For your trees and shrubs, one of the most important and environmentally friendly applications of the year is being done now! Dormant oils are one of our best tools against the unwanted pest population in your landscape shrubs. Insects such as scale, mites, and aphids have laid eggs on many of our shrubs in the mid-south and will soon hatch into larva. In order to greatly reduce this population, we apply dormant oils. Dormant oils are refined petroleum products designed to be sprayed on trees and shrubs. They will smother the future larva by covering their spiracles (breathing tubes). These applications are not toxic to birds or mammals.
Things to know before applying dormant oils:
- Dormant oils should be applied in temperatures above freezing, but below 70 degrees. Applications when temperatures are too low can lead to winter damage to plants. Applying dormant oils when the temperatures are too high will cause the oil not go into solution properly and your coating of the shrubs will not be thorough.
- Plants need to be completely dormant and before new growth occurs to prevent damage to the plants.
- Avoid applying simultaneous applications of dormant oils and insecticides containing sulfur. The mixing of the two can cause a dangerous compound. You must time these applications three to five days apart.
- Check your label to avoid shrubs that should not be sprayed by dormant oils.
- Dormant oils can do damage to annual flowers, so avoid spraying them.
As mentioned before, the insects that are managed by dormant oil applications are scale, mites, and aphids. Some common plants in Memphis that are affected by these insects are crepe myrtles, hollies, euonymus, boxwoods, roses, and other evergreens.
SCALE
One particularly ugly problem that was actually seen first in west tennessee, is soft bodied scale on crepe myrtles. This scale is an unwanted transplant from asian plant farms brought to the states for landscaping material. This sap sucking pest can reach large enough numbers to actually kill the plant. It is easily seen on the crepe myrtles and looks like a white fuzzy spot. They excrete a liquid called honey dew that promotes the growth of a black fungus on the plant that can coat the leaves and drip off onto your patio furniture, other plants, etc.. 
Unfortunately the sooty mold can not be washed off the plants and creates a very unsightly black coating on plants around the tree.The cheapest way to control this pest is by using dormant oils during the period of time when the trees have dropped their leaves and gone dormant.. While it might not completely eradicate a bad problem, the reduction in the pest population in the beginning of the year can make controlling it throughout the year much easier.
A similar scale can be.found on hollies.
Euonymus is easily taken over by another type of scale and must constantly be treated. However, dormant oils are a great way to reduce the pest population in the beginning of the year.
MITES
Many evergreens can have problems with mites. Here is a picture of a japanese cedar with false spider mites. You can see the problem starts at the tips and move back toward the branch. With both spider mites and false spider mites, the test for diagnosis is a simple one. Take a white sheet of paper and hold it below the branch’s affected area. Then simply shake the branch. Afterwards, watch the paper for any movement of the particles that landed on the paper. Spider mites tend to be black and will move shortly after they land on the paper. False spider mites (brownish) will move but might require more patience. So watch for 20 or 30 seconds to be sure.
APHIDS
Roses can benefit for dormant oils to reduce aphid populations. Aphids attack roses early spring on new, tender growth. These pests have piercing and sucking mouthparts that do damage by sucking out the plants sap causing them to wilt.
In conclusion, for pest control on many of our shrubs in the Memphis area, dormant oils give your the biggest bang for your buck. They are cheap and safe for beneficial insects, birds, and mammals. It is the most environmentally friendly pest control you can do! You can pick up dormant oil at most hardware stores or garden centers. I always like to suggest my friends at Urban Earth in Midtown Memphis or Germantown Hardware in Germantown, TN.. If you don’t want to do it on your own, we would love to give you an estimate!