I
Beet Crop Proble01s: Science Helps
Find the Ans-wers
The Beet
Research
Work
of the
United
States
Bureau of Plant Industry
and
How
It Aims to A id the Producer
By E. W.
Brandes and G. H. Coons
0T HE sugar beet crop of the United States is grown in eighteen states. In at least ten of these states the crop is such an important part of the agricul-tural system that abandonment of it for one reason or another would mean serious dislocation in . the agricultural economy of those states. In Tables 1 and 2 are presented some statistics of the crop from 1922 to 1933 for the various states, as given by the Bureau of Agricultural Economics of the United States Department of Agricul-ture. These statistics show that there
rose percentages, particularly from cer-tain sections of those states, are assign-able to the effects brought about by the Cercospora leaf spot. The strong fluc-tuations in California, Utah, and Idaho yields are definitely assignable to curly top. For the purposes of this paper, a less detailed presentation will be more useful and we shall merely indicate what for the several territories are, year in and year out, the principal fac-tors in making the beet crop so variable in its performance. Without minimiz-ing the importance of economic or
po-Table 1. Acreage by States of Sugar Beet Crops in United States, 1922-1933 Acreage harvested 193 31 1932 1931 1930 1929 1928 1927 1926 1925 1924 1923 1922 1,000 acres Ohio ... 46 26 31 22 38 37 35 43 41 41 26 Michigan 163 122 58 74 50 71 99 100 99 150 109 84 Wisconsin ... 15 12 9 8 11 17 15 21 15 8 Nebraska
....
.
.
85 66 65 81 92 86 82 79 60 65 58 55 Montana.
.
....
.
67 54 54 45 37 28 32 32 30 543 371 24• Idaho...
.
80 53 33 44 52 27 29 18 36 39 43 24 Wyoming...
63 40 49 46 49 44 37 36 29 Colorado...
220 156 224 242 230 179 218 211 130 225 164 148 Utah...
76 56 49 44 46 51 55 51 69 81 83 73 California...
113 104 89 65 48 49 59 46 76 84 61 57 Other States . . . . 89 87 92 91 82 63 62 52 60 57 46 31 United States ... 1,017 764 713 775 717 644 721 677 647 817 657 530 1 Acreage planted. : Included in "Other States." 3Montana and Wyoming combined.
Wherever sugar beets are grown de-pendent on natural rainfall, as in Mich-igan, Ohio, Indiana, Iowa, Minnesota, North Dakota, eastern Nebraska, and western Washington, the outstanding problem in sugar beet culture revolves about the securing and maintenance of stand. Disease organisms introduced with the seed and those existing in ag-ricultural soils cause, in the seasons of heavy spring rainfall, such great deci-mation of the seedlings as to reduce, in an alarming percentage of the fields, the initial stand below that which rep-resents a safe figure for efficient utili-zation of the field area. In contrast to this general condition in the humid area, sugar beets which are grown un-der irrigation, because of the superior control of water in the soil and because of other factors, suffer much less, as a rule, from damping-off diseases. While no area is entirely free from their in-fluence, the damping-off diseases and the serious outbreaks of root rot are largely problems of the eastern area rather than of the west.
In western Nebraska, South Dakota, and Colorado the problem overshadow-ing all others is the control of leaf spoi. In these regions, the high summer tem-peratures and the distribution of the rainfall, scant though it is in aggregate amount, are such as to favor the dis-ease. Such conditions also prevail fre-quently in Iowa and Minnesota and, on occasion, in some of the more eastern territory. The leaf-spot disease does its maximum damage in southern Colo-has been great variation in the indi- Table 2. Yields of Sugar Beets by States, 1922-32
vidual state acreages from year to year 2nd that astonishing fluctuations in yields occur. It would be possible to take the various state records and in nearly all cases assign the fluctuations to particular factors. Thus, the low tonnage yields in Michigan, except for the drouth years 1927, 1928, and 1929, are definitely related to poor initial stands caused by damping-off and root rot. The occasional low yields in Colo-rado, and Nebraska, as well as low
sue-*
Excerpt from an article prepared for the Fourth Conference of the Insti-tute International de Recherches de la Betteravieres, at Brussels, Belgium, January 10-12, 1934. The authors are, respectively, Principal Pathologist in Charge and Principal Pathologist of the Division of Sugar Plant Investigations, Bureau of Plant Industry, of the De-partment of Agriculture. 1932 1931 1930 1929 Ohio...
10.0 9.2 8.5 Michigan 10.0 10.0 6.9 5.7 Wisconsin...
.
8.5 7.2 Nebraska.
...
13 .3 13.7 14.0 11.5 Montana...
13.7 11.4 12.7 9.7 Idaho.
.
.
..
....
13.4 9.1 I 0.1 11.0 Wyoming...
.
