Diseases Flashcards
Powdery Mildew
(conditions, symptoms, management)
This is caused by the fungus Erysiphe aka Odium Tuckeri was introduced in Europe in the mid-1800s. Chardonnay and Cabernet Sauvignon are very susceptible.
Preferred Conditions:
Dry, shady conditions around 25C/77F
Symptoms:
1) grey then black patches
2) damage to young shoots, inflorescences, and grapes
3) grape splitting at verasion, creating a target for infection
4) reduction in yields
Management:
1) reduce shade via pruning
2) sulphuric spray a couple weeks after bud burst until verasion
3) systemic fungicides, but if applied enough it grows resistant
Downy Mildew
(conditions, symptoms, management)
This is caused by Peronospora, a water mold that lives in vine tissue. Introduced from North America in the 1800s and is not present in every growing region.
Preferred Conditions:
Rainfall and warm temperatures above 20C/68F
Symptoms:
1) attacks green parts, especially young leaves and flowers
2) yellow circular “oil spots” on leaves
3) white fungal growth under leaves
4) defoliates vine, reducing photosynthesis
Management:
1) cooper salt sprays
2) fungicides
3) good draining and an open canopy
Grey Rot
(conditions, symptoms, management)
This is caused by the fungus Botrytis Cinera. The flowers affected in the spring can hold the dormant fungus until after verasion. Semillon, Sauvignon Blanc, and Pinot Noir are very susceptible.
Preferred Conditions:
Humidity
Symptoms:
1) damaged fruit
2) reduced yield
3) reduced quality
4) creates a target for infection
Management:
1) thick-skinned grapes
2) open canopy around grapes
3) fungicides at the end of flowering, at the end of grape development, and at verasion
4) antagonistic bacteria like Bacuillus subtilis
Eutypa Dieback aka dead arm
(conditions, symptoms, management)
A fungal disease capable of taking down whole vineyards. Present in South Australia, South West France, and California. Grenache, Cabernet Sauvignon, and Sauvignon Blanc are very susceptible.
Preferred Conditions:
Spores are spread via wind and rain in moderate climates, open wounds are especially susceptible.
Symptoms:
1) rotten wood in vines
2) stunted shoot growth
3) yellowing leaves
4) reduction of yields
5) death of the vine within 10 years if not dealt with
Management:
1) pruning late and applying fungicides to wounds
2) cut 5-10cm beyond visible symptoms
3) biological controls, Bacillus subtilis
4) if very bad retrain from low-down sucker
Phomopis Cane and Leaf Spot
(conditions, symptoms, management)
Fungal disease that Grenache is extremely susceptible to.
Preferred Conditions:
Cool, wet springs followed by moderate temperatures and humidity.
Symptoms:
1) canes whiten and break
2) shoots develop brown cracks at base
3) reduction in yields
Management:
1) fungicides 3 weeks after bud burst and every 2 weeks afterwards
2) removal of diseased wood to be burnt or buried
3) canopy management reducing humidity
Esca
(conditions, symptoms, management)
Preferred Conditions:
Warm, dry climates with open wounds on vines.
Symptoms:
1) tiger-striping of leaves
2) splitting inside of the wood
3) reduced yields
4) death within a few years
Management:
1) no chemical controls
2) prevent via sourcing disease free stock, less detrimental pruning, never pruning in the rain, disinfecting pruning wounds, and remove prunings from the vineyard
List all fungal diseases (10)
Powdery mildew
Downy mildew
Grey rot
Eutypa dieback
Phomopis cane and leaf spot
Esca
Black rot
Black-foot disease
Bot canker
Anthracnose
Pierce’s Disease
(symptoms, management)
A bacterial disease where the bacteria clogs the vines sap channels and kills the vine. It originated in South and Central America but the glassy winged sharpshooter caused rapid spread in the 1980s.
Symptoms:
1) lab tests as symptoms are generally unclear
2) grape shriveling
3) leaf dropping
4) death within 5 years
Management:
1) no chemical controls
2) prevent via quarantine or reducing the vector (remove vines near river, insecticides, introduce wasps)
Grapevine Yellows
(symptoms, management)
The most common type of this bacterial disease is flavescence doree which spread through France in the latter half of the 1900s. It is spread via leafhoppers and untreated nursery stock. Now present in Germany, Southern Europe, New York State, and Australia.
Symptoms:
1) delayed bud burst
2) new shoot fails to become woody, causing a droopy posture
3) canopy turns yellow/red
4) reduced yield
5) reduced quality
6) susceptible varietals can die
Management:
1) no chemical controls
2) prevent via bathing nursery stock in hot water and reducing the vector (insecticides, remove cover crops)
List all bacterial diseases (4)
Pierces disease
Grapevine yellows
Bacterial blight
Crown gall
Fanleaf Virus
(symptoms, management)
A long standing group of viruses that cause mass crop loss, found globally. Spread widely via phylloxera and now dagger nematodes.
Symptoms:
1) stunted early shoot growth
2) distorted canes
3) pale leaves, sometimes in the shape of a fan
4) susceptible varietals lose majority of crop (Cabernet Sauvignon)
Management:
None. Test soil for dagger nematodes and replant.
Leaf Roll Virus
(symptoms, management)
A virus largely spread by grafting and mealy bugs in South Africa, the Mediterranean, Argentina, and California.
Symptoms:
1) lab tests as symptoms are unclear
2) slowed root and shoot growth
3) downward rolling of leaves
4) change in leaf color to red/yellow in autumn
5) reduces yields by half
6) reduces quality
7) adds weeks needed to ripen
8) lessens carbohydrate stores
Management:
None.
1) nurseries must screen for viral infections
2) reduce mealy bug populations reducing humidity and introducing natural predators (ladybugs, lacewings)
