BULLETIN 921 DECEMBER 195s 5H7 , E55 Diseases 0/ SMALL GRAINS in Zszas in cooperation with the UNITED STATES DEPARTMENT OF AGRICULTURE TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWIS. DIRECTOR, COLLEGE STATION. TEXAS DIGEST Diseases of small grains are important factors in the growing of these crops for grain or forage in Texas. Damage to the crop may result from reduced stands, reduction in amount or quality of forage or in reduced yields and quality of the grain produced. Losses from diseases occur nearly every year. In excessively wet seasons, such as 1957 and 1958, these losses were estimated to be more than ZELUUELUUU bushels of grain. The control or reduction of losses from many small grain diseases in Texas is not only of local importance, but has national and international signif- icance. The fall infection, winter survival and spring increase in South Texas of airborne pathogens, such as the cereal rusts, may endanger the small grain crops throughout Texas and other states. Diseases of wheat, which consistently cause losses or are potentially dangerous to the crop, include leaf rust, stem rust, speckled leaf blotch and loose and covered smut or bunt. Less frequently present and usually less damaging diseases are stripe rust, mildew, Septoria glume blotch and foot-rot. A brief description of these diseases is given with suggested control measures where these are known. The two most serious diseases of oats in Texas are crown rust and the Helminthosporium blights. Stem rust is a potential threat to the crop every year. Smuts take a moderate toll each season, but can be controlled easily by seed treatment. Recently, the Septoria diseases, powdery mildew and yellow dwarf, have caused local area losses and these diseases may become important in Texas. A brief description of these diseases is given, with suggested measures for reducing losses. Net blotch, leaf rust, mildew and the smuts cause some damage to barley nearly every year. Barley may serve as an overwintering host for stem rust of wheat. Bacterial blight, false stripe, scald and yellow dwarf cause losses less frequently in Texas. A brief description of these diseases is given, with suggested means for control or reducing losses. The treatment of all small grain planting seed with approved fungicides is recommended. Such treatment controls seedbome pathogens and may reduce infection from pathogens in the soil or crop residue. Extensive research is underway to find fungicides capable of controlling such pathogens as the rusts. While some promising materials of this type have been discovered, they are not now practical for use on low-per-acre-value crops such as the small grains. CONTENTS Introduction . . . . . . . _ . . . . , . . . . . . . . . . . . . . . . 4 . ' Diseases of Wheat , , . . . . . . . . . . . . . . . . . . . . . . . . .. . Stem Rust . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . if Leaf Rust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. StripeRust . . . . . . . . . . . . . . . .. Speckled Leaf Blotch . . . . . . . . . . . . . . . . . . . .. Septoria Glume Blotch . . . . . . . . . . . . . . . . . . .. i Powdery Mildew . . . . . . . . . . . . . . . . . . . . . . . .. A Loose Smut . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. l Bunt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. F oot-rot . . . . . . . . . . . Cold Injury . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . ’ Diseases of CrownRust......., StemRust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Smuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Helminthosporium Blights. .. .. A SeptoriaDisease................... YellowDwarf......,...................... Diseases of Barley.............................i NetBlotch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Spot Blotch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Powdery Mildew , , . . . . . . , . . . . . . . . . . . . . . .. Leaf Rust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Stem Bacterial Blight . . . . . . . . . . . . . . . . . . . . . . . . . .. False Stripe . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scald . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Covered Loose Smut . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Yellow Dwarf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgmentswn.......,.................l .‘ L GRAINS ARE GROWN extensively in Texas V- grain or forage, or for-combinations of A, A recent survey showed that all but 18 ~j 54 Texas counties grew some acreage of in. The concentration of acreages var- i; the crop and with the section of the liThe estimated harvested areas for the 10- vriod, 1947-56, were 3,634,000 acres of ,130,900 acres of oats and 120,200 acres ja Unofficial estimates made in 1957 in- éihat an additional one million acres are ixclusively for forage. from diseases are important factors in fling of small grain" crops in Texas. The mid Winters of the southern half of the 6d the long period of seedling growth fa- establishment, survival, increase and of many diseases. While these diseases ostly prevented the growing of small or grain, these crops have recently be- i. important source of winter pasture in yexas. Diseases which become established fwn grain of South Texas may overwinter area and then spread to the larger com- Vely agronomist in charge of small grain re- fTexas Agricultural Experiment Station and p, search Division, Agricultural Research Service, _partment of Agriculture; and plant pathologist, research Division, Agricultural Research Service, lipartment of Agriculture, College Station, Texas. iDzkearer of Small Grains in T exas I M At/cinr and M C. Futrell * mercial grain growing areas farther north in Texas and other states. Losses from diseases may occur in many ways, such as reduced stands as a result of either seed- borneor soilborne pathogens; the foilage may be killed or damaged so that its value for forage is reduced in quality or quantity; the pathogens may attack the plant during the fruiting period and cause reduced yield, shriveled seed or lodging of the crop; and the grain may be destroyed by smut or damaged in quality by the presence of smut balls so that it grades “smutty” and brings a lower return at the market. Losses from plant diseases are staggering when viewed from the standpoint of reductions in total production of Texas grain crops. Unusu- ally severe losses occurred in 1935, 1949 and 1957, as shown in Table 1. indicate normal losses to be expected, but only to show the tremendous loss in income that can oc- cur when conditions are favorable for the spread of diseases. ‘The loss in most years is much less and in some seasons almost negligible. The very high losses shown in Table 1 occur- red in seasons having high rainfall and high humidity over large areas of the State. Wide- spread, severe losses usually depend on a series of conditions and events favorable for disease de- velopment as the crops mature progessively from A TABLE 1. ESTIMATES OF LOSSES FROM SMALL GRAIN DISEASES IN TEXAS, 1935. 1949 AND 1957 Estimated loss in disease 199s 1949 1957 ' Percent Bushels Percent Bushels Percent Bushels 2.0 . 237.000 11.1 12,436,350 3.9 1.468.111 10.0 1.185.000 4.8 5.845.100 0.7 245.157_ 3.4 4.217.550 5.0 1.866.981 .2 179.310 Tr 13.095 3.5 295.000 1.1 1.343.235 1.1 416.522 15.5 1.717.000 20.5 24.021.545 10.7 4.009.904 2.0 954.000 9.0 3.166.800 11.2 5.821.220 10.0 2.386.000 8.9 2.932.800 2.3 1.166.542 3.6 1.170.000 13.7 7.059.696 0.4 175.500 0.3 134.524 0.8 398.177 12.0 3.340.000 21.9 7.445.100 28.1 14.580.541 0.9 26.400 1.1 61.068 5.0 146.000 Tr 0.2 10.042 0.2 6.000 3.7 105.600 5.2 281.850 4.0 . 