f\ I $>. -3:22.4- V. S. DEPARTMENT OF AGRICULTURE BUREAU OF PLANT INDUSTRY BULLETIN NO. 224. B. T. OALLOM IY Ch : 0/ Bureau. TIMOTHY HIST IN THE ONITE BT EDWARP C. JOHNSON, Pathologist in Chargt o/< wed Disease FPbrifc, C^/ft of Grain Investigations. Issued Acocbt 4, 1911. "'ORY GOVERNMENT PRINTING OFFIOE. uni. U. S. DEPARTMENT OF AGRICULTURE. BUREAU OF PLANT INDUSTRY -BULLETIN NO. 224. B. T. GALLOWAY, Chief of Bureau. TIMOTHY IM ST IX THE UNITED STATES. BV EDWARD C. JOHNSON, Pathologist in Charge of Cereal Disease Work, Office of Grain h [8801 D \> gcsi 4. L911. ^SSSssssSS 55 u iSHINQTON •••■\ I i;nmi NT PRIN riNl 01 1911. BUREAU OF PLANT INDUSTRY. Chief af Bureau, Beverly T. Galloway. Assistant Chief of Bureau, William A. Taylor. Editor, J. E. Rockwell. Chief Clerk, James E. Jones. Grain Investigations. scientific staff. Mark Alfred Carleton, Certalist in Charge. C. R. Ball, Charles E. Chambless, and II. B. Derr, Agronomists. Edward C. Johnson, Pathologist. II. J. C. Umberger and II. F. Blanchard, Assistant Agronomists. Cecil Salmon, Physiologist. John F. Hoss. Farm Supirinlauliiit. A. A. Potter, Assistant Pathologist. E. L. Adams, Manley Champlin, V. L. Cory, and II. V. Harlan, Scientific Assistants. F. R. liabcock, Assistant. L. C. IJurnett, P. V. Cardon, J. Mitchell Jenkins, Clyde E. Leighty, and Clyde McKee, Agents. 224 LETTER OF TRANSMITTAL U. S. Department of Agriculture, Bureau of Plant Industry, < )i i i< ■!•: of Chief of Bureau, Washington, I>. C, May W, 1911. Sir: I have the honor to transmit herewith and to recommend for publication as Bulletin No. 22 1 of the series of this Bureau the accom- panying manuscript, entitled "Timothy Rusl in the United States," bj Mi-. Edward ('. Johnson, of the Office of drain Investigations of this Bureau. Timothy rust, first reported in the United States in ivs_\ has become an important problem in recent years. In L906 it was abun- dant in the timothy-breeding plats at the Arlington Experimental Farm, near Washington, D.C. Since then it has become widespread, causing considerable damage in many localities, and it- ultimate dis- tribution over all timothy-gro^ ing regions \\ here conditions arc fav< ir- able to rust development is to he expected. This paper discussesthe present known distribution and relationships of the rust of timothy and summarizes previous investigations of this disease in Europe and America. .New information on its physiological specialization and methods of winter survival and on the resistance of timothy strains and varieties to rust is also presented. Respectfully, Wm. A. Taylor. Acting t TiiefofBun "'/. Hon ,i wins Wilson, Secretary ofAgricuUun . 3 CONTENTS. \ Pago. Distribution of the rust of timothy 7 ption of timothy rusl 8 Relationship and physiological specialization of timothy ru-t 8 JScidial Btage and aomenclature of timothy rust H> Winter survival of timoth) rusl L2 Methods of distribution of timothy rust 13 rieties of timothj to rust 14 Summary 16 Index 19 224 5 Digitized by the Internet Archive in 2013 http://archive.org/details/rustinuniOOunit B. P. 1 I :.' TIMOTHY RUST IX THE UNITED STATES. DISTRIBUTION OF THE RUST OF TIMOTHY. Rust of timothy was reported in this country by Trelease as c.iH\ as L882. 1 Farlow and Seymour, on the basis of this report, mentioned Puccinia graminis on PMeum pratenst h. from the I'nited States in their" Hosl In. lex of the Fungi of the United States" (1888). Rust of timothy was reported as causing considerable damage in the experimental plats at the Iowa experiment station in 1891. 2 From L891 t<> 1906 the parasite seems to have been little in evidence throughout the country, and the writer has been unable to find any mention of it during those years. In lOOti the rust became epidemic in the experimental plats at the Arlington Experimental Farm. In 1907 it was epidemic at points in New York and Virginia; it was also reported from Delaware, West Virginia, and Ontario, Canada. In 1908 this rusl was widespread and caused much damage in New York, Pennsylvania, Delaware, Maryland, and Virginia; it was also reported from West Virginia, Ohio, Michigan. Wisconsin, and Minnesota. In 1909 the rusl was common in many of the States mentioned and in addition was reported from Indiana, Kentucky, Iowa, and Maine. In 1910 it was observed in main States from which it had been previously reported, and in considerable quantity in Virginia, New York, Michigan, and Minnesota. In the last State it was collected at both New Richland and Owatonna, and in Augu-1 was exceedingly abundant in timothy pastures around Crookston. Thus, from being only locally observed in 1906, this rusl was widespread in 1909 and L910, having been reported from Maine to ( mtario and norl hern Minnesota, and south to Iowa, Kentucky, and Virginia. 