Foot and Root Rot 2016 PDF

Fungal Diseases – Foot and Root rots Dr. Josephine Brennan, Department of Agriculture, Fisheries & Food, Celbridge, Kildare. [email protected] 07/11/2016  Types...

Fungal Diseases – Foot and Root rots Dr. Josephine Brennan, Department of Agriculture, Fisheries & Food, Celbridge, Kildare. [email protected] 07/11/2016  Types Cereal Foot of anddiseases Root Rots Seed Caused by fungi including – Diseases Fusarium, Bipolaris, Loose/Covered smut, Bunt, Seedling Gaeumannomyces, Peudocercosporella, Rhizoctonia blight Seed/Soil borne fungi Foliar Diseases – Rhyncosporium, Ramularia, Net blotch, Initial infection usually occurs at the roots or base of the plant Brown rust, Yellow rust, P. Mildew, Septoria Stem The fungi cause based the stemdiseases – Eyespot, base and roots Fusarium to rot causing the leaves to become discoloured. The rot at the base of the plant spreads up the main stem discolouring that as well. If the disease progresses the plant collapses completely  Types Cereal Foot of anddiseases Root Rots Caused by fungi including Fusarium, Bipolaris, Foot/Root diseases – Gaeumannomyces, Peudocercosporella, Rhizoctonia Take-all, Fusarium Seed/Soil borne fungi Ear diseases - Fusarium, Ergot. Initial infection usually occurs at the roots or base of the (Foliar diseases can also effect the ear include – Septoria, plant Yellow/Brown rust, P. Mildew) The fungi cause the stem base and roots to rot causing the Viral Diseases - leaves to become discoloured. BYDV The rot at the base of the plant spreads up the main stem discolouring that as well. If the disease progresses the plant collapses completely  WhatCereal Foot and Root Rots are rusts? Caused by fungi including Fusarium, Bipolaris, What is a haustoria? Gaeumannomyces, Peudocercosporella, Rhizoctonia Function? Seed/Soil borne fungi What is a biotroph? Initial infection usually occurs at the roots or base of the plant What The fungi isthe cause anstem obligate base andparasite? roots to rot causing the leaves to become discoloured. What The rot at the base is aofHeteroecious the plant spreads up the parasite? main stem discolouring that as well. If the disease progresses the plant collapses completely  What are smuts? Cereal Foot and Root Rots Caused by fungi including Fusarium, Bipolaris, Gaeumannomyces, Peudocercosporella, Rhizoctonia What is covered smut? Seed/Soil borne fungi Initial infection usually occurs at the roots or base of the plant What is loose smut? The fungi cause the stem base and roots to rot causing the leaves to become discoloured. What is bunt? The rot at the base of the plant spreads up the main stem discolouring that as well. If the disease progresses the plant collapses completely  Cereal Foot and Root Rots The fungus is normally introduced into an area by the introduction of a plant which is already infected although it can be bought in on implements and machinery. Once in the soil, Foot and Root rot diseases can over winter for several years as spores. It is very difficult, if not impossible to remove it completely.  Foot & Root Rot Diseases Fusarium Foot Rot Complex - F.culmorum, F.avenaceum and F.graminearum, F. poae & M.nivale. Take-All Disease - Gaeumannomyces graminis Sharp Eyespot & True Eyespot – Rhizoctonia cerealis Peudocercosporella herpotrichoide Common Root Rot - Bipolaris sorokiniana Fusarium foot rot complex  Fusarium foot rot complex There are many species of Fusarium that affect cereals. – F.culmorum, M.nivale, F.avenaceum and F.graminearum & F. poae –These fungi form a complex of diseases on seeds, seedlings and adult plants. –The seed-borne pathogen Microdochium nivale (formally known as Fusarium nivale) is also usually included in this group of fungi.  Fusarium Species Fusarium avenaceum, F. culmorum, F. Seedling blight graminearum, F. poae, Microdochium nivale Consequences Foot rot Yield loss Loss in grain quality Diseased Head blight (FHB) Mycotoxin contamination Healthy  Fusarium disease complex Seedling blight Head blight (FHB) Foot rot  Symptoms The most common symptom of a serious attack of Fusarium is very poor plant establishment, i.e a very thin crop. This occurs because of pre-emergence and post-emergence seedling blights - the most important phase of the disease. Root rotting, brown foot rot and leaf blotching (usually following some other form of damage), glume blotch and ear blights can all be caused by these fungi.  