87.000 2.3 61.600 9.2 239.000 6.9 _ 193.600 6.5 352.960 109s from several species. These are not intended to" Figure _l. A normal leaf of wheat is shown at the left in con- trast Wllh a leaf and stems of wheat infected with stem rust. south to north in Texas. Among other things, these include abundant inoculum, susceptible varieties grown over large areas and favorable weather conditions. In other seasons, this chain of events or conditions may be broken by a situa- tion in one area that may block the spread of inoculum to other areas. Such situations may be produced by drouth unfavorable temperatures or resistant varieties. This break may cause the disease to be confined to a small area or to cer- tain crops or varieties. DISEASES OF WHEAT Texas annually grows an estimated 3,634,000 acres of wheat distributed 64 percent in the Pan- handle or on the High Plains, 28 percent on the Rolling Plains and North Central Prairie and 8 percent on the Grand Prairie, Central Blackland and Edwards Plateau. While most of the wheat is grown in low-rainfall areas, some is scattered from the Red River southward to the vicinity of San Antonio in such manner that it may serve as Figure 2. A field of wheat completely destroyed by stem rust at College Station in 1954. 4 ‘ R=resistant. SZ-‘susceptible. a continuing host for diseases such as the r The spores of these diseases are easily airb and they may spread from field to field f, overwintering areas of South Texas intothe p cipal commercial grain areas. Stem Rust Stem rust (black stem rust) __(Puccinia 5 inis var. tritici Eriks. & E. Henna) is caused r fungus that attacks the stems, leaves and f of the wheat plant. It appears as long, na p brick-red pustules that produce thousands of ti red, egg-shaped spores (urediospores). T spores perform the same function for the fu Y as seed do for a crop plant. They are carried wind currents to nearby plants, to other fi or for longer distances. The spores must i free moisture from dew or rain to germin hence, the old theory that rain causes t When the spore germinates, it produces a g, tube that enters the host tissue through nat openings, such as the stomata, and produces f pustules in 5 to 10 days. The disease can sp 1 rapidly under favorable conditions because the tremendous number of spores and the shi time required for reproduction. High infec of stem rust results in shrveled grain, l0 stems and lowered yield. Figure 1 shows r tules of stem rust and Figure 2 a field of completely destroyed by stem rust. l The causal fungus of stem rust has a com life cycle in which the sexual stage of the 0r ism occurs on the common barberry, Berb vulgaris and some other species. However, i sexual stage is not known to occur in ~~j Genetic recombination occurs on this alters host and this may give rise to new races of New races also may arise by hyphal fusion in i wheat plant. Races may be likened to varie of a crop plant and are identified by their l action on certain wheat varieties. There more than 300 known races of stem rust f wheat. Wheat stem rust attacks barley, rye . certain grasses, but it does not attack oats. _ disease gets its name, black stem rust, from’ fact that, as the grain matures, a new kind. spore (teliospore) is formed. This is black color instead of red. This is the beginning of sexual stage of the organism. Table 2 shows the reaction of a selected gro of wheat varieties to certain races of stem rut, TABLE 2. REACTIONS 01-" A SELECTED GROUP or VARIETIES "ro SIX RACES or‘ STEM RUST A Variety Race 15B 17 29 38 48A Austin S R R R R Bowie R MR S R S Concho S R R S R Stewart S R R R R Langdon R R R R R .3 demonstrates the seedling reaction of varieties 0f wheat when inoculated with st in the greenhouse. This reaction is Qn a scale of 1, highly resistant, to 4, fully ible. The reactions of a selected group eties are used in identifying races of rust. , only practical control of stem rust at t is growing resistant varieties. Breeding to develop such varieties was started at fxas Agricultural Experiment Station in a The Austin variety, resistant to races at that time, was distributed in 1941. Supremo, Frisco, Quanah and Crock- fieties have since been developed and dis- R» to growers. Each is resistant to certain nd has given some protection from rust No commercial variety adapted to iis resistant to all races. Quanah is resist- i-some races and also has a degree of field ce to other races which usually permits it rpe serious damage. Additional breeding to combine resistance to prevalent races Ether desirable characteristics is in prog- mild climate of northern Mexico and siTexas makes it possible for rust to over- p and creates a threat to the major wheat- tfing belt of the Midwestern States. Rust may be blown long distances by winds and storm disturbances. Control of rusts in pea, therefore, affords protection to crops or forage and grain in this area and a re- of the amount of inoculum blown north- jinto the extensive wheat-producing areas. 4 shows how windborne spores of rust i} from Mexico to the United States f successive movements into Canada. The movement southward occurs in the fall ly winter as cold air masses move spores g to South Texas. Information on this map Ad on observations of wind movements, sur- gt the occurrence of rust, identification of land other conditions during 1954-56. portant factors in determining whether a 2 will sustain loss from the rusts in a given ‘re Weather conditions, mass air movements, s. e and amount of original infection, the paces present and the wheat varieties grown. fluence of these factors may be illustrated following discussion. e 15B of stem rust originated and was ob- .;for several years prior to 1950, but it did _come widely prevalent in the principal growing areas until that time. This race p» widespread and serious losses, particular- durum wheat during 1950-54. _ ico, United States and Canada developed stributed several new varieties in an effort uce these losses Lerma and Kentana were in northern Mexico; Bowie and Travis developed for growing in South Texas, but I 0t released; and Selkirk was developed in a and released in Canada and the Northern ~ a a’ Scientists a Figure 3. Reaction oi wheat varieties to a race of stem rust; A-rust free or immune; B—resistant: C-moderately resist- ant; D-moderately susceptible; and E—susceptible. The new varieties were resistant to race 15B, but were susceptible to one or more less prev- alent races, such as 17, 29 and 48A. With the commercial growing of Lerma and Kentana in northern Mexico, an opportunity was present for the rapid increase of races 17, 29 and 48A and the exclusion of race 15B. Consequently, stem rust again became a factor in wheat growing during the winter in northern Mexico. Weather records show several mass air movements from this area across the Southern States in the spring of 1954. Evidence from infection on Bowie wheat, grown experimentally throughout this area, indicates that these races were carried throughout this area, as shown in Figure 4. The widespread distribution of race 17, 29 and 48A and the consequent damage to Bowie and Travis wheat in experimental tests in Texas forced cancellation of plans to distribute these varieties. The influence of these races on yield SPREAD OF RUST - MEXICO TO SOUTHERN UNITED STATES TEXAS TO THE DAKOTAS AND CANADA V. a Q NORTH TO SOUTH IN THE FALL Figure 4. The pattern oi wind movement oi rust urediospores from Mexico to the United States and Canada. 5 YIELD IN BUSHELS PER ACRE 50 ISOLATES 4O PERCENTAGE OF ALL RACES l7. 