| Disease |
Symptoms |
Pathogen/Cause |
Management |
| Aster Yellows |
Leaf-like tissue forms where flower
parts should be located. Flower-like parts remain green or light
green. Often flowers on only one side of the spoke show symptoms.
Sepals may be very large or dwarfed. |
Phytoplasm |
Destroy infected plants. Control
leafhoppers. |
| Bacterial Bud Rot, Crown Rot, and
Stem Rot |
Yellowed leaves and stunting occurs.
Blackened stem bases around cracks and wounds mark the point
of entry. Smelly ooze forms under wet conditions. Infected stems
topple. |
Erwinia
carotovora and Erwinia
chrysanthemi |
Promptly destroy infected plants.
Avoid planting in low, wet areas. Avoid overhead irrigation. |
| Bacterial Leaf Spot |
Black, irregularly shaped spots form
on leaves. Seedlings are killed. |
Pseudomonas
syringe |
Destroy infected plants. |
| Diaporthe Blight |
As the plants flower, lower leaves
brown and die. Brown spots form on the stems at the soil line
and expand upward several inches. Small, black, pimple-like
fungal fruiting structures develop on infected tissue. |
Diaporthe |
Destroy infected plants. Use seed
known to be free of the fungus. |
| Fusarium Wilt and Canker |
Small brown spots form on stems and
enlarge. Brown, sunken lesion may occur on petioles. Stem cankers
may be dark brown and 12 inches long. As the canker tissue dies,
masses of pink spores form in clumps. Wilting plants have vascular
tissue that is browned. |
Fusarium
oxysporum |
Destroy infected plants. |
| Powdery Mildew |
Dry, white, mealy, fungal growth
occurs on the upper surface of leaves. Leaves turn yellow and
die from the base of the stem upward. |
Erysiphe
polygoni |
Apply a triadimefon, myclobutanil,
mancozeb, triforine, ziram, Ampelomyces,
or fenarimol when the fungus is first observed. Destroy plant
debris at the end of the season. |
| Storage Rot |
Tubers decay into a soft, smelly
mass. |
Various fungi and bacteria. |
Avoid wounding the tubers when digging
them for storage. Let the tuber surfaces dry after digging and
removing soil and before storing. Store tubers in a cool, dry
location. |
| Virus |
Conspicuous rings and line patterns
may be present and plants are stunted. |
Cucumber and tobacco mosaic viruses. |
Destroy infected plants. |