3 William. Parasitic Fungi of Wis of the Wisconsin Academy of Si is-: p. 131. w isconsin was kindly -ciii lo us for examination by l>r I from i he Missouri Botanical Gardens. It was rather unsatl - I of only one rusted id thus may have i rately determined, leavli i enticity of this early report. m, J., Curtis, C. F., and Kent, D, \. rhni of Sowing Ore a Seed. Bulletin 15, Iowa Agricultural ■ riment Station, If 1 plant pathol ious agricultural experimi ! to J. J. Davis, M.W.Evans, I U Freeman, R. \. n irper, Frank D. Kern, W.J Piper, 1 1. \ . Yin: 1 11. II. l answered letters oi inquiry in regard to (lie rust on timothy or have given information us to its prevalence in various localities. 224 7 8 TIMOTHY RUST IN THE UNITED STATES. DESCRIPTION OF TIMOTHY RUST. The timothy rust is very similar in general appearance and mor- phological characteristics to Puccinia graminis Pers. on wheat. It attacks both leaf and stem, forming long, yellowish-brown uredo pustules and dark-brown to black teleuto pustules, which rupture the epidermis. At times it also attacks the head, often preventing the formation of seed. The uredospores are most prevalent, while the teleutospores are less abundant. The uredospores are 18 to 27 p. in length and 15 to 19/* in width; the teleutospores, 38 to 52 p. in length and 14 to 16 p in width. This is the same range as that of the corresponding spores of Puccinia graminis Pers. on wheat, but the variation is not quite as great as in the wheat rust. The teleutospores are constricted in the middle and have a much thickened, round or pointed apex and pedicels of medium length, and closely resemble those of the typical Puccinia graminis Pers. RELATIONSHIP AND PHYSIOLOGICAL SPECIALIZATION OF TIMOTHY RUST. In 1908 and 1909 inoculation experiments on various grasses were undertaken at Washington, D. C, to determine the relationship of the rust of timothy to rusts of other hosts in this country and to ascertain whether or not it is the same form as that which occurs in Europe. Collections were made at the Arlington Experimental Farm, and fresh material in the uredo stage was kept growing in the greenhouses at Washington, D. C. All inoculations were made on young, fresh leaves of the host plants growing in pots. The plants were kept moist for 48 hours after inoculation by placing the pots in moist chambers consisting of large bell jars placed in pans containing sand and a little water. In this way a thin film of water soon con- densed on the leaves and remained as long as the plants were covered. This gave ideal conditions for spore germination and for infection. The results of these inoculations are reported in Table I. 224 RELATIONSHIP \M> PHYSIOLOGICAL SPECIALIZATION. 9 ! inoculati (h uredosj ■ 1 Inocu latlon. Source of Inoculating material. Varieties of plants Inoculated. Number of leaves lated. Number of suc- cessful infei- during Incuba- rind of 17 to 21 days. 1 Jan, 2 Jan. 25,1908 Phleum pra tense. . . Tritlcum vulgare 1 ■> i ;j in i 1 in A vena sativa 10 ' 5 Jan. Feb. Feb. 1 .n. i Feb. ! Feb. Jan. 27,1909 1.1909 .do 23 25 5 3(j 24 42 22 i 25 16 18 18 3 18 1 33 ■ Id 25 9 Hi 11 21 17 28 44 31 11 40 7 11 i . . . . .do s 1 '1 10 t 11 C 12 i 1 13 1 1 1 i i ...do Vrrhenatherum elatius . .do 17 ti 18 ..do... 2 19 .do. ( ...do... .do 7 21 22 Feb. . Jan. 27. 1909 Jan. 23 1909 Feb. •.' .do ( ...do ...do i L'l .do. . .do... 25 do 26 "7 do do ...do 28 ntale Ilnrdcuiu jubatum Mar. .do.. 31 • 32 1 ! .. 