CIRCULAR 147

CIRCULR 147JANUARY 1964

*

DISEASES of S1IALL GIIAINS
ill

X1L,1611
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Agricultural Experiment Station UNIVERSITY AUBURN
E. V. Smith, Director Auburn, Alabama

CONTENTS

Page
OATS ................................................ .........................

3

WHEAT
BARLEY RYE

........................................................................ ........................................................................

8

.............................................................................

12 15
16

CONTROL MEASURES .......................................................

Resistant Varieties..............................................16 Seed Treatment.................................................20 Rotation and Sanitation........................................22
ACKNOWLEDGMENT ........................................................

23

FIRST PRINTING 3M JANUARY

1964

DISEASES of SMALL GRAINS inALABAMA
J. A. LYLE, Head, Dept. of Botany and Plant Pathology
R. T. GUDAUSKAS, Assoc. Professor, Botany and Plant Pathology

ISEASES are often the greatest single factor limiting forage and grain production of cereal crops. Many diseases can be controlled by chemical seed treatment, use of resistant varieties, crop rotation, and field sanitation. However, identification of the disease involved is essential in selecting appropriate control measures. Small grain diseases are most frequently caused by microscopic, non-green plants called fungi. The parasitic activity of these fungi on plants results in symptoms and/or signs characteristic of a particular disease. Fungi reproduce by tiny, seedlike bodies called spores. Being quite small, spores can be carried by wind currents sometimes hundreds of miles. Man, mechanical equipment, rain, insects, and animals aid in scattering spores. Other causes of small grain diseases include bacteria, nematodes, viruses, and unfavorable environmental conditions. This report contains information obtained during the last decade from evaluations of disease incidence and varietal susceptibility of small grains planted in variety tests, field plots, and private farms throughout Alabama.

D

OATS Crown Rust (causal fungus, Puccinia coronata). Crown rust or leaf rust occurs on oats throughout the State and has been particularly damaging in southern Alabama during recent years. Crown rust is primarily found on leaves but also occurs on stems, leaf sheaths, and floral structures. The disease first appears as small, bright yellow to orange spore masses (pustules) that are round to oblong in shape, Figure 1. Spores are blown to susceptible plants. In later stages of the fungus life cycle, pustules of black spore masses

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Bust control is comllicated becsthtie causal fungus consists of races w5itli capabilities toitijfferent oat varieties. Statei-feet wxidle colilections of crowsn rust are
matle annuialiy to determine num-

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ber and kinds of races present in Alaama. D ata giv en ini faIble I tio none of the conmonly ta pate Iat va rieties are immune to ttack from11 all races, but some hv reitance to more races tian oties obsrxvante of a race or itpart iclar varioety dioes not netttssariix meanu that tihe \vanets xvas sexvercly rusted or that xiedxsrertitt.\cylte cvltl eerdcd vi d
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Fig. 1. Oat leaves infected with crown rust organism. New pustules are yellow to bright orange in color, on right, and later turn black, left.

tiaimagt trollt riust has lbeen iol) servs tinil recinit xvtals on arny of

te ilisttti varieties piamnteti ini t tests tilrouigihount till State except at thet (Guif Coast Suibstation, ill Soutilxwestrnl \abama, wxhere all varieties planttei wxere stxvcreiy ruisteti in 1961 andt 1962. 'I'it, ihigil tiisease' incitience wxas cortelattei xxiti retlimed grauin yields, although folragt prodtucttion wxas nolt afitectedi. Similar rust infestatiolns occurreti tiurinlg tile 1949-1951 seasons.

Helminthosporium Leaf Blotch (causal fungus, 11clouintmospora cell-c ) . Leaf blotch, once regartietd as a minor tlisease, is the most prexvalent anti perhaps most tiestructive tiisease 011 olats ill
ion Ai libam1a. Tlieaf blotih f tiigus caiuses stetiling bligiht. Oin oldter plants, figure 2, tilt tlisease appears as rttl-browxn spouts primnarily o)n leaves anti leaf sheaths bult solmetimes oln stems anti floral parts. Tilese spoIts are sinailI anti iouInti to ovxal wxit tirretgul ar inargins anti frequient stinken centers. Long iinear iblotcihes result from coalescing (If

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Loose smut is shown on wheat at left, on oats, center, and on Fig. 3. barley, right. (Phuto at left courtes~y E. A. Curl, Auburn University Agricultural Experiment Station.)

