Hazards, Pests and Diseases Flashcards
Advective Frosts
Caused by large volumes of cold air moving from very cold areas.
Radiative Frosts
Results from heat loss during cold still nights. Heat loss depends on cloud cover. Windless nights allow cold air to sink just above surface, generally collecting on valley bottoms.
Smoke Taint
Smoke in the vineyard creating Smokey and plastic aromas. Most impacted during veraison onwards. Smoke absorbs by the grape, compounds bind with grape sugars and form aroma less precursors. Aroma comes out during fermentation and increases during aging. Handling of grapes can reduce taint. Gentle pressing and lower fermentation and reduced Maceration can reduce taking. Flash detente can help too.
Phylloxera
Aphid like insect feeds and lay eggs on the roots of grapevines. Phyloxera harm vines by damaging the roots, reducing uptake in nutrients and water. Roots are vulnerable to bacteria and and fungi. American rootstock grafting (v Riparia, v rupestris, v berlandieri) are best solutions
Nematodes
Microscopic worms in soils feed off vine roots reducing yields and vigour. Slow and gradual decline. Others transmit diseases like fanleaf virus. Fumigate, ploug cover crop in mustard crop or rootstock grafting are best solutions.
Grape moths
Feed on grapes and flowers. Wounds are created vulnerable to further attacks from bacteria and fungi. Bacillus (toxic to moths), pheromone capsules (sexual confusion), natural predators (wasps, spiders, green lacewings), insecticides are ways to kill moths.
Spider Mites
Feed on the surface cells of the leaves leading to discoloration and reduction in photosynthesis, delaying ripening and fruit yields. Thrives in dusty conditions. Cures are water sprinklers and cover crops, predatory mites, pesticides.
Powdery Mildew
Caused by fungus Erysiphe Mercator. American species less vulnerable. They attack young green parts of the vine and show a dull grey patch to be black patches as they advance. Grapes can also split at veraison and become targets for other infections. Solutions are open canopy to reduce shade (ie more sun) and density of leaves, sulfur to present and treat diseas, fungicides.
Downy mildew
A water mold that lives on the vine tissue, not on surface. It attacks green parts of the plant, especially young leaves and flowers. Spread through rainfall and warm temps to spread. Warm springs and stormy but warm summers increase risk. Copper salt spray, fungicides and good drainage and open canopy are solutions
Grey Rot
Fungus that can damage fruit. Loss of yield and drop of quality in wine. Grapes with thick skins, open canopy, removing leaves around bunches, sulfur and copper sprays are solutions. Likes humidity.
Eutypa Dieback
AKA Dead arm. Fungal trunk disease that leads to rotten wood. Infection caused by pruning woods in moderate conditions especially rain. Pruning late , applying fungicide cutting back affected trunks can help solve. Affected trunks can be cut back beyond visible symptoms and treated with fungicide. Burn dead wood.
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 impact it. Infected canes whiten and break off easily. Shoots develop brown cracks at their bases. Fungicides, removing diseased and dead wood during pruning and canopy management techniques are best solutions.
Esca
Fungal disease that enters the vine through pruning wounds and are prevalent in warmer and dryer climates. Symptoms are tiger stripe of the leaves and spotting of wood.
Pierce’s Disease
Bacterial disease killing vines. Lives on the sap of the vines. Spread by sharpshooter insect. No chemical control. Strict quarantine for removal of plants help prevent.
Grapevine Yellows
Bacterial Disease with no treatment available. Spreads by vectors including leafhoppers. Canopy turn yellow (white grapes) or red (black varieties. Control leafhopper population (insecticide) and removing cover crops should be removed.