1 | Jan. 2 Jan. 2 I v hvstrix ; : .do.. ...do do lo do do The rusl rather easily transferred to Avena sativa (17 out of 30 inoculations)', Secah cereah (8 out of 11 inoculations), Festuca \ Eriksson 3 in inoculation experiments with this rust on Avena sativa, Secah cereale, and Festuca elatior? No inoculations on Dactylis glomerata, Arrhenatlierum elatius, or Poa compressa arc cited in his report. Direct inoculation on Trvticum vulgare and Hordeum vulgurt gave negative results in 10 trials each, thus corresponding to the negative results in numerous siniilar trials of Eriksson. 3 From these n our work. It Is probable that was used bj Eriks- son, as this is the common form known by that name in Sweden. • Eriksson, Jakob. 1st der Tlmothei elneselbst&i rtodernicht? Sfversigt af Ron . Vetenskaps-Akademiens Forhandlingar, no. .s, 1902, pp. 193-190. 92430 Bui 224 -11 2 10 TIMOTHY RUST IN THE UNITED STATES. experiments it may be concluded that the rust in the United States and the rust in Europe are identical, and the statement by Eriksson ' that it is not a well-fixed species is substantiated. Although timothy rust can easily be transferred to Avena sativa, Eriksson ' and Carle- ton 2 have shown that the uredo of Puccinia graminis avenae Erikss. and Ilenn. can not be made to grow on timothy. This rust, however, can easily be transferred to Dactylis glomerata and Arrhetiatherum elatius. 2 Timothy rust also transfers to these hosts (Table I). These rusts, therefore, although not identical, have many characteristics in common, which indicates that there probably is a very close relation- ship between the two. A small number of experiments to test whether or not the timothy rust can be transferred by means of bridging hosts to various cereals which are not successfully infected directly from timothy were tried and it was found that by using Avena sativa as a bridging host the rust easily transferred to Hordeum vulgare (4 times in 10 trials); by using Festuca elatior it transferred to Hordeum vulgare (twice in 10 trials) and to Triticum vulgare (once in 10 trials); and by using Dactylis glomerata, it transferred to Triticum, vulgare (once in 5 trials). By the use of the bridging hosts the rust undoubtedly could be made to transfer to many grasses on which it will not grow when coining directly- from timothy, but on which it might continue to grow after such a, transfer. That this to some extent takes place in nature is very probable, and these trials, together with recent experiments of a similar nature on the rusts of grains, 3 throw much light on the pos- sible origin of many of the so-called "physiological species" of rust. ffiCIDIAL STAGE AND NOMENCLATURE OF TIMOTHY RUST. The secidial stage of the rust is not definitely known. Eriksson and Henning 4 noticed that the timothy in the neighborhood of bar- berries was not affected, while other grasses in the same locality were rusted. In two trials in 1801 they, were unable to secure infection on timothy with secidiospores from Berberis vulgaris. In 1892-3 aecidia on Berberis vulgaris were obtained by them after inoculation with teleutospores of timothy rust once in nine trials, and that in only one place of inoculation against !»2 places inoculated with negative results. This one positive result may have been due to accidental infection from some other source, as two leaves on the same hush i Loc. oil.. ii leton, Mark Alfred. Cereal Rusts of the Unite, i suites. Bulletin 16, Division of Vegetable Physlot iinl Pathology, U.S. Dept. ol Agriculture, 1899, pp. 61-62. reeman, E. M.. and Jofinson, Edward C. 1 he Rusts ol Orals in the United States. Bulletin 216, I in if Plant Endustry, V. s. Dept. of Agriculture, 1911, p. 16. ■ Eriksson, Jakob, and Henning, Ernst. l>ie Haupt-Resultate einei ueuen Untersuchung fiber die Oetreideroste Zeitschrifl fiir Pflanzenlcrankhelten, vol. •>. 1894, p. 140. 224 iECIMAl. BTAGE \NI> NOMENCLATURE. 11 which had not been artificially inoculated also produced secidia. 1 In L895 Eriksson again made inoculation experiments on the barberry with the teleutospores of this rust, bul in 25 inoculations none was successful. 2 In this couni r\ Kern 3 in L 908 observed eight unsuccessful inoculations on I he barberrj . From their results Eriksson and Henning concluded thai timothy rusl ■!