With their non-existent movement and round, "bump on a log" bodies, scales are among the bugs least likely to have lookalikes. There are, however, dozens of species, which might make you suspect that a pest is "scale-like" simply because you may be more familiar with a scale species that is a different color or size. For example, more than one species of soft scale has a greenish cast. Identifying the scale based on its size and markings can help target the approach, but there are also natural methods that help control scale species in general.
1 Spray shrubs and trees with dormant oil spray if they have been infected with green scales in previous years. Dormant oil spray is best used in early winter or early spring -- after temperatures reach 40 degrees Fahrenheit but before plants develop leaves. These sprays prevent eggs from hatching and hatched scales from maturing. Use a concentration of 1 to 3 percent oil to water and coat problematic plant parts with the spray.
2 Release predator ladybugs, or the predator parasites Microterys kotinskyi or Microterys flavus, to deal with green shield scale. This scale species most frequently attacks ornamental shrubs, avocado trees and tropical fruits, and it is especially a problem on nursery stock. Mail-order predator insects may be more effective in greenhouse situations, but some people order them for outdoor scale control.
3 Draw natural predators to your yard -- and retain those you may have bought -- by setting up an environment that encourages them. Flowering plants such as yarrow, dill and catnip are appropriate choices to grow near scale-bothered plants. Set shallow bowls around to give the "good bugs" that eat scale a reliable source of water.
4 Control ants that harvest the honeydew that green and other soft scales produce. Ants fight off scale predators in order to retain access to the honeydew. Outdoor ant stakes can be pounded in the ground near scale-infested plants. If you find the ant nest, flood it with soapy or boiling water.
5 Remove stems, branches and leaves that are most covered with greenish scale pests such as green shield scale and brown soft scale. Despite its name, brown soft scale has a greenish tint at some stages of its life. It is often found on citrus, avocado, willows, stone fruits, aspens and poplars.
6 Scrub woody plant parts that are infected with scale. This method is especially helpful when you want to deal with trunks and major branches that aren't practical to prune. Use a soft-bristled brush and soapy water to remove any species of scale from the plant.
7 Spray shrubs and trees plants with summer oil sprays once they leaf out but before temperatures reach 65 degrees Fahrenheit. This is useful for controlling older soft scales, including the greenish varieties of green shield scale and brown soft scale. To saturate infested plant parts with a homemade spray, blend 1 cup vegetable oil per 1 gallon of water.
8 Apply neem oil if scales remain a problem during the summer. Neem oil can be applied throughout the year and is effective against a range of problems, including soft scales and the diseases that their honeydew can cause. Use a concentration of 2 tablespoons neem oil per 1 gallon water, and spray plants thoroughly. Use it about once a week, for no more than five to six weeks.
Items you will need
- Spray bottle or orchard sprayer
- Dormant oil spray
- Purchased predator insects
- Ant bait stakes
- Flowering plants
- Shallow bowls or birdbaths
- Pruning shears
- Soft-bristle brush
- Liquid soap
- Vegetable oil
- Dormant oil sprays are often recommended in organic gardening manuals such as "Rodale's Ultimate Encyclopedia of Organic Gardening." They are, however, made with petroleum oils. If your definition of "natural" precludes oils that don't come from plants, then skip the dormant oil treatment and focus on neem and summer-weight vegetable oils.