Chapter 8 - Part 3: Diseases Flashcards
What is powdery mildew
Fungal disease
It overwinters in buds and on canes. Then attacks young green parts of the vine
Show grey patches that become black patches
It damages young shoots, inflorescences, and grapes - reduces yield
Grapes can split at veraison
The fungus thrives around 25C and in shady conditions. does NOT need humidity
Powdery Mildew Management
- keep an open canopy and reduce shade
- application of sulfur to prevent and treat disease from couple wks after budburst up to veraison. Important to spray early because easier to prevent than contain
- systemic fungicides but fungus can become resistant
What is downy mildew?
caused by a water mold that lives in vine tissue
attacks green parts of the plant, esp young leaves and flowers, reducing yields by defoliating vine
needs rainfall and warm temps (20C) - stormy, warm summers, warm springs
Symptoms are yellow, circular oil spots and white, downy fungal growth on underside of leaves
Downy mildew management
- copper spray (Bordeaux mixture)
- fungicides
- good drainage and open canopy that dries quickly
What is grey rot
fungus that results in loss of yield, drop of quality in wine (color, body, aroma)
affected fruit should be removed
punctured grapes are most vulnerable
if the flowers are affected, the fungus can stay dormant in the grape and reemerge after veraison
grapes with tight bunches or thin skin are most at risk
thrive in high humidity
Grey Rot Management
- selecting varietals with thick skins and small berries
- open canopy, removing leaves around bunches
- using antagonistic bacteria
What is eutypa dieback?
AKA Dead arm
fungal trunk disease that leads to rotten wood in vines and affect whole vineyards
reduces yields and kills vines over a 10yr period
spores spread by wind over long distances
infection occurs thru pruning wounds in mod temps and during rain
causes stunted shoot growht and yellow leaves
Eutypa Dieback management
- pruning late and applying fungicide to pruning wounds
- affected trunks can be cut back 5-10 cm beyond the visible symptoms and treated with fungicide. Dead wood must be burnt to avoid spores spreading
What is phomopsis cane and leaf spot
fungal disease that causes a reduction in yield
prevalent in years with cool and wet springs followed by humidity and moderate temps
infected canes whiten and break off easily. The shoots growing from these canes develop brown cracks at their bases
Phomopsis Cane Management
Apply fungicide 3 wks after budburst and then every 2 wks if wet conditions continue
Diseased and dead wood removed and then burned
Improve air flow within canopy to reduce risk of disease
What is Esca
fungal disease caused by a group of organisms prevalent in warmer, drier climates
Enters the vine thru pruning wounds
Symptoms: tiger striping on leaves and spotting inside the wood
reduces yield and leads to plant death
Esca Management
no chemical controls. only prevention
sourcing disease-free stock
gentler pruning techniques, not pruning in the rain, removing prunings promptly from the vneyard, disinfectng pruning wounds
What is Pierce’s Disease
bacterial disease that quickly kills vines
bacteria lives in the sap channels of vines, clogs the channels, causes grape to shrivel, leavess to drop, and death of vine in 1-5 years
spread by the sharpshooter insect (vector)
Pierce’s Disease Management
no chemical control
reduce number of sharpshooter insects - removing vines close to rivers, chemical insecticides, introducing natural predators
strict quarantine rules for moving plants
What are grapevine yellows
group of bacterial diseases
no treatment available
spread by vectors including leafhoppers and diseased stock from nurseries
Symptoms: delayed budburst, drooping posture bc new shoots fail to become woody, canopy turns yellow (in white varieties) and red (in black varieties)
Reduces yields and lowers quality
