Diagnosing

WHEATPRODUCTION

PROBLEMSin Kansas

Kansas State UniversityAgricultural Experiment Stationand Cooperative Extension Service

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heat, like all crops,

may suffer from a number of insect, disease,

weed, nutritional, and environmental stresses.

This publication will help in diagnosing likely

causes of slow growth, distorted

appearance, off-colors, injury, and death

of wheat plants

from planting through harvest.

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Contents

Fall Emergence 3and Growth

Spring Green Up 11to Heading

Heading 36to Maturity

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Seed germination was initiated, as seen by the small radical or seedroot that erupted from the seed, but it has now stopped. Apparently,moisture was sufficient to initiate germination, but was inadequate tosustain it. Dry soil has caused the germination/emergence process tostop. This is common with shallow plantings followed by several daysof hot, drying winds. Seed in this condition can remain viable for alimited time, but if the seed becomes soft and spongy, the chances ofit regrowing are not good.

Fall Emergenceand Growth

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Poor stand establishmentis the first problem produc-ers might encounter afterplanting. Poor stands canbe caused by a number ofproblems, such as aplugged drill, poor seedquality, dry soil, deepplanting, soil crusting,diseases, and insects. Taketime to examine the evi-dence. Look for fieldpatterns. Closer examina-tion of the situation willhelp determine the causesof poor stands.

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Soil crusting limits seedling emergence. The coleoptile is unable topenetrate the crusted layer. Lift the crust to observe the yellow,crinkled first leaf. These seedlings will not emerge.

Preplant herbicide injury can cause emergence problems in certaincases. Some herbicides, such as Treflan and Fargo, cause these prob-lems if used improperly and when cold, wet conditions followplanting. Treflan can cause a short, thickened coleoptile and stuntedroots when wheat is planted directly into herbicide-treated soil. Itshould be surface-applied or shallowly incorporated and the wheatplanted below the incorporation zone.

The coleoptile is theembryonic leaf thatpenetrates the soil so theseedling can reach thesurface. Deep planting,deeper than the coleoptile’sability to elongate, can slowemergence or cause standestablishment problems.Varieties differ in theircoleoptile lengths. Semi-dwarf varieties tend to havegreater problems becausethey have shorter coleop-tiles than taller varieties.Early planting in hot soilsreduces the coleoptile’sability to elongate.

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The seedlings on the left died soon after emergence. Insect injuryand seedling blight are the two major causes of post-emergence deathof seedlings. Carefully dig up plants and examine the root system andthe coleoptile region between the seed and the crown.

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False wireworms are soil-inhabiting, yellowish to orange-coloredworms up to 11/2 inches long. A pair of short antennae are clearlyvisible on the front of the head and the head region does not appearflattened when viewed from the side. See wireworm in photo 77 forcomparison. They commonly follow the drill row in dry soils, feedingon the seeds prior to germination.

These seedlings’ coleoptiles have distinct brown lesions typical ofseedling blight. Several fungi cause seedling blight, and these dis-eases are often worse with early planting. Although seedling diseasesare common, they usually do not kill the seedlings outright. Seedlingpathogens can cause other problems later in the growing season:Cochliobolus can lead to common root rot and crown rot, Rhizoctoniato sharp eyespot, and Fusarium to dryland root rot.

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If young plants are dying, with no aboveground symptoms evident,white grubs may be the cause. Check to see if the roots are pruned andif white “C”-shaped grubs are present in the soil near damaged plants.

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Plants with whitish streaks on the upper surfaces of leaves may havesuffered flea beetle injury. The effects are often present along oneside of the field. If streaking is severe, the plants may die. Olderinjuries can be confused with wind damage or dry weather.

Purple or yellow banding on the young leaves at emergence, calledcolor banding, is an environmental problem caused by warm dayswith cool nights. Seedlings will become cold tolerant and symptomswill fade.

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For this plant, germination and emergence were probably normal, but afew days later, signs of feeding scars appeared on individual leaves. The“window pane” feeding shown was caused by fall armyworms. Asworms grow and demand more food, they may destroy the entire plant.

The larvae of fall armyworms appear as brownish worms crawlingon the ground or hiding just under the soil surface. Symptoms includechewed leaves, missing tillers, or the entire plant being chewed off atground level.

Here the tiny, dark-colored flea beetle is shown feeding on a plant.These beetles quickly drop off or jump 2 to 3 feet from the plantwhen disturbed.

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Dead or injured wheat may be a result of herbicide carry-over fromthe previous crop. Herbicide carry-over often shows up where thesprayer turned or wherever there was a spray overlap that resulted in ahigher rate of application. This condition is most likely to followperiods of dry weather and in soils with pH extremes.

Here a greenbug can be seen on the left and a bird cherry-oat aphidon the right. Greenbugs are light green and have transparent cornicles,“tailpipes.” Bird cherry-oat aphids are usually dark to olive-coloredwith long, dark cornicles. They also have a dark red pattern that encom-passes the bases of the cornicles on the abdomen.

Greenbug infestation is more common after a frost, but beforeChristmas. Initial signs appear on the upper surface of leaves as clus-ters of pin-pricks that turn dark red. At the time of damage, greenbugswill be infesting the undersides of leaves. Affected leaves may turnyellow, and plant growth will slow. Parts of the field may appearyellowish. In advanced cases, plants begin to die in the fall or fail togreen up in the spring.

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Wheat planted into soils with atrazine residues emerges and then diesback from the tips of the oldest leaves first. Atrazine carry-over ismost likely with high application rates, high soil pH, coarse texturedsoils, and dry weather.

The plant near the center of the picture is stunted because of Hessian fly. Note the absence of stem elongation as compared withthe normal plant on the left. Affected plants usually exhibit an unusu-ally large, broad, greenish leaf for about a month in the fall, usuallybetween mid-October and mid-November.