29. AND 48A 4O 3O 2O BOWIE WHEAT |e49 |95o |ss2 |953 |954 |9s5 1956 m5? YEARS Figure 5. Yield oi Bowie wheat and abundance of certain races oi stem rust at College Station. 1949-57. of Bowie Wheat is given in Figure 5 where Bowie shows high yields during 1949-54, but produced low yields of shriveled grain in later years. Systemic fungicides and antibiotics are being tested for their value in controlling rust. While a few of these will protect the plants, they are not now economically practical. For example, the yield of Bowie wheat grown at College Sta- 20 -2o l5 C -I5 l0 .|Q_ 5 I . i5 303 SPRAYED O 2420 7260 YIELD m BCUSHELS PER ACRE YIELD IN BUSHELS PER ACRE NUMBER OF CENTERS PER ACRE Figure 6. Effect of the number of stem rust-infection centers per acre on the yield of wheat compared with non-inoculated and sprayed control, College Station. 1957. 6 tionin 1958, was increased from 18 to 57 bus per acre by spraying with maneb every 5 I Because the crop is susceptible for sev months, the cost of such sprays is prohibi‘ New materials may be developed which will ‘ such spraying practical. The time of infection, weather conditions l quantity of inoculum blowninto a field du the fall in Texas are important factors in de ming the damage that will occur. An experi g was conducted to determine the amount of d' age that varying amounts of initial inocu might cause when introduced into a field. . fection centers were established at 2-foot in, vals (equivalent to 7,260 centers per acre), foot intervals (2,420 centers per acre) and 6- ‘W intervals (303 centers per acre) in Bowie W at College Station in the fall of 1956. The sp of rust and yields of grain from these areas " compared with uninoculated plots and 0t plots where rust was controlled with ma sprays. Data obtained in this experiment ' shown in Figure 6. The plots where rust , controlled by sprays averaged 22 bushels per a while those where rust was introduced eve feet averaged only 3 bushels per acre. The “fall-out” of spores brought in by str wind movementsmay be determined by expos small glass slides covered with vaseline, count the spores and calculating the rate per area. t number of rust spores falling during the fall ‘ spring may range from a few to thousands square foot of area. Although most of these a ish, it is evident that the opportunity for i ‘ tion is tremendous should conditions be favora Leaf Rust Leaf rust of wheat (Puccinia recondita ex. Desm. f. sp. tritici (Eriks.) comb. nov.)’ caused by a fungus parasite similar to that ca ing stem rust, but differing from it in many spects. The disease attacks the leaves and l sheaths, producing small, round, orange-red p’ tules. They may occur on either side of the l but they do not extend through the entire l tissue as stem rust pustules usually do. Leaf rust is favored by moderately cool we er in contrast with the warmer weather requi for the rapid spread of stem rust. The dise may be found in Texas nearly any time du i the fall, winter or spring. It often becomes 4 tablished in the fall and continues to spread sl ly all winter. Infected leaves become yellow w‘ die prematurely when infection is high. ‘ overwintering spores (teliospores) appear c black dots on the yellow or dead leaves. A n mal leaf and leaves infected with varying I centages of leaf rust are shown in Figure 7. The damage caused by leaf rust often is c conspicuous and many growers consider disease of little importance. Closely contro experiments show that infected leaves lose m water than normal leaves as photosynthetic , Normal leaf of wheat (left) shown in contrast with th varying degrees of leaf-rust infection. ye destroyed. Yields are reduced because ler seed and reduced seed setting. During fiepidemics some varieties fail to head, Jare weakened and lodge, tillering is re- nd the production of forage is lowered. isiderable progress has been made in de- >9: leaf rust-resistant varieties adapted to onditions. No variety is resistant to all lrevalent in the State. Races are constant- aging in prevalence and new races may . A hyphal fusion on the wheat plant. Va- gwhich are resistant at one time may later susceptible when races of rust change or es arise. f= varieties with the highest degree of re- to present races of leaf rust are Quanah, aand Frisco. Crockett and Knox are sus- in the seedling stage, but develop a high of resistance from the boot stage to ma- ifConcho, Westar, Mediterranean, Austin, ze and Comanche are resistant to many W are susceptible to others. Figure 8. Normal wheat leaf (left) in contrast with leaves infected with stripe rust. A= measure of the damage caused by leaf rust under field conditions is presented in Table 3. In years when leaf rust was not prevalent at the locations given, Quanah and Crockett yielded ap- proximately the same as Comanche and Wichita, but the yields of Quanah and Crockett were much higher in severe rust years. Stripe Rust Stripe rust (Puccinia striiformis West.) is a cool-season disease and, previous to 1957, had been observed in Texas only twice and then in only trace amounts. Wet, cool weather prevailed during the springs of 1957 and 1958 and the dis- ease developed into an epidemic that spread across the entire State from south to north. Stripe rust attacks the leaf blades and sheaths as does leaf rust, but the lesions are concentrated between the leaf veins in long, narrow stripes. The fungus also attacks the glumes and developing seed and, as teliospores are produced, the wheat spike may become discolored so that the damage may be confused with that caused by glume l. ANNUAL AND AVERAGE YIELDS OF WICHITA, CROCKETT, COMANCHE AND QUANAH WHEAT, AT TWO LOCATIONS IN TEXAS, DURING YEARS OF LEAF-RUST EPIDEMICS AND IN RUST-FREE YEARS Percent rust infection in epidemic years Yield of grain, bushels, in epidemic years Yield of grain, bushels. in rust-free years 1949 1950 1952 Average 1949 1950 1952 Average 1948 1953 1954 Average 65 90 25 60 12.5 17.3 18.0 15.9 13.8 10.8 6.0 10.2 0 10 20 10 12.7 28.0 24.7 21.8 25.0 14.7 6.7 15.5 35 ;.~ 50 35 40 12.9 22.2 18.6 17.9 20.8 26.8 4.9 17.5 0 1" 15 Tr 5 12.7 40.2 20.8 24.8 23.9 14.4 6.6 18.3 1951 1952 1953 Average 95 20 56 31.4 30.2 30.8 20.7 21.7 14.4 18.9 Tr 10 5 41.5 35.2 38.4 23.7 22.9 10.5 19.0 65 5 35 24.0 31.1 27.6 18.8 24.8 12.4 18.7 5 0 2.5 33.0 31.9 32.5 17.2 20.0 8.9 15.4 Figure 9. Leaves infected with speckled leaf blotch are shown in contrast with a normal leaf at the right. blotch. The pustules and spores are bright yel- low. A normal Wheat leaf and leaves infected with stripe rust are shown in Figure 8. Observations on the reaction of some com- mercial varieties of wheat to stripe rust under Texas conditions during 1957 and 1958 are shown in Table 4. Ponca, Quanah and RedChief appear- ed to be the most resistant. Wichita, Westar and Crockett were the most susceptible. Figure 10. Normal head and stem of wheat (left) in contrast with a stem and head infected with glume blotch (right). 8 i WHEAT VARIETIES TO STRIPE RUST AT THREE LOCA TABLE. 4. REACTION OF CERTAIN HARD RED IN TEXAS. 