Go to Mizzou without going to Mizzou
Instant access
Search publications only
Diseases, a major hazard in wheat production, cause losses through reduced yield and quality of grain. Wheat diseases are caused by parasitic bacteria, fungi and viruses. Wheat is subject to attacks from about 50 different pathogens, but not all of the diseases will occur in a particular area or in a certain year.
Estimated annual wheat disease losses vary from 10 to 25 percent, depending upon many factors. In the past, severe diseases have occurred at epidemic levels. In Missouri, two serious Fusarium scab epidemics, in 1982 and 1990, caused significant losses. A wheat streak epidemic in 1981 caused dramatic losses that year in many wheat fields. Yet perhaps more important are the consistent annual losses caused by other diseases. The virus disease barley yellow dwarf, which is found in most wheat fields, causes obvious yield reductions. Septoria leaf blotch, a fungal disease, is more or less serious every year depending upon various weather conditions.
Some disease losses cannot be prevented because no successful means have been devised for controlling some of the most destructive diseases. However, a considerable part of these losses can be prevented by using proven methods for disease prevention and control.
Recognition of the most common and destructive diseases is important to applying control measures whenever possible. Use of resistant varieties is obviously a very important means of control, but certain management practices are also vital for integrated disease control. Fungicide control measures, seed treatments and foliar treatments have a definite place in an integrated pest control program.
Table 2
General control measures for wheat diseases.
Control of diseases of roots, crowns and seedlings
Control of leaf and stem rusts
Control of leaf and head blight diseases
Control of smuts on wheat
Web maintenance 1/25/06
Reviewed October 1993
Exchanges
Use our feedback form for questions or comments about G4319.
Related page
Table 1
Diseases affecting Missouri wheat
| Disease | Symptoms | Remarks | Control |
| Seedling blights, root rots and crown rots | |||
| General | Seedling blights and root rots are usually present every year in most wheat fields. Importance varies greatly with season, locality and cropping practices. Wheat plants are subject to attacks from seed to maturity. Root decay, seedling blight, stunting and premature death of older plants are characteristic of root rot infections. All underground parts are attacked with varying degrees of rots of roots, crowns and lower parts of stems. Diseased tissues often have large light-brown to black areas. | These diseases are not as easily observed as rusts and smuts, but yields are often seriously reduced. Diseased seeds and several soil-borne organisms are sources of root infections and seedling blight. Root rots are caused by many species of fungi, including Pythium root rots are more severe in moist soil. | Root rots cannot be completely prevented, but they can be reduced. General control measures are:
|
| Helminthosporium crown rot and root rot. Bipolaris sorokiniana. | More or less circular patches of dwarfed, reddish-brown plants scattered throughout field. Dark brown lesion on surface of coleoptile of plant that progresses inward and may spread into roots. Infection of crowns, roots and basal portions of stem; distinct rotting of affected parts. Typically a dry rot. | Widely distributed on wheat seedlings, causing failure to emerge because of rotted roots and shoots. Post-emergence death from rotted stems. Fungus does not thrive as well at 40 to 60 degrees F as at higher temperatures. Under favorable conditions for infection, severe injuries occur on wheat as plants approach maturity, causing what is termed as "spot blotch." | Seed treatment with a fungicide such as captan, thiram or mancozeb. Clean seed, sanitation, good soil fertility, rotation of crops. Resistant varieties. Late fall planting of winter wheat. Eradication of susceptible wild grasses such as quackgrass, green foxtail, wild rye, wild barley, etc. Use seed treatment fungicides. |
