Last week, I was pruning shrubs around the foundation of my home. As I pruned my Dwarf Yaupon Hollies, I reached into the center of the plant to remove a long branch. That's when I saw the white blob.
Upon closer inspection, I saw there were 25-30 of these blobs on different branches. The blobs were wax scale. There are many different types of scale insects, and they feed on most of the plants in our landscape. You will find scales on the back of leaves, and on the twigs, branches and trunks of plants
When the young scale, called crawlers, emerge from the egg, they move a short distance and begin feeding by sucking the sap from the plant. They produce a waxy coating that protects them.
To control waxy scale, I will be using Integrated Pest Management (IPM) principles. IPM looks at using methods to prevent insects or reduce their populations.
The first principle is to use resistant plants. Other principles are proper cultural practices such as proper pruning, fertilization and watering; letting beneficial insects build up to take care of the problem; and physical removal. The last includes the use of pesticides.
My first step was to prune out as many of the infested branches as I could without changing the shape of the plant. This removed the majority of the scale. The rest I removed by hand. Next, I will look for new infestations. The crawlers that spread scale hatch in April. In our area, there is usually one generation per year. To check for crawlers, put a piece of double-sided tape around the branches in the area where the scales are located. When the crawlers hatch, they will move across the tape and stick to it. The crawlers will be very small and yellow or reddish. When the crawlers are present on the tape, it is time to treat.
There are a number of products that you can use to control scale. For organic controls, you can use insecticidal soap or horticultural oils. Malathion will control the crawler stage. Any of these products must contact the insect to work, so you have to spray the interior of the plant or underside of the leaf. If you want to use a systemic insecticide, you can use imidacloprid, which is mixed with water and poured around the roots. It is then translocated throughout the plant.
There are two other common insects that we need to plan on controlling now. These are whiteflies and Azalea lace bugs. Whiteflies are a major pest on many shrubs, but I get more questions on controlling whiteflies on gardenias than any other shrub. The top side of the leaves turn black on gardenias that are infested with whiteflies. This is called sooty mold. The excrement of the whitefly is called honeydew; mold grows on its high sugar content.
Whiteflies have two generations per year. If you control the first generation that hatches in April, your chance of a second infestation is very small.
There are two methods of control for whiteflies. The first is to spray when you first see adult whiteflies. The products that are used to control whiteflies are insecticidal soaps, pyrethrins, pyrethrums and bifenthrin. These products need to be applied to the bottom side of the leaf. Other products to use are systemic insecticides such as imidacloprid and disulfoton. They are mixed with water and applied to the roots. These products need to be applied now.
If your azaleas have white or yellow mottling on the top of the leaf and black specks on the bottom of the leaf, you have azalea lace bugs.
The lace bugs over-winter as eggs, and will start emerging near the end of March, with numerous generations during the year.
Again, the key is to control the first generation. Acephate and imidacloprid are useful insecticides.
When using pesticides, remember to always read the label and follow the directions.
By detecting the scale on my hollies early in the season, I have a better chance of eliminating the problem. This will free up more time to do other projects in my yard.
Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at firstname.lastname@example.org. The Extension Web address is www.ugaextension.com/columbia.
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