1957-58 Stripe rust response‘ Variety Amarillo Chillicothe low 1957 1958 l A Triumph 35MS Wichita 50S 70S? Early Blackhull zoMs 4o1vfs Crockett ZOMS 40MS RedChief 5R 15R Blackhull 20MR Bison 25S 50S Tenmarq 50S 45S Ponca 10R Comanche 25S Z5MS Westar 70S 85S Pawnee 50S Concho 50S 60S Kh arkof 5R 5R ‘R = resistant. MR = moderately resistant. MS = mod susceptible, S = susceptible. Speckled Leaf Blotch Speckled leaf blotch (Septoria tritici R0 a cool-weather disease which occurs throu the principal wheat-growing areas nearly year. However, the damage caused is rath conspicuous and is generally overlooked by 1.11 ers, except in very wet seasons such as Moderate damage by killing of the leaf of lower leaves occurs nearly every year. a ‘ The disease appears first as pale green low spots on the leaf. These are caused b breakdown of chlorophyll just ahead of th vading pathogen in the tissue. The lesion large as the pathogen invades new tissue. lesion becomes brown as the tissue is killed, later ashen gray as the fruiting bodies, pyc are formed. These tiny pinpoint black pyc are evident inFigure 9. The disease is no stroyed by temperatures below freezing and g continue to spread throughout most of the w under Texas conditions. Adapted varieties resistant to speckled blotch in 1957 include Crockett, RedChief Mediterranean, while Quanah and Ponca sh considerable tolerance. Other measures of j in reducing damage by this disease include treatment with organic mercury fungicid reduce seedling infection, rotation of cropsf plowing under of crop residues to prevent it tion from old straw, and destruction of volu crops. 5 Septoria Glume Blotch The glume blotch (Leptosphaeria no Muller, Septoria, nodorum Berk. conidial s A of wheat is less common than the speckled: blotch and severe epidemics have occurr Texas only in seasons of excessive spring » fall and below normal temperatures, suc those of 1957 and 1941. The fungus ca glume blotch attacks the culms and spikes ca teristic blackening of the affected areas. lms are weakened and may break or bend st above the nodes. A head and stem of damaged by glume blotch are shown in t; 10 in contrast with a normal head and jt left. Severe lodging, as shown in Figure fy occur as a result of the damage to the f‘ Shriveling of seed and reduced yields re- m such damage. ‘ ltively little is known about varietal re- or susceptibility to this disease. Knox pecially susceptible in commercial fields h Central Texas during 1957. Cultural _g es and seed treatment may aid in reducing from the disease. ry Mildew l eW (Erysiphe graminis D. C. f. sp. tritici irchal) normally is of only minor impor- Sven in the more humid parts of the State, sionally it causes severe damage in small It usually occurs during the winter or ppring when humidity is high and tempera- gimoderate, and it disappears when warm gr prevails. Mildew appears on the leaf h as a mass of white mycelium, but the leaf are invaded by the organism at the same lWater and plant food are taken from the lant so the leaf tissue becomes yellow and pies. Black fruiting bodies appear in this mycelium as the leaf is killed. Normal ildew-infected leaves of wheat are shown p_ re 12. flds of wheat grain and the value of the Winter pasture are reduced when mildew > f» is severe. Growing resistant varieties l only practical means of control. Under , ‘conditions, the Austin, Coker 47-27, Atlas . Knox soft wheat varieties are moderately p t. The hard red winter wheat varieties, a ,, , Ponca, RedChief and Wichita, are mod- resistant. ' f Smut loose smut (Ustilago tritici (Pers.) _ of wheat is normally most prevalent in id sections of Texas, but the widespread lg of several highly susceptible varieties sed the disease to become of increasing ince throughout the State. This smut de- the entire head, replacing it with a mass of pores which are soon blown away by the leaving only the central stem or rachis. V}: of normal wheat are shown in Figure contrast with heads destroyed by loose Ase smut is caused by a fungus that invades A ng ovary at flowering time. Smut spores iseased heads are blown to healthy heads, och they germinate and penetrate the young he fungus hyphae remain in the seed un- erminates. As the hyphae is within the d not on the surface, it cannot be killed »- .1 r 7" 31% Y- . s. . Figure 11. Wheat damaged by Septoria glume blotch near Chiildress. 1941. with fungicides. When the seed is sown, the fungus resumes growth and advances systemical- ly within the plant tissues, finally producing masses of smut instead of the normal grain and chaff. A Varieties differ in their reaction to this dis- ease and to races of the fungus. Ponca, Pawnee, Triumph and Austin are resistant. Quanah, Concho, Kiowa and Bison are extremely suscepti- ble and it is difficult to maintain disease-free seed. Other varieties, such as Comanche, Wich- ita and Westar, are susceptible when inoculated artificially, but seldom develop high infection under field conditions. The reactions of certain commercial varieties to artificial inoculation with loose smut are given in Table 5. Damage from loose smut is inconspicuous be- cause the spores are soon blown away, leaving only the bare rachis of the head, hence, the dam- age may be overlooked. Experimental tests have proved that, with moderate infections, the loss is roughly proportional to the percentage of spikes destroyed. Table 6 shows the results of a replicated test at Denton during 1949-52 where infected seed were introduced in given amounts into seed lots. Figure 12. A‘ normal wheat leaf (left) is shown in contrast with leaves infected in varying degrees with mildew. Figure 13. Normal heads of wheat (left) contrasted with heads destroyed by loose smut. Loose smut can be controlled by a rather complex soak and hot water treatment, but it is difficult to carry out on farms. A water-soak treatment was devised recentlyl. Briefly, this treatment is: partially fill burlap bags with wheat and soak in water at room temperatures for 6 hours, then place in a closed container (oil drum or barrel )With a tight lid for 72 hours and then spread out to dry. By this method, the or- ganism is killed by excluding oxygen with little damage to the seed. Treated seed should be sown in a field isolated from fields sown with infected seed so the crop will not become reinfected. Bunt or Stinking Smut Stinking smut or bunt (Tilletia foetida (Wallr.) Liro) of wheat differs from loose smut in that the glumes and other parts of the head ‘ Weibel, D. E. and Atkins, I. M. The long water-soak method for controlling loose smut of Wheat. Texas Sta- tion Progress Report 1986, 1947. TABLE 5. REACTICNS OF COMMERCIAL VARIETIES TO ARTIFICIAL INOCULATION WITH LOOSE SMUT AT DENTON, 1956-57 Variety 1956 1957 Triumph R R Wichita S VS RedChief S S Ponca MS S Comanche MS S Westar MS S Pawnee R R Concho S VS Crockett MR MR Quanah S VS Frisco S VS Knox MS MS Z resistant, MR = moderately resistant, MS = moderately susceptible, S = susceptible, VS = very susceptible. 10 TABLE 6. YIELD REDUCTIONS IN RED MAY WHEAT CA BY VARYING PERCENTAGES OF LOOSE SMUT AT D ‘ 1949-52 Percent Average yield. Percent red I smut bushels per acre in yieli 0 26.2 f 5 24.5 __ —7.ll :1 10 24.2 M —9.0 _. 25 21.4 ' ‘ ‘5 —l9.0 5U 19.5 —26.Q__’ remain intact and only the internal part of; kernel is replaced by smut. The smut ball semble seed and often are overlooked threshing time, when they are broken and,“ black spores scattered to healthy grain W_ they lodge in the brush at the end or in the A ice of the kernel. They remain there until ' ing time when they germinate and the fut germ tube enters the young seedling. The a gus hyphae then grow within the tissues of host plant, finally replacing the kernels wi mass of spores. Normal and bunted heads p healthy kernels and smut balls are shown in ii ure 14. ' Bunt infection is influenced greatly by, temperature of the soil at seeding time. y temperatures below 68° F. are favorable f0 1 fection, higher temperatures are less favor, This explains why the disease is more impo on the High Plains of Texas than in Ce Texas where soil temperatures are less favo I at seeding time. i" Wheat grain from smutted plants will if a fishy odor, and if 14 or more smut balls? present in 250 grams of seed, the grain is “smutty” and sells at a lower price. The con of bunt is inexpensive and most comme§ cleaning establishments have modern equip g1 for applying fungicides. These fungicides Figure 14. Normal head and grain oi wheat (right) comp‘ with a head in which the kernels were replaced with p balls. 