<>«'-; in ■ t form its secidial stage on tin- barberry, while Kern 3 says 1 1 in i "'Im' one positive result mentioned ought, it seems, [to] bo accorded more weighl than all the negative ones together, and pro - * < thai it [timothy rust] does, even if with difficulty, form its stage upon the barberry." Eriksson an. I Henning regard the rusl a distinct species and name it Puccinia phlei-pratensis, while Kern considers it "a race of Puccinia poculifoi • • •!■ a so-called physiological species." Evans accepts the name Puccinia phlei- pnili nsis,* and in a discussion of t lie development of the uredo my eel i a of the cereal rusts shows that there are differences in the details of infection of this rusl and Uredo graminis, which, although slight, are well marked. In a later paper Kern states that he is still of the opinion that this rusl is nol entitled to specific rank and would include it under ''Puccinia poculiformis (Jacq. Wettst.," i. c.. Puc- cinia graminis Pers. Me modifies his previous statement as to its being a physiological species and thinks it mighl better be considered a variety or subspecies, •'since it does, as previousl} pointed out. possess some slight morphological differences from the typical form. particularly in the smaller recial cups and the more delicate uredinial mycelium." From the physiological specialization of this rust, as shown in experiments above reported: from it< distinctive method of infection from the uredospore, as described i>\ Evans; from the difficulty with which it produces its secidium on barberries, as shown by Eriksson and Henning; and from the delicacy of ilu- mycelium of the uredo stage a- compared with the typical graminis form, as cited by I. it i- evident that the rust of timothy has many distinctive character- istics, and, even if not well fixed, is highly specialized. Whether or not it should he regarded as a distinct species is, perhaps, debatal I. i Eriksson, Jakob, and Henning, Ernst. DIo Gob i:s7. : Kriksson. Jakob, l i der PI <.»rt oder nicht? Ofversigt af 191. i ' I ■ i Lmothj . ["on I < ■ i i 09, p. 4 > Evan ,I.B. Pol of! hell Un ol Botany, vol.21, i " The sub >sely re- sembling that of Uredo graminis, but narrower * * *. It differs from Uredo graminis chiefly in 1 thai the end from which thehypha Bprln of the guard cell." i, K. l>. Further Notes on Timothy Rust. Pro Indiana Acad 224 12 TIMOTHY RUST IN THE UNITED STATES. Some method <>t : differentiating this rust in literature from the com- mon gramlnls forms is necessary, however, and unless further experi- ments should show that it can produce its avidium on the barberry, and until such experiments have been performed, the writer favors the use of the specific name Puccinia flilei-'pratensis Erikss. and Henn. WINTER SURVIVAL OF TIMOTHY RUST. In 1908 an effort was made to determine how the rust survives the winter at the Arlington Experimental Farm. Timothy plants were removed from the field on January 19 and March 12 and were imme- diately potted and placed in a greenhouse at Washington, D. C, where they could be carefully watched and any further development of rust noted. Table II shows the results of these experiments. Table II. — Results of experiments on the wintei survival of the rust of timothy. Observations Serial Placed No. in green- house. Date. Result. Date. Result. Date. Result. 1908. 1908. 1908. 1908. 1 Jan. _'ii Jan. 22 Pour unopened pustules near tip of one leaf, several flecks in center. Jan. 28 Pustules near tip not open, three fresh open pus- tules at center where flecks oc- curred. Feb. 3 Endofleaf dried, numerous fresh pustules over remainder -o( leaf. 2 ...do ...do.... No rust pus- tules, no flecks. ...do.... ...do No rust. 3 ...do ...do Seven unopened pustules on ...do Several fresh open pustules on both sides of ...do Leaf covered \vi th vigorous upper side of pustules. one leaf, sev- leaf, several eral on lower. new pustules. 4 ...do ...do Six pustules near tip on up- per side of one leaf, six on ...do Six pustules on upper side of ...do.... New pustules still forming, leaf, six on old ones vigor- lower near tip, ously produc- lower. vigorous; three fresh pustules on upper side: three on lower near center, two of them open. ing spores. 5 do . . . ...do One pustule on middle of up- ...do Leaf drying ...do Leaf almost dead, no new per side of one leaf, leaf pustules. partly dried. 