How Can I Control Sycamore Scale?

Do you want to control scales using the biological control method?

Do you want to control scales using insecticides?

Do you want to use residual, foliar sprays?

Do you want to use combination sprays for disease and scale control?

Several species of lady beetles feed on sycamore scales. These include the twicestabbed lady beetle (Chilocorus orbus), the pine ladybird (Exochomus quadripustulatus), and Axion plagiatum. Adults and last-instar, or oldest, larvae are about 1/5 inch long. Adults are mostly black with two red to orangish spots on the wing covers of Axion plagiatum and the twicestabbed lady beetle and four yellow to orangish spots on the pine ladybird’s back. Larvae are a mixture of black, brown, gray, and white that varies with the instar’s age and species. Larvae of Axion plagiatum and the twicestabbed lady beetle are distinctly spiny.

Bud break through early leafing out is the most effective time to spray for sycamore scale, because first instars, the stage most susceptible to insecticides, emerge from eggs at the same time as bud break. If scales are abundant and damage cannot be tolerated, apply 1% horticultural oil (narrow-range or supreme) or insecticidal soap. Thoroughly spray branch tips, large limbs, and the trunk using a commercial, high-pressure sprayer. Because of the equipment and experience needed to effectively treat large trees, spraying sycamores usually requires hiring a professional applicator.

Oil sprayed at bud break or early leaf flush helps control powdery mildew disease in addition to sycamore scale. A combination of oil and copper spray (e.g., Bordeaux mixture) or oil combined with chlorothalonil can help to control anthracnose disease and scales. Other fungicides also are available for mixing with oil.

Although soil application of the systemic insecticide imidacloprid has been suggested for managing sycamore scale, there is little research data on its efficacy. In contrast to oil, which must be sprayed to cover the whole tree, home-use systemic products are relatively easy to mix in a bucket and apply as a soil drench. Professional applicators can apply imidacloprid with soil injection equipment. Trees take the pesticide up through their roots. Soil application of imidacloprid is more likely to be effective if applied in late winter or early spring.

Provide the appropriate growing conditions and cultural requirements for your species of sycamore, and protect trees from injuries. Healthy trees are better able to tolerate pest damage, such as premature leaf drop. Choose pest-resistant cultivars when planting sycamores, such as those resistant to anthracnose or powdery mildew. The best choice varies according to the growing location and how trees will be managed. Although sycamore scale reportedly does not damage P. occidentalis, this species, which is native to the Eastern United States, might not be a good choice for most urban California landscapes.