Wheat plants that emerge and have a chlorotic or bleached appearancemay be injured from Command carry-over. Command herbicidedestroys chlorophyll in plants, thus they lose their green color. Plantsoften recover from early-season Command injury.

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The Hessian fly adult, rarely seen in the field, is orange to brown incolor. It deposits reddish eggs in grooves on the upper leaf surface.

Hessian fly maggots are white and legless. Later, they become dark-colored, hard-shelled “flaxseeds” behind the lower leaf sheath at or justbelow the soil line. Symptoms are the same as those in the photo 20.

Fuzzy roots are caused bydry soil conditions in thefall. Root hairs and outerplant cells are not sloughedoff under dry conditions.This is a normal plantreaction to dry soil.

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Plants in some areas of the field may be slow or fail to green up. Lookat soil conditions and location in the field. Loose, dry soil can be anindication plants died due to winterkill . Winterkill symptoms gener-ally will be seen on terrace tops and north-facing slopes. Look closelyat the crowns for discoloration and water-soaking.

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Some areas of the field may not initiate spring growth as wheatbegins to green up in the spring. Look for field patterns. Plants inthis terrace channel were killed by drowning or standing ice. Wheatcannot tolerate long periods of being submerged under water or ice.

Spring Green Upto Heading

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As wheat begins its spring green up, some plants may begin to die.Close inspection of this plant shows the crown is above the soilsurface with only a few roots into the soil. Heaving is a commonproblem in soils with high clay contents. Note the cracks in the soilindicating shrinking and swelling.

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Pink snow mold can attack wheat during cold, wet periods, or undersnow cover. Initial leaf lesions are light brown with a dark brownborder. Later, leaves become matted down and are bleached white asseen here. Close inspection usually reveals a pinkish orange funguson the dead leaves. Patches of pink snow mold range from a fewinches across to whole fields.

26The base of the plant hasbeen split open to revealthe dark brown discolora-tion of crown rot. Thisplant will not survivebecause the connectionbetween the roots and thetillers has been destroyed.A healthy crown is yellow-ish white inside. Crown rotis often initiated by winterinjury . However, it alsocan be initiated by com-mon root rot. Commonroot rot causes browningof roots, especially thesubcrown internode.

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Army cutworms cause brown patches to appear in fields soon aftergreen up. Spots may continue to increase in size over a period ofdays. Close inspection may reveal brown leaves that are the oldleaves from last fall, with spring growth missing. Below the soil,plants appear normal.

This plant shows the dam-age done by the armycutworm described inphoto 29.

Army cutworms feed aboveground, usually more on warm days, orhide just under the soil surface. They move out of the center of dam-aged spots and tend to be more abundant toward the periphery ofaffected areas.

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In extreme western Kansas, plant death in the spring (March to April)could be due to pale western cutworm. Damage is often limited tospots where loose or windblown soil was present in September orOctober. Occasionally, damage is uniform over the whole field.

Pale western cutworms are transparent, gray to white larvae up to11/4 inches long that remain below the soil surface.

The lower areas of this field are turning yellow in the early spring.Possible causes might be nitrogen deficiency, soilborne mosaicvirus, or spindle streak mosaic virus. The pattern of yellowing onindividual plants must be examined in order to make a diagnosis.

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Leaves show a mosaicpattern with green islandson a yellow background.The disease is wheat soil-borne mosaic. Varietieshave large differences intheir reaction to soilbornemosaic. Variety informa-tion can help confirm thediagnosis. Soilbornemosaic foliar symptomsfade as the weather warmsup and the plants beginjointing. However, plantsmay remain permanentlystunted.

Leaves show a mosaic pattern with short spindle-shaped yellowstreaks on a dark green background. These are characteristic symp-toms of wheat spindle streak mosaic. Spindle streak symptoms fadeas the weather warms up and the plants begin jointing. Infected plantsusually do not suffer stunting.

In this field, there is a pattern that suggests two varieties wereplanted. There is an obvious variety difference in yellowing. Theyellowing appears to be more severe on the sidehill where soil ero-sion has exposed lower organic matter, more calcareous subsoil. Thisis an example of iron chlorosis. Look closer at the leaves.

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Individual plants show a yellow striping with the leaf veins remaininggreen. Striping is most severe on the newly emerging leaves. Thesesymptoms are consistent with iron chlorosis. Soil tests would show ahigh pH, and more importantly, a highly calcareous soil. Iron chloro-sis is rare on wheat, and as shown in the previous photo, varietiesdiffer in their sensitivity.

Weeds can decrease yields, lower quality, and interfere with harvest.Fields should be scouted throughout the season for weed problems andtreated as needed. Winter annual brome grasses such as cheat,downy brome, and Japanese brome usually emerge in the fall and aresimilar in appearance. They have narrow, erect leaves with a clockwisetwist, red stems, and short hairs covering the leaf blades and sheaths.

The cheatgrasses head and mature about the same time as wheat.Pictured here are cheat, Japanese brome, and downy brome heads.Cheat and Japanese brome often are as tall or taller than wheat, whiledowny brome is usually shorter than wheat. Downy brome has longerawns, a drooping seedhead, and often has gray or purple coloredstems. Cheat leaves and sheaths are sparsely hairy, Japanese bromeleaves and sheaths are covered with dense long hairs, and downybrome leaves and sheaths are covered with dense short hairs.

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Jointed goatgrass is a winter annual grass closely related to wheat.The easiest way to identify young jointed goatgrass seedlings is to digup the young plant and locate the joint that contains the seeds. Thejoint is cylindrical shaped, about 3/8 to 1/2 inch long, and may containas many as four seeds.

Jointed goatgrass is aboutthe same height andmatures about the sametime as wheat. The seedjoints are stacked in acolumn in the seedhead,and shatter at harvest time.The joints are similar insize to wheat kernels andare difficult to separate andclean out of harvestedgrain.

Volunteer rye is similar in appearance to wheat, but is generallytaller and heads earlier.

