TOMATO DISEASES & INSECT PESTS Suann Leighow, Penn State Extension Master Gardener of Columbia County
As vegetable gardeners, we look forward to bringing in an armful of vegetables. Of these, tomatoes win the prize. Tomatoes may be the nation’s most popular garden vegetable. Whether you grow them in pots, raised beds, or a large garden, you must know about tomato diseases. Some of the most common fungal diseases that affect home-grown tomatoes include early blight, septoria leaf spot, and late blight. Early blight ( Alternaria solani ) is present worldwide wherever tomatoes are grown. Spores can spread in spring via wind or splashing rain. This fungus needs a wet surface to germinate and grow. Low leaves that drip with morning dew provide perfect conditions for early blight. Early blight first appears as circular,
irregular black or brown spots on older tomato leaves. As these lesions enlarge, a series of dark concentric rings develops in the center of the spot, creating the distinct target pattern of early blight. Septoria leaf spot is a destructive disease of tomato foliage. The petioles and stems are affected by the fungus Septoria lycopersici, but not the tomato fruit. Infection usually occurs on the lower leaves near the ground after plants begin to set fruit. Early septoria leaf spot symptoms are typically dark spots; eventually, the center of the spot becomes whitish to tan, sometimes with tiny, dark specks. The fungus is not soil-borne but can overwinter on residue from previous crops.
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