Phytotoxicity of mineral oil treatments

Under certain conditions of application, mineral oils - which are used for seed potato production to limit the spread of non-persistent viruses - can cause various types of damage on foliage (burns, brown necroses, shrivelling, hardening of the leaves with metallic reflections, etc.), especially on young leaves at the top of the plants.

These symptoms, which are accompanied by delayed growth, are exacerbated and clearly visible when the temperature is high and following the application of repeated high doses. However, they have no repercussions on the daughter tubers (photo 1).

Some late blight fungicides are incompatible with mineral oils (e.g. fluazinam) (photo 2).

Prevention involves following the general instructions for applying treatments with mineral oils (rates, concentration) and avoiding overdosing, especially in hot weather.