiochemicals for monitoring and control of wireworms

Wireworms are major pests of cereal crops and root vegetables in Europe and also in North America. Seed treatments and other contact insecticides are used to protect crops from larval feeding damage. However, current chemical options are being withdrawn in Europe and it is very questionable when and if at all a new soil insecticide could be registered for wireworm management. Semiochemicals (naturally occurring development- and behaviour-modifying chemicals, such as different volatiles) are not harmful to the environment at the level they are required and can provide a "green" alternative for soil pest management. Similar to aboveground insects, soil-dwelling arthropods are also attracted to or repelled by root volatiles that occur in the gas phase and diffuse in soil pores. Whereas carbon dioxide is a universal attractant, root-emitted volatiles are more specific, mid-range signals that help soil pests to track and find their host plant.

We have identified from crop roots and created synthetic volatile blends that attract wireworms in laboratory behavioural studies. We now aim to test if they retain their attractive properties in more realistic setups, i.e. crop fields. The main aim of this project is to thus carry out field trials with these synthetic blends (lures) to check if they are able to attract large numbers of wireworms into traps, containing germinating seeds, that we will build during the project. Such traps with and without the lures will be sunk in the soil in agricultural fields and checked regularly for captured wireworms. On the one hand, we want to see if traps with lures catch more wireworms then those without lures, which will indicate that they are suitable for precise pest monitoring before seed sowing. On the other hand, we will test lured traps to see if they can catch enough wireworms to reduce crop damage, and we will compare their performance with pesticide treatments. This will tell us if traps with lures can replace pesticides and provide growers with an alternative wireworm management tool.

The proposed study is an important step in the development of monitoring and attract-and-kill strategies for wireworm management, which could also be extended to the management of other soil-dwelling pests.

Soil-borne pests are a major limiting constraint in crop production. Agriotes spp. wireworms (Coleoptera: Elateridae) are major soil-dwelling pests of cereal and root vegetable crops in Europe and North America, with A. lineatus, A. obscurus and A. sputator causing significant annual crop yield losses (10-100%) in the UK alone through larval feeding behaviour.

Management of Agriotes spp. currently involves deployment of pheromones to monitor adult populations, and use of seed treatments and organophosphate insecticides to protect crops from larval feeding damage. However, current chemical options are challenged in Europe, and uncertainty remains if at all new soil insecticides could be registered for wireworm management in the near future. Furthermore, predicting the extent of subsequent larval damage from pheromone trap catch is problematic and has its shortfalls.

To address the problem with management of wireworms at the feeding stage, we are investigating the use of rhizosphere-derived volatile organic compounds (rVOCs) as novel, environmentally benign biopesticides for larval management. Similar to aboveground insects, soil-dwelling insects are also attracted to or repelled by semiochemicals (behaviour-modifying chemical signals) that occur in the gas phase and diffuse in soil pores. Whilst carbon dioxide is a generic attractant, rVOCs provide more specific, mid-range host location cues for soil pests.

Our lab has recently isolated and identified rVOCs which attract wireworms in soil olfactometer (behaviour) assays. We will test rVOC synthetic blends against wireworms in proof-of-concept field experiments using slow-release prototype formulations. The proposed study is an important step in the development of attract-and-kill strategies for wireworm management, which could also be extended to the management of other soil-dwelling pests.