CWA Dip. - Pests and diseases Flashcards
Oidium. What is it and how does it affect vines?
- Powdery Mildew. A Fungal Disease.
- occurs in dry warm weather.
- Affects all the green parts of the vine.
- Inhibits bunch development and ripening.
- If the vine is infected prior to flowering, yields will be reduced.
- If the vine is infected after fruit set, berries will struggle to achieve veraison and full size.
- Can lead to sour rot.
Peronospora. What is it and how does it affect vines?
Downy Mildew a Fungal Disease.
White downy fungal growth on underside of leaves that occurs in the wet, early part on tha season.
Attacks the green portions of the plant causing leaves to fall off and limiting the vines ability to photosynthesize.
Difficult treatment so preventation is practiced.
Arid climate and Bordeaux Mixture (Copper sulfate, water and lime) prevent outbreaks.
Botrytis (Grey rot), what is it and how does it affect the vines?
Botrytis Cinerea. Fungal disease
Infects ripe berries in humid weather.
Mainly attacks berries whith “tight” bunches such as Riesling, Gewurstraminer, Chenin, Pinot Noir and Semillon,
Also needed for “Noble rot” wines such as Barsac and Sauternes.
Sour rot, What is it and how does it affect the vines?
Secondary infection.
Cannot penetrate healthy grapes.
Normally enters grapes damamaged by hail, insects, or mildew.
Phylloxera, What is it and how does it affect the vines?
The infamous root louse that necessitates grafting of all vine plants.
Feeds on the roots
causes damage that leads to plant death.
No effective treatment except grafting onto resistant rootstock
Nematodes. What is it and how does it affect the vines?
Microscopic roundworms that feed on the roots.
Seldom terminal but affect health and vigour.
Gan be gassed pior to planting.
No effective erradication after planting.
Known to spread the fan leaf virus.
Mealy bug. What is it and how does it affect the vines?
Damages vines by feeding on plant fluids.
This doesn’t damage vines but, the bug excretes a sugary fluid (Honey dew) which attracts ants, makes the bunches sticky and unsutable for wine production.
Additional danger as they spread the Leaf roll virus.
Natural predators are effective. ie Wasps and ladybirds.
Snout beetle. What is it and how does it affect the vines?
Feeds on leaves and shoots of vines.
Oct to December
Very dangerous to young vines.
Can be controlled though spraying but the chemicals kill the predators of the Erinose beetle.
Erinose beetle. What is it and how does it affect the vines?
Tiny insects that attack leaves, causing blistering on top of the leaf and inhibiting photosynthesis.
Treated when evident with chemical sprays or sulphur dust.
Snails. How do they affect the vines?
Feed on young leaves and shoots.
Cause deformities and deficient leaf growth.
Controlled with snail bait before infestation.
ducks/geese.
Crown Gall. What is it and how does it affect the vines?
Bacterial infection.
Causes calluses on the roots just above or below soil level.
Similair to cancer causes cellular changes.
Compromises growth
Wastes growing energy.
Prevention before planting rather than cure.
Pierce’s Disease. What is it and how does it affect the vines?
Bacterial infection
“Anaheim Disease”
spread by sharpshooters (insects)
Affects vines and stone fruit.
Normally not found in areas with cold winters.
Shriveled fruit, leaf scorching, and premature shedding of leaves, with bare petioles remaining on the stem.
Viruses. What are they and how does it affect the vines?
Viruses are extremely small.
Don’t kill the vine but lead to poor yield.
No chemical treatment.
New infections are introduced by vectors (mealy bugs eg)
Plant virus free.
Leafroll virus - What is it and how does it affect the vines?
Very prevalent in SA
Causes leaves to curl.
Leaves turn dark purple on red varietals.
Leaves turn yellow with prominet green veins on white varietals.
Affects plants ability to photosynthesize.
