Crystal Floyd
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SEPTORIA LEAF SPOT OF TOMATO
Crystal Floyd |
Septoria leaf spot is caused by the fungus Septoria lycopersici. Septoria can affect many parts of tomato plants, commonly causing leaf spots and stem lesions. The fungus can survive winter on diseased plant debris or on perennial weeds such as nightshade. In the spring, the fungus produces spores that are windblown or rain-splashed to healthy tomato leaves, causing primary infections.
Symptoms usually begin to appear on the lower leaves after fruit set. Initially round, yellow spots develop. Later, these spots enlarge and turn brown to gray. Tiny black fruiting bodies (pycnidia) eventually form in the center of the leaf spots. These pycnidia produce spores which cause secondary infections, usually in an upward direction, throughout the plant. Heavily infected leaves turn yellow, then brown and fall from the plant. Exposed fruit, due to defoliation, may be damaged by overexposure to the sun (sunscald).
Control of septoria leaf spot should focus on reducing the number of spores that survive winter and the number of secondary infections. Reducing the number of spores that cause primary infections can be accomplished through cultural practices such as sanitation, crop rotation, and planting resistant varieties. Sanitation involves the removal of all plant material and weeds throughout the season, as well as after harvest. Planting disease-free seeds, plants, or resistant varieties can help control septoria leaf spot. To reduce secondary infections, limit standing water on the leaves by watering plants at the base in the morning and staking plants to improve air circulation. Apply mulch around the base of plants to minimize water splash.
Fungicide applications may be necessary during rainy seasons. Read the label carefully and apply only as directed. Fungicides currently labeled for use are:
Representative trade names may be included along with generic names. This information is supplied with the understanding that no discrimination is intended and no endorsement is implied.
P232S
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