The plump red strawberry you see at your farm stand or supermarket is the end product of the growing season. Along the way, the leaves of the strawberry plant give the fruit the sustenance it needs to grow. Pests and disease can cause a variety of leaf symptoms that may damage your crop.
Discolouration of strawberry leaves can be an indication that the plant is the victim of disease or insect pests. Bugs that feed off the plants, including the strawberry root weevil, spider mite and spittlebug, can cause a widespread, uneven darkening of the leaves called stippling. Mold, fungus and powdery mildew can also appear on strawberry leaves, altering the colour. Cultural and chemical controls may be required for pest and disease management.
Slugs, tarnished plant bugs and strawberry root weevils all get their nourishment from the leaves of the strawberry plant, thus leaving the leaves damaged. Slug damage is evident by the large, non-uniformly shaped holes in the leaves. Root weevils feed mainly on the roots of the plant but can also eat notches into the sides of the leaves, thus making themselves evident. Holes in the leaves are not generally as large a problem as leaf discolouration or damage to the fruit, which can stunt growth.
Sticky substances surrounding the leaves of a strawberry plant can be a sign of problems. Spider mites make themselves known by the sticky web they leave, and a silvery trail of goop is the calling card of the slug. Gray mould and powdery mildew on the leaves of the strawberry plant also can be sticky to the touch.
Cultural controls are preferable to chemical controls to lessen the exposure of toxins to the fruit of the strawberry plant. Keeping the fields adequately irrigated without leaving them excessively moist can combat mildew, rot and some insect pests. Tilling the soil under the plants before planting next year can upset any remaining root weevils and may prevent an infestation. Vinegar-based herbicides may be effective in driving away pests in lieu of commercial pesticides, but in cases of severe infestation, chemicals may be the only option.