12.6 11.3 14.0 10.2 Colorado...
11.4 11.3 13,7 12.5 Utah.
..
...
.
15.1 l 0.3 12.6 12.2 California.
.
....
12.4 11.9 11.8 11.2 Other States . . . . 9,8 9.4 9.5 8.0 United States. 11.9 11.1 11.9 10.7 1 Included in "Other States." 2Montana
litical considerations, it may safely be said that agricultural problems have been paramount in determining the success or failure of sugar beet enter.-prises wherever factories have been established. Of these, the plant dis-ease problems have been outstanding in importance.
Yield per Acre, Tons
1928 1927 1926 1925 1924 1923 1922 7.0 8.8 9.7 9.9 7.7 9.4 8.5 6.4 7.0 7.9 9.8 7.2 8.1 8.2 9.2 8.2 9.3 11.2 6.5 8.4 8.3 11.9 12.6 11.7 15.6 11.8 11.0 12.8 9.2 11.4 10.9 10.3 10.42 11.62 10,7° 11.0 13, 1 6.0 12.7 6.9 11.7 11.6 10.5 11.6 10.5 12.6 13.4 12.7 13.8 12.6 11.3 12.2 9.9 12.5 12,3 8.1 15.4 7.0 12.9 11.3 13.0 8.1 8.0 6.4 9.4 9.6 7.4 9.6 8.1 9.0 9.4 8.5 8.4 8.1 11.0 10.8 10.7 11.4 9.2 10.7 9:8 and Wyoming combined.
rado, where the sugar beet rarely reaches the tonnage and sucrose per-centage which the environmental con -ditions would permit were the disease factor absent or controlled.
In the areas west of the Rocky Moun-tains the outstanding problem is curly top. In years of serious outbreak, this
virus disease may close more than half of the factories. It has rendered thou-sands of acres of otherwise suitable land unusable for sugar beets, and in years of severe outbreak, such as 1923 and 1929, caused losses of from $10,-000,000 to $15,000,000 to farmers. As is well known, curly top is a virus dis-ease transmitted by the beet leaf hop-per. This insect is a native of the desert lands, overwintering and breed-ing on various weed plants of these
desert locations. Some of the weed
hosts of the beet leaf hopper definitely have been shown to serve as reservoirs of the curly-top virus. As the desert dries up in the spring, the leaf hoppers migrate to the irrigated valleys, bring-ing the curly-top virus to the cultivated crops. The disease thus introduced by the viruliferous leaf hoppers from the desert and by the straggler leaf hop-pers overwintering in or near the beet fields, soon becomes widespread in the fields. It is not uncommon for the in-cidence to build up from the primary cases to involve by midseason from 50 to 60 per cent of the plants. The in-festation may reach totality before
mid-August or September.
In commercial brands of sugar beets little or no resistance to curly top has been found. Individual plants here and there are to be found in fields planted with commercial varieties which show more tolerance than the majority, but no commercial brand so far tested has shown enough resistance to be note-worthy. Use of the standard seed supply has, in curly-top years, meant loss of crop. Thus the curly-top prob-lem has become in the affected area the limiting factor of the industry. Since no factory can continue with the con-stant threat of crop failure, and since farmers will not continue to plant a crop that presents such hazards, curly top, unless controlled, threatened to de-stroy all sugar beet production in the affected regions.
This situation was recognized by the United States Congress in 1929 and in-tensive research on the problem was inaugurated. Because of the emphasis given to curly top in the investigational work of this division, and its emergency nature, this report will deal rather fully with these activities, outlining the dis-coveries which have been made which give promise of averting the threatened destruction, and which, if the research continues, we hope will ultimately re-move curly top from the list of major
factors in American sugar beet
pro-duction.
Besides the outstanding disease prob-lems, damping-off, root rot, leaf spot, and curly top, the sugar beet nematode situation should be mentioned. Many of the western areas now have become definitely infested with the sugar beet nematode and beet growing is
pre-eluded on many acreages unless
long-time rotations are used. The
impor-tance and immediacy of the other dis-ease problems have led, in many dis-tricts, to lessened emphasis on the soil surveys, and strict rotational control that the nematode infestation demands, but always with unfortunate results.
As in Europe, there exists in the United States another class of problems than the disease problems. These are the agronomic problems with th3ir im-portant bearing on successful beet agri-culture. For each particular section there must be established the cultural methods which assure stable produc-tion, thus greatly contributing to de-pendable crop and factory returns. The fertilizer requirements of the soil and the varieties adapted to the locality must be determined. Associated with these are the problems of beet seed production and beet breeding, so that desirable varieties may be brought to commercial quantity, economically, and their quality maintained. In agronomic investigations, the research can only proceed by the method of controlled field experiment, whence investigation of methods of plot experimentation is fundamental. Such investigations teach how the experiments should be designed and controlled.