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Rye has longer kernels and heads than wheat, and usually is morebluish.

Henbit emerges in the fall and has round cotyledons about 1/4 inch indiameter, square stems, and scallop-shaped leaves.

Henbit only grows a few inches tall. It is one of the first plants toflower in the spring with purple blossoms appearing in March.

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Bushy wallflower or treacle mustard is a common weed in centraland eastern Kansas. It usually emerges in the fall and forms rosetteswith long narrow leaves and irregular leaf margins.

Tansy mustard and flixweed are two similar mustard species com-mon in central and western Kansas. These weeds emerge in the falland grow as a rosette with finely lobed compound leaves.

Bushy wallflower rosettesbolt in the spring and bearbright yellow flowers at thetop of the plant, which onlygrows to about 1 to 11/2 feettall. Seeds are produced inlong, narrow seed pods.

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Tansy mustard and flixweed bolt in the spring and produce yellowflowers at the top of the plant, which may grow to 3 feet tall. Smallorange seeds are produced in long, narrow seed pods. Seed pods oftansy mustard are usually about 1/2 inch long, while flixweed seedpods are generally 1 to 11/2 inches long.

Field pennycress is a winter annual weed common to central andeastern Kansas that usually germinates in the fall and grows as arosette. Leaves are club-shaped and have a waxy leaf surface. Fieldpennycress has a strong garlicky odor, especially when the leaves arebruised.

Field pennycress bolts in the spring and bears white flowers at thetop of the plant, which may grow from 1 to 2 feet tall. Small brownseed with a thumb print pattern on the side are produced in flattenedseed pods about 1/2 inch in diameter.

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Blue mustard is a winter annual that germinates in the fall and pro-duces a rosette similar in appearance to a dandelion.

Blue mustard bolts in the spring and bears purple or blue flowers atthe top of the plant, which may grow from 1 to 11/2 feet tall. Seeds areproduced in long, narrow seed pods 1 to 2 inches long.

Kochia, sometimes called fireweed or firebush, is a summer annualweed that germinates early in the spring, often starting in earlyMarch. Kochia seedlings have a series of long, narrow, pubescentleaves attached directly to the stem.

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Kochia branches and produces a globe-shaped plant that will growseveral feet tall. Leaves are linear and up to 2 inches long. Kochiafrequently causes harvest-related problems. Plants break off at groundlevel in the fall and blow across the landscape, spreading seed as theygo. They are frequently called tumbleweeds.

Russian thistle is similar to kochia, except that it has very narrow,needlelike leaves. Young seedlings emerge early in the spring andresemble a miniature pine tree.

Mature Russian thistle branches and produces a globular plant likekochia. Leaves get a sharp, spiny tip. Russian thistles break off atground level in the fall and become tumbleweeds.

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Wild buckwheat also is an early-spring-germinating summer annualweed. Wild buckwheat has two crescent-shaped cotyledons, redstems, heart-shaped leaves, and an alternating leaf arrangement. Itbegins to emerge in March and has a vining growth habit.

Wild buckwheat wraps around wheat plants and creates harvestproblems. It often is confused with field bindweed because of thevining growth habit and similar leaf shape. However, buckwheat is anannual that grows from seed, while field bindweed is a perennial thatoften regrows from roots. Wild buckwheat has small inconspicuousgreen flowers and produces black pyramid-shaped seed.

Field bindweed is a perennial species that can grow from seed orestablished roots. Cotyledons of field bindweed seedlings are kidney-shaped, and true leaves are arrowhead-shaped. Field bindweed shootsemerging from established roots would not have cotyledons.

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Field bindweed has a vining growth habit and alternating leaves. Itproduces white or pink flowers about 1 inch in diameter. Field bind-weed seeds have a roughened appearance with two flattened sides andone rounded side.

In this field, a dry fertilizer spreader with the spreader fan notoperating properly appears to have caused streaks. Wheat is veryresponsive to nitrogen fertilization, and on fields low in availablenitrogen, poor fertilizer spread patterns can be quite obvious. Thepale color and lack of vigorous growth of the plants outside the streaksuggest nitrogen deficiency.

The bottom leaf of this plant is showing a symptom of nitrogendeficiency with yellowing starting at the tip and extending back alongthe midrib forming an inverted V. This characteristic dieback is notfrequently observed on wheat as bottom leaves often die from shadingand diseases before symptoms appear. Plant analysis and fertilizationhistory would help to confirm this diagnosis.

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Grazed wheat fields that have not been adequately fertilized (nitro-gen deficiency) with nitrogen will commonly show spots with apronounced greener color and more vigorous growth reflecting theadded nitrogen supplied through animals’ urine. Close inspection ofplants in the spots would likely reveal an increased tiller number.

Sometimes mistaken for soilborne mosaic, early spring greenbuginfestation is characterized by yellowish spots in fields, usually worsein one corner or one portion of the field, but not apt to be confined tolow areas. Symptoms are more pronounced on the lower leaves.Where severe, the plants may be stunted or dying.

Pictured is a greenbug colony. Either the insects or their parasitizedremains should be visible if yellowing, as previously described, is dueto greenbugs.

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Good early growth appears to be taking place at the left, but a strip tothe right appears either void of plants or has plants of poor vigor.Judging from the pattern of the symptoms, plants in the strip areshowing a lack of starter fertilizer because the applicator chainbroke.

This is a close-up of the two strips from the previous picture. Plantswithout the starter fertilizer show a lack of vigor and poor tillering, asymptom of phosphorous deficiency. Although these plants do notshow any purpling, you may see purpling of leaves with phosphorusdeficiency. Collect a soil sample to confirm the diagnosis and plannext year’s fertility program.

