The leaves of an apple tree should provide a lush, green backdrop to the shiny skins of the maturing apples during the late summer and fall, and the bright flowers the tree produces preceding fruit production. When the leaves become discolored, unhealthy and brown, however, the health of the harvest is at stake.
Effects of Brown Leaves
As the leaves become brown, they stop photosynthesizing. The leaves might die and fall from the tree, or curl and remain on the branches, where they can host pests and fungi. Leaves that are not photosynthesizing are not aiding in the tree's process of growth; this failure to photosynthesize stops the production of nutrients and energy for growing fruit, which leads to weak or emaciated apples. Brown leaves are a symptom of a larger problem.
Brown leaves are caused by a variety of problems, some of them working alone and some of them working in tandem to attack the apple tree. Pests are one source of brown leaves; severe and uncontrolled infestations of pests like aphids, mites, scale insects, caterpillars and beetles leads to severe defoliation of the tree, and dead, brown leaves. Fungal problems like root rot cause brown leaves, as can problems within the apple tree's growing environment.
Pesticides and Fungicides
Control external threats to an apple tree, like apple scab, fire blight, powdery mildew and aphids, with the application of pesticides and fungicides throughout the growing season. Adding chemical protection to the apple tree makes it less likely that the apple tree will become susceptible to pest and disease problems that cause its leaves and later its apples to become affected. Follow all directions when applying chemicals to an apple tree for the best results.
The growing conditions of an apple tree affect the health of its leaves, the apples and the longevity of the tree itself. Standing water or a total lack of water are equally damaging, and both conditions can lead to brown leaves on the apple tree. Apple trees growing in the shade and without the proper nutrients in the soil are more likely to have problems with brown leaves than those with healthy soil and sunshine.