1. Diseases

Mostly caused by fungi and viruses.

Infection may come from:

1. Soil (soil borne)

2. Seed (seed borne)

3. Residue of previous crop.

4. Green bridge (volunteer plants or alternative hosts).

5. Transfer from another crop.

1. Cultural◦ Rotations.

◦ Cultivations to destroy crop residues.

◦ Use of good quality seed.

2. Resistant varieties

3. Fungicides◦ Seed dressings

◦ Foliar sprays

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

• Essential to detect disease outbreaks early.

• Inspect crops during the growing season every 7 -14 days.

Seed borne – Seedling Blight

Root and Stem – Eyespot, Take All

Foliar Disease – Septoria, Rhynchosporium

Ear Diseases – Fusarium, Ergot

Seed borne disease

Seedling blight –

Microdochium nivale

Controlled by

Good seed treatment

– important if using farm saved seed

Root & Stem Disease

Take all

Controlled by

Rotation

Take all Decline

Eyespot

Controlled by

Fungicide Spray (T1)

Risk to crop depends on

Sowing date

Infection rates

Rainfall

Tillage

Soil type

Previous crop

Foliar Disease

Septoria

Controlled by

Fungicide Sprays (T1, T2)

Resistant varieties

Rusts

Control

Fungicide spray

Resistant variety

Control volunteers

Good frost

Mildew

Controlled by

Fungicide

(T0, T1, later for ear)

Resistant variety

Avoid excessive nitrogen

Rhynchosporium

Controlled by

Fungicide spray Minimise trash Resistant

variety

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

Sooty Moulds Septoria nodorum Mildew Fusarium – pink grains (mycotoxins)

Can effect yield

Bigger significance when marketing grain (shrivelled grain, low specific weights, mycotoxins, ergot)

Ergot Fusarium

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

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

Estimating Disease Risk

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%

Phoma Leaf Spot / Stem Canker

Light Leaf Spot

Sclerotinia Stem Rot

Clubroot

Verticillium Wilt

‣Can affect crops fromemergence onwards

‣ The fungus grows down thepetiole and invades the stem toproduce stem cankers that causepremature ripening and lodging

‣Plants with large leaves are lessvulnerable than small plants

‣Managed at the leaf spot stagein autumn/winter using resistantvarieties and fungicide sprays

‣Risk can be predicted fromdisease levels on the pods ofthe previous year andsummer temperatures

‣Managed using resistantvarieties and fungicide sprays

‣Control may be affected byfungicide resistance but spraytiming is more important

‣Often causes little damagebut can halve yields whensevere and poses a threatto other broad-leaved cropsin the rotation

‣Risk is dependent on theamount of spore productionduring flowering and theoccurrence of suitableweather for petals to stickto the leaves

‣Fungicides give veryeffective control but mustbe applied before infectiontakes place

‣Widespread in the UK

‣Yield losses in affected crops

can exceed 50%

‣Lengthening rotationsremains the most

sustainablelong-term strategy on-farm

‣Use lime to maintain soil pH

near 7

‣An emerging soil-borneproblem that is now

common

‣Yet to have much impact on yield

Bacterial – Blackleg, Dickeya, Soft Rots.

Viral – Leaf Roll, Potato Mop Top Virus.

Fungal – Late Blight, Common Scab, Silver Scurf

Seed Borne – Silver Scurf, Blackleg

Soil Borne – Common Scab

Volunteers – Blight

Dumps - Blight

In Store – Blight, Silver Scurf, Bacterial Rot, Dry Rot

Powdery scab(Spongospora subterranea)

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

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

Sources of infection

Superficial blister-like pimples on the skin of developing tubersThese erupt to liberate powdery sporesLeaving a jagged edged scab

Produces cankers when scab infects an eye

Managing the risk of powdery scab

Risk factor Low risk High risk

Variety Less susceptible varietiesE.g. Sante, King Edward, Desiree, Culta

Highly susceptible varietiesE.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 plantingWet soils at tuber initiation

Fungicides Only available to seed growers – Shirlan soil drench at planting as SOLA

•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

Key points

Identifying powdery scab

Common scab(Streptomyces scabies)

Common scab is a disfiguring skin blemishing disease, it does not impact on crop yield but can significantly effect crop value.