7. REACTIONS OF SELECTED WHEAT VARIETIES CIALLY INOCULATED WITH BUNT, DENTON, 1955-56 Percent infection “v 1955 1956 ’h 50 50 a 50 10 _ Blackhull 80 5 tt 60 10 h 0 5 y at 90 80 10 15 1 .~ 60 15 iche 5 3 0 50 ‘ 50 1U 5 80 tive in controlling bunt and they aid in con- kng seedling diseases. Seed treatment is i‘; mended even for resistant varieties since a y prevent an increase of rare races of bunt. arieties differ greatly in their reaction to idisease and to races of the organism. Quan- jomanche, Concho, Bison, Kiowa and Apache ifesistant to the more prevalent races in Texas. ever, races that can attack these varieties are a to occur in small amounts and, therefore, treatment is advised. Table 7 gives the re- i, s of selected commercial varieties to arti- inoculation with bunt spores at Denton it g 1955 and 1956. -rot or Root-rot a ent research has indicated that Helmin- a sativum (Pamm., King & Bakke) is Qbly the most important pathogen of this a e in Wheat in Texas. In some other areas United States, Fusarium spp., Rhizoctonia land some other species of fungi have been _, d as pathogens causing foot-rots of wheat. rly season symptoms of the foot-rot ob- j» on the Rolling Plains include stunting, rifty plants, reduced seedling growth and for pasture, and extreme susceptibility to . The disease is more severe when tem- res are slightly above optimum for the plant. Near maturity, one or more tillers, n‘ entire plants, are killed, appearing as heads” throughout the field. Seed from jdead tillers and plants usually are shriv- esulting in lowered yields and tests weights Qthe field. Although the disease often is not int until tillers and plants begin to die maturity, the infection takes place at the seedlings}. emerge. The organism invades its, crown and base of the culms of the i Roots are destroyed or reduced in extent faefulness, as shown in Figure 15. t-rot of wheat has been destructive in i; Baylor and Hardeman counties during est 10 years and has been observed in sev- ther counties. A field of wheat infected Figure 15. Normahhealthy roots of wheat plant are shown (left) 1n contrast with plants whose roots were damaged by toot-rot. " with foot-rot near Crowell in 1954 is shown in Figure 16. The control of foot-rot is difficult where con- tinuous cropping of wheat is practiced. Con- tinuous cropping provides a favorable situation for the pathogens that cause foot-rot to increase in the soil. Crop rotation with non-grass crops, such as legumes, is desirable, but difficult to carry out because few such crops are profitable 1n the major wheat-growing areas. Summer fai- low will reduce the soil population of the causal pathogens, but usually is not economically feasi- ble. Relatively little is known about varietal re- action, but no resistant, adapted variety is known. Seed treatment with organic mercury Figure 16. Wheat field near Crowell in 1954 showing normal plants and other plants killed by foot-rot. 11 Figure 17. A normal head of wheat (right) contrasted with heads in which seed were set in only parts of the head because of the killing of the pollen by low temperatures. fungicides will give some protection from seedling infection, but cannot control the disease because infection can occur at any time during the groW- s ing season. Cold Injury Injury from low temperatures at several stages of growth may be confused with disease or hail injury. Sometimes, these abnormalities are evident considerably later than the freeze and are not associated with the low temperature. Wheat can be injured by low temperatures in such a manner that part of the tillers will break down, turn white and die several weeks later. Late-spring freezes may kill or damage the fo- liage and cause stunting until new tillers develop from the crown. Under some conditions, the leaves may produce new growth, then later the entire plant may die. Damaged or dead leaves and stems may be invaded by molds and other fungi so that the entire field may present a blackened, abnormal appearance. Figure 18. Normal leaf of oats (left) contrasted with leaves infected with crown rust. 12 The most commonly observed abnormalit sterile or partly sterile heads as a result of killing of the pollen or young ovary. This g happen with some varieties and under some p ditions when the headis still in the boot. 5 peratures below freezing as the crop is head usually cause such abnormalities, but there evidence that a temperature of 36° F. may i] the pollen. The stage of grovézifth of each fl determines the degree of damage so that r heads may be sterile at the top while others l damaged at the base. Figure 17 shows exam of freeze damage. a DISEASES OF OATS Oats were grown on an average of 1,130,, acres during the 10-year period, 1947-56, but use of oats has expanded in recent years- official estimate of harvested area in 1958 1,861,000 acres, but the seeded area, which. cludes that sown exclusively for winter past was 2,323,000 acres Most of the Texas acr is fall sown, but when spring moisture conditi are favorable or the crop is winterkilled, la acreages may be spring sown. i Diseases are limiting factors in the gro a of oats for grain and major factors in the f of the crop for forage in the humid sections; Texas. Many Texas growers seed oats as ea, l in the fall as moisture conditions permit to :0 maximum use of the crop for livestock past l Rusts and other diseases may infect these fi in early fall in South Texas and, if conditi are favorable, may produce epidemics that l duce the value for pasture and may spread i the major grain-producing areas farther no Crown (leaf) rust, stem rust, blights and sm are major diseases of oats in Texas. Mild Septoria disease and virus diseases are relativ minor, but may be important locally. ’ Crown Rust Crown or leaf rust (Puccinia coronata, t} var. avenue Fraser & Led.) is probably the I; destructive disease of oats in Texas. This dise is called crown rust because the teliospore, overwintering spore, has a crown-like -.j Crown rust, like other rusts, is caused by a f , gus that attacks the leaves and leaf sheath of o. and certain related grasses. The disease appe as tiny, round, yellowish-red pustules on eith surface of the leaf blade. These pustules p duce tiny yellowish-red spores that are spread t other plants by wind currents and germinate 5 free moisture from dews or rain Temperatu, of 70 to 85° F. are most favorable for gro of the fungus and, under such conditions, a n pustule is formed in about 8 days. The pustu give rise to the teliospore or black overwinteri spore as conditions become unfavorable or t, crop matures. - o Crown rust infection usually occurs in t fall in South Texas from spores blown south y 5*. ‘a .. B or “northers,” or they may be blown gth Texas from summer crops in Mexico. f» of these facts, the development of this jduring the Winter in South Texas is of to growers throughout the Central Normal and crown-rust infected leaves n in Figure 18. Figure 19 shows a field that was destroyed by crown rust at Col- ition in 1957. ildamage caused by crown rust may result Led yields of grain and, where the crop is tr Winter pasture as in South Texas, the lay be killed