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ground before germination or seedlings blighted after emergence. Leaves of affected seedlings become reddened and necrotic. A symptom in mature infected plants is a blackening of the lower joints. Plants tend to break just above these joints and lodging results. There may be deterioration of roots. High temperatures and abundant moisture favor development of this disease. Under these conditions, a susceptible variety, seeded early, may suffer losses in stand, making reseeding necessary. Such losses occurred in Alabama on early-planted oats during the period 1946-1956. Of the many varieties planted, only Victorgrain 48-93 is highly susceptible to Victoria blight. Chemical seed treatment and crop rotation must be practiced when a susceptible variety is grown. Septoria Leaf Blotch (causal fungus, Septoria avenae). Septoria leaf blotch occurs frequently and causes damage to oats in Alabama. This disease appears as brown, irregular-shaped blotches on leaves. The blotches may spread over the entire leaf blade and sheath, frequently extending into the stem causing it to become necrotic and blackened. Blotching of floral parts and subsequent kernel discoloration sometime occur. Some oat varieties grown in Alabama are relatively unaffected by the disease. Red Leaf (causal virus, Barley Yellow Dwarf Virus). Red leaf (yellow dwarf) of oats is caused by a virus transmitted by certain species of aphids. The disease occurs generally throughout the State on barley, rye, wheat, and other grasses. Symptoms of this disease are sometimes difficult to distinguish from those of soil mineral imbalance, aphid damage, or some root and crown diseases. The most typical symptom is leaf discoloration. At first, there are yellowish-green blotches near the tips of leaves. The blotches, irregular in size and shape, become red, enlarge and fuse, making leaves entirely red. Frequently, symptoms appear after aphid infestation. Infected plants are often stunted. Reduction in forage quality and yield, grain yields, size, and test weight can result from infection by this virus. Symptoms of red leaf or yellow dwarf on oats have been observed in Alabama since 1947. In the 1949-1950 season, a severe outbreak of the disease occurred in Alabama. The prevalence and severity of the disease varied from field to field and from year to year. Previous observations have indicated that, if an aphid infestation occurs early in the growing season and populations build up rapidly, many fields may be seriously affected.

[7]

No practical control measure is available. Aphid control has proved ineffective to date. Miscellaneous Diseases of Oats. Other diseases occasionally found on oats in Alabama but not of economic importance during the past 10 years are: Halo Blight Bacterial Stripe Downy Mildew Stem Rust Blast Powdery Mildew Mosaic Gray Leaf Spot (causal bacterium, Pseudomonas coronafacians) (causal bacterium, Pseudomonas striafaciens) (causal fungus, Sclerospora macrospora) (causal fungus, Puccinia graminis avenae) (adverse environmental conditions) (causal fungus, Erysiphe graminis avenae) (soil-borne virus) (manganese deficiency) WHEAT Leaf Rust (causal fungus, Puccinia rubigo-vera tritici). Leaf rust is usually an important and widespread disease wherever wheat is grown in Alabama. Barley and a number of uncultivated grasses are also susceptible. Like crown rust of oats, leaf rust is characterized by the small, yellow-orange pustules on the leaves, Figure 5. These masses of spores turn black as the wheat matures. Infected leaves turn yellow and die. Damage from leaf rust is usually underestimated because there is seldom severe shriveling of grain. However, there may be a reduction in number of kernels. There is a severe loss in yield when infection occurs early and continues throughout the growing season. In general, grazed wheat has been observed to be less seriously affected by this disease than ungrazed wheat. Physiologic races of leaf rust, like those of crown rust on oats, show selectivity to the wheat varieties they attack. In 1959, a total of 124 collections of wheat leaf rust was made throughout Alabama, Table 2. Race 15, and the similar race 2, comprised 67.7 per cent of all those isolated. Second in importance was the group composed of similar races 54, 77, and 122. These three comprised 21.0 per cent [8]

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TABLE 2. OCCURRENCE OF PHYSIOLOGIC RACES OF LEAF RUST FUNGUS ON WHEAT GROWN IN VARIETY TESTS IN 1959

Physiologic Races Variety Anderson Atlas 66 Axminster Carala Chancellor Chul C. I. 12185 Coastal Coker 47-27 Coker 55-3 Coker 57-6 C. U. L. 6 C. U. L. 22-1 Hope Leap M. P. 242428 Norka R. L. 1888 Purplestraw Taylor Taylor 49 T 1123-3-20 Vermillion 2 2 2 2 2 1 3 6 1 3 3 1 1 1 2 2 3 10 1 1 4 6 2 1 1 1 2 1 1 1 4 1 5 1 5 2 1 6 15 3 6 1 20 52 54 58 77 122 143

