Feasibility of using rapeseed oil as a carrier in pesticide applications

Abstract

A commercial twin-fluid nozzle coupled with an electric gear pump was used to apply rapeseed oil to several plant species at volume rates of less than 10 l/ha. An aqueous spray system delivering 220 l/ha was used for comparison. The droplet spectra of the oil sprays were extremely fine compared to the aqueous system and were only variable to a limited degree by alterations to oil flow rate and air pressure.

Oil sprays were particularly well retained on cereal plants, deposits being seven-fold greater than aqueous sprays. On fat-hen seedlings, oil deposition efficiency was increased approximately three-fold compared with water. Rapeseed oil applied to young wheat, sugar beet and tomato plants produced no visible phytotoxic symptoms or significant changes to plant weights. Topik 240EC (clodinafop-propargyl), a species-specific graminicide, applied to oat seedlings in 6 l/ha of rapeseed oil had an ED50 value of 4.0 g a.i./ha compared with an aqueous spray value of 9.0 g a.i./ha. In contrast, applications of Betanal E (phenmedipham) to fat-hen seedlings were less effective in oil compared with water by a factor of almost four. Topik applied to oats at two sub-lethal doses was more effective in methylated rapeseed oil than un-methylated oil while a mineral oil had an intermediate efficacy.

These results are discussed with reference to relevant literature. The practical problems relating to the use of oils as carriers for pesticides are highlighted.