Ch. 8: Hazards, Pests, and Diseases Flashcards
Advective frosts
A type of frost caused by large volumes of cold air moving in from very cold areas. Sprinklers are the only method that manages this type of frost. They work by freezing water around the plant, which releases latent heat, protecting it.
Radiative frosts
A type of frost caused by heat being lost from the ground on still, cool, nights, and which covers the soil on the valley floor.
Creates cold vinyeard conditions with warmer air above
Smoke taint
Smoke taint occurs when grapes are exposed to, and absorb, smoke. This gives off-aromas of plastic and smoke to the final wine.
Gentle grape handling, lab analysis of musts, reverse osmosis, Flash detente, blending with unaffected grapes can all help to mitigate the affects of smoke taint.
Phylloxera
What is it. How does it spread. What it does to the vine. Prevention.
An aphid-like insect that lays eggs and feeds on the roots of grapevines. They are spread mostly through humans via farm equipment, soil, irrigation, and roots of young vines. Damage to the roots can encourage disease and inhibit water and nutrient uptake, weakening and eventually, killing the vine.
American rootstocks, particularly V. berlandieri, V. riparia, and V. rupestris, are a key prevention tactic as they develop hard surfaces around the eggs, and create sap that heals wounds.
Pest
Nematodes
What is it. How does it spread. What it does to the vine. Management.
A microscopic worm common in most soils. They are spread through vehicles, irrigation. Nematodes feed on the roots of the vine, reducing yield and vigor, or spread viruses. The cannot be eliminated, only managed.
Management options include fumigation, if legal; incorporating mustard pant into the soil; and nematode-resistant rootstocks, such as Dog Ridge and Ramsey.
Pest
Grape moths
What is it. How does it spread. What it does to the vine. Management.
Damage the vine by feeding on flowers and grapes. The wounds are then vulnerable to bacteria and fungi, which leads to significant crop loss.
Management options include: Bacteria that are toxic to the moths, Pheromone capsules that confuse mating, natural predators: wasps.
Pest
Spider mites
What is it. Ideal conditions. What it does to the vine. Management.
Feed on the leaf surface, leading to discoloration, a disruption in photosynthesis, delayed ripening, and a reduction in yields.
They thrive in dusty conditions and are most damaging when the vines are water stressed.
Management options include: reducing dust by using sprinklers, mulch, and cover crops; Plant crops that host predatory mites; Targeted pesticides that kill only destructive mites, as general pesticides may kill beneficial mites.
Pest
Powdery mildew
What is it. Causes. What it does to the vine. Management.
A fungal disease caused by Oiduim tuckeri and is one of the most widespread vine diseases in the world. The affected vine will show dull, grey patches, damaging shoots, inflorescences, and grapes, and lowering yields. It thrives in shady, warm temperatures.
Management options include: Opening the canopy to reduce shade and leaf density; spraying sulfur on the vine early in the cycle (bud burst to veraison), and fungicides.
Fungal disease
Downy mildew
What is it. Causes. What it does to the vine. Management.
A fungal disease caused by Peronospora, a water mold that lives within the vines. It attacks the green parts of the plant forming a downy fungal growth on the underside of the leaves, removing leaves and thus, reducing yields. It needs rain and warm temperatures to spread.
Management options include: Bordeaux Mixture, a mixture of copper sulfate and lime; fungicides; good drainage and an open canopy that dries quickly.
Fungal disease
Grey rot
What is it. Causes. What it does to the vine. Management.
Botrytis cinerea, a fungus that damages the fruit, resulting in loss of yield and reduced quality of fruit. Grapes that are damaged by skins rubbing together or animals are vulnerable. Varieties with thin skins in tight bunches are vulnerable (Pinot, Semillon, Sauv Blanc). The spores become active in rainfall and high humidity.
Management options include planting grapes with thick skins and protecting grapes agains pests; opening the canopy; Fungicides; bacteria that are toxic to the fungus.
Fungal disease
Eutypa dieback
What is it. Causes. What it does to the vine. Management.
Also known as Dead Arm, it is a fungal trunk disease that rots the wood in vines, leading to significantly lower yields. Spores are spread by wind, over long distances.
The infection occurs in pruning wounds, especially in rainy season. Grenache, Cab Sauv, and Sauv Blanc are particularly susceptible.
Management options: Protect the wood at pruning: pruning late, applying fungicide to pruning wounds. Dead wood must be burnt to avoid spreading. Bacteria that is toxic to the fungus can also be used.
Fungal disease
Bacillus subtillis
A common biological treatment for various vine diseases. It is a bacteria that is applied to the effected vine and toxic to a variety of pests and fungal diseases.
Phomopsis cane & leaf spot
What is it. Causes. What it does to the vine. Management.
A fungal disease that causes a reduction in yield. It thrives in seasons where the spring is cool and wet, followed humidity and moderate temperatures. Infected canes whiten and break off easily, and infected shoots form brown cracks at the base.
Grenache is very susceptible.
Management options include applying fungicides beginning 3 weeks after budburst, removing dead wood and burning or burying it, and canopy management that the improves airflow.
Fungal disease
Esca
What is it. Causes. What it does to the vine. Management.
A fungal disease found in warm, dry climates like Southern Europe and California. It typically enters the vine via pruning wounds and causes tiger-striping of the leaves and spotting inside the wood.
Reduces yield and leads to death of the plant.
Management options include prevention measures like gentle pruning techniques, and disinfecting pruning wounds.
Fungal disease
Pierce’s disease
Definition, effect on the vine, management
A bacterial infection spread by the sharpshooter insect (vector).
It lives in the sap of the vine and clogs the channels, causing the grapes to shrivel, dropping leaves, and the eventual death of the vine.
Control is by reducing vector populations by things like not planing vines near rivers, insecticides, and introducing natural predators, such as the wasp.
Bacteria
