| Disease |
Symptoms |
Pathogen/Cause |
Management |
| Anthracnose |
Dead spots 1/8 to 1/4 inch with dark-brown margins
and gray centers form on leaves. Dark concentric lines form
within the spots. Sunken brown to tan spots form on stems, girdle
them, and kill the plant. |
Colletotrichum violae-tricoloris |
Apply mancozeb or thiophanate methyl + mancozeb
during wet weather. Destroy plant debris at the end of the season. |
| Cercospora Leaf Spot |
Small black,
circular spots form on the lower leaves under moist conditions. |
Cercospora |
Apply mancozeb, myclobutanil, triadimefon, chlorothalonil,
or thiophanate methyl + mancozeb to protect plants. |
| Fusarium Wilt |
Plants wilt and die quickly. Roots are rotted. |
Fusarium oxysporum |
Destroy infected plants. |
| Pythium Root Rot |
Lower leave yellow as root rot. This is easily
confused with Thielaviopsis root rot. |
Pythium |
Plant in pathogen-free potting mix. Avoid overwatering.
Discard flats of infected plants. Apply mefenoxam, propamocarb,
etridiazole + thiophanate methyl, metalaxyl, or fosetyl-Al carefully,
especially to young plants that can be stunted by fungicides. |
| Scab |
Round spots up to 1/4 inch in diameter that are
yellow or cream colored form on any part of the plant. Spots
are slightly raised and appear scabby. Infected leaf tissue
may fall out leaving holes in the leaf. Stems are girdled and
plants die. |
Spaceloma violae |
Apply mancozeb, or thiophanate methyl + mancozeb
during wet weather. |
| Stunt |
Young plants are stunted and thick. |
Lack of boron |
Maintain a soil pH below 7. Have a water test
done to be certain calcium and sodium are not too high. |
| Thielaviopsis Root Rot |
Roots have black spots as dark walled microscopic
spores form in them. Many roots are killed. Microscopic
thin walled spores
also form on infected tissue. Lower leaves yellow. This is easily
confused with Pythium root rot. |
Thielaviopsis basicola |
Plant in pathogen-free potting mix. Avoid water
and heat stress, particularly on plugs. Discard flats of infected
plants. Fungicides will not cure plants once infected. Apply
thiophanate methyl or triflumizole to protect plants. |
| Virus |
Plants are stunted and rosetted. Plants may be
completely yellow. Abnormal streaks of color form in the flowers.
Flower parts may curl inward. |
Curly top and cucumber mosaic viruses |
Destroy infected plants. |
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