Squash, Summer
Symptom Cause  
Water-soaked spots on leaves
Angular Leaf Spots
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Small, dark spots on leaves; eventually leaves turn black; fruits may blacken/drop
Anthracnose (on plants)
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Leaves wrinkled or curled; discolored, stunted, tend to fall off
Aphids
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Plants wilt quickly; white, sticky material might be seen when a stem is cut
Bacterial Wilt
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Holes in leaves
Corn Earworms
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Holes chewed in leaves, leaf stalk, stems; plant wilts, dies.
Cucumber Beetles
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Gray patches on lower leaves spread upward
Downy Mildew
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Meager harvest
Few Male Blossoms
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Yellowing of the leaf margins (chlorosis) is an early symptom on the plant, and light- to dark-brown spots (necrosis) can appear, plus water-soaked regions on the stem.
Gummy Stem Blight (black rot)
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Foliage yellowed or white mottling, glaze of honeydew; plant weakens
Leafhoppers
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Leaves skeletonized
Mexican Bean Beetles
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Mottled, crinkled foliage; brown specks appear on fruit, and plants may droop and die prematurely
Mosaic Viruses
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White spots on leaves; eventually entire leaf is covered with powder
Powdery Mildew
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Sunken green spots on squash
Scab
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Wilted; dried-up leaves
Squash Bugs
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Sudden wilting of plant
Squash Vine Borers
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Leaves discolored; black fecal spots on underside of leaf.
Thrips
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Weakened plants; yellow leaves; leaves discolored; covered with honeydew
White fly
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