Fragrant leaves from the bay leaf plant (Laurus nobilis), also known as the bay laurel, are prized for the delicate flavor they impart to cooked foods. The tree itself originates in the Mediterranean and can grow as tall as 40 feet, although they can also be trimmed and grown as shrubs. The plants are ideal for U.S. Department of Agriculture plant hardiness zones 5 through 9, but require some care to keep them safe from pests and disease.
Armored scales are tiny insects with a hard, flat shell. Both greedy and Oleander scales feed with sharp mouthparts, affixing themselves to trees like barnacles. Though these species typically don't cause much harm, in large numbers they're problematic and may cause bay leaves to yellow and die. Scales are best controlled by introducing predators, such as lacewings and parasitic wasps, and avoiding pesticides, which kill these natural enemies.
Canker diseases are caused by fungus and leave sores on affected plants. Dark, sunken nectaria cankers grow slowly, becoming large and target-shaped as they develop. To treat canker, infected branches should be pruned and the shears sterilized between cuts to prevent spreading the fungi. Botryosphaeria canker works below the tree's bark, causing dieback and wilting as it progresses, in addition to recessed sores. There is no cure for this disease, so keep bay leaf plants hearty and stress-free to avoid infection.
Taking their name from their ability to burrow into the wood of trees, borers can cause serious damage. Branch and twig borers, a type of beetle, make their way into branches and twigs to lay eggs, often weakening them to the point of death. Lead cable borers are similar, tunneling through wood as they feed on it. To fight both kinds of borers, bay leaf plants should be kept vigorous so they can withstand damage, while infested branches and twigs require pruning.
Wood Decay Diseases
There are various types of wood decay disease, all of which develop quickly and are caused by fungus. Often taking the form of rotted wood and fungual fruiting bodies, like mushrooms, wood decay may also be contained in the tree's internal heartwood. The disease is is best avoided by avoiding injury to bay leaf plants, as it typically begins in wounds. Keeping the plants well watered, mulched and fertilized also helps them fight infection.
- University of California Davis:
- University of California Davis: Scales
- University of Wisconsin Cooperative Extension: Nectaria Canker
- Virginia Cooperative Extension: Botryosphaeria Canker and Dieback of Trees and Shrubs in the Landscape
- University of California Davis: Branch and Twig Borers
- University of California Davis: Lead cable borer
- University of California Davis: Wood Decay Fungi in Landscape Trees
- Royal Horticultural Society: Bay Laurel Tree
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