Control of aphid-borne potato virus Y in potatoes with oil emulsions

Tests were made at Presque Isle, Maine, from 1963 through 1965 to measure the effect of oil sprays on the spread of potato virus Y (PVY) in Green Mountain potatoes. In 1963, 4 weekly applications of a 1% mineral oil emulsion at 1.25 gal oil/acre(4.71/.41 ha) did notaffect significantly (P = 0.05) the spread of PVY. In 1964, the 64% control of PVY spread from 5 weekly applications of mineral oil emulsion at 1.25 gal/acre was not significantly different at that level from the 55% control from 5 weekly applications of the oil emulsion at 2.5 gal/acre (9.5 1/.41 ha). Three or 5 weekly applications of an alkylated naphthalene (Velsicol AR-60®) spray at 1.25 gal/acre significantly increased spread of PVY compared to that from 5 applications of the oil at 1.25 or at 2.5 gal/acre. In 1965, from 69 to 75% control of PVY spread resulted from 6 weekly applications of a paraffin oil emulsion at 2.5 gal/acre. The percent spread from the 6 weekly applications was smaller, but not significantly so (P = 0.05), than from 3 weekly applications made during the first half of the same 6-week period. In these tests, relatively light spread of PVY occurred, and control of spread was rather variable but the results indicate that oil emulsion sprays offer promise for protecting potato plants from PVY infection.