2

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Crop rotation, plowing under volunteer wheat and wheat residue, and chemical seed treatment aid in reducing losses from this disease. Loose Smut (causal fungus, Ustilago tritici). Loose smut is common in wheat fields, but has rarely caused serious or widespread losses in this State. Symptoms of this disease are similar to those described for loose smut of oats. Spores of the fungus from smutted heads are wind and insect borne to healthy flowers. Seed thus infected are planted the following year and fungus develops with the plant, eventually resulting in the characteristic smutted head, Figure 3. This fungus also has physiologic races, Table 3. Since this fungus occurs within tissues of seed, chemical seed treatment will not control loose smut of wheat. Use of resistant varieties is the most practical control, Table 5. Certified seed, free from the disease, should be obtained. Scab (causal fungus, Gibberella zeae). Scab occurs every year, usually to a minor degree, on wheat and other small grains throughout the State. The disease causes a blight of seedlings and heads. Infected seedlings are stunted, yellowed, and frequently killed. The infected parts [10]

Fig. 6. Here is powdery mildew on wheat. powdery patches on leaf surfaces.

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Miscellaneous Diseases of Barley. cur on barley in Alabama include: Anthracnose Bacterial Blight Covered and Loose Smuts (see Fig. 3) Scab Septoria Leaf Blotch Stem Rust Yellow Dwarf

Diseases that sometime oc-

(causal fungus, Colletotrichum graminicolum) (causal bacterium, Xanthomonas translucens) (causal fungi, Ustilago hordei and Ustilago nigra, respectively) (causal fungus, Gibberella zeae) (causal fungus, Septoria passerinii) (causal fungus, Pucciniagraminis secalis) (causal virus, Barley Yellow Dwarf Virus) RYE

Anthracnose (causal fungus, Colletotrichum graminicolum). Anthracnose appears on leaves, leaf sheaths, and stems as long, narrow lesions that are light brown. Frequently, the small, black fruiting bodies of the fungus can be seen on the surface of the lesions. Stem discoloration is often strongly evident. Many affected rye plants are stunted and blighted, and the portion of the head above a lesion is often killed, resulting in shriveled grain in that part of the head. Reduction of vigor, premature ripening, and death of plants can result. Crop rotation, field sanitation, use of clean seed, and chemical seed treatment aid in minimizing losses from this disease. Explorer, Gator, and Wren's Abruzzi, the varieties recommended for planting, have not appeared to be susceptible. Powdery Mildew (causal fungus, Erysiphe graminis secalis). Powdery mildew is commonly found on rye and occasionally causes severe damage. The disease is similar in appearance to that found on wheat. All varieties recommended for planting are susceptible. Leaf Rust (causal fungus, Puccinia rubigo-vera secalis). Rust is found every year on rye but to date no appreciable damage has been observed in Alabama. Symptoms and control are similar to those of leaf rust of wheat. None of the recommended varieties is resistant.
[15]

Miscellaneous Diseases of Rye. Some less important diseases occasionally found on rye in Alabama are: Scab Scald (causal fungus, Gibberella zeae) (causal fungus, Rhynchosporium secalis) Septoria Leaf Blotch (causal fungus, Septoria secalis) CONTROL MEASURES Resistant Varieties The use of resistant varieties is the most practical method of controlling small grain diseases. Some of the small grain varieties recommended for planting in Alabama contain no specific factors for disease resistance and frequently vary in susceptibility to diseases. Such variation may result from differences in environment, type, race, and prevalence of the disease-causing agent, and the development and physiological condition of the host. To determine varietal reactions to diseases as well as disease prevalence, yearly evaluations were made on entries in small grain variety tests planted at 15 locations in the State. Summaries of these evaluations for commonly grown varieties of oats, wheat, barley, and rye are given in Tables 4, 5, and 6. These reactions are averages of data obtained over a period of years, a minimum of 2 years for some of the newer varieties and up to 10 years for the older varieties.

[16]

TABLE 4. REACTIONS OF OAT VARIETIES TO SOME DISEASES INALABAMA

VreyRust

aryCrown Helminthosporium Leaf Blotch S R R R R R R R R R R S S R R R R S S R R S R

Loose

Smut.