This stand is thin and lacks vigor. Plants do not show any insectfeeding or disease symptoms. Herbicides have not been used formany years on the field. The color and poor tillering might suggest aphosphorus deficiency, but soil tests show an adequate level. Exami-nation of the roots finds discolored tips (see photo 71). A soil testreveals a pH of less than 5 and KCl-extractable aluminum of greaterthan 25 ppm. These plants exhibit aluminum toxicity caused by avery low soil pH. Varietal differences do exist.

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A close-up of the root system of plants with aluminum toxicity from alow-pH soil shows poor root development (length and number). Rootsare frequently discolored (brownish), and plants may actually die insome cases, hence the thin stand. You would need to soil test to confirmthe diagnosis and plan a lime application to correct the problem.

Misapplied 2,4-D can inhibit tillering and reduce plant vigor (fore-ground) if applied before wheat is fully tillered. 2,4-D should not beapplied in the fall or until wheat is fully tillered in the spring.

This is a field that has developed a brownish cast suddenly in earlyspring. There appears to be a definite pattern, and if you look closeryou see leaf burning on the upper leaves. The wheel tracks suggestliquid nitrogen fertilizer has been applied recently and caused burn-ing. Symptoms should disappear as new leaves develop, and nodetrimental effect on yields should result.

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Wheat loses its cold hardiness as it greens up in the spring. Lowtemperatures may cause leaf tip burning, which is a symptom of mildfreeze damage. These symptoms may be confused with leaf burningcaused by liquid nitrogen fertilizer. This damage will have little or noeffect on yields. A more severe freeze can kill tillers.

The premature death of individual tillers, usually prior to heading,may indicate the presence of wireworms.

Carefully examine the underground portion of affected tillers bylooking for a circular hole cut by the wireworm larva to gainentrance. The growing point is usually destroyed by the larva asit tunnels within the stem.

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Wireworms are hard-shelled, plainly segmented, yellow to orangelarvae. Unlike false wireworms (see photo 8), their antennae are notreadily visible, and the head area often appears flattened from top tobottom.

Brown wheat mites may cause fields or spots in fields to turn brownor bronze. This is more common during dry periods of fall, winter, orearly spring and more often in fields where wheat follows wheat orwhere volunteer wheat was present during the previous spring.

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Examine leaves for a faintpattern of white pin-pricks.The dark-colored brownwheat mites also are visiblein this photo. Frequently,brown wheat mites concen-trate their feeding near theend of the leaf causing thetips to become noticeablybrown.

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Here wheat is either showing stress or disappearing in spots along oneside of the field adjacent to wheat stubble. Affected areas may besmall at first, but gradually enlarge during mild weather in the fall orearly spring. At greenup in the spring, these spots may appear to bewinterkill where the condition was not observed earlier. This could beBanks grass mite that moved from nearby infestations on volunteerwheat, grasses or other crops.

This leaf has a yellowish spot composed of numerous tiny, yellowpin-pricks. Severely affected leaves may be dead or dying. Affectedareas are seldom as distinct as the yellowish spot on this leaf appears.Look on the undersides of affected leaves for slight webbing andpresence of Banks grass mites.

Brown wheat mites, about the size of a period in newsprint, may beseen on the surface of leaves when plants are viewed from a few feetaway. They drop from leaves when disturbed. The front legs are atleast twice as long as the remaining legs. This mite is easily confusedwith the winter grain mite (photo 85).

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Banks grass mites are very small and best seen with a hand lens.Their bodies are nearly transparent or brownish and often have acouple of spots visible between the mid and rear sections of the body.If mites are visible on leaves from a distance, check for brown wheatmites or winter grain mites.

In central Kansas, the winter grain mite may be of concern in eitherfall or spring. Mites often hide at the base of plants during the dayand feed at night. Mites are brown, globe-shaped, and have brightorange legs.

Winter grain mite infesta-tions cause wheat to have asilver-gray appearance,sometimes with stunting,rolled leaves, and death ofleaves beginning at the tip.Note the symptoms of theleft leaf compared to thehealthy leaf on the right.

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This field has wheat streak mosaic. Plants in the foreground arestunted and yellow. A stubble field with volunteer wheat is visible onthe left side of the affected field. The field pattern suggests some pestor disease is coming out of the volunteer wheat. Take a close look atthe affected plants for disease symptoms.

Where damage is due to chinch bugs, the black-and-silver-wingedadults or reddish nymphs will be apparent in the soil, in the crownregion, and around the base of affected plants. Sometimes they willappear behind the lower leaf sheaths.

Stunted, dying, or stressedplants in eastern Kansascould be the result of chinchbug damage. Chinch bugsprefer thin wheat, usually indrier parts of the field.

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A new disease was foundrecently that is similar towheat streak mosaic. It isprovisionally being calledHigh Plains mosaic.Symptoms are similar towheat streak mosaic, butthey tend to be spottier. Thelife cycle of the High Plainsmosaic pathogen is similar towheat streak mosaic virus,and they are frequentlyfound together.

This is a close up view of wheat curl mites. You need about a 20Xmagnifier to see their white, cigar-shaped bodies. The round, whitestructures are eggs. These mites can carry both wheat streak mosaicvirus and the High Plains mosaic pathogen. Wheat curl mites oftencause the edge of wheat leaves to roll inwards. The mites congregatein the protected area under the rolled edge.

Wheat streak mosaic symp-toms are quite variable,depending on variety, envi-ronment, and strain of thevirus. Typically, symptomsconsist of long yellowstreaks that are concentratedat the leaf tips. As leavesbecome progressively moreyellow with time, the leafveins often remain green.Wheat streak mosaic symp-toms could be confused withnutrient deficiency problemssuch as iron chlorosis.

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Barley yellow dwarf often occurs in patches in the field. Plants arestunted and have yellow or purple leaf tips. Barley yellow dwarf iscarried by several species of aphids including the greenbug and birdcherry-oat aphid. Fall infections seem to cause the most damage.

These are symptoms of barley yellow dwarf. Notice that the leaf tipsare yellow or purple, but the leaf bases tend to remain green. Themidrib stays green longer than the leaf blade. Normally, barley yellowdwarf symptoms first appear at the boot stage.

