D1 Hazards, Pests and Diseases Flashcards
Hazards, pests and Disease
It reduce yields, affect the quality of the fruit, can add a considerable annual costs.
Hazards
Drought
A lack of water cause the stomata to close to limit water loss, this reduces photosynthesis and slows ripening and hence lower yield and bad quality.
Management options are:
- choice of grape variety, clone and rootstock
- Irrigation system should be considered
Excess of water
Can lead to too much vegetative growth, competing with yield of fruit.
Increase risk of fungal disease because of high density therefore humidity.
If soil are not free draining, water logging may reduce oxygen, slowing down growth.
Management options are:
- Planting on a slope or on free draining soil
- Drainage system should be considered.
Rainfall
During pollination, can cause millerandage or coulure, reducing yields and quality.
During summer can slow ripening.
Before harvest may dilute flavour, cause grape splitting (leading to grey rot), more difficult to use machinery.
Management options are:
- Site selection (slope, climate)
- Soil texture and structure
- Choice of grass between row spaces
- Drainage system
- Monitor forecast for a possible early harvest
Freeze (winter)
At -20 the vine can be damaged, reducing yields, or even killed.
Management options are:
- Choice of grape variety, clone and rootstock
- Site selection:
Hillside is warmer (5 degrees) than valley floor.
Bodies of water has moderating effect.
A deep layer of snow can provide insulation.
- Protecting the vine by:
Insulating the vine by hilling up soil around it. Burying vines, however is costly as requires labour.
Vine can be pruned to have several trunks so that the dead one can be replaced.
Frosts (at bud burst)
Occurs when cold air below 0 degrees collects at ground level, freezing water in the buds and shoots, killing them. As the new one will take time to grow back, this lead to reduce yields and less fruitfulness.
There are two types of frost:
1. Advective frost: cold air moves in from a cold area.
2. Radiative frost: heat being lost on cool night due to lack of cloud cover and winds.
Management options to reduce risk:
- Choice of variety, clone and rootstock
- Site selection (hillside sites drain cold air away)
- Delaying pruning to postpone bud burst
- Training vines off the ground
- Bare soil (no cover crop) absorb more heat and radiates at night.
Management options to combat threat:
- Water sprinklers is the only method to combat advective frost. The cost is for equipment and water, can be lower than wind machine and heaters.
- Wind machine: pull warm air from above to the ground. The initial investment is considerable.
Oil, gas heaters, candles: High cost of fuel and labour, low heating efficiency and contribution to air pollution.
Hail
Can damage buds, shoots and leaves in spring. and grape during summer. A point of entry favour fungal disease. Yields can be seriously reduced.
Management option:
- Rockets (with silver iodide) may be fired into thunderclouds
- Netting the vines (may cause too much shade)
- Have plots in different areas
- Additional cost of crop insurance against hail
Sunburn
Impact grape quality, browning the grapes, releasing a bitter taste and (due to skin damage) offer a point of entry for other diseases.
Sunburn grape are remove at sorting, therefore also reduces yields.
Management options:
- row orientation and aspect can mitigate hottest afternoon sunlight.
- Canopy management may share the fruit zone.
- Irrigation may reduce water stress, and hence the chance of sunburn.
- Net shading.
Fire
Vineyard with cover crops and mulches can provide fuel for the fire. Fire can damage equipment, irrigation system and trellising.
Management options:
- installing detectors and sprinklers
- Installing and maintaining a water tank
- Training employees
Smoke taint
When smoke touch the growing grapes (veraison onwards) result in smoky or plastic aroma in the final wine. Aroma compound in smoke binds with sugar and form aroma precursor that become aromatic through the fermentation process.
Management options:
- Affected must has to be tested to establish the extent of the problem
- Lower fermentation temperature and reduced maceration can reduce the uptake of the compounds.
- Flash detente and reverse osmosis can help.
Pests
Pests may compete for water and nutrients or directly attack the vine and grapes, affecting yields and quality. Measures has always and economic cost.
Phylloxera (Europe 1863, introduces from USA)
This insect lays eggs on the roots on the vine, reducing the uptake of nutrients and water, and offering a point of entry for other diseases.
It spreads by human through machinery and by irrigation water.
Symptoms:
- Vine dies of drought in patches
- Visible yellow eggs on vine’s roots, swelling roots
- Pale green leaf, leaf yellowing
- Slow, stunted shoot growth
Management options:
- American rootstock hybrid can seals wounds and prevent diseases and deal with European calcareous soils. (as American rootstock has little lime tolerance)
Rootstock is a standard costs when establishing a vineyard.