| Fusarium root rot (Gibberella root rot). Fusarium spp. | First noticed when infected plants appear stunted. Later plants turn yellow and die. Roots of diseased seedlings are rotted, reddish-brown in color and may be covered with a mass of grayish or pink mold. Root rots or crown rots, which occur as plants approach maturity, cause premature ripening or dying plants. Dead plants may have a bleached appearance. | Major importance in Missouri, especially when following corn with late maturing wheat varieties. Seedling blight is caused by infection carried in the seed or by spores on healthy seed, or from fungus living on decaying crop residues of corn or other cereals. If only part of the root system is involved, the plant does not stool and sends up only a single stem with a small head. | Sanitation is the first important step. Thorough plowing or burning of infected stubble, straw, corn stalks, rotten ears and weed grasses. Crop rotation. Do not follow corn with wheat. Remove all light, shriveled seed by fanning. Treat seed with a recommended fungicide. Delay sowing until soil temperature is 60 degrees F or less. Plant resistant or tolerant varieties. |
| Pythium root rot (Browning root rot). Pythium spp. | Symptoms produced by Pythium may be confused with other types of root rot. Leaves of infected plants, particularly the lower ones, tend to lose green color. Light- brown soft rot of rootlets and roots, and pale green stuntedgrowth of tillers. Infected roots develop reddish-brown lesions. | Usually a root rot of mature plants and seedling blight of wheat (also oats and barley). Severe development of disease may result in soft rot of leaf sheaths and crown below the soil surface and browning of the leaves. Pythium root rot is increased by tightly compacted fine soils, high ratio of N to P, continuous cropping of cereals. | Methods of control of Pythium root rot are inadequate. Resistance in wheat varieties not demonstrated. Legumes in the crop rotation system may help. Balanced soil fertility. Good soil drainage. Delayed seeding retards progress of the disease under wet conditions. Systemic seed treatment fungicide (e.g. metalaxyl "Apron") is labeled for wheat. Usually not needed except in serious situations. |
| Rhizoctonia root rot (Bare patch, Purple patch). Rhizoctonia solani. | Disease appears in patches in which plants are stunted or killed (bare patch). Leaves in many varieties show a purple case (purple patch). Plants are weakened and killed, or more generally recover with delayed maturity and low yield. Tan-colored cortical rot of root system and tan-zonate lesions on basal leaf sheaths. Mycelium of fungus is present in rotted tissues and root stubs near crown. | Widely distributed on wheat (also oats and many grasses) but not considered serious on wheat except under certain local situations. Development is greatest at low temperatures, although strains of the fungus incite disease at high temperatures. Favored by reduced or no-till practices. Sharp eyespot (R. cerealis), a related disease, may be seen occasionally. | Good soil drainage. Balanced fertility. Proper rate of seeding. Seed treatment with recommended fungicides such as captan, thiram, mancozeb or terraclor will provide some benefit. See table on Seed Treatment Fungicides. Crop rotation has limitations because Rhizoctonia can survive on many hosts. |
| Take-all. Gaeuman-nomyces graminisvar. tritici. | Diseased plants usually occur in localized, more or less circular areas up to several feet in diameter. Affected plants are severely stunted, lose green color and rapidly become bleached. Dry rots of roots, crown and stem bases are brown to black -- a distinct diagnostic character. A dark brown layer of coarse fungus hyphae under leaf sheath. Infected plants die prematurely with unfilled white heads; "white head" disease. | Severity of the crown and basal rots varies from year to year -- some years high in individual fields. Affects most cereals and several domesticated and wild grass hosts. Fungus lives in soil on diseased straw and root residues. Builds up greatly in several forage grasses (e.g. bromegrass and wheat grass) Wheat after such grasses can be devastated. Nitrate fertilizers favor take-all. | Sanitation -- remove affected crop residues. Eradicate wild grass hosts and volunteer grain. Crop rotation leaving wheat, barley, rye and grasses out for three years. Do not plant immediately after grass crop. Maintain balanced NPK levels. Ammonium or area-based nitrogen fertilizers tend to reduce take-all. The seed treatment fungicide triadimenol (Baytan) may provide some control. |
| Leaf diseases | |||