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.

Sources of infection

Managing the risk of common scab

Risk factor Low risk High risk

Variety Less susceptible varietiesE.g. King Edward, Desiree,

Highly susceptible varietiesE.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

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

•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

Key points

Identifying common scab

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

Black scurf(Rhizoctonia solani)

Sources of infection

Managing the risk of black scurf

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)

•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

Key points

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

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

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

Silver scurf(Helminthosporium solani)

Sources of infection

Managing the risk of silver scurf

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

•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

Key points

Identifying silver scurf

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

Disease is primarily seed borne, but most spread occurs during storage. Spores from silver scurf patches are carried in air, dust and machinery

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

Dry rotF. coeruleum, F. avenaceum, F. sulphureum

Sources of infection

Managing the risk of dry rot

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 storageClean equipment and stores

Dirty equipmentGrading sprouted tubers

Fungicides Fungazil 100 SL, Extratect at harvest

•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.

Key points

Identifying dry rot

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

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

Skin spotPolyscytalum pustulans

Sources of infection

Managing the risk of skin spot

Risk factor Low risk High risk

Variety Most varieties Kerr’s 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 storageClean equipment and stores

Damp, cold, unventilated storage

Fungicides Fungazil 100 SL, Extratect, pre-planting or at harvest

•Wash seed to look for symptoms

•Apply a fungicide before planting if skin spot is present

•Harvest early

•Keep tubers dry during storage

Key points

Identifying skin spot

Planting diseased tubers increases skin spot on progeny. Fields in colder, wet areas can carry infection

Raised brown/black pimples on the skin of tubers. Often surrounded by a small halo of black tissue.

Skin blemishing disease. Also kills eyes, delays emergence and reduces yield.

Blight Blight

How does blight spread and How does blight spread and survive?survive?

Sporangia: Sporangia: air-borne or spread inair-borne or spread inrain (short-lived: days not months)rain (short-lived: days not months)

Infected plant material Infected plant material e.g. potato tubers e.g. potato tubers (can survive months, best method for long-(can survive months, best method for long-distance spread)distance spread)

Oospores: Oospores: long-term survival in soil long-term survival in soil (several years)(several years)

Infected tubers remain the Infected tubers remain the keykey source of primary source of primary inoculum for late blightinoculum for late blight

Use healthy seedUse healthy seed

Implications for blight controlImplications for blight control

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

Start spraying when there's a risk of blight or the Start spraying when there's a risk of blight or the crop meets within the drills (whichever is earlier)crop meets within the drills (whichever is earlier)

How do you know when there’s a risk of blight?How do you know when there’s a risk of blight?

Blight forecasts/warnings issued by CAFRE & AFBIBlight forecasts/warnings issued by CAFRE & AFBI

We look at temperature trends and outbreaks when We look at temperature trends and outbreaks when issuing theseissuing these

Implications for blight control Implications for blight control

Blightnet

Recommendations for blight controlRecommendations for blight control Start with healthy seed, eliminate dumpsStart with healthy seed, eliminate dumps

Start spraying when there's a risk of blight or the crop Start spraying when there's a risk of blight or the crop meets within the drills (whichever is earlier)meets within the drills (whichever is earlier)

Start with a product containing a systemic or translaminarStart with a product containing a systemic or translaminar

Continue with either a translaminar or a protectant ensuring Continue with either a translaminar or a protectant ensuring that spray intervals are not over-extendedthat spray intervals are not over-extended

Complete the programme with at least 3 sprays of a Complete the programme with at least 3 sprays of a product with tuber blight activity, reducing the interval if product with tuber blight activity, reducing the interval if there’s severe riskthere’s severe risk

Ensure protection is maintained by regular spraying until Ensure protection is maintained by regular spraying until the haulm is deadthe haulm is dead