Effect of combined insecticide and fungicide treatments on newly sown swards of Italian and perennial ryegrass using two methods of sowing, two rates of seed and N fertilizer, with and without herbicide

Abstract

The effects of six factors, each at two levels and in all combinations, on herbage yield and weed content of perennial (Lolium perenne) and Italian (L. multiflorum) ryegrass were assessed in four autumn sowings of field plots, in 3 years and at two sites. The factors were (i) perennial (PRG) or Italian (IRG), (ii) normal or low seed rate, (iii) drilling or broadcasting the seed, (iv) normal or low N fertilizer rate, (v) ryegrass fungicide seed treatment and post‐emergence insecticide sprays (F + I) or untreated, and (vi) herbicide treatment or untreated. Overall, herbage yield at the first harvest was increased by F + I and IRG (all sowings), and the higher rates of seed (three sowings) and N (two sowings). Variable results were obtained for the other two factors. Increased yield was often associated with reduced weed content. Significant interactions between factors were obtained at two sowings; in particular, F + I increased yield of IRG by 12% and 22%, but had no effect on PRG. A second harvest, in the following spring, was taken for two sowings and there was no effect of F + I or the higher rates of seed and N. Thus, it is concluded that the desired aim when establishing grass swards of an adequate plant population without excessive competition from weeds appeared to be obtained even with plots receiving the least inputs.