The Federal Research Program The Division of Sugar Plant Investi-gations in its sugar beet project has been organized to deal with all of the above-mentioned major problems. For each line of work, specialists have been assigned, chiefly in the field at the cen-ters of beet production, to carry on in-vestigations. The investigational work has been divided into projects as fol-lows, the number of professional em-ployees being indicated for each major activity: Botanical Investigations (2) ; Pathological Investigations-Leaf Spot and Root Rot (8) ; Curly Top (13) ;
Agronomic Investigations - in
Non-Curly-Top Areas (7), in Curly-Top Areas (6).
The scientific work is carried on at Washington, D. C. (including Arling-ton, Va.) and at ten field stations lo-cated in Michigan, Minnesota,
Ne-braska, Colorado (two), New Mexico,
Utah, Idaho, and California (two). In some states the work is cooperative with the state experiment stations.
Botanical Investigat~ons The botanical investigations have concerned themselves with the anatomy and cytology of the sugar beet. The contributions by Ernst Artschwager are well known to European workers. A few of these earlier studies are cited
(1, 2, 3). These investigations form an
important groundwork for the other in-vestigations of the division, and appli-cations of these studies are now being published by Artschwager and others.
There has recently appeared a contribu-tion in which it is shown that under ordinary temperature and humidity conditions, such as would be given in storage piles, wound healing does not take place or at least does so to a very limited extent (4). The great losses of sugar beets in storage piles have been a matter of much concern, and now at least we know a contributing factor. With other crops, it has been possible to manipulate storage conditions to re-duce loss from rotting. Such eventually may be discovered for the sugar beet. In a cytological contribution shortly to appear, Artschwager and Starrett (5) continue their studies on the embryo sac and its development and show some of the underlying facts concerning
pol-lination and embryo formation. In
studies directly connected with the problems of securing selfed seed for be~t breeding investigations, Brew-baker (6) will publish his confirmatory studies on seed setting on sugar beet branches covered with various types of sacks and cages. These botanical stud-ies, technical in their nature, have definite bearing on the more applied phases of the research program.
Investigations on Beet Diseases ROOT-ROT AND DAMPING-OFF Drs-EASES.-The pathological investigations are at the outset more definitely related to some major ill for which relief must be found. But in these problems it is constantly found that advance on the scientific front is necessary if the ulti-mate aim, control, is to be secured. This is well illustrated in the research on the Rhizoctonia disease carried on by LeClerg (7). In many sections of the United States the rotting of maturing sugar beets in the field has been the
(1.) Artschwager, E. Anatomy of the
Vegetative Organs of the Sugar Beet. J our. Agr. Res., 33: 143-176, 1926.
(2.) Artschwager, E. Development
of Flowers and Seed in the Sugar Beet. Jour. Agr. Res., 34: 1-25, 1927.
(3.) Artschwager, E. A Study of Sugar Beets in Relation to Sugar Con-tent and Type. Jour. Agr. Res., 40:
867-915, 1930.
(4.) Artschwager, E., and Starrett,
R. C. Suberization and Wound-Cork
Formation in Sugar Beets as Affected by Temperature and Relative Humidity. Jour. Agr. Res., 47, No. 9, Nov. 1, 1933.
(5.) Artschwager, E., and Starrett,
R. C. The Time Factor in Fertilization and Embryo Development in Sugar Beets. Jour Agr. Res., 47: No. 11, Dec.
1, 1933.
(6.) Brewbaker, H. E. Self-Fertili-zation in Sugar Beets as Influenced by Type of Isolator and Other Factors. Jour. Agr. Res., 47 (In press). 1934.
(7.) LeClerg, E. L. The Parasitism of Rhizoctonia solani on the Suv.ar Beet. Jour. Agr. Res. (Submitted for publication).
occasion of grave concern. Fields of
good promise have lost a large part of their stand because of late appearing root rot. This has been especially true of Minnesota. Because of the fact that the disease was caused by Rhizoctonia solani, well known as a parasite of the potato, and because of the important place the potato crop has had in the crop rotations in that area, it was as-sumed that the diseases on the two crops were interrelated. LeClerg has
shown that the strains of Rhizoctonia from the potato are non-pathogenic to sugar beet roots of fair size, and the strains of Rhizoctonia cause only a lim-ited amount of seedling damp-off. Thus, clear-cut evidence is given of the exis-tence within the group of organisms commonly grouped as Rhizoctonia solani of physiological forms, definite and re-stricted in their pathogenicity. These results have immediate applicability for the area, since they remove from the potato crop the suspicion that it has been responsible for the root rot of the sugar beet, and extreme dislocation of the crop rotation system is avoided. Fur-ther, the recognition of the existence of physiological strains among the Rhizoc-tonias parasitic on sugar beets can not but have important bearing upon subse-quent breeding work which seeks to utilize disease-resistance factors to counteract root-rot losses.
