Disease Descriptions and Management
When planting strawberry varieties, plant disease-resistant varieties when possible. For strawberry variety descriptions, see Table 8.1. Basic cultural guidelines for the control of plant diseases are discussed under Pest Management. Table 2.4 lists pesticides available on various fruit crops for the control of diseases.
Fruit growers can use many methods to control strawberry diseases, all of which are important to successful disease control. Fungicides are only one of the control options and are not always successful. Table 8.2 summarizes the control options and their effectiveness for each of the strawberry diseases. Table 8.3 describes the effectiveness of fungicides on strawberries. Table 8.4 describes the occurrence of insects and mites on strawberries, and Table 8.5 and Table 8.6 provide information about pesticide use. A general discussion of insect management appears in Pests and Pesticides.
Anthracnose is caused by several different species in the genus Colletotrichum. These fungi cause a fruit rot, crown rot, and/or leaf spots, as well as lesions on petioles and runner stolons.
Black root rot is known as a "disease complex," meaning that it can be caused by several factors.
Gray mold, or botrytis blight, is a common disease of a number of nonwoody plants worldwide and causes a greater loss of strawberry flowers and fruit than any other disease. It is found on green as well as ripening and harvested fruit.
A wide array of leaf spots infect cultivated and wild strawberry species, including birds-eye leaf spot, black leaf spot, septoria leaf spot, cercospora leaf spot, alternaria leaf spot, red spot, and angular leaf spot.
Angular leaf spot is caused by the bacterium Xanthomonas fragariae, which causes a water-soaked lesion on the lower leaf surface. Under moist conditions, the bacterium produces an exudate that appears as a whitish, scaly film when dry.
Leather or crown rot occurs in most temperate regions of the world on a wide variety of plants. Infection is favored by warm, wet weather and poorly drained soil.
Powdery mildew occurs on a wide range of hosts and almost everywhere the strawberry is grown. It is observed mostly as a foliage disease, but it occasionally causes a serious fruit rot. Severe foliar infection can damage leaves and reduce photosynthesis.
Red stele, or red core, is the most serious disease of strawberry in areas with cool, moist soil conditions. This disease develops primarily in soils that are heavy in clay content and saturated with water during cool weather.
Verticillium wilt of strawberry, caused by the soilborne fungus Verticillium albo-atrum, occurs throughout the temperate zones of the world, infecting more than 300 kinds of cultivated plants. Its hosts are annual and perennial crops as well as weed species.
The following practices will help reduce damage from insects and diseases.