Victoria
Blight

Septoria
Leaf Blotch

Red
Leaf

Arkwin Arlington Carolee Coker 57-11 Coker 58-7 Fairfax Fulwood Mid South Moregrain Roanoke Victorgrain 48-93 Arkwin Carolee Coker 57-11 Coker 58-7 Delta Red 88 Fairfax Fulwood Mid South
Moregrain

NORTHERN ALABAMA R R S S R R R R R S R R R R R R R R S R R S R R S R R R R R S S R CENTRAL ALABAMA S R S R S R S R S R R R S R S R S R S R S R S R R R R R R R S R R R R S R R R R R R R R R R R

R R S S R R S S S R R S S S R S R S S S R S R S R S S R S S S S R R

S S S S R R S S S R S

Roanoke Suregrain Victorgrain 48-93 Carolee Coker 57-11

SOUTHERN ALABAMA S S R R S R S S R Coker 58-7 R S R Delta Red 88 S R Fuiwood S S S R Mid South S S R Moregrain S S Radar I R S S Radar II R R R S Suregrain S Victorgrain_48-93 R R R-Resistant, never or only slightly affected. S-Susceptible.

[17]

TABLE

5.

REACTIONS OF WHEAT VARIETIES TO SOME DISEASES

IN ALABAMA

VreyPowdery

MidwRust

Scab

Leaf

Septoria Blotch S S S R S S S R

Loose Smut R R R R R R R R R R R R R R R R R R R R R R R R R R R

Ace Anderson Atlas 66 Bledsoe Coker 47-27 Ga. 1123 Knox Wakeland Ace Anderson Atlas 66 Bledsoe Coker 47-27 Coker 59-11 Coker 59-36 Ga. 1123 Wakeland

NORTHERN ALABAMA R R R S R S R R R S R R R S R R CENTRAL ALABAMA R R R S R S R S R S R R R R R R R R
SOUTHERN ALABAMA

Ace S R Anderson S R Atlas 66 S R Bledsoe S R Coastal S R Coker 47-27 S R Coker 59-11 S R Coker 59-36 S R Ga. 1123 S R Wakeland S R R-Resistant, never or only slightly affected. S-Susceptible.

S S s S S S R R R R

[18]

TABLE 6.

REACTIONS

OF BARLEY AND RYE VARIETIES TO SOME DISEASES IN ALABAMA

Variety

PowderyAnthracnose Mildew

Spot Blotch

Net Blotch

Leaf Rust

Scald

Colonial 2 Dayton Ga. Jet Pace Explorer Gator Wren's Abruzzi

S S S S** S S S R R R

BARLEY S S S R*** RYE

S S R*** R***

S S S RR*** S S S

S S** S

R-Resistant, never or only slightly affected. S-Susceptible. *-R in southern Alabama in central Alabama '-S in central Alabama

**-R

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Seed Treatment Seed treatment is the practice of applying fungicides in the form of dusts, slurries, or liquids to seed before planting. Seed treatment protects the seed against certain disease-causing organisms and substantially improves the chances for survival for each seedling. Thus, there are fewer failures to obtain a good stand and fewer cases in which stands are irregular. It is advisable to treat small grain seed either with chemicals or hot water before planting. The type of treatment will depend upon the disease or diseases to be controlled. Chemical treatments vary in their effect on surface seed-borne, internal seed-borne, and soilborne organisms. Hot-water seed treatment is used to destroy disease organisms within the seed. Various chemical seed protectants have been evaluated to determine their effect in disease control. In experiments conducted in 1954-1955 with Victorgrain 48-93 oat seed artificially inoculated with the Victoria blight fungus, Helminthosporium victoriae, the relative effectiveness of certain treatments was determined from average emergences in the greenhouse, Table 7, and from green forage and grain yields taken at six locations throughout the State, Tables 8 and 9. In general, the organic mercurials were more effective than the non-mercurials in control of Victoria blight.
TABLE

7.

AVERAGE SEEDLING EMERGENCES IN THE OAT SEED PROTECTANT
EXPERIMENT IN THE GREENHOUSE AT AUBURN,

1956

Locations from which samples were taken

Treatment

Main
Station

Black Belt
station

Piedmont
station

Tennessee Valley Substation

Cppoastaer

Plain Substation

Sub-

Sub-

Wiregrass Substation

Pct.

Pct.

Pct.

Pct.

Pct.

Pct.

