Horticultural (hort) oil suffocates insect and mite eggs when applied in the Winter. Mites and insects cannot become resistant to suffocation like they can with other chemicals. It’s also cost effective because the oil is inexpensive. Finally, lower Winter temperatures mean there is no sweating through this task!
Apply hort. oil in Feb-March to your evergreens to kill pest eggs.
I’ve been applying oil on my evergreen trees and shrubs since February 2007. Emerald Green Arborvitae is susceptible to the the two-spotted spider mite. It’s expensive and difficult to kill the mite during the Summer growing season. Prevent insect and mite problems by killing the population before it becomes damaging.
Disclaimer: read the label or instructions. Don’t deviate from the instructions. Some oils hurt trees and shrubs if you apply them over a certain temperature. I have never had problems, but I always follow the instructions.
- Buy a pump sprayer or opt for a Solo brand backpack sprayer. You should apply dormant oil every Winter. February is a great month to do this. The days are getting longer so find the time on a weekend to coat your evergreen plants with oil.
- Purchase horticultural or dormant oil if applying in Winter. There is refined hort. oil for Summer applications that may be more expensive.
- Spray under the needles and broadleaves. Mite and insect eggs will certainly exist there. Spray the bottoms of the needles by flipping the spray wand upside down and make a up and down motion with your arm.
- Covering every needle and leaf is essential. Leaving gaps allows the insect or mite eggs to survive. Take your time and coat everything well until droplets form.
- Rinse the tank with clean water. Avoid using the same pump sprayer or backpack sprayer with herbicides.
Question: What landscape plants do you have insect or disease problems with?
