Wireworms and leatherjackets, the larvae of click beetles (Agriotes spp) and crane flies (Tipula spp) respectively, are subterranean pests of grass, cereals and vegetables and are present throughout the UK and Europe. Soil cores, pheromone traps and water traps were used to measure populations. The populations of larvae were compared to those of adults. Leatherjackets and crane flies were found to be correlated, as were A. obscurus click beetle and wireworm populations. Annual variation in trap catches was observed. Populations were related at a number of spatial scales to cultural, physical and chemical variables. Spatial structure of populations was identified at all scales (sub field, field and landscape) using SADIE analysis, Moran's I and Taylor's Power Law, but the presence or absence of discernable spatial structure was dependant on species, population and annual variation. Environmental variables were linked to populations using multiple regression; the most common variable for all species were the number of years in grass, but the populations of each species and life stage were defined by its own set of variables. Important population defining variables were assessed as potential organically compliant cultural pest control methods. These included rolling, cultivation and crop rotation, but none could be definitively recommended as control methods without further work. In addition, pheromone traps for click beetles were characterised, it was found that the three species of click beetles had differential speeds of travel and the traps had differing effective ranges. A. lineatus were found to travel the fastest, A. obscurus slower and A. sputator travelled slowest. The maximum sampling range (over 30 days) was greatest for A. lineatus, less for A. obscurus and least for A. sputator.

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