The laburnum, more commonly known as the golden chain tree, is a deciduous tree blossoming with bright yellow panicle-shaped flowers. Before planting this tree, be aware that there are several plant diseases associated with the laburnum.
Leaf Spot Disease
Leaf spot disease, which causes brown blotches on leaves, is a common problem for many trees and shrubs, including the laburnum. It is usually caused by fungal infections. The fungi thrive best in cool wet weather, and leaf spot disease is rarely a problem when the weather is warm and dry. Leaf spot disease is not a threat to a tree unless it has been recently transplanted. In this case, home gardeners should apply two to three applications of fungicide: first early in the spring when the leaves are just unfolding, and again after a week or two. If it is very rainy, a third spray may be necessary.
Twig blight is another common disease in laburnum trees. Like leaf spot, it causes discoloration of branches, especially newly developing branches, and is also caused by a fungus. To control this disease, prune infected twigs when the tree is dry to prevent further infection. Weekly applications of benomyl or fixed copper should also be applied all season to protect from infection.
Laburnum trees that are over-watered or have a fungus in their soil may be at risk for root rot. The symptoms of this disease are yellow leaves and a wilted appearance. If a laburnum tree looks like this, check the roots--black, mushy roots are affected by root rot, while healthy roots are firm and pliable. To treat root rot, remove the tree from the soil and gently wash away as much soil as possible from the roots. Use scissors or shears to trim off the affected roots. If you must remove many roots, compensate by trimming away a third to half of the leaves as well. Get rid of any soil that was around the tree roots, and treat the remaining roots with a fungicide. Replant the tree in clean, unaffected soil. If the tree is very large, it may be impossible to treat this disease.