6 Mar. 13 Mar. 13 Several pustules at base of one leaf. Mar. 19 No further de- velopment of rust. Mar. 25 No further de- velopment of rust. 7 ...do.... ...do.... Unopened pus- tules at base of ...do Three fresh pus- tules on leaf; ...do Three fresh pus- tules on leaf, cine leaf, other more than 2 per and several leaves flecked. cent of the fresh pustules on leaves spores from these pustules which were • germinated in water. flecked. 8 ...do .. do ... Unopened pus- tules on many ...do Two open pus- ...do Fresh open pus- tules on one tules on many leaves. leaf. leaves. 9 ...do ...do.... One pustule on each side of ...do No further de- ...do No further de- velopment of velopment of one leaf near tip. Leaves with sev- rust. rust. io ...do ...do ...do do ...do Do. eral unopened pustules. 224 METHODS OF DISTRIBUTION. 13 It is soon that some of the plants broughl in on January 19 and March 12, notably Nos. 1, 3, 4, 7, and 8, continued to produce uredo- spores. At Arlington, in 1908, fresh rusl pustules on new growth of timothy were common after March L5. Undoubtedly the old rust mycelium living in the plants had produced these pustules. Spores collected on January 20 and March 13, 1908, were found to be viable. Similar conditions undoubtedly prevail in other localities of the same latitude and similar climate where this rust is found. How the rust winters farther north has not been determined, hut in the light of recent investigations ' it is very probable that it lives through the winter in the uredo stage much farther north than the latitude cited. As shown by specimens sent to the Office of Grain Investi- gations, it seems that teleutospores of this rust are more abundant m northern latitudes than at the Arlington Experimental Farm, where they were very scarce in lt»i>7 and 190S. At the latter place the parasite Darluca filv/m (Biv.) Cast, largely prevents the forma- tion of the teleuto stage, as almost every pustule ready to produce teleutospores is attacked by this fungus and further development is prevented. However, as the secidial stage, if present, is undoubt- edly rare in this country, the teleuto stage is o'i doubtful importance in the wintering and dissemination of the rust. METHODS OF DISTRIBUTION OF TIMOTHY RUST. The rapid distribution of timothy rust in recent years is doubtless due to the dissemination of the uredospore by the usual agencies. Insects have been shown to be carriers of spores, birds and other animals may carry them from place to place, they maj be transferred from one region to another by man through the shipment of rusted timothy hay. etc., but most important is the agency of the wind. It lias been shown probable 3 that the uredospores of rusts are dis- tributed by the wind Dol only from field to held, but, rising into the upper air, are carried by currents for hundreds of miles. With a quantity of uredospores on hand in various localities early in the spring, their distribution thus becomes an easy matter and the general dissemination of rusl over large areas is accounted for. Undoubtedly, in the course of a few years, the distribution of I rust is to he expected over all timothy-growing sections where con- ditions are favorable for its development. With the ultimate dissemination of rusl over the greater part of the timothy area a practical certainty, methods of preventing any 1 Freeman ;it>'l Johnson, loo < ii . ■Johnson, Edward C I s In the Southwest. Phytopathology, vol 1, 1911, p. 18. • Freeman and Johnson, loc.olt.; and EClebahn, it.. Die wirtsweohselnden RostpUxe, 1904, pp. .... j 14 TIMOTHY RUST IN THE UNITED STATES. considerable damage to the timothy crop from this parasite become necessary. Only one method at present known can be employed against it with any promise of success, and that is the development of varieties of timothy resistant to rust. To this end work has been commenced. RESISTANCE OF VARIETIES OF TIMOTHY TO RUST. A fair opportunity was offered to study the resistance of varie- ties of timothy to rust and to make selections for rust resistance at the Arlington Experimental Farm during 1908 and 1909, as the disease was plentiful in those years. Mr. W. J. Morse, of the Office of Forage-Crop Investigations, who had charge of timothy-breeding work at that place, says in an unpublished report : By July 30 (1908) no tirnothies were found to be