Of the several diseases that attack strawberries in Indiana, the leaf spot diseases -- leafspot, leaf scorch and leaf blight -- are by far the most common and conspicuous. None of them will destroy infected plants. But they may destroy enough leaves so that the plant will look ragged, produce poor quality berries and frequently winter kill.
The early symptoms of leafspot and leaf scorch are very similar. Leafspot usually occurs early in the spring. The first symptoms are round, purple spots 1/8 to 1/4 inch across on the upper side of the leaves. At first, the whole spot is purple. Later, the center becomes tan or gray, then almost white. The border remains purple. On the underside of the leaves the spots appear as irregular tan or bluish areas. Leafspot may also occur on the leaf and fruit stems, runners and green fruit caps. On the fruit it causes black areas, referred to as black-seed.
Leaf scorch is found only on the leaves. It usually occurs later in the season than leafspot. The early symptoms are small, dark purple spots on the upper surface of the leaf. But unlike leafspot, the spots remain purple, and the centers never turn tan or gray. When the spots cover most of the surface, the leaf dries up and looks scorched.
A third disease -- leaf blight -- usually damages the leaves of old plants after harvest. it seldom damages vigorous old plants or young runner plants. Leaf Blight is easily distinguished from the other leaf diseases. Large red to brown spots are usually surrounded by a purplish margin. These spots will vary from 1/4 inch to more than 1 inch in diameter and may be circular, elliptical or triangular.
These diseases are caused by fungi that survive the winter on old, dead, infected leaves. In the spring the fungi produce spores that infect young leaves and start the disease for another season. Leaf spots are not a problem in newly established patches, but may be expected to become progressively more serious as plants get older.
Frequent and heavy showers in the spring, when strawberry leaves are developing, usually lead to leaf spot troubles. Shady locations and poorly-drained soils also favor development.
To reduce the damage of leaf spot diseases in the home garden, follow these suggestions:
Plant strawberries in sunny locations with good drainage, whenever possible. Keep weeds and grass out of the planting since they give rise to shade and moisture. Don t plant varieties susceptible to leaf spots if these diseases have been a problem in the past.
Fungicide applications are generally not needed if beds are fruited one season. When needed, fungicides should be applied during the spring and fall months. Captan is the suggested fungicide of choice for control of leaf spot diseases. Be sure to follow ALL label instructions when using pesticides.
It is the policy of the Purdue University Cooperative Extension Service, David C. Petritz, Director, that all persons shall have equal opportunity and access to its programs and facilities without regard to race, color, sex, religion, national origin, age, marital status, parental status, sexual orientation, or disability.
Purdue University is an Affirmative Action employer.
This material may be available in alternative formats.