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Early symptoms of Ameri-can wheat striate mosaicare thin, white striationsparallel to the leaf veins.They are most prominent onthe leaf’s underside. Thisviral disease is carried byleafhoppers and tends to berandomly scattered throughthe field. Many varieties arehighly resistant. Americanwheat striate mosaic couldbe confused with mite orthrips damage. See photo129 for symptoms later inthe season.

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Similar in color to greenbugs, Russian wheat aphids are light green,with cigar-shaped bodies. Their cornicles are absent, but they have aforked tail process visible with a hand lens when viewed from theside. Winged or wingless forms may be present in rolled leaves,within the boot, or in emerging (and usually trapped) heads.

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Infestation by Russian wheat aphids may occur any time of the yearin the western half of Kansas—more likely in the counties nearest tothe Colorado border. Look for purple to pink discoloration on rolled-up leaves. Long, white streaks, usually on the upper leaf surface, arecommon on infested leaves.

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This thin stand of wheat appears to be the result of factors existingearly in the growth cycle. Plant and soil samples from the poor-growth area and normal-growth areas would be quite helpful inassessing the reason for this thin stand. Samples from this area wouldshow a low soil pH, less than 5, with greater than 25 ppm KCl-extractable aluminum. Liming would correct this problem.

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Patches of white heads in the field may indicate problems at thecrown or below the soil line. Examine the roots and the lower stemsof the plants. Possible causes of white heads include drowning, take-all root rot, dryland root rot, wheat stem maggot, sharp eyespot,freeze damage, scab, and Cephalosporium stripe. The pattern in thefield is often useful in diagnosing the problem. This picture shows thepatchy field pattern of take-all root rot .

Headingto Maturity

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Take-all root rot causes theroots and lower stems to turndark, shiny, black. The dis-ease usually occurs in largepatches in the field, and alltillers on affected plants arediseased. Plants are oftenstunted, have white heads,and pull up easily becausethe roots have rotted. Take-all is most likely to occur incontinuous wheat fields withmoderate to high residuelevels and is favored bymoisture.

Dryland root rot, alsoknown as dryland foot rot,is another disease that causeswhite heads. It is caused by afungus called Fusarium.Often the stem base turnspink. The inside of the culmis filled with cottony pink orpinkish-white fungal myce-lium. All tillers on the plantare usually affected. Thedisease occurs in low rainfallareas and is favored bydrought stress. The disease iseasily mistaken for droughtstress or take-all.

Sharp eyespot causeslesions with light tan centersand dark brown margins onthe lower stems. The ends ofthe lesions are typicallypointed. If stems are girdled,the tiller may be stunted andmature prematurely, result-ing in a white headsymptom. Each tiller can beaffected differently. Com-mon in Kansas, it rarelycauses significant yield loss.When sharp eyespot attacksyoung seedlings, it can causeseedling blight. See photo 7.

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Close-up of the vascularbrowning in the nodescaused by Cephalosporiumstripe.

White heads can be a sign ofdamage by wheat stemmaggots. Common in mostfields, damage is limited toindividual, scattered heads.White heads can easily beremoved by lightly pullingthem. Chewing damage isapparent at the base of thestem just above the upper-most node. If most of thetillers on a plant have whiteheads, the damage is morelikely due to other causes.Wheat stem maggots are palegreen.

These leaves each have oneor two broad yellow stripesrunning the length of theleaf. In the center of theyellow stripes are somebrown leaf veins. You canfollow these discolored veinsdown into the leaf sheath andeven into the lower nodes.The yellow stripes withbrown veins are diagnosticfor Cephalosporium stripe.This vascular disease causesan uneven stunting of tillersand can cause white heads.

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The cereal leaf beetlelarvae feed on the upperepidermal layer of the leafcausing long, whitishstreaks. The damaged area istransparent. Primary damageis on the flag leaf, but dam-age may occur on otherleaves and the head. Whileall small grains may be ahost, this insect prefers oats.

The cereal leaf beetle larvais responsible for the “win-dow-pane” damage to theleaf. Eggs placed on the leafsurface hatch into tiny larvaethat cause longitudinalstreaks. Larvae may beoverlooked since they tend toremain hidden beneath aprotective, brown grasslikecamouflage. Exposed larvaeare about 1/4 inch long atmaturity, yellowish, andsomewhat grub-shaped,resembling an immatureColorado potato beetle.

The adult cereal leaf beetleis about 3/16 inch long with areddish thorax and a metal-lic, blue-black abdomen.Adults hibernate soon aftersmall-grain harvest and donot become active again untilthe following spring whenmating and egg layingbegins.

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There are several different kinds of leaf spots on wheat. This is anexample of tan spot. It is most likely to occur in continuous wheatfields with moderate to high residue levels.

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This is a close-up of tan spot. Lesions are tan and usually have ayellow border. There is often a small dark spot in the center of thelesions. Varieties differ greatly in their response to tan spot.

Chloride deficiency can cause leaf spotting that resembles tan spot(see photo 108). Symptoms appear uniformly and suddenly after flagleaf emergence. Only a few varieties, such as Cimarron and Triumph64, show these severe symptoms. Symptoms occur on soils that havelow chloride levels.

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Septoria blotch, also known as speckled leaf blotch, has tan lesionswith distinct black fungal structures easily seen with the naked eye. Itis possible to confuse this disease with Stagonospora nodorum blotch,but tan spot lacks the speckles.

One way to identify Stagonospora nodorum blotch is to look for thesmall, caramel-colored fungal structures in the lesions. These areusually difficult to see and will require a 10X hand lens.

Stagonospora nodorum blotch is very similar to tan spot. Thelesions tend to be longer and more variable in shape than tan spot.However, it is often impossible to distinguish these two diseaseswithout close examination (photo 112).

