| Disease |
Symptoms |
Pathogen/Cause |
Management |
| Aster Yellows |
Plants are stunted with excessive branching and
yellow, strap-shaped leaves. |
Phytoplasm |
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 azoxystrobin
or chlorothalonil |
| Damping-Off |
Seedlings wilt and die. |
Pythium |
Plant in pasteurized potting mix. Discard infected
plants. |
| Phytophthora Root Rot |
Roots rot and plants wilt and die. |
Phytophthora primulae |
Plant in pasteurized potting mix. Discard infected
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 PCNB or iprodione as a soil drench 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. |
| 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. |