Severe foot rot, usually affecting plants under stress (especially moisture stress) can result in premature ripening and whiteheads'. What is a mycotoxin? A mycotoxin is a toxic secondary metabolite produced certain fungi. Mycotoxins are poisonous chemical compounds produced by certain fungi “ The term 'mycotoxin' is usually reserved for the toxic chemical products produced by fungi that readily colonize crops”. DON  TABLE 1. MYCOTOXINS IN GRAINS AND SEEDS. Mycotoxin Commodity Fungal source(s) Effects of ingestion Fusarium graminearum Human toxicoses India, wheat, maize, barley Fusarium crookwellense China, Japan, and Korea. deoxynivalenol/nivalenol reported from Toxic to animals, especially Fusarium culmorum pigs zearalenone maize, wheat F. graminearum Identified by the F. culmorum International Agency for F. crookwellense Research on Cancer (IARC) as a possible human carcinogen. Affects reproductive system in female pigs ochratoxin A barley, wheat, and many Aspergillus ochraceus Suspected by IARC as other commodities Penicillium verrucosum human carcinogen. Carcinogenic in laboratory animals and pigs fumonisin B1 maize Fusarium moniliforme plus Suspected by IARC as several less common human carcinogen. Toxic to species pigs and poultry. Cause of equine eucoencephalomalacia (ELEM), a fatal disease of horses Aflatoxin B1, and naturally occurring mixtures of aflatoxins, identified as maize, peanuts, and many aflatoxin B1, B2 Aspergillus flavus potent human carcinogens other commodities by IARC. Adverse effects in various animals, especially chickens Trichothecene Mycotoxins Deoxynivalenol (DON) DON Adverse effect on Human & Animal Health Plant Health Inhibitors of protein synthesis What range of mycotoxin producing Fusarium species do we have in Ireland? DNA-based detection of Fusarium species and GC-MS-based detection of mycotoxins – M. nivale – F. avenaceum (enniatins, beauvericin, moniliformin) – F. graminearum (trichothecenes, DON zearalenone) – F. culmorum (trichothecenes, zearalenone) – F. poae (trichothecenes)  Legislation imposes a limit for the level of certain mycotoxins in grain e.g. DON for human consumption of 1250ppb The presence of Fusariun ear blight is not a good indication of likely mycotoxin risk in cereal crops DON  Seedling blight is a fungal infection that causes the seed or seedling to rot and die. Seedling Blight Seedlings are attacked before or shortly after emergence There may be brown spots on the coleoptile, roots It can be characterized by patches in the field that fail to germinate. If the seedlings do manage to germinate, they may not emerge, or they may emerge and then become brown, pinched, and die.  Other symptoms include stunted and yellow growth, or reduced root growth with brown spots on the roots and coleoptile There are many fungi present in the soil that can cause seedling death. Among these fungi are Pythium spp., Fusarium spp., and Rhizoctonia spp. Most infection is soil borne, but it can also be seed borne. M. nivale is the primary pathogen in the fusarium group which causes seedling blight resulting in seedling death and thinning of the plant stand..  Life Cycle The most important source of Microdochium nivale for wheat crops is the seed. In seasons where weather conditions are wet during flowering and grain formation, ear infection is common and can result in very high levels of seed- borne infection. In such seasons seed-borne infection can pose a serious threat to crop establishment unless seed is treated to control the disease. Many true Fusarium species are common in soil but these play little part in seedling blight. Most have competitive saprophytic abilities which allow them to colonise debris and stubble in soil and they play a part in Fusarium foot rot and Fusarium ear diseases.  Fusarium complex The most important source of Fusarium for wheat crops is the seed but the fungus can also survive on debris in the soil. In seasons where weather conditions are wet during flowering and grain formation, spores are splashed from lower in the canopy causing earblights and seed-borne infection. In such seasons seed-borne infection can pose a serious threat to crop establishment unless seed is treated to control Fusarium. All the cereal Fusarium species are common in soil. Most have competitive saprophytic abilities which allow them to colonise debris and stubble in soil. Volunteers may also act as a source of inoculums.  Economic Importance Disease development: Spores in the soil infect the growing roots and crowns and cause a discrete lesion or discoloured infected spot. The more spores there are in the soil the more lesions will appear. When many lesions are present on the crown and root system, the plant is weakened and yield reduced. New infections continue to arise throughout the growing season, so that crown roots and side tillers also become infected. These lesions can lead to complete decay of the root system.  