Plant Health

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Plant Health

• 1. Diseases

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Sources of Infection

• Mostly caused by fungi and viruses.
• Infection may come from
• Soil (soil borne)
• Seed (seed borne)
• Residue of previous crop.
• Green bridge (volunteer plants or alternative
  hosts).
• Transfer from another crop.

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Methods of control

• Cultural
• Rotations.
• Cultivations to destroy crop residues.
• Use of good quality seed.
• Resistant varieties
• Fungicides
• Seed dressings
• Foliar sprays

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Monitoring Disease

• Essential to detect disease outbreaks early.
• Inspect crops during the growing season every 7
  -14 days.

• Pay particular attention to
• Susceptible varieties
• Late sown spring crops
• Lush crops
• Crops adjacent to the same species.
• Disease outbreak warnings.
• Eg-Blightnet, Crop Monitor Aphid Monitor

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Cereal Diseases

• Seed borne Seedling Blight
• Root and Stem Eyespot, Take All
• Foliar Disease Septoria, Rhynchosporium
• Ear Diseases Fusarium, Ergot

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WHEAT

• Seed borne disease
• Seedling blight
• Microdochium nivale
• Controlled by
• Good seed treatment
• important if using farm saved seed

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WHEAT

• Root Stem Disease
• Take all
• Controlled by
• Rotation
• Take all Decline

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WHEAT

• Eyespot
• Controlled by
• Fungicide Spray (T1)
• Risk to crop depends on
• Sowing date
• Infection rates
• Rainfall
• Tillage
• Soil type
• Previous crop

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WHEAT

• Foliar Disease
• Septoria
• Controlled by
• Fungicide Sprays (T1, T2)
• Resistant varieties

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WHEAT

• Rusts
• Control
• Fungicide spray
• Resistant variety
• Control volunteers
• Good frost

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WHEAT

• Mildew
• Controlled by
• Fungicide
• (T0, T1, later for ear)
• Resistant variety
• Avoid excessive nitrogen

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BARLEY

• Rhynchosporium
• Controlled by
• Fungicide spray
• Minimise trash
• Resistant variety

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BARLEY

• BYDV
• High risk in crops after grass
• Direct Indirect transfer
• Controlled by
• Long cultivation window 3 weeks
• Bury grass trash
• Seed treatment to control virus vectors
• Monitor aphid migration Spray aphicide

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EAR DISEASES

• Sooty Moulds
• Septoria nodorum
• Mildew
• Fusarium pink grains (mycotoxins)
• Can effect yield
• Bigger significance when marketing grain
  (shrivelled grain, low specific weights,
  mycotoxins, ergot)

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Grain Diseases

• Ergot

• Fusarium

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Disease Control Cereal Fungicide timings

• Main timings
• T1 timing Leaf 3 emerged (usually coincides
  with GS32, but
• can be as early as GS31 or as late as GS33).
• T2 timing Flag leaf emerged (GS39).
• Additional timings
• T0 timing 2-4 weeks earlier than T1 but not
  fixed.
• Used when
• Early planted winter crops with lush growth in
  early spring
• Where mildew, yellow or brown rusts are active
• When eyespot requires earlier treatment
• T3 timing Ear spray
• - May be used to control ear diseases and 'top
  up' foliar disease control on the flag leaf on
  susceptible varieties under high disease
  pressure.
• - Should be timed at mid flowering

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DISEASE RISK

• Severity of disease depends on
• Disease pressure
• - amount of inoculum present
• - weather conditions - Spread through rain splash
• - Dry humid important for rusts
• - Moist humid important for
  Septoria Rhynchosporium
• Resistance of plant to disease pressure
• - choose resistant varieties, lower input costs

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DISEASE RISK

• Estimating Disease Risk

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WHY PROTECT

• Up to 80 of wheat yield is from top 3 leaves
• VITAL to protect them.
• Ear 22
• Flag leaf 43
• Leaf 2 23
• Leaf 3 9
• Leaf 4 3

