Hazards Pests And Diseases Flashcards
Drought
Min needs 500mm/year in cool climate and 750mm/year in warm
Stomata close and reduce photosynthesis
Drought management
Irrigation where allowed
Drought resistant rootstock from Rupestris and Berlandieri parentage
Drought tolerant varieties like Garnacha
Excessive water
In summer = vegetative growth (divert nutrients from bunches and shade bunches)
Fungus
Waterlogged soil reduces oxygen availability and compacts soil
Excessive rainfall mgmt
Slope, free draining soil, or drainage system
Untimely rainfall
During pollination and fruit set can lead to millerandage or coulure reducing size of crop and lowering quality
Rainfall around harvest swells grapes to splitting and can lead to grey rot, makes harvest work difficult
Freeze
-4*F can damage or kill vine
Freeze mitigation
Site selection- hillside is warmer, near body of water, allow depth of snow to insulate
Variety choice- cab franc/riesling, hybrid or American varieties
Protect vines- hilling up for insulation, burying the vine, pruned to have several trunks
Frost
Advective frost- large volumes of cold air moving in from cold areas
Radiative frost- heat lost on still, cold nights
Frost risk reduction
Site selection to avoid frost pockets
Delayed pruning postpones budburst
Late budding varieties like Riesling
High trained vines
Bare soil between vines absorb more heat and radiate it
Frost mitigation
Sprinklers - aspersion - only method to combat advective frost
Wind machine- pull warm air down can use helicopter
Oil or propane heater (smudge pot) or wax candle (bougies)- low heating efficiency
Hail
Damage to vines at all stages of development
Hail mgmt
Silver iodide seeding- causes rain rather than hail
Netting- only good in high sunlight areas
Plots in varied areas
Crop insurance
Sunburn
Scars skin possible death of grape
Bitter taste
Increased susceptibility to rot
Sunburn mgmt
Row orientation and aspect reduce impact of hottest afternoon sun
Canopy mgmt techniques to adjust direct exposure
Irrigation to lower water stress
Agricultural sunscreen or cloth/net
Fire
Damage to property, equipment, irrigation system, vines, trellises
Smoke taint
Fire mgmt
Fire detection and sprinklers
Water tank install
Employee training
Smoke taint
Effect on fruit increases from veraison onward
Aroma compounds in smoke absorbed in grapes and bind with sugars to form precursors that become aromatic through fermentation
Strength of aroma increases during aging
Smoke taint mgmt
Musts tested analytically or by micro fermentation to establish extent of problem
Thought to be in skin so reducing skin contact reduces taint - hand harvest/gentle or whole bunch press/ low temp fermentation/ reduced maceration
Flash detente- can help but not remove completely
Can blend into unaffected wines to dilute
Phylloxera
Vines die of drought in larger and larger patches
Vine roots covered with insects and yellow eggs
Swelling on older roots
Pale green galls underside of leaves
Slow, stunted growth and leaf yellowing in three years after exposure, death in 5
Phylloxera mgmt
Grafting however American rootstock has poor like tolerance
Rootstock hybrids add lime tolerance
Now rootstocks offer protection from various pests/hazards
Nematodes
Microscopic worms
Feed off roots and transmit disease
Either present in soil or spread by unclean nursery stock, irrigation water, or vehicles
Once present they are only managed not eliminated
Nematode management
Fumigate soil - most chemicals now banned but ploughed mustard plant has compounds that work as biofumigants
Nematode resistant rootstock from champini
Grape moths
Feed on flowers and grapes
Wounds lead to susceptibility to bacteria and fungus
Significant crop loss
Grape moth mgmt
Biological control- use of bacillus thuringiensis that produces substances toxic to moths
Pheromone capsules to disrupt mating
Natural predators- parasitic wasps, green lacewings, some spiders)
Insecticide
Spider mites
Feed on surface cells of leaves reducing photosynthesis, delaying ripening, reducing yields
Most damaging when vines are water stressed
Spider mite mitigation