| Leaf rust. Puccinia recondita fsp. tritici | Leaf rust is found mainly on leaves but may occur on stems, especially between head and flag leaf. First appears on older leaves and spreads up the plant to the flag leaf as season advances. Small, round or oblong, raised orange-red pustules (uredia) on surface of leaves. Most abundant on upper surface. Also found on chaff in the heads. | Widely distributed and occurs more regularly than stem rust. In most years it arrives too late to cause major injury, except in certain susceptible cultivars. If serious it causes shriveling of grain. Losses are from reduction in number and size of kernels. Rust spores are disseminated from infected fields in the south (Mexico, Texas, Oklahoma, etc.) There are many races of the leaf rust fungus. | Use of resistant varieties is most important control measure. For example, Caldwell, Cardinal and Saluda have moderate resistance. Arthur 71, Becker and Clark are moderately susceptible. Hart and McNair 1003 are susceptible. |
| Stripe rust (Yellow rust). Puccinia striiformis | Pustules are light yellow and are arranged in distinct, straight-sided stripes about 1/16-inch wide and of irregular length. Heavily invaded leaves may die. | Stripe rust is not common to Missouri wheat, but it has been identified in variety trials in the late 1980s. The disease, like leaf rust, develops from spores blown in from southern wheat growing regions. | Resistant varieties can be selected if this disease becomes serious. Foliar fungicides also are labeled for stripe rust. |
| Powdery mildew. Erysiphe graminis fsp. tritici | Wheat plants affected by powdery mildew are usually in parts of field where growth is dense and the air moist, conditions ideal for infection. Small, irregular or circular light gray spots on the upper surface of the leaves. Spots enlarge as fungus grows. Spots take on a floury appearance due to production of an enormous number of spores. Lower surface of leaves beneath diseased spots turn yellow and older parts of spots turn brownish. Grayish-white powdery spots on spikelets. Small black fruiting bodies (Cleistothecia) develop in mature lesions. Can develop on stems and heads under favorable conditions. | Powdery mildew displays a superficial habit of infection. In the floury grayish spots on the leaves, summer spores are produced in great abundance and can cause new infections that serve to spread fungus to healthy plants during growing season. Overwintering occurs on wheat residues. High nitrogen fertilization and high populations can increase powdery mildew. | This disease generally is present every year. Because of superficial habit, chemical control can be easily obtained. Resistant varieties have been developed for use where the disease is destructive. Clark shows moderate resistance. Saluda has good resistance. Cardinal is moderately susceptible and Caldwell is classified as susceptible, but under average conditions they will not be seriously hurt. Foliar fungicides such as triadimefon (Bayleton) and propiconazole (Tilt) provide excellent control of powdery mildew. |
| Septoria leaf blotch (Speckled leaf blotch). Septoria tritici | Appears first as light green to yellow spots between the veins of the leaves. Lesions spread rapidly to form light brown irregular blotches with a speckled appearance (pycnidial development). The small submerged brown pycnidia in the blotches are the final diagnostic symptom. Moves from lower leaves upward toward flag leaves. Also attacks leaf sheaths, stems and flumes occasionally. Some of the symptoms are similar to Septoria glume blotch. See under Diseases of heads. | Major importance in Missouri One of the most serious leaf diseases of wheat. Distributed over a wide area in both the hard red winter and soft red winter wheat sections. Generally on the leaves of winter wheat in fall. Early spring spread occurs from overwintering inoculation. Favored by high nitrogen fertilization and high populations. |
Crop rotation, with non-host crop (soybeans, sorghum), sanitation, and plowing down volunteer wheat plant. Seed treatment with a recommended fungicide (e.g. Vitavax 200). Avoid excess nitrogen fertilization. Most current varieties are susceptible or moderately susceptible. Foliar fungicides that provide effective control: propiconazole (Tilt), benomyl (Benlate) + mancozeb (Manzate 200) or mancozeb alone (Dithane M-45, Manzate 200, Penncozeb). |
| Downy mildew (Crazy top). Sclerospora macrospora | Infected plants are erect, yellowish green, somewhat dwarfed, and they tiller excessively -- many tillers only a few inches tall. The thickened leaves may be twisted, curled and stiff, and stand erect. Plants rarely produce heads. Stems may be thick and deformed, especially at base of head. Heads may be distorted and open; chaff fleshy, green. | Occurs in locally restricted outbreaks on wheat. Not a major disease in Missouri. Found in low, poorly drained areas when seedlings are exposed to excessive moisture. More common to corn. | Good farm practices, such as proper surface drainage, sanitation and crop rotation, help to control disease. Avoid planting in areas that may flood. No resistant varieties or chemical controls exist. |