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The bright orange pustules containing dusty orange spores are charac-teristic of leaf rust. Pustules occur primarily on the upper leafsurface. Infection requires moisture, so this disease is more commonin areas with higher rainfall. There are large differences in suscepti-bility among varieties.

The initial symptoms of bacterial streak are water-soaked dots asseen next to the thumb. These water-soaked areas expand into narrow,yellowish, water-soaked streaks confined by the veins as seen near thetop of the leaf. A key diagnostic symptom is that the lesions appeartranslucent when viewed with back lighting. As lesions age, theybecome dark brown and are no longer translucent. When the diseaseattacks the glumes, it is called black chaff.

Bacterial leaf blight causesgreenish-gray, water-soakedspots or large blotches thatlater dry and turn white. Itoccurs when several days ofcool, rainy weather coincidewith flag leaf emergence.Usually, symptoms are firstseen on the flag leaf at bootstage. In severe cases, theentire leaf dies.

43

Stem rust attacks the leaves,stems, and heads of wheat. Itis the only kind of rust thatattacks the stems, so this isdiagnostic. Pustules of stemrust tend to be longer, moreragged, and darker brownthan leaf rust. As pustulesage, they turn dark (see stemon left), therefore this dis-ease is sometimes calledblack stem rust. Stem rustrequires higher temperaturesthan the other rusts, so it ismore commonly seen at theend of the season.

Unlike leaf rust, stripe rust pustules tend to occur in long stripes.Also, the pustules of stripe rust tend to be yellower than leaf rust.Stripe rust requires cool temperatures, so it is more commonly seen inthe early spring in the Great Plains.

Powdery mildew is one of the easiest diseases to diagnose. It lookslike small pieces of white cotton on the leaves. The small, black dotson the mildew pustules are fungal overwintering structures. Althoughcommon, powdery mildew usually is not serious in Kansas. On highlysusceptible varieties, it can attack the heads and cause significantyield loss.

117

118

119

44

120

121

122

Loose smut is most notice-able soon after heading. Thefloral parts of the wheat headare replaced by loose massesof brownish-black, powderyfungal spores. These sporesare easily blown off orwashed off by rain. After afew days, only a bare rachisremains, and the affectedtillers become less noticeable.Loose smut is seedborne andusually affects all the tillerson a plant.

Lodging can be caused by many factors. Heavy winds and rains at theheading stage are responsible for most lodging problems. Knowingthe variety, nitrogen rate, field location, and incidence of diseases orinsects will help determine the reason for lodging. Lodging tends tooccur on bottomland, or when high nitrogen rates, tall varieties, andhigh seeding rates are used.

Any time stem breakage or lodging occurs just above the first orsecond node, suspect Hessian fly.

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123

125

124

You can verify Hessian fly infestation by using a pocket knife tocarefully remove the leaf sheath from the node nearest the point of thebreak and looking for maggots or flaxseeds just above the node. Seephoto 21 for another close-up of flaxseeds.

Strawbreaker, or foot rot,causes lodging with stemsbuckling near the base. Dark,eye-shaped lesions appear onlower stems just above thesoil. Later, these lesionsappear charred. The symp-toms on the lower stemcould be confused with take-all, but there are differences:strawbreaker lesions are notshiny black (see photo 99);the roots do not rot, so plantsare not easily pulled up; andstems break just above thesoil line.

True armyworms are head-attacking insects associatedwith lodged wheat. Watchfor them in rainy periods inMay to early June. They stripthe leaves prematurely andmay clip the awns. Theyrarely cut wheat heads ordamage the kernels, buthead-clipping in barley is aproblem. True armywormscan be yellow, green, orblack. They always havevarious-colored stripes; atleast one thin, yellow band isvisible. The armyworm’shead is prominent and shiny,light brown.

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126

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128

Wheat head armyworm often is found in conjunction with truearmyworm outbreaks. It spends more time during the day feeding ondeveloping heads, and with longer mandibles, it is able to damagekernels prior to hard dough stage. This worm has green and whitestripes. Its body tapers distinctly from head to tail.

Initial symptoms of glumeblotch are small brown spotson the glumes or awns.These expand to darkblotches, darkening the head.As lesions age, they maybleach white and containvery small caramel-coloredround fungal structures.Glume blotch can be causedby the same fungus thatcauses Stagonosporanodorum blotch (photos 111and 112) or the fungus thatcauses speckled leaf blotch(photo 113).

Basal glume rot is a bacterial disease that attacks the heads whenrainy weather coincides with head emergence. It is similar to glumeblotch, but is less common. Dark brown lesions start at the base of theglumes and may extend into the rachis. Whole spikelets may die andturn white, but the discoloration at the base of the glumes remainsvisible. Often, only one or a few spikelets per head are affected.

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129

130

131

American wheat striatemosaic can cause darkbrown stripes or blotches onthe glumes of some varietiesof wheat. Symptoms tend tobe more uniform than withglume blotch. Usually thestem below the head is alsodarkened. Leaves have amosaic symptom of finewhite, green, or yellowlengthwise striations. All ofthe tillers on an infectedplant are usually affected,but adjacent plants can besymptomless. See photo 92for early symptoms.

Trapped heads, missing florets, and twisted awns can be caused bymisapplied 2,4-D, MCPA, Banvel, or Tordon. This type of injuryusually results from application at the wrong growth stage for theseherbicides. The safest time to apply 2,4-D, MCPA, or Banvel is whenthe wheat is fully tillered, but prior to jointing.

Downy mildew may occurin low, wet areas of fields.Plants are stunted and haveyellow, thickened, leatheryleaves. Heads are oftendistorted, causing a symptomcalled crazy-top, which mayresemble herbicide injury,see photo 130.

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132

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134

Hail damage at the boot stage may cause the head to be entrapped inthe boot, not allowing it to emerge normally, which results in agnarled or misshaped head. Hail may cause damage to the whole heador only slight damage to areas where the hail stones struck.