by the disease in the seedling Thousands of acres were killed by crown January 1951, resulting in the loss of fl; months of grazing. New races which ii k all present varieties grown in Texas, evalent in South Texas in 1958 and re- e grazing period of oats in that area by mQHth. f} organism causing crown rust of oats is ipof many races. These races differ in ility to attack varieties and vary in prev- ifrom year to year, depending on the va- igrown and environmental conditions. New the crown rust fungus develop from time on the alternate host plants, the buck- Jihamnus spp., and probably by hyphal fin the oat plant. The Victoria variety ed extensively in breeding oats in the liynd the resistance to crown rust found in Ranger, Victorgrain, Mustang and Qwas derived from this source. While this ice was very effective before 1957, new 13 and 216, which can attack these var- i: re now prevalent. Landhafer, Santa Fe ‘ispernia are resistant to many races, in- 213 and 216, but new races, 264 and 276, und in Florida in 1955 that can attack arieties. No presently adapted commer- iety is resistant to all races of crown rust. gponses of certain commercial varieties to ces are given in Table 8. Rust i“ rust (Puccrinia graminis Pers. f. sp. Eriks. e& E. Henn.) of oats is similar in ,_ REACTION OF SOME COMMERCIAL VARIETIES ,ATS TO CERTAIN RACES OF CROWN RUST Older c3335“ Bram‘ T531265“ “£53233? n MS s s R R S S ox MS - MS MS S R R S S R R S S MR MR MS S 1 R S S S no R R ’ R S tant, MR = moderately resistant. MS = moderately lo. S = susceptible. Figure 19. A field of oats destroyed by crown rust in 1957 at College Station. appearance and behavior to that described for wheat. This subspecies, however, attacks oats and related grasses, but not wheat or barley. The red stage of the fungus attacks the leaves, stems and panicles of oats; the black spore stage (teliospore) is evident as the crop matures or the plants are killed. Rust-free and oat stems infected with stem rust are shown in Figure 20. The only practical method for controlling stem rust is growing resistant varieties. Alamo is the only variety adapted in Texas which is re- sistant to present prevalent races, but it is sus- ceptible to race 7A. All other Texas varieties are susceptible to stem rust. Early varieties, such as Fulgrain, Frazier, Cimarron and Victor- grain, may escape damage because of early matu- rity. Like those of the stem rust of wheat, the spores of stem rust of oats may be carried into Texas from Mexico, or from northern growing areas by cold fronts in the fall. Temperatures and moisture conditions often are favorable dur- ing the South Texas winters for establishing stem rust in the fall. The disease may reduce grain Figure 20. Normal panicle, stems and grain of oats (left) contrasted with panicle and stems infected with stem rust (right). Note shriveled seed from rust-infected plant. 13 Figure 21. A healthy panicle of oats (leit) compared with one infected with covered smut and two infected with loose smut. The smut spores have been washed or blown ofl the panicle at the right. yields and the forage value of oats sown for win- ter pasture. The disease spreads northward as the crop develops progressively from south to north. Smuts Two species of smuts (Ustilago avenae (Pers.) Rostr.) and (Ustilago kolleri Wille.) at- tack oats in Texas. Black loose smut destroys the entire panicle leaving only the central rachis; covered smut tends to be retained by the glumes and membranes. However, under field condi- tions, it sometimes is difficult to differentiate between them because rains or winds soon scat- ter the spores. The spores of the pathogens are spread by winds and by threshing of the grain. Spores lodge on healthy kernels and beneath the glumes where they remain as spores or as dor- mant mycelium until seeding time. The fungus penetrates the young seedling at germination time and grows systematically with the plant, TABLE 9. YIELDS OF SMUTTED AND SMUT-FREE FRAZIER. MUSTANG AND NEW NORTEX OATS AT COLLEGE STATION, 1958 v _ Periien; Yield of grain. bushels per acre “new Srgrtllitglees Smutted seed Smut-free seed Frazier 2 23.41 69.8 Mustang 54 15.5 66.4 New Nortex 38 57.1 76.6 ‘Yield reduction was due to poor germination of smutted seed. 14 ,, grain damaged by high infestations of f finally, replacing the panicle with a mass of s if spores. Figure 21 shows the two types of s g in contrast with a healthy panicle of oats. i Yields of oats are reduced and the quality?‘ Some varieties may be damaged more than A ers. An experiment was conducted at Coll Station in 1958, where seed werejinoculated i smut. Results obtained with three varieties =Y shown in Table 9. t Physiological races of both smuts g known and varieties differ in reaction to th’ races. Bronco and Alamo are resistant t0 races, while Mustang and Fultex are very s ceptible to Texas collections of smut. New N tex is susceptible, but usually does not deve high percentages of smut under field conditiop The smuts are easily controlled by seed tr ment with the organic mercury compounds. M commercial seed-cleaning establishments hf equipment for applying fungicides. Seed =5 ment is recommended for all oat seed used y planting, regardless of whether smut was i; served in the ‘crop. Smut infection of seed _ occur by windblown spores, through custom c, bines or by contamination from trucks, sacks f other means. Seed treatment usually impro germination by protecting the seedling from organisms that may attack it. Fungicides shot be handled carefully and according to directi, of the manufacturer. These products are pois ous to man and animals, and treated seed surp] to planting needs should not be fed to livest Helminthosporium Blights Three different blights (Helminthospofl avenue Eidam, H elminthosporium sativum Pa King & Bakke, and Helminthosporium victo . Meehan & Murphy) attack oats in Texas. i, leaf blotch caused by H. avenue is characteri by oblong, linear, irregular blotches. The 16810; are purplish-brown with sunken centers. infection is high, the leaves turn brown and t The causal fungus is carried from one season the next on seed and crop residue. Crop rotati sanitation and seed treatment with organic m cury fungicides reduce seedling infection. ’ s 4 t The species H. sativum causes some seedli and leaf damage. It appears as severe black ing and rotting of the crown and lower part “ the culm. Severe lodging, lowered yields f test weight result. i ‘ The blight caused by H. vietoriae becap widespread soon after varieties of Victoria =5 entage were distributed. The disease is 0f ‘ called Victoria blight. Characteristic symptog are seedling blight, reduced stands, reddeni of the leaves, decay of the roots and blacken“ of stems and nodes followed by lodging. Gra yields are reduced considerably, the grain i? be of low test weight and discolored and it of heats in storage. The fungus produces a t0 p a e 22. A normal plant oi oats (leit) contrasted with ‘J- affected in varying degrees oi severity by blight p?) ed by Helminthosporium victoriae. ¢ moves systematically through the plant and pluses many of the symptoms. As the plant ma- es or is killed, blackened fruiting bodies with ve-black spores are formed on plant surfaces, ecially at the nodes. Normal plants and oth- } damaged in varying degrees by Helmintho- prium blight are shown in Figure 22. a f The control of blight is difficult when sus- tible varieties are grown because the disease jboth seed and soilborne. Warm weather fa- the disease; so, it is of greater importance South Texas. Late-seeded spring oats are dam- f. more