Detailed profiles of common plant diseases, pests, nutrient deficiencies and environmental problems.
White root rot is a serious soil-borne fungal disease caused primarily by Rosellinia necatrix. It attacks roots and root crowns of many woody plants,…
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Maple tar spot is a conspicuous fungal leaf disease caused by Rhytisma acerinum, most characteristically affecting Norway maple and some other European maples. Pale…
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Barley scald is a cool-weather fungal leaf disease caused by Rhynchosporium commune, formerly often identified as R. secalis. It produces water-soaked gray-green lesions that…
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Rhizopus stolonifer causes a rapidly spreading, watery soft rot of ripe fruits, vegetables, and storage roots, especially after harvest. Infection usually begins in bruises,…
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Rhizoctonia solani is a soilborne fungus that causes damping-off, wirestem, root and crown rot, stem and stolon canker, aerial blight, and tuber or fruit…
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Rhabdocline needle cast is a fungal disease of Douglas-fir that causes yellow spots, reddish-brown blotches, orange-brown fruiting bodies, and premature loss of current-season needles.…
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Raspberry bushy dwarf virus (RBDV) is a pollen- and seed-borne viral disease of raspberries, blackberries and related Rubus plants. Infected plants may show yellowing,…
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Ramularia leaf spot is a late-season fungal disease of barley caused by Ramularia collo-cygni. Infected plants may carry the fungus silently before flowering, then…
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Bacterial wilt is a serious vascular disease caused by the soilborne bacterium Ralstonia solanacearum species complex. It commonly affects tomato, potato, eggplant, pepper, tobacco,…
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Pythium ultimum is a soilborne oomycete that commonly causes seed decay, pre-emergence and post-emergence damping-off, and root rot, especially in seedlings grown in saturated…
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Pythium debaryanum is a soilborne oomycete, or water mold, historically associated with damping-off and root diseases in many crops and ornamentals. In the United…
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Pythium aphanidermatum is a warm-weather water mold that causes seed rot, seedling damping-off, root and crown rot, sudden wilt, and—in some crops—foliar blight. It…
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