Freeze damage at the lateboot and heading stagescauses the head to have ayellowish-white, water-soaked appearance. Theawns will be bleached.

Shredded leaves and broken stems are typical symptoms of haildamage. Damage can range from slight leaf damage to a total cropfailure by breaking stems near the soil surface. A silage smell is oftendetectable soon after hail.

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135

A healthy wheat head hasgreen anthers and whitestigmas as in the lower leftfloret. The yellow anthers ofthe middle floret indicatepollen has recently been shedand the developing kernel inthe upper floret indicatesthere has been no freezedamage.

Tordon applied prior to wheat planting for field bindweed control cancause head sterility, especially if applied too late, at excessive rates,and if dry conditions prevail following herbicide application. Thedark areas in this wheat field are related to spot treatments of fieldbindweed with Tordon prior to planting the wheat. Wheat appearednormal until grain filling.

A close look inside the flo-rets will help assess theextent of freeze damage.The pollen-shedding antherswill become shriveled andturn whitish-brown insteadof having a normal turgid,green appearance as in photo136. The feathery, whitishstigmas will not open andthey will become whitish-brown and water-soaked.

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140

As wheat begins to mature, plants in some areas of the field may havean off-white color resembling take-all, instead of the normal goldencolor. This is premature ripening due to hot, dry weather. Patternsfollow the different soil types in the field that are lighter or shallower.The grain will be shriveled and have low test weights.

Scab, also called Fusariumhead blight, causes whiteheads when periods of rainyweather coincide with flow-ering. Commonly, only theupper portion of the head isblighted. Close inspectionmay reveal masses of pink-ish-orange fungal spores onthe spikelets or on the rachis.Scab causes seed to be dis-colored (photo 141).

Nodes of the wheat plants shown in the previous picture are swollenand dark green. Swollen nodes are a symptom of misapplied 2,4-D,Banvel or Tordon. The stems turn red due to an accumulation ofphotosynthates that could not be translocated to the heads becausethey were sterilized by Tordon.

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Bunt is a type of smut that replaces the contents of wheat kernelswith brown spores that have a fishy odor. The outer hull of the wheatkernel may remain intact and such seeds are called bunt balls. Duringharvest and handling, these bunt balls break open and contaminatehealthy seed with the spores. Formerly common, bunt is now con-trolled with seed certification programs and seed treatments.

Delayed harvest and con-tinual moist conditions afterthe grain is mature maycause the grain to germinateresulting in head sprouting.Varieties differ in suscepti-bility to sprouting. Whitewheat varieties tend to havemore sprouting problemsthan red wheats.

Scab causes wheat seed to become pink or white and chalky in tex-ture. It is lighter in test weight and may contain certain mycotoxinsinjurious to nonruminant livestock. Scab-infected grain is often diffi-cult to market.

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This mature head is coveredwith a dark fungus calledsooty mold. Sooty moldfungi are opportunisticinvaders of dead tissue.They are favored by periodsof rain after the wheat hasmatured. After long periodsof rain, sooty mold maypenetrate the glumes andcause black point on kernels(see photo 146).

Black point or black tip fungus is a dark, discoloration of the em-bryo end of the kernel. This may result in a discount if the grain isgraded as damaged. The germination rate of the affected grain maybe reduced. Black point is caused by the same fungi that cause sootymold and is favored by rainy weather after wheat has matured.

Ergot sclerotia are large (1/4to 1/2 inch long) purple-blackfungal structures that replacethe developing grain andprotrude from the head. Theycould be confused with buntballs, but ergots are largerthan bunt. Ergot sclerotia arehard with a solid white orgray interior, while buntballs are fragile and filledwith smelly, dark spores.Ergot is rare in wheat butfairly common in triticaleand rye.

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Index

A

B

C

Aluminum toxicity, 26, 27, 36American wheat striate mosaic, 34, 47Aphid

See Bird cherry-oat aphid, 8Greenbug, 8, 25Russian wheat aphid, 35

Army cutworm, 13Army Worm

See Fall armyworm, 7True armyworm, 45Wheat head armyworm, 46

Atrazine carry-over, 9

Bacterial leaf blight, 42Bacterial streak, 42Banks grass mite, 30, 31Banvel, 47, 50Barley yellow dwarf, 34Basal glume rot, 46Bird cherry-oat aphid, 8Black chaff, 42Black point, 52

See alsoSooty mold, 52Black stem rust, 43Black tip fungus, 52Blue mustard, 21Brome grasses, 16Brown wheat mite, 29Bunt, 51Bushy wallflower, 19

Cephalosporium stripe, 36, 38Cereal leaf beetle, 39Cheat, 16Chinch bug, 32Chloride deficiency, 40Color banding, 6Command carry-over, 9Common root rot, 12Crazy-top, 47Crown rot, 12Cutworms

See Army cutworm, 13Pale western cutworm, 14

54

F

H

JK

G

I

E

Deep planting, 4Downy brome, 16Downy mildew, 47

See alsoHerbicide injuryDrowning, 11, 36Dry soil, 3, 10Dryland foot rot, 37Dryland root rot, 36, 37

Ergot, 52

Fall armyworm, 7See alsoArmy Worm

False wireworm, 5See alsoWireworm, 28, 29

Fargo, 4Fertilizer, lack of starter, 26Fertilizer spread patterns, 24Field bindweed, 23, 24Field pennycress, 20Flea beetle, 6, 7Flixweed, 19, 20Freeze damage, 28, 36, 48, 49Fusarium head blight, 50

Glume blotch, 46Greenbug, 8, 25Grubs, 6

Hail damage, 48Head sprouting, 51Healthy wheat, 49Heaving, 12Henbit, 18Herbicide carry-over, 8Herbicide injury, 4