Use sprinklers - they thrive in dusty conditions
Encourage predators- mites that feed on spider mites
General pesticides kill beneficial mites, specific spider mite sprays are costly
Birds
Can destroy an entire crop
Bird damage allows bacteria and fungi to enter bunches - rot
Bird mgmt
Netting - Mornington Peninsula - expensive
Bird scares or noises - rotated
Falcons
Mammals
Eat vines, grapes, damage trellis
Deer, rabbits, kangaroos, raccoons, wild boar, baboons
Mammal mgmt
Fencing
Powdery mildew
Oidium
Chard/Cab susceptible- PN/Ries less so
Overwinters in buds and on canes
Attacks young green parts
Thrives in shady conditions
Does not require humidity
Powdery mildew mgmt
Open canopy to reduce shading
Sulfur application from budburst to veraison to prevent, easier than containing
Systemic fungicides can be effective however fungus can become resistant so use is limited
Downy mildew
Water lives in vine tissue
Attacks green parts of plant
Defoliation
Needs rainfall and warmth to spread
Downy mildew mgmt
Copper salt spray (bordeaux mix) only work in drier conditions- builds heavy metals in soil. Only available treatment in organic
Fungicides
Good drainage and open canopy
Grey Rot
Botrytis cinerea
Loss of yield, drop of quality (color, body, aroma)
Can affect flowers and stay dormant until veraison
Grey rot mgmt
Thick skinned varieties
Protection from pests
Open canopy, removing leaves
Fungicide (Bordeaux mix ineffective)
Antagonistic bacteria- bacillus subtilis
Eutypa Dieback
Dead arm
Fungal trunk disease
Reduced yield kills vine in 10 yrs
Spores spread by wind into pruning wounds
Eutypa dieback mgmt
Late pruning pre application of fungicides
Cut trunks back if affected and treat with fungicides- burn affected wood
Bacillus subtillis
If badly affected- retrain from sucker or remove vine and replant
Phomopsis cane and leaf spot
Fungal disease
Prevalent in years with cool wet springs followed by humidity and moderate temps
Infected canes whiten and break
Grenache susceptible
Phomopsis cane and leaf spot mgmt
Fungicides applied after budburst and every two weeks as wet conditions continue
Diseased and deadwood removed and burned
Canopy mgmt to improve air flow
Esca
Complex fungal disease caused by a group of organisms particularly prevalent in warm/dry climates
Enters through pruning wounds
Tiger striping of leaves and spotting inside wood
Reduces yield and leads to vine death
Esca mgmt
Prevention - disease free stock
Minimal wound pruning
Disinfection of pruning wounds
Bacillus subtillis
Pierce’s disease
Bacterial disease- quickly kills vine
Bacteria live in sap channels- clogs channels- grape shrivel/ leaf drop. Death in 1-5 years
Spread by sharpshooter insect (vector)
Vector
Organism that spreads disease
Pierce’s disease mgmt
No chemicals control
Control by reducing vector - insecticide, predatory wasps
Strict quarantine to prevent spread
Working to create disease resistant vines
Grapevine yellows
Group of diseases caused by bacteria
No treatment available
Spread by leaf hoppers and nurseries selling untreated, diseased stock
Delayed budburst, failure to lignify, yellow canopy (white variety) red canopy (red variety)
Chard/riesling susceptible
Sometimes death/sometimes recovery
Reduced yield, high acid low sugar
Grapevine yellows mgmt
No control
Control vector - insecticide, remove cover crops
Bathe pruning wood in hot water to kill disease
Fanleaf virus
Early shoot growth stunted
Canes grow distorted
Leaves are pale/malformed like a fan
Can have little effect or lose whole crop
Spread by dagger nematodes and infected plant matter
Fanleaf virus mgmt
No cure
Vines must be replaced
Test for dagger nematodes and only use clean plant material
Leaf roll virus
Spread by grafting and mealy bugs
Can reduce yield up to half and negatively affect quality
Surviving fruit takes longer to ripen, will have more acid, less color, lower sugar
Vine stores less carbs
Fall yellow leaves for white/ red leaves for black
Some plant material shows no symptoms but carries
Leaf roll virus mgmt
No cure
Screen vines for infection at nursery
Open canopy to reduce mealy bugs
Encourage natural predators- ladybugs, lacewings
