Bay trees are tender evergreens with leathery lance-like leaves. The dried leaves are widely used as a seasoning for soups and stews. They are a component of the herbal "bouquet garni," which is a bundle of herbs added to flavor a simmering soup stock. The several varieties of bay trees are relatively pest and disease free, but are susceptible to attack by insects. Most of these can be successfully eradicated with consistent treatment until the infestation has passed.
Scales are insects that appear as brown-colored bumps on the stems and twigs of bay trees. They exude a sticky substance which adheres to the leaves and surfaces beneath the tree. Treat by applying rubbing alcohol with a cotton swab to the scales. Follow-up by spraying with rubbing alcohol at 10-day intervals until the infestation is gone.
Aphids are small white insects that suck on the juices of the plants. They concentrate on the leaves, stems and small twigs and can completely defoliate an untreated plant. Spray infected bay trees with insecticidal oil, following the manufacturer's directions.
Laurel wilt is caused by a non-native beetle, thought to have been introduced by infected firewood. These so-called ambrosia beetles primarily attack already stressed bay trees by boring into the wood. Symptoms include wilted foliage discolored to shades of red or purple. The foliage eventually turns brown but remains on the branches.