often than that seeded at normal dates. ' _e disease usually is not destructive in the drier ,rts of the State and susceptible varieties may lgrown on the Rolling and High Plains without ‘Ipreciable damage. Crop rotation and the use disease-free seed treated properly with fungi- oi the Helminthosporium blight organism. re 23. Germination oi New Nortex (resistant), Mustang Fultex (susceptible) oat seed in the presence oi pure Figure 24. A—A normal leai oi oats compared with B—Sep- toria-iniected leai; C—Normal culm oi oats compared with D—-Septoria-iniected culm. cides will greatly reduce the chances of damage to the crop. Varities resistant to Victoria blight should be grown when possible. Resistant varieties available include New Nortex (and other Red Rustproof strains), Camellia, Alber, Arkwin, Midsouth and Suregrain. Mustang and Bronco have shown some field tolerance in most years, but are susceptible in seasons favorable to the disease. Alamo, Fultex, Victorgrain, Ranger and Rustler are susceptible. A method of eval- uating varieties for reaction to the disease has been developed. It consists of germinating seed in the presence of large amounts of inoculum. The results of such a test and its effect on Ful- tex, Mustang and New Nortex are shown in Fig- ure 23. Septoria Disease The Septoria disease (Septoria, avenue Frank (Leptosphaeria aivenaria Weber the perfect stage) or Septoria tritici Rob. ex Desm. avenue (Desm.) Sprague) had not been observed in Texas until the very wet, cool seasons of 1957 and .__.E Figure 25. Normal panicle oi oats (leit) contrasted with panicles damaged by blast. 15 Figure 26. Normal leaf of barley (right) contrasted with leaves infected with net blotch. 1958. The behavior of the disease was differ- ent in the two seasons. On the basis of field reaction and laboratory tests, it is believed that both the species listed above were involved. The leaf blotch was observed even before the heading stage as dark-purple to brown spots of varying size. Some leaves were nearly destroyed by the infection. Later infection was observed on the stems as blackened spots spreading and coalescing until much of the stem was discolored. There was considerable lodging before the crop Figure 27. Symptoms of spot blotch of barley. 1B Q matured. The Red Rustproof strains were ately resistant in 1957, but no variety we served to be resistant in 1958. Whether th ease will continue to be of importance canni determined at this time. Diseased and f culms and leaves are shown in Figure 24. § Yellow Dwari Yellow dwarf is a virus disease: of oats‘: barley. Under some conditions it has been l; red leaf. Infected oat plants have a char‘ istic salmon-pink to red color and the plan l dwarfed. The degree of dwarfing that t depends on the stage of growth reached b’? plant at the time of infection. When a pl‘ infected immediately after emergence it m? dwarfed so severely that it will fail to headQ duced spike formation and filling of kernels, result from midseason infection. Infectionffi takes place at later stages may not damagf plant seriously. A barley plant infected by low dwarf is shown in Figure 35. Blast Blast is a nonparasitic abnormality which be found in varying degrees depending on; vironmental conditions and the variety. o varieties are much more subject to this i t than others. The lower part of the panicl most of it, may produce white, sterile flo The condition is most prevalent under ad conditions such as high temperature, defii moisture and probably other factors. Figu shows normal and blasted panicles of oats. DISEASES or BARLEY The average harvested area of barley in a as during the 10-year period, 1947-56, 120,200 acres and was distributed over a i portion of the State. A 1957 survey showed] barley was grown in 182 of the 254 cou_ Diseases cause less damage to barley than to"; er small grains because the crop matures when conditions are somewhat unfavorabl many diseases. Net blotch, powdery mildew. leaf rust are the most important diseas though stem rust and the smuts cause some age. Spot blotch, barley scald, false stripeyf; terial blight and yellow dwarf have been obs in some seasons, but have caused only losses. Y NGt Net blotch (Pyrenopirhora, teres (l), Drechs.) has increased in importance in r1 years because of the expanded acreages of, Goliad variety which is highly susceptible. ley may be attacked in the seedling or stages. Characteristic symptoms are brown on the leaves that expand and coalesce with?‘ spots to form elongated, brown-netted which finally may cover most of the leaff destroy its usefulness. The glumes of the g or spike also may be attacked, resulting in i 28. Normal barley leaves at right in contrast with infected with barley mildew. yields and shriveled seed. The fungus -. net blotch may be carried on the seed or "on may come from old straw. Sanitation, grotation and seed treatment with organic ry fungicides aid in controlling the disease, i. most effective control is growing resist- rieties. Unfortunately, none of the Texas ‘d varieties is highly resistant although i appear to be more tolerant than others to lotch. A normal leaf and leaves infected fnet blotch are shown in Figure 26. new. organism causing spot blotch (Helmin- rium sativum Pam., King & Bakke) of ‘also attacks mrheat and several grasses. ~ Normal leaves of barley (left) contrasted with - acted with leaf rust. Figure 30. Healthy leaves of barley (left) contrasted with leaves infected with bacterial blight. The young seedling, crown and roots are attacked soon after emergence, often resulting in reduced stands and a weak root system. The leaf spot occurs on the leaves, leaf sheath and floral parts, forming a characteristic “black point” kernel. Plants are weakened by the disease, resulting in lower yields and reduced bushel weight. The pathogen causing spot blotch can be soil or seedborne, or it may be on crop residues. Seed treatment with organic mercury fungicides reduces losses from seedling infection. Destruc- tion of crop residues and crop rotation aid in control. The use of resistant varieties offers the most practical means of control, but, of adapted varieties grown in Texas, only Goliad is resistant. Symptoms of spot blotch are shown in Figure 27. Powdery Mildew Mildew (Erysiphe grammes DC. f. sp. hordei Em. Marchal) occurs on barley in Texas during cool, humid weather, usually during the winter or early spring. The gray, fluffy mycelium of the fungus observed on the leaves and leaf sheaths also penetrates and invades the leaf tis- sue. As the disease progresses, the leaf turns 2Q Figure 31. Normal leaves of barley (left) contrasted with leaves infected with barley false stripe. 17 l l s a Figure 32. L, Normal leaf oi barley (right) contrasted with leaves infected with barley scald. yellow and is gradually killed. Later, dark fruit- ing bodies containing the overwintering spores occur throughout the mass of fungus mycelium on the leaf. The spores are carried from plant to plant by wind currents. While the disease can be con- trolled by fungicides, such control is not practi- cal. Fortunately, most of the recommended va- Figure 33. Normal head oi barley (right) contrasted with heads destroyed by covered smut. 18 rieties have considerable resistance to races p f? alent in Texas. Goliad, Cordova, Texan and A bine have been resistant for a number of 3 p but Wintex, Tenkow and the Tennessee Wi strains are highly susceptible. Normal leav; barley and others infected with powdery mil are shown in Figure 28. Leai Rust Leaf rust (Pcwcinia hordei Otth.) of ba is similar to the related species that attack W t. and oats, previously described. Barley leaf a attacks barley and a few related grasses, usually not wheat or oats. The tiny, round tules of rust are light red and relatively in spicuous. Like spores of other rusts, they ma . carried into South Texas in the fall by fronts or may be blown in from Mexico. disease may develop slowly in South Texas ~?