Sparking wine is prone to Fungal Disease and Virus infections Flashcards
Describe Powdery mildew in a vineyard?
Fungal disease Erysiphe Necator commonly called Oidium Tuckeri
V. vinifera more vulnerable than AM species
Introduced to EU in mid 1800s, most widespread around the world
-high susceptible: Chard & Cab Sauv
-less susceptible: PN and Riesling
Symptoms of Powdery Mildew?
Overwinters in buds and on canes. Attacks young, green parts
- starts to dull grey in patches then turns black
- attacks young shoots, inflorescences & grapes =reduce yield
- split at veraisoin è target for other infections
- growth rate determined by temp. optimum around 25c/77F
Thrives in shade, can spread in relatively dry, dense, shady conditions
What are management options for Powdery Mildew?
-keep open canopy, reduce shade & density of leaves
-application of Sulfur
- spray vines from couple of weeks after budburst up to veraison
- systemic fungicides can be effective if they penetrate green tissues and are not washed off by rain
- some fungus can become resistant – limited application in one year
Describe Downy Milder in a vineyard?
Fungal disease caused by Peronospora (water mold that lives in vine tissue)
-introduced from N AM in late 1800s
Symptoms of Downy Mildew
-attacks green parts of plants, especially young leaves & flowers
Threat of defoliation
- needs rainfall and warm temp (20C/ 68F) to spread
- high risk periods are warm spring & stormy warm summer
- symptoms are yellow, circular ‘oil spots’ on underside of leaf
What are management options for Downy Milder?
- spray made from copper salts
- Bordeaux Mixture is a combo of copper sulfate and lime
Standard treatment from the 1880s
- protection only until 20mm or rain fallen
- other fungicides can be used applied from about a month after budburst to veraison
- good drainage and open canopy that dries quickly help to avoid spreading
Describe Fanleaf Virus in a vineyard?
Viruses
- long standing group of diseases found around the world
- early shoot stunted, canes grow in distorted ways & leaves very pale, malformed and can look like a fan
- effect: can vary from little effect to loosing most of the crop
- Susceptible: Cab Sauv
How does Fanleaf virus spread?
- spread by move to grafted vines following Phylloxera and the inadvertent use of infected plant material
- otherwise spread by daggered nematode
What are management options for Fanleaf Virus?
no cure, eventually affected vines will have to be removed
- adding to cost
- before vineyards are replanted, soil tests should be done to check for the presence of dagger nematodes and only virus tested
- clean planting material should be used
Describe Leafroll Virus in a vineyard?
Viruses -widely present around the world
- spread by grafting & by mealy bugs
- key pest in South Africa, the Mediterranean, Argentina, and some parts of California
What are the symptoms of leafroll virus?
- condition will not kill vines, it will reduce yields by up to half
- slows down growth of roots & shoots
- surviving fruit may take additional weeks to ripen & have more acidity, less color, and lower sugar levels
- health of vine also affected- store less carbohydrates
- typically, downward rolling leaf – usually occurs in autumn
- symptoms not always clear, must be tested in lab
- mealy bug in S Africa, Med, Argentina, and some parts of CA
What are management options for Leafroll Virus?
- no cure – only solution is to remove unproductive vines and replant
- nurseries can screen vines for virus infections
- mealy bugs favor humid env & therefore open canopies help to reduce
- spray is difficult b/c mealy bug’s waxy coating
- natural predators are ladybugs, lacewings
Describe Gray Rot in a vineyard?
Fungal disease Botrytis Cincerea
- affects yield, quality, color, body, aroma
- affected fruit selected out at harvest
- spores are present in vineyard & become active after rainfall & high humitidy
Vulnerable species: Semillon, sauv blanc, PN
Symptoms of Grey Rot
Affected at any point- grapes rubbed against each other in tight bunches, or punctured by birds/ insects
- whole bunch can then be attacked
- varieties w/ tight bunches or thin skins are most at risk
Semillon, sauv blanc, PN
-if flowers are affected, fungus can stay dormant in grape and re-emerge after verasion
What are management options for Gray Rot?
- selecting grape varieties that have small grape w/ thick skins (PV)
- keep open canopy and remove leaves around bunches
- traditional sulfur and copper sprays are ineffective- but other fungicides can be used used:
- Applied when flowering is complete,
- at end of grape formation
- at bunch closure (when grapes start touching each other) -at veraison
