Dormant Oil – What and Why and When
What: In days past, dormant oil was always a petroleum based product. They are very effective but of course are not approved for an organic growing program. Many are now called horticultural oil.
Today you can choose products with a vegetable oil or soybean base. JMS Stylet Oil uses a mineral oil base and approved for organic production. I will also provide a recipe if you want to make your own.
Why: Many insects over winter in the bark of fruit trees. Aphids, mites and scale can be targeted with an early application.
When: You want to spray when the weather has warmed and just before leaves and buds open. The insects need to be active. The oil is non selective so helpful insects can be killed as well. You can not use a sulfur based product within 14 days of an oil application, leaf burning will occur. Only use a horticultural oil labeled ‘summer oil’ in the warm months. A heavier oil will burn the leaves in hot weather.
For more detailed information:
Recipe: 1 gallon water, 2 tbsp. ultra-fine canola oil or horticultural oil, 1 tbsp. baking soda. Mix well and apply to the point of dripping off the tree.