See alsoAtrazine carry-over, 9Banvel, 47, 50Command carry-over, 9Fargo, 4MCPA, 47Misapplied 2,4-D, 27, 47Tordon, 47, 49, 50Treflan, 4

Hessian fly, 9, 10, 44, 45High Plains mosaic, 33Hot, dry weather, 50

Ice, 11Insect injury, 5Iron chlorosis, 15, 16

Japanese brome, 16Jointed goatgrass, 17

Kochia, 21, 22

D

55

N

P

R

S

LLeaf burning, 27, 28Leaf rust, 42Lodging, 44Loose smut, 44

MCPA, 47Misapplied 2,4-D, 27, 47Missing florets, 47Mites

See Banks grass mite, 30, 31Brown wheat mite, 29, 30Wheat curl mite, 33Winter grain mite, 31

MosaicsSee American wheat striate mosaic, 34, 47

High Plains mosaic, 33Soilborne mosaic virus, 14Spindle streak mosaic virus, 14Wheat soilborne mosaic, 15Wheat spindle streak mosaic, 15

MustardSee Blue mustard, 21

Bushy wallflower, 19Field pennycress, 20Flixweed, 19, 20Tansy mustard, 19, 20Treacle mustard, 19

Nitrogen deficiency, 14, 24, 25See alsoFertilizer, lack of starter, 26

Nitrogen fertilizer, 27

Pale western cutworm, 14pH, low, 26, 27, 36pH, high

See Iron chlorosisPhosphorous deficiency, 26

See alsoFertilizer, lack of starter, 26Pink snow mold, 12Powdery mildew, 43Premature ripening, 50

Root-rotSee Common root rot, 12

Crown rot, 12Dryland foot rot, 37Dryland root rot, 37, 36Seedling blight, 5Take-all root rot, 36, 37

Roots, fuzzy, 10Russian thistle, 22Russian wheat aphid, 35Rust

See Leaf rust, 42Stem rust, 43Stripe rust, 43

Rye, 18See alsoVolunteer rye, 17

Scab, 50, 51Seedling blight, 5Septoria blotch, 41

M

56

WV

T

Sharp eyespot, 37Soil crusting, 4Soilborne mosaic virus, 14Sooty mold, 52Speckled leaf blotch, 41Spindle streak mosaic virus, 14Spreader fan not operating properly, 24Stagonospora nodorum blotch, 41Stand establishment, 3Starter fertilizer, lack of, 26Stem rust, 43Strawbreaker, 45Stripe rust, 43

Take-all root rot, 36, 37Tan spot, 40Tansy mustard, 19, 20Tordon, 47, 49, 50Trapped heads, 47Treacle mustard, 19Treflan, 4True armyworm, 45Tumbleweeds, 22Twisted awns, 472,4-D, 47, 50

Volunteer rye, 17See alsoRye, 18

Wheat curl mite, 33Wheat head armyworm, 46Wheat soilborne mosaic, 15Wheat spindle streak mosaic, 15Wheat stem maggot, 36, 38Wheat streak mosaic, 32, 33White grub, 6White heads, 36

See alsoCephalosporium stripe, 36, 38Drowning, 11, 36Dryland root rot, 36, 37Freeze damage, 28, 36, 48, 49Scab, 50, 51Sharp eyespot, 37Take-all root rot, 36, 37Wheat stem maggot, 36, 38

Wild buckwheat, 23Winter grain mite, 31Winter injury, 12Winterkill, 11Wireworm, 28, 29

See alsoFalse wireworm, 5

Reference & CreditsYou will find additional reference

information on this topic in these Kansas StateUniversity publications:Chemical Weed Control for Field Crops, Pastures,Rangeland, and Noncropland, (For current year)

The Greenbug: A pest in Wheat, MF-925Hessian Fly, Understanding its Importance andManagement, MF-1076

Spring Freeze Injury to Kansas Wheat, C-646Wheat Insect Management Recommendations, (Forcurrent year)

Wheat Production Handbook, C-529Wheat Variety Disease and Insect Ratings, MF-991

Photographs used in this publication wereprovided by Extension and research workerslocated within Kansas and across the country.Special thanks are offered to the following peoplefor helping us complete this series: Wayne Bailey,Bill Berg, Vance Ehmke, Jimmy Hatchett, MarkHodges, Frank Pears, Jim Schaffer, PhilSloderbeck, Jerry Wilde, and Bill Willis.

AuthorsJames P. Shroyer

Extension Agronomy

Robert L. BowdenExtension Plant Pathology

H. Leroy BrooksExtension Entomology

Dallas PetersonExtension Agronomy

David A. WhitneyExtension Agronomy

We would like to acknowledge the support of the:Kansas Wheat Commission,Kansas Association of Wheat Growers,and the Finnup Foundation.

Brand names appearing in this publication are for productidentification purposes only. No endorsement is intended, nor is

criticism implied of similar products not mentioned. Persons usingsuch products assume responsibility for their use in accordance with

current label directions of the manufacturer.

Publications from Kansas State University are available on the WorldWide Web at: http://www.oznet.ksu.edu

Contents of this publication may be freely reproduced for educationalpurposes. All other rights reserved. In each case, credit James P.

Shroyer et al., Diagnosing Wheat Production Problems in Kansas,Kansas State University, October 1998.

Kansas State UniversityAgricultural Experiment Stationand Cooperative Extension Service

S-84 October 1998

It is the policy of Kansas State University Agricultural Experiment Station andCooperative Extension Service that all persons shall have equal opportunity andaccess to its educational programs, services, activities, and materials withoutregard to race, color, religion, national origin, sex, age or disability. Kansas StateUniversity is an equal opportunity organization. Issued in furtherance of Coopera-tive Extension Work, Acts of May 8 and June 30, 1914, as amended. Kansas StateUniversity, County Extension Councils, Extension Districts, and United StatesDepartment of Agriculture Cooperating, Marc A. Johnson, Director.

File code: Crops and Soils 1-1 MS 10-98—5M