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Leaves turn slightly yellow, then brown, then wither.Įarly Blight: dark, sunken lesions at or above the soil line, sometimes called collar rot. Disease spreads upwards from oldest to youngest.

Leaf Spot: numerous brown spots appear on the leaves 1/16 to 1/4 inch in diameter spots are circular with dark brown margins and tan to gray center–a black speck in the center spots do not have a yellow halo. In humid, wet conditions, a fuzzy ring of mold around spot appears on the undersides of leaves.

Late Blight: water-soaked spots show first on lower leaves spots start out pale green diffuse irregular spots on upper side of leaf, usually near the edges of tips of leaves spots turn brown to purplish-black and velvety with pale green border on underside of leaf spots appear on young leaves at the top of the plant spots look water-soaked no concentric rings or defined border around necrotic spots. Large portion of leaf becomes a diffuse yellow and may drop. Leaf Spot: high humidity temperatures between 60° and 80☏.Įarly Blight: symptoms appear first on older, mature leaves near the base of the plant–one or two spots per leaf, spots ¼ to ½ inch in diameter spots have tan centers with concentric rings and yellow halos around the edges, target-shape appearance with defined border spots enlarge and coalesce. Watch for disease when cool, moist nights are followed by warm, muggy days. Infection often occurs before blossoming. Late Blight: high humidity temperatures between 60° and 80☏ wind-, rain-, and soil-borne. Early Blight: high humidity temperatures above 75☏ transmission hastened by wind, heavy dew, and frequent rain poor plant nutrition contributes.