The damage potential of the black field cricket Teleogryllus commodus

Regressions of herbage loss on population density of black field cricket (Teleogryllus commodus Walker) (Orthoptera: Gryllidae) were obtained by caging different life stages at a range of densities over ryegrass (Lolium perenne )–white clover (Trifolium repenss –dominant pasture. Significant (P<0.001) relationships between herbage loss and insect density were found only in trials involving adult crickets. The different life stages used markedly affected the slope of the regression of herbage loss on cricket density. The early adult stages caused the greatest herbage loss, large nymphs and late adults were intermediate, and the small nymphs caused the least loss. A field population of five crickets per m 2 , which was regarded as low, was estimated to cause pasture loss of 1.8 kg. ha –1 . d –1 of dry matter (DM), a grazing pressure equivalent to 1.5 ewes per hectare per day. A field population of 60 adult cricket per m 2 , which is regarded as high, was estimated to cause pasture loss of 25.1 kg. ha –1 .d –1 of DM (equivalent to 21 ewes per hectare per day) and the same population over all stages throughout one summer, a total seasonal pasture loss of 2920 kg. ha –1 of DM. These results show that black field crickets cause considerable pasture losses at all developmental stages, and should be controlled as early as possible each year to reduce pasture loss and damage.