Control Because the fungus is present within the seed coat, rather than as a superficial contaminant on the seed surface, seed-borne infection is not easily controlled by surface-acting fungicides. Despite this, fungicides are used to give acceptable control. Fungicides applied for the control of other diseases can give good control of stem base Fusarium infection. Cultural control  Foot & root rot diseases Fusarium foot rot complex - F.culmorum, F.avenaceum and F.graminearum, F. poae & M.nivale. Take-all disease - Gaeumannomyces graminis Sharp eyespot & True eyespot – Rhizoctonia cerealis Peudocercosporella herpotrichoides – Common root rot - Bipolaris sorokiniana  Gaeumannomyces graminis - Take-All Take all is a root & foot rot disease of cereals & grasses caused by the fungus Gaeumannomyces graminis. All varieties of wheat and barley are susceptible. Usually more destructive on winter crops, and is favoured by conditions of intensive production and exacerbated by monoculture. –when the same crop is grown year after year in a site. It survives in the infected residues of one crop, then invades the roots of the following crop, progressively destroying the root system. In exceptional cases it can kill the whole crop; hence the name "take-all".  Take-all Take-all is a cereal disease that infects the plant's roots, – blocking the conductive tissue and reducing water uptake. – Early signs of the disease include stunting and yellowing. Plants mature earlier, may have fewer tillers and can be recognised by the characteristic ‘white heads’ that appear within a healthy crop. The fungus attacks the plant roots at any growth stage, early infections causing stunting and yellowing. Affected roots are blackened, sometimes severely. After earing in spring patches of the crop appear stunted. In severe attacks the worst affected plants are bleached and dead even before flowering. These symptoms give rise to an alternative name for the disease, "whiteheads". Yield loss levels of 40 to 50 % are often recorded in severe attacks.  The disease can affect plants without causing obvious symptoms. However, infection can limit root development over winter, which restricts canopy development and carbohydrate accumulation. Where infections occur, patches of whiteheads (bleached ears) may be seen as grain fills. Early signs The fungus attacks the plant roots at any growth stage, early infections causing stunting and yellowing. Early signs of the disease include stunting and yellowing. Large circular patches of premature white heads are often seen.  Roots can be seen to be blackened and rotten and have a "rat-tail" appearance. In severe outbreaks the base of infected plants may also show blackening. Affected plants are easy to pull out of the ground due to poor root development Above ground symptoms are seen as patches of stunted plants and white heads ("bleached" ears) in mature plants. White-heads generally contain small grains or, occasionally, no grain at all. Ascospores Gaeumannomyces graminis - Take-All  Life cycle: Take-all survives the winter primarily as mycelium on roots or stubble debris, volunteer cereals, early autumn-sown crops and some grass weeds. Primary infection occurs in autumn from inoculums in the soil. Secondary (root-to-root) infection occurs mostly in spring and summer. The disease spreads from infected seedling roots to developing crown roots. As the disease progresses during the season, the root area lost to the disease increases and the ability of the plant to absorb water and nutrients from the soil declines. When root rotting is severe plants are unable to absorb water and nutrients. As a result the plants ripen prematurely, resulting in white-heads and often poor grain filling.  Early sown crops are more prone to infection. Take-all survives in the soil on infected cereal and grass residues. The fungus on these residues then infects the root tissue of young plants. Take-all can also form hyphae which spread the disease through the soil between plants, and for this reason the disease is often seen in patches. Disease levels build up where successive cereal crops are grown or if grass weed control is poor. Grass control in preceding crops should occur early to give root residues an adequate chance of breaking down. Summer rainfall can enhance decomposition of root matter in the soil provided volunteer weeds are controlled throughout this period. Gaeumannomyces graminis - Take-All  Gaeumannomyces graminis - Take-All Importance