There are brown streaks in my apples. What is the cause and how can it be prevented?
The brown streaks in the apples are probably due to the apple maggot. The apple maggot is the most serious insect pest of apples in Iowa. Apple maggot damage appears as knobby, misshapen fruit with small pits or blemishes on the fruit surface. In addition, brownish streaks run through the flesh of the apple. The apple maggot is occasionally referred to as the “railroad worm” because of the slender brown streaks or tracks in the apple’s flesh.
The apple maggot is a type of fruit fly. Female apple maggot flies insert eggs beneath the skin of fruit from about mid-June until shortly before harvest. The punctures produce small holes that later appear as blemishes on the fruit. Upon egg hatch, the larvae tunnel through the flesh of the apple producing the distinctive brown streaks.
Control of apple maggot is difficult. Picking up and destroying apple maggot infested apples that have fallen to the ground is somewhat helpful. Placing apple maggot traps (red spheres or yellow cards coated with a sticky substance) in apple trees usually provide satisfactory levels of control. Insecticides are the most commonly used method of controlling apple maggots in commercial and home orchards. Insecticides should be applied from mid-June through September. Suitable insecticides for home gardeners include Sevin and any of the home orchard type sprays. Despite regular spraying, apples in many home gardens suffer substantial apple maggot damage due to poor spraying techniques, rainy weather, and other factors.