Global: Mineral Oil Sprays Cut PVY Spread in Seed Potatoes by 43–58% in Field Trials

Mineral oil sprays remain one of the main tools to slow the spread of potato virus Y (PVY) in seed crops. Several peer-reviewed field studies have measured their effect. The results are good, but protection is never complete.

Finland: oil and straw mulch

Kirchner and colleagues tested four methods over three years in the High Grade seed area of Finland. Their results were published in Potato Research in 2014. Mineral oil reduced PVY incidence by 43–58% in two of the years.

Straw mulch performed even better. It cut PVY incidence by 50–70% in all three years in small-scale trials. At farm level, the reduction was 25–47% over two years. The insecticide esfenvalerate reduced PVY in progeny tubers by 29%, but only in one of three years. Birch extract had no significant effect.

Canada: oil plus insecticide

MacKenzie and colleagues ran trials in New Brunswick in 2014 and 2015. Their paper appeared in the American Journal of Potato Research. In untreated plots, PVY spread to 18% of virus-free plants in 2014 and 22% in 2015.

Combined sprays of mineral oil and insecticide gave the best results. Spread fell to as low as 4% in 2014 and 12% in 2015. Mineral oil alone also reduced spread significantly, but less. Insecticide alone did not significantly reduce PVY spread. The authors stress the importance of planting low-PVY seed and spraying early.

Belgium: six years of data

Rolot, Seutin and Deveux ran a six-year trial in the Ardenne region of Belgium. Their paper appeared in Potato Research in 2021. They conclude that mineral oil is efficient against PVY spread, although protection is incomplete.

Systemic insecticides mixed with oil gave added protection when winged aphid activity was high. Straw mulch increased the effect of oil and may reduce the number of sprays needed. Early haulm killing reduced PVY in seed lots. Rapeseed oil gave lower protection than mineral oil. Plant slurries and a silicon product did not control PVY.

Why it matters

In seed production, virus levels decide the class of a seed lot. The studies agree on three points. Mineral oil works but is incomplete. Insecticide alone is weak. Combinations of oil with mulch, insecticide or early haulm killing work best.

For seed growers, the first line of defence is clean starting seed. Oil programmes should start early and continue while aphids fly.

Photo: Green peach aphid (Myzus persicae) on a leaf (illustrative). Jules Verne Times Two / Wikimedia Commons, CC BY-SA 4.0