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Oilseed Rape Diseases

• Phoma Leaf Spot / Stem Canker
• Light Leaf Spot
• Sclerotinia Stem Rot
• Clubroot
• Verticillium Wilt

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Phoma Leaf Spot/Stem Canker

• Can affect crops from
• emergence onwards
• The fungus grows down the
• petiole and invades the stem to
• produce stem cankers that cause
• premature ripening and lodging
• Plants with large leaves are less
• vulnerable than small plants
• Managed at the leaf spot stage
• in autumn/winter using resistant
• varieties and fungicide sprays

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Light Leaf Spot

• Risk can be predicted from
• disease levels on the pods of
• the previous year and
• summer temperatures
• Managed using resistant
• varieties and fungicide sprays
• Control may be affected by
• fungicide resistance but spray
• timing is more important

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Sclerotinia Stem Rot

• Often causes little damage
• but can halve yields when
• severe and poses a threat
• to other broad-leaved crops
• in the rotation
• Risk is dependent on the
• amount of spore production
• during flowering and the
• occurrence of suitable
• weather for petals to stick
• to the leaves
• Fungicides give very
• effective control but must
• be applied before infection
• takes place

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Clubroot

• Widespread in the UK
• Yield losses in affected crops
• can exceed 50
• Lengthening rotations
• remains the most sustainable
• long-term strategy on-farm
• Use lime to maintain soil pH
• near 7

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Verticillium Wilt

• An emerging soil-borne
• problem that is now common
• Yet to have much impact on yield

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Potato Diseases

• Bacterial Blackleg, Dickeya, Soft Rots.
• Viral Leaf Roll, Potato Mop Top Virus.
• Fungal Late Blight, Common Scab,
• Silver Scurf

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Source of Infection

• Seed Borne Silver Scurf, Blackleg
• Soil Borne Common Scab
• Volunteers Blight
• Dumps - Blight
• In Store Blight, Silver Scurf, Bacterial Rot,
  Dry Rot

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Gangerene
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Powdery scab (Spongospora subterranea)
Identifying powdery scab
Superficial blister-like pimples on the skin of
developing tubers These erupt to liberate powdery
spores Leaving a jagged edged scab Produces
cankers when scab infects an eye
Powdery scab is a particularly difficult disease
to control due to presence of soil and seed borne
infection. Spores can survive for at least 6
years in the soil, and possibly far longer
Sources of infection
Key points
Planting infected seed into clean soil will
threaten the current and future crops. high
proportion of seed can have trace levels
infected. Continuing to multiply seed in
infected soils will compound the problems for
seed growers and transfer the problems more
rapidly to the ware grower

• Know market tolerance for powdery scab
• Check varietal susceptibility
• Field history infected tubers
• Only plant less susceptible varieties in fields
  with a history of powdery scab
• Source seed of an appropriate health status to
  meet customer quality standards
• Do no plant seed tubers infected with powdery
  scab if you want to control this disease in the
  long-term

Managing the risk of powdery scab
Risk factor Low risk High risk
Variety Less susceptible varieties E.g. Sante, King Edward, Desiree, Culta Highly susceptible varieties E.g. Premiere, Cara, Maris Piper Estima
Site Long crop rotation (greater than 10 years) Previous history of powdery scab
Seed Health Seed tubers with no powdery scab Powdery scab present
Growing conditions Dry soils at tuber initiation Deep planting Wet soils at tuber initiation
Fungicides Only available to seed growers Shirlan soil drench at planting as SOLA Only available to seed growers Shirlan soil drench at planting as SOLA
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Common scab (Streptomyces scabies)
Identifying common scab
Common scab is a disfiguring skin blemishing
disease, it does not impact on crop yield but can
significantly effect crop value.
Severe infection results in corky lesions that
can be pitted, raised lumps on the skin or areas
with a raised brown reticulated netted pattern.
Symptoms can also be more superficial brown
flecks on the surface of the tuber
Sources of infection
Streptomyces is present in every soil, but
incidence is determined by variety
susceptibility. Infection occurs in potatoes
only when soil is dry at tuber initiation.
Key points
Managing the risk of common scab