_ ing the winter and then move northward as ~ season progesses. The only practical contro growing resistant varieties. None of the ada~ commercial varieties grown in Texas is hi resistant to present prevalent races, althol Goliad, Harbine and Rogers are moderately sistant. A normal leaf of barley is shown in v1 trast with leaves infected with leaf rust in ure 29. Stem Rust Barley is attacked by the same organ (Puccinia. graminis tritici Pers. var. Eriks.) y causes stem rust of wheat and rye. Stem c‘ of wheat was described previously. LOSSGSi barley from this disease usually are small, 3 barley may serve as a host for overwinterin the pathogen in South Texas. Goliad is re ant to many races of stem rust and was deve ed to reduce the opportunity for overwinte p, of rust in South Texas. All other commer varieties grown in the State are susceptible. f Bacterial Blight Bacterial blight (Xaozthovnonas translu " (L. R. Jones, A. G. Johnson, and Reddy) son) usually is a minor disease in Texas, but , cause damage in some fields. The symptoms; linear, water-soaked areas on the leaves which" velop usually during damp, rainy weati Small droplets of white exudate form on the li yellow to brown colored diseased areas. Ins are attracted by this gummy material and cl it along with bacteria to other plants. So far .1, known, all commercial varieties adapted in T‘ are susceptible. Bacterial blight-infected leer are shown in contrast with healthy leaves in ure 80. False Stripe False stripe is caused by a seedborne vi The most evident symptoms are on the leaves, though, in severe attacks, some sterility of head may result. Long, light-brown, mot streaks appear on the leaves and these enla . t stripes with irregular margins. The is spread by contact of leaf to leaf. As nts become infected, there is a gradual in grain yields and quality. Seed from f» fields should be discarded and a new "of disease-free seed obtained. No other I control is known. The relative resist- A susceptibility of Texas varieties is not Normal barley leaves are contrasted ives infected with false stripe in Figure 2- scald (Rhynchosporium secalis (Oud.) lvis) attacks barley, rye and some grasses. ijse was observed in Texas during 1957 8. Typical symptoms are inconspicuous varying from a fraction of an inch in to lesions that cover most of a leaf. ons are at first water-soaked in appear- t, as the name implies, the leaf later itif it had been scalded. When large areas are involved, the yield of grain may be a greatly. ‘xi-pathogen causing scald is carried to the son on seed and crop residues. Seed ‘t with organic mercury fungicides Will seedling infection. Crop rotation and the residues under will aid in controlling se. Varieties differ in their reaction Ysease. A normal barley leaf and others “with scald are shown in Figure 32. Smut ed smut (Ustilago hordei (Pers.) is so-called because the fungus destroys A ,y kernels, but usually the floral bracts tact and hold the balls of smut until the threshed. The threshing operation scat- 5 smut spores to healthy seed, where they or under the glumes and remain there seed are planted. infection occurs as the seed germinate. itime, the spore also germinates and the gnters the young seedling. Infection is p)» by temperature and moisture; there- amount of smut varies greatly from j season, depending on weather condi- iseeding time. The fungus grows within t tissues and, at maturity, replaces the lith a mass of smut spores. Since the @_ e carried on the seed, they may be killed ycides. Seed treatment is inexpensive and ended to control smuts and other seed- iseases. Although some varieties are l be resistant, the adapted Texas va- e susceptible. A healthy barley head and a have been destroyed by covered smut in Figure 33. mut types of loose smut (Ustilago nuda iiRostr.) and (Ustilago nigra. Tapke) Figure 34. Normal head of barley (right) contrasted with heads destroyed by loose smut. attack barley and they cannot be distinguished in the field. The true loose or brown smut, U. nuda, is similar to wheat loose smut in that it infects the ovary at blooming time and remains as dormant mycelium within the seed. When the seed are sown, the fungus resumes growth and Figure 35. A barley plant stunted by yellow dwarf is shown in the foreground and contrasted with normal plants in the background. 19 systemically invades the tissues, finally replacing the floral parts with a mass of spores. The amount of infection which takes place is influ- enced greatly by humidity and temperature at flowering time. Because the fungus causing loose smut is within the mature seed as dormant mycelium, it is difficult to control and cannot be killed by surface fungicides. Until recently a complex hot- water treatment was used to kill the fungus in seed. A new method has now been devised. This method” is: soak the seed in water at room tem- perature for 2 to 6 hours. Place them in a barrel or other container with a tight lid and hold them under these conditions for 34 to 38 hours. Dry the grain immediately to prevent sprouting and to permit normal seeding. Varieties differ in their reaction to loose smut. Some are highly resistant. Fortunately, several adapted varieties have resistance to some races and have remained free of the disease un- der commercial conditions in Texas. These in- clude Goliad, Wintex, Texan, Cordova and Har- bine. Reno and Ward are susceptible. The black or semiloose smut, U. nigm, differs from brown loose smut in that the spores lodge on or within the glumes so that they can be reached by surface disinfectants. The smutted heads are similar to those of the true loose smut, but the smut usually appears later and the spores are shed over a longer time because the mem- branes are less damaged. Wintex, Texan and Cordova are susceptible to the black loose smut, as are most other adapted varieties. Seed treat- ’ Brown loose smut of barley. North Carolina Extension Folder 132 by J. C. Wells and T. T. Herbert. 20 ment with mercury fungicides is recom I for the control of this smut. A normal y barley and heads destroyed by loose sm_ shown in Figure 34. Yellow Dwarf Yellow dwarf is a virus disease of 0a barley. It has been present for __some ti California, causing serious losses-gin 195 was observed in Texas in 1956. The diseaf have been present for some time, but pre~ was assumed to be non-parasitic in nature r_ to nutritional disturbances. On barley symptoms include bright-yellow coloration, u blades and severe dwarfing of plants, as 2 in Figure 35. The disease is transmitted by insects. al species of aphids are known to be vec, perhaps other insects may transmit the n The control of these insects with insecticid aid in controlling the spread of the vi this usually is not practical with smal crops. No other control method is kno 1' ACKNOWLEDGMENTS All research work reported herein w,“ ducted cooperatively by the Texas Agri, Experiment Station and the Crops R” Division, Agricultural Research Service, _ Department of Agriculture. ‘yi Acknowledgment is made of the coo V of the members of the staffs of the Depa" 1 of Agronomy and Plant Physiology andJ-i ology and of cooperators at substations W; made observations or assisted in conductin» experiments. i ~ i 3 .4- "f