Take-all survives in the infected residues of one crop then invades the roots of the following crop, progressively destroying the root system. Potentially the most damaging wheat disease and, at its most severe, can result in no harvestable grain, hence the name “take-all”. Take-all is arguably the most important disease of wheat, partly because it cannot be fully controlled chemically and relies on rotational strategies for control. Losses of 10-20% are common in second and third wheat crops. Grain from plants showing whiteheads is usually small and shrivelled or, in severe attacks, there may be no grain present in the ear. The disease is usually most severe in the third or fourth successive cereal crop, but generally declines in importance in continuous cereals.  Continuous Wheat Trial Avatar - 105 JB Diego - 104 KWS Lumos -105 (C =10.6 t/ha/ 4.3 t/ac) KWS Croft-87 /(C =9.7 t/ha/ 3.9 t/ac) SY Epson - 94 Take-All – What are the consequences? It reduces yield by blocking water and nutrient uptake in infected roots. Severity depends on weather and other factors including soil type. Phases of infection – Primary infection occurs in autumn from inoculum in the soil. There is usually very little inoculum after a non-susceptible crop, – Secondary (root-to-root) infection occurs mostly in spring and summer. The disease spreads from infected seedling roots to developing crown roots. High levels of primary infection lead to increased secondary infection, especially when soils are warm and moist. Affected plants have black lesions on roots.  Importance Take-all is a serious soil-borne disease of cereals. It is estimated thathalf of UK wheat crops are affected and that they suffer averageyield losses of 5–20%. More than half of the crop can be lost when disease is severe. The cost to farmers is estimated to be up to £60 million a year. The take-all fungus, Gaeumannomyces graminis var. tritici, infects winter wheat roots (also barley, rye and triticale but not oats) in the autumn. Another strain of the fungus, var. avenae, affects oats as well as other cereals but is currently very rare.  Factors influencing take-all Environmental Weather Regional differences in take-all relate to weather, soil type and cropping systems. Soil type Crops on light soils (sand, sandy loams and loams),where the fungus spreads more easily, tend to have most disease. Management: Crop rotation A well-managed one-year break normally controls take-all in a following cereal. Cultivations Ploughing - buries most of the take-all inoculum, which is in the top 10cm of soil at harvest, and brings less infective soil to the surface. Min-till - of first wheat stubble leaves highly infective soil near the surface allowing a second wheat to be infected more rapidly but has the advantage that it leaves a firmer seedbed than ploughing. Volunteer cereals and grass weeds: Cereal volunteers carry the take-all fungus through break crops. In first wheats the risk of take-all increases in proportion to the density of volunteers or weeds. Varieties: Drilling date: Take-all inoculum starts to decrease soon after harvest. Therefore, risk to the next crop decreases. Seed rate: Take-all can develop more quickly and become more severe at higher seed rates, which allow more primary and secondary infection because of greater root density. Reducing seed rates can increase yield where take-all is severe but this may not be practical with later-sown at-risk crops. Crop nutrition: Maintaining correct nutrition is important in minimising take-all and its effects; deficiency of any nutrient should be avoided. Seed treatment fungicides: can help reduce the effect in conjunction with cultural control methods.  Control Treat seed with seed treatment Avoid sowing into previous grass-based ground Utilise rotations to avoid growing consecutive cereal crops  Foot & root rot diseases Fusarium foot rot complex - F.culmorum, F.avenaceum and F.graminearum, F. poae & M.nivale. Take-all disease - Gaeumannomyces graminis Sharp eyespot & True eyespot – Rhizoctonia cerealis Peudocercosporella herpotrichoides Common root rot - Bipolaris sorokiniana Sharp eye spot - Rhizoctonia cerealis Sharp eyespot of wheat is caused by the soil-borne fungus Rhizoctonia cerealis. The name "sharp eyespot" comes from the characteristic symptoms that occur on the lower wheat stems. Rhizoctonia cerealis produces no spores but has mycelium branching at right angles  Symptoms Sharply defined lesions on the outer leaf sheaths. Young lesions have a sharply defined dark margin and frequently have shredding of the epidermis within the lesion. Later in the season lesions on the stem have a pale cream centre with a dark brown, sharply defined edge. Sharp eyespot lesions are often superficial, but severe sharp eyespot is not uncommon and can cause whiteheads or lodging. Eyespot reduces yield and grain quality by restricting water and nutrient uptake. Yield losses may be large 10-30 % Severe eyespot can cause lodging from weakened stems.  