Agrox Ceresan M Ethyl B-856 Gy-Trete Mercusol Orthocide Panogen Inoculated Check Uninoculated Check L.S.D.-5% Level L.S.D-1% Level

98.80 98.40 98.40 94.80 98.80 96.00 97.60 88.40 91.20 4.29 5.78

99.75 100.00 98.00 92.00 98.80 97.60 99.25 92.00 89.25 3.53 4.76

95.60 96.40 91.60 86.40 94.40 90.00 95.20 81.60 84.00 5.60 7.54

96.00 98.00 94.40 84.40 96.40 92.80 98.80 66.40 83.20 6.09 8.20

99.2 96.4 96.4 90.0 90.4 97.2 98.4 85.2 93.2 3.45 4.65

99.75 99.75 98.00 96.00 95.20 97.60 99.75 90.40 94.00 3.47 4.68

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TABLE 8. AVERAGE YIELDS OF GREEN OAT FORAGE PER ACRE, SEED PROTECTANT EXPERIMENT AT Six LOCATIONS, 19561

Black Treatment Main Station Belt Substation Lb. 17,548 18,939 14,429 19,328 14,766 14,940 18,233 12,799 14,540

Piedmont Tennessee sSubValley SuSubstation Lb. 9,924 10,659 7,592 8,061 6,886 7,998 10,491 8,045 8,669

Upper
Plain ubstation Lb. 5,001 5,001 4,856 4,356 5,404 4,449 5,081 5,234 5,375

Wiregrass Substation Lb. 18,233 19,528 14,940 15,614 14,429 14,799 18,939 12,799 17,548

Agrox Ceresan M Ethyl B-856 Gy-Trete Mercusol Orthocide Panogen Inoculated Check Uninoculated Check

Lb. 3,748 3,791 2,549 3,364 1,906 3,271 4,122 2,429 3,194

Lb. 11,969 12,351 9,138 9,855 8,757 9,502 12,623 10,209 12,069

L. S. D. - 5% Level, 1,008 L. S. D.1% Level, 1,162 1 Two clippings made at the Black Belt, Piedmont, Tennessee Valley, and Upper Coastal Plain Substations; one clipping made at the Main Station (Auburn) and at the Wiregrass Substation.

TABLE 9. AVERAGE YIELDS OF GRAIN PER ACRE, SEED PROTECTANT EXPERIMENT AT Six LOCATIONS, 1956

Treatment

Main Station Bu. 85.94 83.44 71.18 79.05 53.14 72.65 76.59 53.32 73.64

Black Belt Substation Bu. 70.71 86.20 64.59 61.95 56.65 68.06 73.16 55.23 58.69

Piedmont Substation Bu. 84.74 101.07 84.71 81.53 77.59 87.80 98.18 82.69 82.46

Tennessee Valley Substation Bu. 103.02 109.09 84.64 92.36 91.69 92.38 107.94 84.08 101.05

Coastal Plain Substation Bu. 95.41 94.81 88.76 94.68 91.81 80.07 101.19 74.26 94.59

iregrass Substation Bu. 43.66 45.92 36.88 36.90 30.18 43.66 46.58 31.36 36.08

Agrox
Ceresan M

Ethyl B-856 Gy-Trete Mercusol
Orthocide
Panogen

Inoculated Check Uninoculated Check

L. S. D. - 5% Level, 6.6 L. S. D. - 1% level, 7.6

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Rotation and Sanitation Losses from small grain diseases can be reduced by crop rotation and sanitation. In addition, crop rotation does much to control weeds and reduce destructive damage caused by insects. Continuous cropping may result in establishing in the soil a high population of organisms infectious to that particular crop; the higher this population becomes, the greater is the potential loss. With rotation the continuity of susceptible hosts is broken and the population of destructive organisms is reduced. Some disease-causing organisms decrease in abundance as the host material disappears. A rotation system that allows decay of crop residue before the same crop is replanted in a field reduces materially the number of these organisms. In sanitation the elimination or destruction of disease-carrying materials is necessary. Bacteria and fungi often inhabit crop residue, volunteer crop plants, weeds, or alternate hosts. Practicing sanitary measures, including plowing under and rotting diseased plant parts as completely as possible, burning, deep tillage, chemical control of weeds, use of clean seed, reduces or eliminates this inoculum before the new crop is planted.

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ACKNOWLEDGMENT Grateful acknowledgment is made to the following for race identification of fungi: W. M. Bever, University of Illinois, loose smut of wheat; C. O. Johnston, Kansas State University, wheat leaf rust; M. D. Simons, Iowa State University, crown rust of oats; assistance: C. C. King, Jr., Auburn University, and personnel of the Auburn University Agricultural Experiment Station at the Black Belt, Gulf Coast, Lower Coastal Plain, and Wiregrass Substations; the Alexandria, Brewton, Monroeville, Prattville, and Tuskegee Experiment Fields; and the Plant Breeding Unit, Tallassee.

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