Gardening Help FAQs

Here are answers to some of the most common questions we receive about garden plants. You will find concise information on general gardening techniques as well as plant selection and care. For detailed information on specific plant pests and problems refer to our Common Garden Pests and Problems page.

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Horticulture Questions and Answers

What is causing my sycamore tree to drop leaves?

Anthracnose is a group of related fungal diseases that infect shade trees. Anthracnose generally infects the leaf veins and causes death of the veins and surrounding tissue. Symptoms include irregular, light brown spots of dead tissue which develops along the veins of the leaves. Affected plants may have the appearance of being sun scorched. Sunken red ovals, containing fungal spores develop on infected twigs. The fungal spores overwinter on fallen leaves and twigs infected the preceding year. Spread of the disease is favored by cool, moist spring weather. Unlike many anthracnose diseases that effect just the leaves of other species of trees, sycamore anthracnose will also attack the twigs and stem. Consequently, dead or dying twigs are evident.

Since the fungus overwinters in dead, infected leaves, fallen leaves should be collected and destroyed in the fall. Dead branches can also be pruned out of the trees if this is feasible. Disinfect pruning tools in a 10% bleach solution between cuts to prevent spreading the disease. Pruning will also provide better air circulation in the plant and reduce the period of time the leaves remain wet and vulnerable to inoculation. During the summer water during dry periods and fertilize as required to promote good plant vigor. For more complete control, use a spray, such as, Bordeaux mixture or Daconil. Begin spraying when the leaves begin to enlarge from the buds and reapply at 7-10 day intervals for two or three more times. Available fungicides are preventatives, not curative. Therefore they must be applied before spotting occurs. Since pruning and spraying of large trees can be expensive and require a tree care professional, evaluate how much of the disease you can tolerate.