Cercospora is a very common disease of vegetables, ornamentals and other plants. It is a fungal leaf spot disease that usually occurs in late spring to early summer. Cercospora of strawberries can adversely affect crop yields and plant health. Get some tips on recognizing this strawberry leaf spot disease and how to prevent its occurrence.
Symptoms of Strawberry Cercospora Leaf Spot
We all look forward to those first chubby, ripe, red strawberries. The resulting strawberry shortcake and strawberry topped ice cream are just some of the joys. Leaf spot on strawberry can threaten the amount of fruit the plants produce, so it is important to know the initial signs of the disease and how to control cercospora, the fungus that causes the ailment.
The initial signs are small, round to irregular purple spots on the leaves. As these mature, they turn tan to whitish gray at the centers with purple edges. The center becomes necrotic and dry, often falling out of the leaf. The undersides of the leaves develop spots that are blue to tan in color.
The amount of infection depends upon the variety as some are more susceptible than others. Leaf drop often occurs and, in extreme infections of leaf spot on strawberry, the plant’s vitality is compromised, leading to less fruit development. The leaves on flowers will also turn yellow and dry up.
Causes of Cercospora of Strawberries
Strawberries with leaf spot begin to occur in late spring. This is when temperatures are warm enough but weather is still wet, both conditions that encourage the formation of the spores. The cercospora fungi overwinter on infected or host plants, seed and plant debris.
The fungus spreads quickly in periods of warm, humid, wet weather and where leaves remain damp much of the time. Because strawberries are colony plants, their close proximity allows the fungus to spread quickly. The fungi are spread by rain splash, irrigation and wind.
Preventing Strawberry Cercospora Leaf Spot
As with most plant diseases, sanitation, good watering techniques and proper plant spacing can prevent the occurrence of strawberries with leaf spot.
Keep weeds free of the bed, as some are hosts for the disease. Avoid irrigating plants from overhead when they will not experience enough sunlight to dry the leaves. Bury plant debris deeply or rake it up and remove it.
An application of fungicide at blossom time and just before fruiting can reduce the spread and incidence of the disease. Strawberry leaf spot disease rarely kills plants but they are limited in their ability to harvest solar energy to turn to plant sugars, which can diminish their health and productivity.