entirely free from rust. * * * The rust, resistance varied greatly, ranging from zero to 98 per cent . In some instances a few small rust spots appeared on the culms and no rust on the leaves. Several selec- tions made no growth at all, the rust appearing to stunt the growth. In other instances the plants made some growth, but the production of seed was prevented. In 1909 the rust attack at the Arlington Experimental Farm was even more severe than in 1908, although the rust did not appear to any extent until the middle of May. This severe attack brought to light the fact that many of the strains marked "resist- ant" in 1908 appeared to be much less resistant in 1909. It was noticeable, however, that the relative resistance of the different strains was very little different in 1909 from what it was in 1908. In 1910 the rust attack on the same farm was not nearly so severe as in the two preceding years. Under such conditions the distinc- tion between resistant and nonresistant strains is not nearly as well marked as when rusts are abundant. As a result many strains failed to retain in their resistance percentages the same relative posi- tion Avhich they occupied in 1908 and 1909. This corroborates the experience of the writer that the value of rust-resistance figures obtained in years when the rust is not abundant or at places where the rust attacks are not severe is questionable and shows that the notes taken at such times and places may often be misleading. Dependable data can be secured only either in "rust years" or in places where vigorous rust attacks occur or are artificially pro- duced every year. 1 In order to determine whether or not the figures on rust resist- ance obtained in the field during seasons when rust is abundant are comparable to data secured where different strains are placed under identical conditions and subjected to artificial inoculation, experi- ments were undertaken in 1909 in the greenhouses at Washington, D. C. Seed of various strains of timothies from the 1908 selections at the Arlington Experimental Farm was planted in 4-inch pots. ' Freeman and Johnson, loc. cit. 224 RESISTANCE OF VARIETIES OF TIMOTHY. 15 When the timothy was aboul _' inches high, it was thinned to It) plants or less in a pol and the ! i i--> t leaf of each plant was inoculated by placing on it. by means of a flattened inoculating needle, a small quantity of fresh uredospores. The pots were placed in a moist chamber for '• as described on pairc s of this paper, ami were then removed and allowed to stand for 17 to 21 days, when final notes were taken. The percentage of noninfection from uredo- spore inoculations of timothy selections and the rust-resistance percentages of these -elections in the field during L908 and 1909 are shown in Table 1 If. Table 111. -Tht percen om uredospore inoculations of timothy selections and th< ru percentages of thesi selections in the field during 1908 and 1909. Serial 1 > ite of Inoculation. Timothy tions. inocu- Scuba"- not in- fected. ince in field. 1909 1 1909. 2 i 29 \ IS 1! 52 B 1 K 16 19 7.". C 15 \ :(7 \ 19 \ 2s is 12 19 5 11 11 O 11 Hi 14 8 8 7 is 17 19 ■ 11 is 11 8 Nitmber. Id 17 4 17 6 17 I'ir cult. 64 77 Per cud. 98 80 CO 70 60 98 90 OS 50 2 30 3 .do (') 4 do 12 17 :(7 17 6 is 40 1 Is 71 5 20 6 7 s ...do IS 1 - 13 is .'1 21 11 :«; 91 19 7 9 .do 10 11 in 12 40 13 do it; on 40 1 1 15 21 25 70 6 21 11 15 21 17 98 17 1.-, 21 21 21 60 21 is 12 21 34 77, 7 is 50 3 is 16 17 do 40 In ....do. .. (') 20 . ...do 10 7scs and cereals will develop rusl to some extent when carefully inoculated in the greenhouse with the rust most com- mon on the respective hosts. It is always noticeable, however, that although every inoculated leaf of a rust-resistanl strain may he affected, the rusl infei tion is much less severe on them than on sus- ceptible varieties. Therefore in making observations on rust resist- ance not only the percentage of leaves developing rust pustules hut also the severitj of the infection must he considered. Although such observations arc not noted in Table III il was found that , in so far as 22 1 16 TIMOTHY RUST IN THE UNITED STATES. the vigor of the infection was concerned, the relative rust resistance of strains as obtained in the field was fairly well