| Tan spot (Yellow leaf spot). Pyrenophora trichostoma (P. tritici-repentis)(Helminthosporium tritici repentis). | Appears early in the season. At first the spots are yellow-brown, bordered by yellow. Young spots are oval to elongated, usually less than 1/16-inch long. Found on both surfaces of leaves. Spots increase in size as season advances; the dead brown area of a spot may be 1/4-inch wide and 3/4-inch long and usually tapered. | In most years not severe in Missouri, but in some years some fields may have losses. Overwinters on infested wheat stubble or straw. Continuous wheat will increase possibility of occurrence. Requires 6 to 48 hours of leaf wetness for infection. Survives on other grass hosts. | Crop rotation, sanitation, good cultural practices and resistant varieties should help to reduce severity of the disease. Foliar ungicides that are effective are Mancozeb (Dithane M-45, Manzate 200, Penncozeb); triadimefon (Bayleton); propiconazole (Tilt); benomyl (Benlate) + mancozeb (Manzate 200). |
| Cephalosporium stripe (Fungal stripe; C-stripe). Cephalosporium gramineum | C-stripe is a vascular disease. Infected seedlings show yellowing, but most conspicuous symptoms appear after jointing. Long, chlorotic stripes form on sides of the leaf midribs and run the entire length of leaf. Stripes extend down into leaf sheaths. | Currently not as important in Missouri as in some neighboringstates. Favored by wet soils, low pH, fluctuating winter temperatures. Rotations with susceptible forage grasses or other cereals can increase potential. Downy brome is a host. | Reduce soil inoculation levels by rotation with non-host crops (e.g. soybeans, cotton). Control grass weeds. Delay seeding date. |
| Diseases of stems | |||
| Stem rust. Puccinia graminis fisp. tritici | Wheat stem rust usually appears in Missouri every year, but severity of attack will vary. Red spore stage (uredospores) is encountered during growing season and may occur on any above-ground parts. Elongated ragged pustules on stem, leaf sheath, blade or chaff usually begin to appear in mid-June. Pustules rupture tissue, exposing powdery, brick red mass of summer spores. As wheat nears maturity, black pustules filled with black spores (teliospores) appear. | Puccinia graminis has many specialized races. P. graminis tritici attacks wheat and barley.P. graminis avenaeoccurs chiefly on oats. P. graminis secalis occurs chiefly on rye. Alternate host is common barberry, a tall erect woody shrub with bristle-toothed leaves. However, virtually all of the stem rust infections come by way of spores blown in from infected fields in the southern regions. | Usually, stem rust is not a serious disease in Missouri as its appearance is late. Resistant varieties: wheat varieties entirely immune to stem rust do not exist but varieties with various degrees of resistance do. Eradication of common barberry has been ongoing in the U.S. and is about complete. Fungicides are available for control of rust when needed (e.g. Bayleton, Tilt). |
| Leaf rust. Puccinia recondita fsp. tritici. | See Leaf diseases. | ||
| Diseases of heads | |||
| Loose smut. Ustilago tritici. | Easily recognized by the characteristic dusty black appearance of diseased heads. As a rule, glumes and grain are completely transformed to black powder, which shatters off, leaving a bare spike at harvest. | Loose smut fungus grows down in the flower and establishes itself inside developing kernel. When infected wheat seed is sown, the fungus grows into the young shoots and develops with the plant, replacing the spikelets with black spores, which can infect flowers of healthy plants. | Foundation and certified seed should be relatively free of loose smut. Carboxin (Vitavax) seed treatment should be applied on all wheat used for seed. |
| Common bunt (Covered smut, "Stinking smut"). Tilletia foetida and T. caries | Heads affected by bunt, when they emerge from the boot, have blue cast. Infected kernels are transformed into smut balls during growth. Smut balls consist of masses of foul-smelling, dark-brown powder -- the spores of the fungus. | In the field, smutted heads usually stand more nearly erect than healthy heads because of lighter weights. Many smut balls are shattered during threshing, and spores lodge on healthy kernels. | Seed treatment with approved fungicide, e.g. thiram, maneb, mancozeb, terraclor, terraclor-terrazole, carboxin, carboxin-thiram, will provide good control. Resistant varieties have greatly reduced smut. |
