Pear Tree Problem: No Leaves
Spotting and preventing leaf loss is crucial to your pear tree's health in two ways. First, dropped foliage may be your first sign that a serious infestation or disease exists. Failing to address this initial symptom may ultimately lead to poor pear yield through blossom drop, damaged fruit and a general decline in the tree's health. Second, all trees need leaves in order to turn the light energy around them into chemical energy for growth and vigor -- the process known as photosynthesis. A tree's foliage is the only part of the pear tree that contains the green pigment, chlorophyll, necessary for transforming light into plant food.
Pear decline is a disease caused by the tiny foliage-feeding organisms known as pear psylla. The disease may cause pear trees to drop their leaves earlier than normal in late summer or fall. Other signs include rolled-up leaves, sooty mold on the trunk, distorted fruit and poor branch development. Cankers caused by the bacteria Pseudomonas syringae may cause leaves to drop in early spring. Other than the timing of the foliage loss, look for cankers that exude dark resin. Additional diseases to consider include blossom blast and fire blight, which affect foliage as well as other parts of the pear tree. In these cases, blackened and falling leaves will likely be accompanied by blackened branches, damaged fruit, and distortions on the trunk and branches.
In large enough numbers, spider mites are capable of causing total leaf drop on pear trees. The pest themselves look like tiny spiders, and are generally either bright red or brown. Even if you can't spot them, look for a lacy look to the dropped leaves, as well as decayed and misshaped flowers and fruit. Worms known as leafrollers can also cause pear trees to lose foliage. Examine the trees for damage to young leaves, partially consumed fruit, and rolled-up or lacy-looking leaves. The worms are either green or black depending on the subspecies.
Pest Control and Prevention
Keeping your pear trees from dropping their leaves obviously depends largely on diagnosing the underlying cause of the leaf drop. In general, pests known to cause pear leaf drop will themselves fall prey to beneficial insects. For example, destructive mites can be controlled with predaceous mites, lady bugs or lacewings. Encourage their presence in the garden by purchasing these beneficial insects at your local garden supply store, or by growing flat-blossomed herbs and flowers such as dill, yarrow and Queen Ann's lace. Making your pear orchard a friendly place for birds with water baths and shelters will reduce damage from fruit worms.
Disease Control and Prevention
Avoid diseases spread by pear psylla by choosing young pear trees created with hardy, disease-resistant rootstock. Some Asian rootstocks, for example, may be more vulnerable to the destructive organisms, and therefore more likely to drop leaves. Copper sprays and oil sprays can control diseases as well as some pests, but check with your extension service before resorting to them. Your first line of defense should be proper orchard sanitation practices, such as cleaning pruners and other tools between use; removing damaged tree parts, fallen leaves and fruit; and encouraging the beneficial insects that prey on disease-carrying bugs.
Ellen Douglas has written on food, gardening, education and the arts since 1992. Douglas has worked as a staff reporter for the Lakeville Journal newspaper group. Previously, she served as a communication specialist in the nonprofit field. She received her Bachelor of Arts from the University of Connecticut.