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 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)

ErgotFusarium

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 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

‣ 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

‣ 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

‣ 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

‣ An emerging soil-borne problem 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 tubers These erupt to liberate powdery spores Leaving a jagged edged scab Produces cankers when scab infects an eye Managing the risk of powdery scab Risk factorLow riskHigh risk VarietyLess susceptible varieties E.g. Sante, King Edward, Desiree, Culta Highly susceptible varieties E.g. Premiere, Cara, Maris Piper Estima SiteLong crop rotation (greater than 10 years) Previous history of powdery scab Seed HealthSeed tubers with no powdery scabPowdery scab present Growing conditionsDry soils at tuber initiationDeep planting Wet soils at tuber initiation FungicidesOnly 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 factorLow riskHigh risk VarietyLess susceptible varieties E.g. King Edward, Desiree, Highly susceptible varieties E.g. Maris Piper, Markies, Up-to- date, Kerrs Pink SiteHigh organic matter, cultivated to a fine tilth Light soils on a slope and clay soils poorly cultivated Seed HealthPlanting seed infected by common scab increases risk but only to a small extent Growing conditionsCrops irrigated to 4-6 weeks after tuber initiation Cloddy soils Chemical controlNo 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 factorLow riskHigh risk VarietyAll varieties are equally susceptible SiteLong crop rotationPotato crops grown in succession Seed HealthSeed without black scurf planted in ley ground Seed with black scurf Potatoes rotated with vegetables Growing conditionsDry years increase risk FungicidesRhiNo, 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 factorLow riskHigh risk VarietyAll varieties equally susceptibleMore obvious on red skinned tubers SiteNo clear effect Seed HealthCompletely clean seedSilver scurf on seed planted increases risk Growing conditionsEarly harvest (before mid- September) Late harvest Storage conditionsClean stores, rapid drying, cold stored Unventilated ambient storage FungicidesFungazil 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 rot F. coeruleum, F. avenaceum, F. sulphureum Sources of infection Managing the risk of dry rot Risk factorLow riskHigh risk VarietyLady Rosetta, SanteNavan, Desiree Estima, Maris Piper SiteLey ground, long rotationShort rotations including cereals Seed HealthStocks free of dry rotTubers with rots from farms with a history of dry rot Growing conditionsCold wet summersWarm summers Harvesting conditions Ensure skins are set and minimize damage Late harvesting and rough handling Storage conditionsQuick drying and cool dry storage Clean equipment and stores Dirty equipment Grading sprouted tubers FungicidesFungazil 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 spot Polyscytalum pustulans Sources of infection Managing the risk of skin spot Risk factorLow riskHigh risk VarietyMost varietiesKerr’s Pink, King Edward SiteLey ground, long rotationShort rotations Seed HealthStocks free of skin spotStocks with skin spot on tubers Growing conditionsDry summersCold wet summers Harvesting conditions Early harvestsLate harvesting from wet soils Storage conditionsQuick drying and dry storage Clean equipment and stores Damp, cold, unventilated storage FungicidesFungazil 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.

Brown Rot Ring Rot Notifiable Diseases Colorado Beetle Potato Cyst Nematode Notifiable Pests

Blight

How does blight spread and survive?  Sporangia: air-borne or spread in rain (short-lived: days not months)  Infected plant material e.g. potato tubers (can survive months, best method for long- distance spread)  Oospores: long-term survival in soil (several years)

 Infected tubers remain the key source of primary inoculum for late blight  Use healthy seed Implications for blight control  Prevent/destroy potatoes sprouting in dumps or growing as volunteers in other crops

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

Blightnet

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 there’s severe risk  Ensure protection is maintained by regular spraying until the haulm is dead