The effect of frit fly (Oscinella frit) control measures on the establishment of seedling ryegrass (Lolium spp.)

SUMMARY In four experiments from 1981 to 1983 August-sown perennial (Lolium perenne) and Italian (L. multiflorum) ryegrass were exposed to frit fly attack by oviposition on the seedlings. Responses to pesticide treatment were detected at autumn harvests. Even at low sowing rates pesticide application did not ultimately establish a better sward and, owing to a tendency towards spring reversal of autumn yield responses, even temporary returns were negligible. As frit fly numbers were unusually low the autumn response to pesticide was sufficient to suggest that frit fly is always likely to be an influential factor in ryegrass sown in early August in this area. Later sowings are less likely to be affected. The yield response was related to the numbers of adult flies present 2–7 wk after sowing. Neither grass species was consistently more affected than the other. Additional seed (compared with a sowing rate below normal commercial rates) and the inclusion of fertiliser at sowing also gave only small temporary returns and failed to establish a better sward. It is suggested that routine protection against frit fly attack is of at least equal value to the other two variables in an early August sowing.