Rhizoctonia cerealis – Life cycle The fungus overwinters primarily as mycelium on infected stubble with volunteers and some grass weeds acting as sources of inoculum. Rhizoctonia cerealis produces no spores, but lives on crop residues and in the soil as mycelium and as small resistant structures called sclerotia. This fungus differentiates into hardened mycelial masses or sclerotia, on host plants and in culture. The sclerotia, which are very small and irregular in shape, germinate to form mycelia.  Rhizoctonia cerealis is the name given to the asexual state of this fungus, characterized by white to brown mycelium, the presence of sclerotia and the absence of spores. The damage due to infection by Rhizoctonia cerealis is very dependent on environment. Observations indicate that wet, cold conditions favor disease development. Infections are most serious when they are initiated on seedlings. Seedlings may be killed out right, but most survive through the growing season some of which then die before maturity and produce white heads. Rhizoctonia cerealis – Life cycle  The fungus overwinters primarily as mycelium on infected stubble with volunteers and some grass weeds acting as sources of inoculum. The fungus can also produce sclerotia which may act as overwintering structures. Infection may occur at any time during the growing season, but the disease is favoured by temperatures of around 9OC. Dry and sandy soils and early sowing favour the disease. Cool autumn or spring temperatures may result in early infection by the fungus which can lead to severe disease. Rhizoctonia cerealis produces no spores, but lives on crop residues and in the soil as mycelium and as small resistant structures called sclerotia. This fungus differentiates into hardened mycelial masses or sclerotia, on host plants and in culture. The sclerotia, which are very small and irregular in shape, germinate to form mycelia.  Rhizoctonia cerealis is the name given to the asexual state of this fungus, characterized by white to brown mycelium, the presence of sclerotia and the absence of spores. This fungus has been found to have a sexual stage, known as Ceratobasidium, but the Ceratobasidium stage is not important in the disease cycle. While Rhizoctonia cerealis is common in the soil and on host debris as mycelium and sclerotia, the damage due to infection is very dependent on environment. The exact conditions under which the disease is important have not been determined, but observations indicate that protracted wet, cold conditions favour disease development. Infections are most serious when they are initiated on seedlings. Seedlings may be killed out right, but most survive through the growing season some of which then die before maturity and produce white heads.  Importance Sharp eyespot is of little economic importance. Infections are most serious when they are initiated on seedlings. Seedlings may be killed out right, but most survive through the growing season some of which then die before maturity and produce white heads.  Control Because sharp eyespot is of little economic importance, no specific recommendations are made for its control. Management practices which favor good, vigorous growth of the wheat plant generally limit damage due to sharp eyespot. Proper seed bed preparation, good soil drainage, balanced fertility and crop rotation are considered most important.  Foot & root rot diseases Fusarium foot rot complex - F.culmorum, F.avenaceum and F.graminearum, F. poae & M.nivale. Take-all disease - Gaeumannomyces graminis Sharp eyespot & True eyespot – Rhizoctonia cerealis Peudocercosporella herpotrichoides Common root rot - Bipolaris sorokiniana  True eyespot - Peudocercosporella herpotrichoides Eyespot is an important fungal disease caused by the fungus Pseudocercosporella herpotrichoides W- type [anamorph - asexual]) and Pseudocercosporella herpotrichoides R-type. It is also called It is more severe where the wheat is grown continuously and the weather is cool and moist. It can reduce the yield up to 40%.  