Nematodes (root-knot and dagger)
Nematode worm feeds on vine’s roots, reducing yields and vigour.
Can be present in the soil or transported by human through machinery and irrigation water.
Management option:
- Fumigate the soil by plough in a cover crop of mustard plant.
- Use of Nematode-resistant rootstocks
Grape moths
Feeds on flower and grapes, offering a point of entry for other diseases.
Management options:
- Biological control: Use of bacterium Bacillus Thuringiensis, pheromone (disrupt mating), natural predators (wasp, spider)
- Insecticides
Spider mites
Feeds on the leaves, reducing photosynthesis, delaying ripening and reducing yields.
Prefers dusty condition and vines that are water stressed.
Managing options:
- Use of water sprinklers and cover crops to reduce dust
- Natural predators
- Pesticides (but its costly)
Birds
Can destroy grapes, offering a point of entry for other diseases and reducing yields.
Management options:
- Netting
- Bird or noises scarers
Mammals
Can damage the whole vine and trellising
Management options:
- Fencing
Fungal diseases
Powdery Mildew
Caused by the fungus Oidium tuckeri.
Damages green part of the vine, reducing yield.
Optimum temperature at 25 degrees, dry conditions, dense, shady canopy.
Symptoms are dull, grey patches.
Management options:
- Open canopy to reduce shade and density.
- Sulfur applications prevent disease
- Fungicides. However, the fungus may become resistant.
Downy mildew
Caused by the fungus Peronospora.
Damages green part of the vine, reducing yield.
Optimum temperature 20 degrees, wet conditions.
Symptoms are yellow oil spots and white downy fungal growth on the underside of the leaves.
Management options:
- Copper salt sprays (copper sulfate and lime)
- Fungicides
- Good drainage and open canopy (to dry quickly)
Grey rot
Caused by Botrytis Cinerea.
Damages the fruit, reducing yield and dropping quality.
Optimum condition are grapes with point of entry and wet and humid.
Management options:
- Choice of grapes with thick skin
- Open canopy
- Sulfur and copper spray
- Fungicides
- Using antagonist bacteria Bacillus Subtilis
Eutypa Dieback (dead arm)
Damage the trunk, leading to rotten wood, and hence reduce yield and dead vines.
Infection occurs through pruning wounds.
Symptoms are stunted shoot growth and yellow leaves.
Management options:
- Fungicides
- Cut back the affected trunk, burning the dead wood to avoid further spreading.
- Biological control, using bacteria Bacillus Subtilis
Phomopsis cane and leaf spot
Whiten and break off canes and shoots, and hence reducing yield.
Prevalent in cool, wet, humid spring.
Management option:
- Fungicides
- Removal and burnt of the diseased wood
- Open canopy to improve air flow.
Esca
Enter the vine through pruning wounds, reducing yield and killing it.
Prevalent in warmer and drier climate.
Symptoms are tiger-striping on the leaves.
Management option:
- No pruning in the rain
- Disinfecting pruning wounds
Bacterial disease
Pierce
Quickly kills the vine, by clogging the sap channels leading to grape shrivelling, dropping leaves and consequent death of the vine.
The symptoms are unclear, the vine must be tested in laboratory.
The bacterium is spread by the sharpshooter insect.
Management option:
- Reducing the number of the vector (away from rivers, introducing predators such as wasp)
Grapevine yellows
There is no cure for it, reduce yield and quality.
The disease is spread by leafhoppers and by nursery selling diseased stock.
Symptoms include delayed bud burst and the canopy turning red or yellow.
Management option:
- Reducing the number of leafhopper by insecticides
- Nursery should bath the pruning wood in hot water to kill the disease
Viruses
Fanleaf
Stunts shoot growth, very pale leafs.
Spread by the dagger nematode.
Management option:
- there is no cure, vine has to be replaced, adding costs.
- Before vineyards are planted, the soil should get tested.
- Clean planting material should be used.
Leafroll
Slows down roots (less carbo for winter) and shoots (delaying ripening) growth.
Spread by grafting and by mealy bugs.
Symptoms, leaves change colour to red and yellow.
Prefers humid environment.
Management option:
- There is no cure, remove the vine and plant new one, adding cost.
- Vines have to be tested in a laboratory as symptoms may not be clear
- Open canopy to reduce humidity
- Encourage natural predators