| Scab (Head blight). Fusarium graminearum (Gibberella zea). | Premature ripening or bleaching of one or more spikelets of a head any time after flowering. When wheat is in dough stage, light yellow color of diseased spikelets of the head show in sharp contrast with healthy green of rest of head. Light pink or salmon color may appear at bases of infected pikelets. Kernels become grayish-white, badly shrunken and wrinkled, with rough, flaky seed coat; called "tombstone." | Blighting of heads is prevalent in moist, warm seasons from heading time onward. Severity of scab varies from year to year; associated with weather conditions. Same fungus are involved in seedling blight root rot, crown rot and stem blight. Grain containing 10 percent or more scabby kernels fed to hogs may cause vomiting (vomitoxin). Epidemics in Missouri, 1982 and 1990. | Avoid scabby grain for seed. Remove light, shriveled seed by fanning. Treat with< approved fungicide such as Vitavax 200 or one containing TBZ to reduce seedling blight potential. Avoid scabby grain for seed. Remove light, shriveled seed by fanning. Treat with approved fungicide such as Vitavax 200 or one containing TBZ to reduce seedling blight potential. See MU publication G4317, Scab of Wheat. |
| Glume blotch. Septoria nodorum | Causative fungus attacks heads most often. Produces brownish blotches near the tip of the chaff. Severely infected heads are chocolate brown and produce shriveled kernels. Also may be found on leaves and joints. Hard to distinguish from Septoria leaf blotch on leaves. | Glume blotch should not be confused with either black chaff or basal glume rot, which are bacterial infections. Attack on heads occurs mostly during warm weather. Severity varies from year to year. Usually more in southeast Missouri. | Sanitation and crop rotation to cut down on overwintering fungus. Clean seed severely and discard shriveled kernels. Use seed treatment with approved fungicide. |
| Basal glume rot. Pseudomonas atrofaciens (Bacterial disease). | Dull, brownish-black discolored area found at the base of each of the glumes covering a kernel. Discoloration is more pronounced on the inside than on outside of diseased glume. Some kernels faint brown or black at germ ends. | Rare and of minor importance on wheat (and barley) in Missouri. Infected chaff and leaf fragments blown about at threshing time serve to perpetuate the disease. | Same as for black chaff. |
| Black chaff. Xanthomonas campestris fsp. translucens(Bacterial disease). | Attacks wheat (also barley, rye, timothy, brome grass, quackgrass and wild barley). (Known as bacterial blight on barley and rye.) Occurs chiefly on the chaff or glumes. Longitudinal, dark, more or less sunken stripes or spots, more abundant and noticeable as a rule on the upper than the lower halves of the glumes. Coalesce to form blotches. In moist weather, tiny yellow beads of bacteria ooze to surface of black lesions and dry as minute, yellow scales. Symptoms on leaves appear as water-soaked spots and streaksthat eventually turn brown. There may be a yellow halo. Glumes develop brown streaks toward the bases. | Attacks leaves, sheaths, stems, glumes and kernels of wheat. Usually becomes prevalent in summers of excessive rainfall. Does not do appreciable amount of damage, and in most years will pass unnoticed. Certain years may sustain slight reductions in yield. Bacteria remain alive on >kernels or in diseased tissues in dry storage for at least two years. Frequently part of a complex of diseases, when it occurs in association with pseudo-black chaff and brown necrosis-physiological disorders of high temperature and humidity, inducing melanism. | Use clean seed. Discard shriveled kernels. Seed treatment with approved fungicide will help somewhat. Sanitation and crop rotation. Usually not a threatening disease in soft red winter wheat in Missouri. |
| Black point (Kernel smudge). Alternaria sp., Fusarium sp., "Helminthosporium," Species-Bipolaris spp. (more than 100 species possible). | Diseased kernels are discolored and appear weathered. Black point describes the darkened and sometimes shriveled embryo end of the seed. Germinability decreased. | Rainfall during seed maturation favors black point infections. Premature senescence also promotes black point. | It is impossible to exclude field fungi from maturing wheat seed. Foliar fungicides may have some preventive effects, but this has not been well demonstrated. Prompt storage; bring down to 13 percent moisture. |
