| Abstract: | Grassland pests often cause obvious damage at the establishment phase, but it is rare for established swards to be visibly affected. Despite this, insidious damage to established grass is widespread and there are several reasons why it is not easily detected. Insidious pest damage is particularly prevalent in sown ryegrass-dominant swards in the lowlands. Permanent pastures, in the uplands at least, appear to suffer less from pest damage. In one experiment, established legumes did not suffer markedly from pest damage. Sward damage varies considerably from year to year, during the season, with location, with sward age and with botanical composition. Much of the blame for damage to established swards and to those being established can be attributed to stem-boring Dipterans, such as the frit fly (Oscinella frit L.). Certain non-persistent insecticides can be used to control the pest, but are unlikely to be cost-effective except when used at the establishment stage or, possibly, on efficiently utilised lowland ryegrass swards. Alterations in management practice do not seem feasible in controlling frit fly. However, large differences have been found between the varieties of perennial and Italian ryegrass, in the level of susceptibility to pests (especially frit fly), and it may be possible to develop resistant varieties. |
