Botrytis Bunch Rot in Grapes - Vineyards add to line
Symptoms
Brown lesions on the trunk at the beginning of the season; grapes covered with a gray to tan powder; stems and grape clusters shrivel
Agent
Fungus
Conditions for Disease Development
The disease occurs at high levels of humidity and high temperatures.
Control Methods
Plant less sensitive varieties; reduce the amount of vegetative growth on vines; do not over-fertilize; use appropriate trellises to increase air circulation in the canopy and expose grape clusters to the sun; the disease usually warrants chemical control.
Root Rot in Grapes
Symptoms
Weak, short shoots; white fungal mats under the bark at the soil line; unproductive vines; rapid wilting
Agent
Fungus
Conditions for Disease Development
No known Armillaria-resistant grape variety
Control Methods
Fumigation may be necessary in soils known or suspected to carry the disease.
Eutypa in Grapes - Vineyards
Symptoms
Stunted, wilted leaves curled in the shape of a cup; dark-colored cankers on the wood; cross-section of the wood reveals wedge-shaped discoloration
Agent
Fungus
Conditions for Disease Development
Affects older vines that are five to six years old
Control Methods
No known resistant variety; a disease that is almost impossible to control without chemicals in areas where alternative hosts are present; using an appropriate fungicide on pruning wounds can prevent the fungus from entering the plant; fungicide should be applied during pruning.
Powdery Mildew in Vineyards
Symptoms
red spots on canes; yellow spots on the upper surface of leaves; white powdery growth on leaves; white powdery growth on fruit
Agent
Fungus
Conditions for Disease Development
The disease favors mild temperatures and high humidity
Control Methods
Plant vines in locations with good air circulation and sun exposure; use a training system that promotes air circulation throughout the canopy; apply sulfur or copper-based fungicide
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