• Know market tolerance for common scab
• Check varietal susceptibility
• Avoid planting susceptible varieties in fields
  with a history of common scab
• Cultivate to produce a clod-free fine tilth
• Irrigation at tuber initiation is the only
  reliable control measure

Risk factor Low risk High risk
Variety Less susceptible varieties E.g. King Edward, Desiree, Highly susceptible varieties E.g. Maris Piper, Markies, Up-to-date, Kerrs Pink
Site High organic matter, cultivated to a fine tilth Light soils on a slope and clay soils poorly cultivated
Seed Health Planting seed infected by common scab increases risk but only to a small extent Planting seed infected by common scab increases risk but only to a small extent
Growing conditions Crops irrigated to 4-6 weeks after tuber initiation Cloddy soils
Chemical control No means of chemical control. Applying a sulphur product can reduce scab incidence but only sometimes No means of chemical control. Applying a sulphur product can reduce scab incidence but only sometimes
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Common Scab
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Black scurf (Rhizoctonia solani)
Identifying black scurf
Black scurf can impact on tuber yield and
quality. The disease can kill eyes during
storage, effect stems before emergence (stem
canker) and form black scurf on progeny tubers
after senescence
Infected sprouts become blackened and may not
emerge in severe cases Clusters of black fungal
structures on the potato skin which form 7-10
days after haulm death. Can be picked off by the
thumb nail
Sources of infection
In Northern Ireland black scurf on seed planted
is the main source of infection. Sometimes
infection can come from residues of the previous
crop in that ground
Key points
Managing the risk of black scurf

• Kills eyes, delays emergence, increases tuber
  defects (cracks, misshapen, netted skin)
• Pre-planting fungicides very effective
• To assess seed risk
• Wash 50 tubers and count number with black scurf
• If more than 5 tubers have black scurf treat seed
  with fungicide pre-planting

Risk factor Low risk High risk
Variety All varieties are equally susceptible All varieties are equally susceptible
Site Long crop rotation Potato crops grown in succession
Seed Health Seed without black scurf planted in ley ground Seed with black scurf Potatoes rotated with vegetables
Growing conditions Dry years increase risk
Fungicides RhiNo, Monceren, Rizolex, Rovral, (Amistar, as a soil drench) RhiNo, Monceren, Rizolex, Rovral, (Amistar, as a soil drench)
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Silver scurf (Helminthosporium solani)
Identifying silver scurf
Blemishes on the tuber surface are present in
almost all potato stocks and lesions develop
during storage resulting in weight loss and
blemishing reducing the value of tubers for the
seed and mare markets
Silver lesions on the surface of the tuber which
often coalesce to form large silver patches.
These can cause the skin to shrivel and flake off
Symptoms are not always present at harvest, wash
tubers and check for development during storage
Sources of infection
Disease is primarily seed borne, but most spread
occurs during storage. Spores from silver scurf
patches are carried in air, dust and machinery
Key points
Managing the risk of silver scurf

• Use fungicide treated seed to reduce infection on
  progeny
• Harvest early
• Rapid drying using forced ventilation after
  harvest
• Silver scurf needs a warm humid environment to
  spread quickly
• Cold dry storage controls silver scurf better
  than the use of post harvest fungicides
• Store hygiene important