maintained in the greenhouse experiments and that the differences in resistant and sus- ceptible strains were marked. Having determined, then, that there are wide differences in timothy strains with regard to resistance and susceptibility to rust, the prob- lem in timothy-rust prevention is one of breeding. This may not be as difficult as it appears at first, since up to the present time timo- thies have not been highly bred and there are not only great differ- ences between varieties but apparently unusual variations within a variety. Response to selection, therefore, may be both rapid and well marked. Such breeding, however, to be of any value must be carried on in places where the rust is abundant or where either natur- ally or artificially a rust attack occurs every year. SUMMARY. Timothy rust was reported in the United States as early as 1882. It was reported from Iowa in 1891. From 1891 to 1906 no men- tion of the parasite has been found. In 1906 the rust became epi- demic at the Arlington Experimental Farm, near Washington, D. C, and since then has been found to be widespread, having been reported from Maine to Ontario and northern Minnesota and south to Iowa, Kentucky, and Virginia. Timothy rust is similar in general appearance and morphological characteristics to Puccinia graminis Pers. on wheat. Inoculation experiments with timothy rust at Washington, D. C, show that it can be transferred easily to various grasses. Similar results have been obtained by Eriksson in Europe. This demonstrates that the rust in the United States and the rust in Europe are identical. That it is not a well-fixed species is substantiated. By using bridging hosts timothy rust can be made to transfer to various cereals which it will not attack directly. That such transfers take place in nature to some extent is probable. The a?cidial stage of this rust is not definitely known. Eriksson and Henning in numerous inoculations with the teleutospores on bar- berries obtained negative results except in one instance. On this basis they consider the rust a distinct species, naming it Puccinia phlei-pratensis. Kern has observed several unsuccessful inoculations on the barberry in this country. From the one apparently positive result of Eriksson and Henning, however, he believes that the rust is not entitled to specific rank and should be included under Puccinia graminis Pers. Evans accepts the name Puccinia pMei-pratensis and shows that there are well-marked differences in the details of the infection from the uredospore of tliis rust and the graminis form on 224 SUMMARY. 17 cereals. From the physiological specialization of the rust, from its distinct method of uredospore infection, from the numerous negative results of inoculations with the teleutospore on barberries, and from the delicacy of i he uredo m\ celium, as compared wit li t \ pica] gramin Is forms, it is evident that this rust has many distinctive characteristics. Unless further experiments should showthal the rusl can produce its recidium on the barberry and until such experiment have been per- formed, the writer favors the use of the specific name Pucdnia pMt i- pratt nsis Erikss. and I [enn. At the Arlington Experimental Farm the rust.mycehum lives through the winter. It is very probable that it lives over winter in the uredo stage much farther north than the latitude cited. As the SBcidial stage, it' present, is undoubtedly rare in the United State the teleuto stage is of doubtful importance in the wintering and dis- seminat ion of t he i ust. The rapid distribution of timothy rust in recenl years is undoubt- edly due to the dissemination of the uredospores l>\ the usual agencies, namely, insects, birds, animals, man. surface winds, and upper air' currents. Its ultimate distribution over all timothy-growing sec- tions favorable to it is to he expected, and methods of preventing any considerable damage to the timothy crop become necessary. In a study of the resistance of varieties of timothy to rust in 1908 and 1909, W. J. Morse found that the resistance "varied greatly, ranging from zero to 98 percent." The resistance of differenl strains relative to each other varied little during the two years. Under a less severe rust attack in L910 these strains