True eyespot - Peudocercosporella herpotrichoides Eyespot is one of a number of diseases that can affect the stem base of cereals. Under Irish conditions, true eyespot is the most damaging of these stem base diseases, and potentially the biggest yield robber The host range of eyespot includes wheat, barley, oats, rye and many grass species, but it is most damaging on winter and spring wheat and winter barley.  Symptoms Early symptoms can be confused with sharp eyespot and Fusarium spp. Frequently all that is visible is a brown smudge on the leaf sheath at the stem-base. If crops are early-sown eyespot lesions may penetrate one or two leaf sheaths, making identification more conclusive. Later in the season eyespot symptoms become more distinct and appear as an eye-shaped lesion with a dark margin, usually below the first node. Later still, the margin of the eyespot lesion is often dark and diffuse with a central black 'pupil' occasionally visible. Colonisation of the stem by the eyespot fungus weakens the stem and can cause lodging, which is the most obvious and serious consequence of severe eyespot.  In severe attacks of eyespot,whiteheads ("bleached" ears) are commonly seen scattered through the crop, later in the season these may become colonized by sooty moulds. Flattened Crops - evidence of poor eyespot control in the past. Lesions usually occur below the first node and at GS 31/32 it is difficult to identify clear symptoms. Lesions are often indistinct and usually consist of a brown, smudgy lesion In the eyespot lesion the fungus grows inside the plant and stem tissues and clogs up the plant 's plumbing system. This disrupts the flow of nutrients and water to the plant and reduces yield.  True eyespot disease There are two fungi involved in the eyespot disease. Pseudocercosporella herpotrichoides W-type (Tapesia Yallundae), and Pseudocercosporella herpotrichoides R-type (Tapesia acuformis). R-type (Oculimacula acuformis) and the W-type (O. yallundae). The W-type was the dominant type until the late 1980s, at which time there was a shift in the Irish eyespot populations to the R-type. The reason for the shift is being attributed to the widespread use of triazoles. The R-type is still the dominant species and recent work carried out at Teagasc, Oakpark Calow showed that over 70% of the eyespot isolates found are of the R-type. It was originally thought that the W-types were more aggressive and patho-genic than the R-types but recent research shows that both types are equally damaging. Life cycle of Peudocercosporella herpotrichoides The fungus overwinters on infected stubble, volunteers and grass weeds can also act as sources of inoculum. It can survive on stubble for as long as 3 years which is why a one year break from cereals does not necessarily reduce eyespot risk in following crops. Spores are produced throughout the autumn and winter, posing a threat to early-sown crops. Infection occurs at temperatures above 5OC and during wet periods. Spores are rain splashed short distances from infected stubble. The development of symptoms following infection normally takes 6-8 weeks, depending upon environmental conditions. Eyespot can be a serious problem in continuous cereals, where inoculum may build up from year to year. The sexual stage of both eyespot fungi, play an important part in the pathogen life cycle. This stage of the fungus is produced on stubble at the end of the season and after harvest, ascospores may travel long distances and infect emerging or young plants.  Economic importance Yield reduction can be 10% to 15% when eyespot is severe. Colonisation of the stem by the eyespot fungus weakens the stem and can cause lodging, which is the most obvious and serious consequence of severe eyespot. If lodging is widespread, then yield losses can be greater than 35%.  Control of True eyespot The optimum growth stage for controlling the W types is. Because the R types sporulate slightly later than the W types, the optimum time to control these is GS 32, which coincides well with Septoria control measures. There are major difficulties in deciding whether or not eyespot control is necessary in a particular crop. In the UK, treatment is recommended if 20% or more of –the tillers are affected by eyespot at GS 30/31.  Control of True eyespot The only guide that a grower has as to whether or not his crop is at risk from eyespot is to evaluate thevarious risk factors. Winter wheat, winter barley and spring wheat are the crops at greatest risk. If there has not been a two-year non-cereal break, then the risk is increased. Early sowing, as well as wet weather in winter and spring, will increase the chances of infection. Variety is also important, as there are some differences in varietal susceptibility.  