| Black (sooty) head molds. Alternaria, Cladisporium and other species of fungi. | Superficial head molds develop on heads, especially if rainfall is high after senescence. Then infections can progress to seed, causing black point. | Usually occurs in summer of excess rainfall or irrigation. Prematurely rotted plants from take-all or other root or stem infections are subject to these molds. | Prompt harvest. Usually does not cause kernel infections. |
| Ergot. Claviceps purpurea | Empty florets occur in addition to kernels replaced by a plump, hard, purplish body larger than healthy kernel; usually two to five per head. | Ergot is most characteristic of rye, but will be found occasionally on wheat, triticale oats, barley and several grasses. Ergot bodies on ground germinate, infecting heads at blossoming time. "Honey dew" containing spores is produced, and insects and wind carry it to other heads. | Control measures are seldom necessary for this disease in wheat. If sclerotia are found in grain, the grain should not be fed to animals. |
| Virus diseases | |||
| Barley yellow dwarf (BYD). | Most widespread virus disease of wheat in Missouri. Stunting and yellowing are most noticeable symptoms. Symptoms are usually observed in late spring at about jointing. Leaf yellowing begins at leaf tips and along midribs. Flag leaves may have reddish-purple tips. Also causes "red leaf" in oats and "yellow dwarf" in barley. | Virus (BYVD) is complicated with many strains. Transmitted by more than 20 aphid species (e.g. corn leaf aphid, English grain aphid, greenbug, oat bird cherry aphid, etc.) Persistent virus in vectors. Not seed, soil or sap transmitted. | No high resistance. Commercial wheat varieties vary in tolerance. Early planting may accentuate aphid invasion and virus inoculations. Cooler temperatures may slow aphid activity. |
| Soil-borne wheat mosaic (SBWM). | Occurs on fall-sown wheat (also rye, barley and a few related wild grasses). Detected in spring by presence of light green to yellow patches in the fields, from small areas to areas 50 feet or more in diameter. Plants are dwarfed, tiller excessively and have mottled leaves consisting of light green or pale yellowish stripes or blotches that tend to run parallel with the long axis of the leaves. | Virus lives over from year to year in the soil and can persist in association with root fungus, Polymyxa graminis. Occurrence of the disease depends on weather of fall and winter, which influences growth and dormancy of the plants. Virus is not seed-borne. Vector and virus are spread by movement of soil in infested field. | With a few exceptions, soft wheat varieties are moderately resistant. Most hard red winter wheats are susceptible. Crop rotation is not successful. |
| Wheat yellow mosaic (WYM). (Wheat spindle streak mosaic) (WSSM). | Another soil-borne virus common to Missouri. More commonly seen in Southeast Missouri, but can occur in other areas. Tends to be more uniformly spread than soil-borne mosaic. Symptoms appear in early spring as yellow-green mottling, dashes and streaks on leaves. Streaks running parallel to veins taper to form chlorotic spindles. Reddish streaking at the leaf tips often precede necrosis. Some stunting and poor tillering. | Virus (WSSMV) has some fungus vector as wheat soil-borne mosaic, Polymyxa graminis. Occurrence of disease depends on weather conditions in fall and winter. | Late fall planting reduces or retards spindle streak infections. Crop rotation may help to limit incidence. |
| Wheat streak mosaic virus (WSMV). | Most infections occur in the fall, but symptoms are observed after the arrival of warm spring weather. Yellowish streaking and mottling of leaves; plants may be stunted. Leaf margins often rolled toward midrib. As plants approach maturity, mottling disappears, leaves tend to turn brown and die. Heads that form may be totally or partially sterile. | Usually not serious in Missouri but is present and has caused epidemic proportions (1981). Disease is most severe in warm, dry weather -- Western Great Plains states. In Kansas, most abundant in western half of state. Neither soil- nor seed-borne. Microscopic wheat curl mite carrier, (Aceria tulipae) comes from volunteer wheat or grasses. | Commercial wheat varieties vary in tolerance. In problem areas, delay of fall seeding reduces number of days the virus can spread in the fall. Destroy volunteer wheat before planting, within a half-mile and preferably one mile of field to be planted. |
University of Missouri Extension
© 1993 to 2007 Curators of the University of Missouri, all rights reserved
