Interactions between pesticide treatment, cutting frequency and rate of N fertilizer on white clover growth in mixture with perennial ryegrass

The effects of a combined pesticide and fungicide (P + F) treatment on the proportion of white clover in an established perennial ryegrass/white clover sward were assessed on six occasions during 1988 and 1989, under two cutting frequencies (2- or 6-week intervals) and with or without N fertilizer (120 kg ha-1 per annum). In 1988 P + F treatment significantly increased the proportion of clover in August and October, with an increase at the latter harvest being much greater where N was also applied. There was no significant interaction between P + F treatment and cutting frequency, although less frequent cutting increased significantly the proportion of clover in October where N was not applied. In 1989, drought prevented the proportion of clover from exceeding 1% throughout, regardless of management factors. P + F treatment significantly increased the proportion of clover in August, and significantly reduced populations of slugs, foliar-feeding insects (mainly Collembola; Sminthuridae) and the area of clover leaf damaged by pests. No marked effect of P + F treatment on populations of plant parasitic nematodes was detected. No appreciable incidence of fungal diseases was observed in either year.