Foot & root rot diseases Fusarium foot rot complex - F.culmorum, F.avenaceum and F.graminearum, F. poae & M.nivale. Take-all disease - Gaeumannomyces graminis Sharp eyespot & True eyespot – Rhizoctonia cerealis Peudocercosporella herpotrichoides Common root rot - Bipolaris sorokiniana  Bipolaris sorokiniana – Common Root Rot Common root rot is caused by the fungus Bipolaris sorokiniana Bipolaris sorokiniana is a saprophyte Hosts include barley, spring wheat, rye, and weed and grass species. Wheat and barley are the most economically important hosts Common root rot occurs in cereal- growing areas, and is prevalent in the warmer cereal-growing regions.  Symptoms » Initial symptoms originate on young seedlings from inoculum carried on the seed or from infections originating from soilborne conidia near the seedling. »Dark brown lesions appear on the outer coleoptile tissue and/or on the leaf base. Lesions may coalesce into long areas of necrotic brown tissue. »In extreme cases, the entire seedling may die. In most cases, however, the seedling will survive but growth of the developing plant may be stunted. Symptoms Plants with common root rot produce fewer tillers and fewer kernels per ear. For example grain yield losses due to common root rot and seedling blight for Canada, Scotland, and Brazil have been estimated at 15, 10, and 20%, respectively White heads can result from plant stress associated with root disease  Conidia of Bipolaris sorokiniana Conidiophore and conidia of Bipolaris sorokiniana Dark lesions on the coleoptile and leaf bases. Stunting of seedlings infected by the common root rot organism Dark fungal conidia and conidiophores of Bipolaris sorokiniana on leaf blade Spot blotch on Barley leaves caused by Bipolaris sorokiniana  Life cycle Bipolaris sorokiniana is a saprophyte and survives primarily as thick-walled conidia. It can also survive as mycelium in soil or crop debris. The sexual stage (Cochliobolus sativus) is not important in the disease cycle. Primary inoculum includes mycelium from infected seed, conidia in the soil, and conidia on the seed surface. Conidia germinate in the presence of susceptible hosts and initiate primary infection on the coleoptile, or primary roots. B. sorokinana penetrates the host tissue either directly through the epidermis, or through natural openings or wounds.  Appressoria and dome-shaped infection cushions are formed prior to penetration. Infection pegs form beneath the appressoria and infection cushions. Infection continues from the epidermis to the cortex and endodermis, resulting in disintegration of the tissue. Colonization of infected plant parts progresses by the spread of conidia. Environmental factors play an important role in the severity of disease caused by B. sorokinana and other root rot fung. Warm soil temperatures favor growth of B. sorokinana. Moist soils during planting promote infection and colonization by soilborne inoculum as well. Any movement of soil by wind, water, and implements can move inoculum of the pathogen. Infested seed can also serve as a means of dissemination of the pathogen over long distances. Dissemination of secondary inoculum is not important for continued disease development below ground, but provides inoculum for subsequent crops.  Control of root rot Seed treatment Historically, cultural methods, especially crop rotation, have been important in the control of eyespot. The importance of cultural control of eyespot is now increasing because more non-cereal break crops are being grown and fungicide use is declining.  White-head - prematurely ripened ears of cereals often caused by pathogens attacking the roots or stem base Lodging - when a standing crop is caused to lean or bend due to adverse weather or soil conditions Mycelium - the mass of hyphae forming the body of a fungus Inoculum - micro-organisms or virus particles which act as a source of infection Sclerotia - compact mass of fungal hyphae e.g. ergot, capable of being dormant for long periods, and giving rise to fruiting bodies or mycellium Saprophytic = grow & live on dead organic matter such as fallen trees, dead leaves, and even dead insects and animals. These fungi have enzymes that work to "rot" or "digest" the cellulose and lignin found in the organic matter. Anamorph - the imperfect or asexual stage of a fungus Teleomorph - the sexual or so-called perfect growth stage or phase in fungi  Take All Shary eyespot Common root rot Causal organism Symptoms spores References: https://cereals.ahdb.org.uk/ AHDH publications Diseases of Small Grain Cereal Crops: A Colour Handbook By T.D. Murray, David W. Parry, Nigel D. Cattlin