in many instances failed to retain the same relative position as in previous years. Tin-- lends to show that dependable data can he obtained only when vigorous rust attacks occur. In greenhouse experiments where strains which had been tested in the held were subjected to similar inoculation and identical condi- tions during the period of incubation, the percentage of inoculated leaves which did not become infected did not correspond with I lie figures on rust resistance obtained in the field. When the severity of infection and not the percentage of leaves developing pustules was considered, however, the relative resistance of strains as obtained in the field was fairly well maintained in the greenhouse. A - t here are wide differences in timothy strains with regard to rusl resistance, the problem in t imot li\ -rust prevention become- one of breeding. This maj qoI be as difficult as it appears at first. Such work, however, to be of value must be carried on when the rust is abundant and where either naturally or artificially a rust attack occurs every year. ..I INDEX. Page. id( Mai.- host of timothy rust 9 iosI of timothy rust 9 Airhenatherum i lostof timothy rusl 9, 10 A. vena Eativa, bosl of timothy rust 9, L0 Barberry, attempts at inoculation with timothy rust 10-11, 12, 16 17 Berberis \ ul .in Set Bai berry. Funis, agency in the ili--ciniyuuii.il of rust spores 13, 17 Breeding, rust-resistant varieties, methods I I 17 Bromus unioloide . I ost of timothy rust 9 i larleton, M \ . on host plants of grain rusts 10 (urn-, c. !•'., Wilson, J., and Kent, 1>. A , on the occurrence of timothy rust . . 7 Dactylis g] rata, host of timothy rust 9, 10 Darluca Slum, parasite of timothy rust 13 111 yimis spp., Iii i- 1- "i timothy rusl 9 Eriksson, Jakob, and Eenning, Ernst, on experiments with timothy rust 10, 1 1 ■ ■11 inoculation experiments with timothy rust 9, 10, II Evans, 1 B P., on investigal ions of rusts II Experiments, inoculation, with timothy rusl 8 10, 14 17 Farlow, W, G . and Seymour, A. B., on the rust of timothy i Fescue, tall meadow, use in inoculation i cperiments with i inn ithy rust 9 Festuca elatdor, host of timothy rust 9, 10 Freeman, E.M., and John on, E ' , on the rusts of grain in the United States. 10,13,14 Benning, Ernst, and Eriksson, Jakob, on experiments with timothy rust 10 Bolcus ianatus, host of timothy rusl 9 Bordeum Bpp . boste of timothy rust 9, 10 Bo i . bridging, use in transfer of nu 1 10, 16 Bystrix hystrix, host of timothy rust 9 Inoculation experiments. Sa Experiments, inoculation. Insects, agency in the dissemination of rust spores 13, 17 Johnson, E. C.,and Freeman E.M., on the rusts of grain in the United States. L0, 13, 14 on the dissemination of rusl Bpores 13 Kent, D. A., Wilson, J., and t urtis, < . F., on the occurrence of timothj rust. 7 Kern, F. D , on the rust of timothy II Morse, W. J., on rust resistance of timothy 14, 17 Phalarie arundinacea, ho i of timothy rust 9 Phleum pratense, host of timothy rust 7. 9 Poa Bpp . mothy rusl 9 I'm ri ma graminis, occurrence on stated host plants 7. 8 relationship to timothy rust 11,16 avenae, failure to transfer to timothj 10 phlei-pratensis, name proposed for timothy rust II. 12, 16, 17 poculiformis, name proposed for timothy rust 11 JIM |!l 20 TIMOTHY RUST IN THE UNITED STATES. Page. Rust, breeding for resistance, methods 14-17 timothy, secidial stage 10-11, 13, 16 description 8 distribution in the United States 7, 16 agencies 13-14, 17 identity in the United States and Europe 9-10, 16 nomenclature 11-12, 16-17 relationship and physiological specialization 8-10, 11 resemblance to Puccinia graminis 8, 10, 11, 16 winter survival 12-13, 17 Secale cereale, host of timothy rust 9 Seymour, A. B., and Farlow, W. G., on the rust of timothy 7 Summary of bulletin 16-17 Timothy, unaffected by barberry rust 10 varieties, resistance to rust 14-16 See Rust, timothy. Trelease, William, on the rust of timothy 7 Triticum vulgare, host of timothy rust 9, 10 Uredo graminis, comparison with timothy rust 11 Uredospores, measurements of timothy rust 8 Wilson, J., Curtis, C. F., and Kent, D. A., on the occurrence of timothy rust. . 7 Wind, agency in the dissemination of rust spores 13, 17 224 o UNIVERSITY OF FLORIDA 3 1262 08928 3377