Incidence and severity of pest and disease damage to white clover foliage at 16 sites in England and Wales

From 1985 to 1987, leaves of white clover ( Trifolium repens ) cv. Grasslands Huia were examined for damage by pests and fungal diseases on seven occasions at up to 16 sites in England and Wales. Pest damage was recorded at all sites on all sampling dates. Over all sampling dates, the mean number of leaves damaged by slugs ranged from 23% to 67%, and that by weevils ( Sitona spp.) ranged from 3% to 62%. Also, up to 30% of leaves were damaged by other, unidentified pests. At individual sites, total pest damage frequently exceeded 90% of leaves. The area of leaf damaged by pests ranged from 2 - 12%. Fungal diseases were recorded in July and September but not in May, and were more prevalent in September 1985 than in September 1986 or 1987. Black blotch ( Cymadothea trifolii ) was the most frequently recorded disease, and the mean number of leaves damaged ranged from 4% to 21%. The mean area of leaves covered by lesions was 1–2%. Infections by viruses were assessed on two occasions, using indicator plants and electron microscopy, and only a very low incidence of arabis mosaic virus and red clover necrotic mosaic virus was recorded.