Risk factor Low risk High risk
Variety All varieties equally susceptible More obvious on red skinned tubers
Site No clear effect No clear effect
Seed Health Completely clean seed Silver scurf on seed planted increases risk
Growing conditions Early harvest (before mid-September) Late harvest
Storage conditions Clean stores, rapid drying, cold stored Unventilated ambient storage
Fungicides Fungazil 100Sl, Storite, Extratect Fungazil 100Sl, Storite, Extratect
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Silver Scurf
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Dry rot F. coeruleum, F. avenaceum, F. sulphureum
Identifying dry rot
Light brown rot which develops concentric rings
with white or light blue pustules on the surface
The main cause of blanking in potato crops,
reducing yield and tuber uniformity
Sources of infection
Soil borne fungus which infects the tuber through
wounds caused at harvest and grading. Dirt in
stores, machinery and boxes can harbour disease.
Planting infected seed can increase the risk.
Disease can be carried over in soil residues
from previous crops
Key points
Managing the risk of dry rot

• Wash and disinfect stores, boxes and equipment
  every year
• Tuber susceptibility to infection is low in
  Autumn but greatly increases from December. Aim
  to grade seed potatoes before December.
• Be gentle at planting. Rots starting then
  increase the risk of dry rot in the progeny crop.

Risk factor Low risk High risk
Variety Lady Rosetta, Sante Navan, Desiree Estima, Maris Piper
Site Ley ground, long rotation Short rotations including cereals
Seed Health Stocks free of dry rot Tubers with rots from farms with a history of dry rot
Growing conditions Cold wet summers Warm summers
Harvesting conditions Ensure skins are set and minimize damage Late harvesting and rough handling
Storage conditions Quick drying and cool dry storage Clean equipment and stores Dirty equipment Grading sprouted tubers
Fungicides Fungazil 100 SL, Extratect at harvest Fungazil 100 SL, Extratect at harvest
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Skin spot Polyscytalum pustulans
Identifying skin spot
Skin blemishing disease. Also kills eyes, delays
emergence and reduces yield.
Raised brown/black pimples on the skin of tubers.
Often surrounded by a small halo of black tissue.
Sources of infection
Planting diseased tubers increases skin spot on
progeny. Fields in colder, wet areas can carry
infection
Key points
Managing the risk of skin spot

• Wash seed to look for symptoms
• Apply a fungicide before planting if skin spot is
  present
• Harvest early
• Keep tubers dry during storage

Risk factor Low risk High risk
Variety Most varieties Kerrs Pink, King Edward
Site Ley ground, long rotation Short rotations
Seed Health Stocks free of skin spot Stocks with skin spot on tubers
Growing conditions Dry summers Cold wet summers
Harvesting conditions Early harvests Late harvesting from wet soils
Storage conditions Quick drying and dry storage Clean equipment and stores Damp, cold, unventilated storage
Fungicides Fungazil 100 SL, Extratect, pre-planting or at harvest Fungazil 100 SL, Extratect, pre-planting or at harvest
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Who to contact if you suspect a notifiable
disease? DARD Plant health inspection branch
Forest Service
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Blight
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How does blight spread and survive?
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Implications for blight control

• Infected tubers remain the key source of primary
  inoculum for late blight
• Use healthy seed

• Prevent/destroy potatoes sprouting in dumps or
  growing as volunteers in other crops

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Implications for blight control

• Start spraying when there's a risk of blight or
  the crop meets within the drills (whichever is
  earlier)
• How do you know when theres a risk of blight?
• Blight forecasts/warnings issued by CAFRE AFBI
• We look at temperature trends and outbreaks when
  issuing these

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Blightnet
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• Recommendations for blight control
• Start with healthy seed, eliminate dumps
• Start spraying when there's a risk of blight or
  the crop meets within the drills (whichever is
  earlier)
• Start with a product containing a systemic or
  translaminar
• Continue with either a translaminar or a
  protectant ensuring that spray intervals are not
  over-extended
• Complete the programme with at least 3 sprays of
  a product with tuber blight activity, reducing
  the interval if theres severe risk
• Ensure protection is maintained by regular
  spraying until the haulm is dead