Gary W. Moorman, Professor of Plant Pathology
|ASTER YELLOWS||Plants are stunted with excessive branching and yellow, strap-shaped leaves.||Phytoplasma||Destroy infected plants. Maintain good insect and weed control in the greenhouse.|
|BOTRYTIS BLIGHT||Leaves, especially those near the soil surface, rot and become covered with gray fungal growth as do fading flowers.||Botrytis cinerea||Heat and ventilate to maintain low humidity. Remove dead and dying tissue from the greenhouse. Apply a fungicide.|
|DAMPING-OFF||Seedlings wilt and die.||Pythium spp.||Plant in pasteurized potting mix. Discard infected plants. Apply a fungicide.|
|PHYTOPHTHORA ROOT ROT||Roots rot and plants wilt and die.||Phytophthora primulae||Plant in pasteurized potting mix. Discard infected plants. Apply a fungicide to protect healthy plants.|
|RHIZOCTONIA CROWN ROT AND BUD BLIGHT||Roots and stems brown. Plants wilt and die. Older plants may fail to flower or produce new leaves.||Rhizoctonia solani||Plant in pasteurized potting mix. Discard infected plants. Apply a fungicide to protect healthy plants.|
|THIELAVIOPSIS ROOT ROT||Small black spots form on roots. Gradually, the entire root system browns. Old leaves die while younger leaves yellow.||Thielaviopsis basicola||Plant in pasteurized potting mix. Discard infected plants. Apply a fungicide to protect healthy plants.|
|VIRUSES||Leaves may be mottled, yellowed, or have dead spots or be curled. Plants are stunted. Flower color may break. Entire plants may die.||Tobacco necrosis, primrose mosaic, cucumber mosaic, impatiens necrotic spot, tomato bushy stunt, alfalfa mosaic, or tobacco ringspot.||Discard infected plants. Maintain good insect control, especially aphids and thrips.|
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