Scale insects commonly infest bay tree plants. They are harmless -- although unsightly -- in small numbers. But if the infestation is allowed to flourish, they can damage the tree. The leaves may turn yellow, develop deformities or drop prematurely. They can even stunt the bay tree's growth or kill twigs and branches. To avoid permanent damage to your bay tree, get rid of scales as soon as you spot them. And keep an eye out after the scale infestation is gone. Once infested, a bay tree is likely to be revisited by scales. Catch it early and your tree will be fine.
Spray the bay tree with narrow-range horticultural oil. Cover the branches, leaves and twigs with the spray. Concentrate on places where the scale population is the most concentrated. They love to congregate in the nooks and crannies between branches and the underside of leaves. Follow the manufacturer's instructions when spraying.
Monitor the bay tree in late winter or early summer -- whichever is closest. During both of these seasons, scale insects become active and crawlers move up and down the branches. This is the best time to achieve effective control of scale populations.
Circle each infested branch with a strip or two of double-sided sticky tape. Make each sticky tape ring tight against the branch or twig so that the tiny nymphs cannot easily crawl underneath it.
Remove the tape once weekly and observe it with a magnifying glass. Count the yellow or orange crawlers stuck to the surface. Record the number.
Place a new strip of tape in the same locations.
Spray the bay tree a second time when the number of nymphs counted weekly declines slightly.
Spray again if necessary. Do not spray again before the interval recommended by the narrow-range horticultural oil.
Do not apply narrow-range horticultural oil when it is foggy, freezing, above 32.2 degrees Celsius or raining; on plants that are drought stressed; or within 30 days of a fungicidal treatment.