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. Cultural 1. ◦ Rotations. ◦ Cultivations to destroy crop residues. ◦ Use of good quality seed. 2. Resistant varieties 3. Fungicides ◦ Seed dressings ◦ Foliar sprays • 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 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 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 Identifying 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 Sources of infection 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 Managing the risk of powdery scab Risk factor Variety Low risk High risk 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 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 Key points •Know market powdery scab tolerance for •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 longterm 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. 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. 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 Key points Managing the risk of common scab Risk factor •Know market common scab Low risk High risk Variety Less susceptible varieties E.g. King Edward, Desiree, Highly susceptible varieties E.g. Maris Piper, Markies, Up-todate, 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 Chemical control No means of chemical control. Applying a sulphur product can reduce scab incidence but only sometimes Cloddy soils tolerance for •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 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 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 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 Fungicides Dry years increase risk RhiNo, Monceren, Rizolex, Rovral, (Amistar, as a soil drench) 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 Key points •Kills eyes, delays emergence, increases tuber defects (cracks, misshapen, netted skin) •Pre-planting effective fungicides very •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 Silver scurf Identifying silver scurf (Helminthosporium solani) 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 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 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 Key points Managing the risk of silver scurf Risk factor Low risk High risk •Use fungicide treated seed to reduce infection on progeny •Harvest early Variety All varieties equally susceptible More obvious on red skinned tubers Site No clear effect No clear effect •Rapid drying using ventilation after harvest Seed Health Completely clean seed Silver scurf on seed planted increases risk •Silver scurf needs a warm humid environment to spread quickly Growing conditions Early harvest (before midSeptember) Late harvest Storage conditions Clean stores, rapid drying, cold stored Unventilated ambient storage •Cold dry storage controls silver scurf better than the use of post harvest fungicides Fungicides Fungazil 100Sl, Storite, Extratect •Store hygiene important forced Dry rot F. coeruleum, F. avenaceum, F. sulphureum 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 Identifying dry rot Light brown rot which develops concentric rings with white or light blue pustules on the surface Key points 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 storage Clean equipment and stores Dirty equipment Grading 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. 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 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 storage Clean 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 Notifiable •Brown Rot Diseases •Ring Rot Notifiable •Colorado Beetle •Potato Cyst Nematode 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 longdistance spread) Oospores: long-term survival in soil (several years) 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 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 there’s a risk of blight? Blight forecasts/warnings issued by CAFRE & AFBI We look at temperature trends and outbreaks when issuing these 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