Evaluation of mineral oil sprays for reduction of virus Y spread in potatoes

In 1979 and 1980 field tests were made at Fredericton, New Brunswick to evaluate the effect of various oil application methods on the spread of potato virus Y (PVY) and the phytotoxicity they might cause. Control of PVY by oil sprays reached 64%. Control of spread depended largely on the concentration of the oil, and to a lesser extent, on its delivery rate. Tests did not show any significant effect of the spray pressure. There was no significant difference between eight commercial oil formulations. No significant foliar phytotoxicity or yield reduction resulted from applications of oil, except when a combination of high oil concentration (3% water emulsion) and high rate of application (2240 L/ha) was used. Fungicides mixed with oil or applied immediately after oil produced foliar phytotoxicity. Less phytotoxicity occurred when they were applied 24 h later than oil.