Reduction of soldier fly damage to ryegrass seedlings by insecticidal seed treatments

Abstract

A trial compared three types of seed treatments using five different insecticides: trichlorfon, isophenphos, carbofuran, methomyl, and omethoate. Coating method had no effect on insecticidal activity, although seedling growth and subsequent pasture production were greater from ryegrass seed loaded with fertiliser than from experimental or commercial ('Prillcote') dressings incorporating insecticide only. Only isophenphos and carbofuran controlled larvae, and the former gave greater pasture production than all other treatments. These results were supported by analyses of insecticide residues which showed isophenphos and carbofuran to be the most persistent.

Use of insecticides during autumn to control soldier fly larvae and increase pasture production

“…Rowe & Mackay (1975) in their autumn seed treatment trial obtained a reduction of larval population from 3000 to 1200/m 2 and an associated increase in winter-spring production from 3500 to 4800 kg DM/ha, Le., a 37% increase in pasture growth resulting from a drop in larval numbers of 1800 Iarvae/rn-. Dixon & Holland (1976) in an autumn seed treatment trial obtained a reduction of larval density from 2197 to 716/m 2 and an increase in winter-spring pasture production from 5840 to 6460 kg DM/ha, Le., a 10.6% increase resulting from a 1481/m 2 decline in larval population. The largest response reported is by Mackay et ale (1974) who obtained a reduction in larval population in existing pasture from 8137 to 3233/m 2 and an increase in pasture growth during winter from 1275 to 2728 kg DM/ha, Le., a 114°;& increase in pasture growth resulting from a 4904/m 2 decline in larval population.…”

“…Harris (1969) reported that biological activity of carbofuran in soil persisted for 16 weeks, but that phorate disappeared within 2-4 weeks. Dixon & Holland (1976) found that 17 days after treatment with carbofuran and isophenphos the proportion remaining in the plants and surrounding soil was respectively 63 and 95% of the amount applied. After 30 days the proportions were both about 25 0/0.…”