Extensive field experiments have been carried on to evaluate for American conditions the matter of sugar beet seed treatment to prevent damping-off of beet seedlings (8, 9). Damping-off is initiated, not only by organisms borne on the seed (Phoma betae) but in large part comes from the common damping-off organisms of the soil, Rhizoctonia, Pythium, and Aphan-omyces. Seed treatments have been found which not only disinfect the seed but which ward off the invaders from the soil. Because this latter protec-tive action is probably the more im-portant function, dust treatments have been found more effective, and at the same time more practical, than liquid or steeping treatments. The most ef-fective dusts contain both mercury bichloride and copper carbonate, the latter serving both as a diluent and a lasting disinfectant. It has been pos-sible by dusting the seed with suitable disinfecting dusts to maintain seedlings in complete stands for thirty days, whereas the untreated controls grown in adjacent rows have been greatly re-duced in stand. In addition it has been
(8.) Coons, G. H., and Stewart, Dewey. Prevention of Seedling Dis-eases of Sugar Beets. Phytopath, 17: 259-296, 1927.
(9.) Coons, G. H. Sugar-Beet Dis-ease Control Progressing Toward Solu -tion. Yearbook,
U.
S. Dept. Agr. 1928: 4 pp.found that the proper fertilizer applied with the seed plays an important role in stand maintenance, undoubtedly through its direct effect on the rate of growth and establishment through the supplying of readily available nutri-ents. Striking beneficial results have been obtained in greenhouse and small field trials, but the large-scale tests have uncovered a very complex situa-tion which needs further analysis be-fore seed treatment can take its place as a routine matter. Thus, not only the environmental conditions have influ-enced the results, but the type of path-ogene present and the quantity present have been found exceedingly important. Certain preceding crops apparently strongly augment the quantity of one pathogene in the soil. Other crops re-press the pathogenic forms. It seems extremely likely that by manipulation of the rotation systems by use of prop-er crop sequences, coupled with seed treatment and the improvement of soil conditions by drainage and fertilizer application, dependable stands should be secured in all but the most refractory situations.
The control of damping-off may have an important bearing on the general root-rot problem. On the basis of ob-servation it has long been assumed that the root-rot condition was a delayed ap-pearance of a disease contracted in the seedling stage (10) . Nuckols (11) has
shown that young plants definitely known to be affected with "black root", while showing some recovery, have a pronounced mortality throughout the season. While late infections undoubt-edly occur, as for example with sugar-beet strains of Rhizoctonia, much of the root rot in the fields at mid-season or later may be a delayed outcropping of the early infection. Thus, the sim-ple sugar beet seed treatments may have a far-reaching, beneficial effect.
The root rots of plants and their con-trol form a field in phytopathology which is largely unexplored. Here the complexity of soil problems is super-imposed on organismal complexity. In addition, the newer findings indicate that the existence of physiological strains within the soil organisms may be a factor. Recently, antagonistic ac-tion between members of the soil flora has been shown to have profound ef-fects. The root-rot problem as it af-fects the sugar beet will not yield rapidly to solution, but the results so far obtained are very promising.
Leaf Spot
While the acute curly-top situation in (10.) Coons, G. H. The Root Dis-eases of the Sugar Heet. Michigan Su-gar Beet Institute, 1924: 28-34, 1924.
(11.) Nuckols, S. B. Effects of Black Root in Beets. FACTS ABOUT SUGAR, 26: 260, 262, 264, 1931.
the states west of the Rocky Mountains should not be minimized in its impor-tance, an at least equally serious prob-lem, leaf spot, exists in the states im-mediately east of the Rockies. Because leaf-spot losses are insidious and wast-ing in their nature, they have not been fully recognized or their seriousness fuliy appreciated by growers and fac-tories. Since large acreages in Colo-rado and other states are involved, the year-in and year-out reductions in both tonnage and quality of the crop make the losses from this disease assume in the aggregate an enormous figure. They take the form of a drain on the crop returns less likely to arouse concern than the sharp crop destruction which curly top inflicts. In their effects, how-ever, these depredations of leaf spot are a serious menace to a profitable
sugar-beet industry in the affected areas.
In 1925, active research on the leaf-spot problem was started by this divi-sion. At that time the life history of the organism was known, its depend-ence on environmental conditions had been outlined, and its direct control by Bordeaux sprays recognized as a possi-bility. In the first few years of in-Yestigation, largely in the section of Colorado which was worst affected, it was possible to demonstrate that suc-cessful control of leaf spot could be
obtained by dusting the fields with a copper dust containing 80 per cent hydrated lime and 20 per cent dehy-drated copper sulphate. The cost of control for a season ranged from $4 to $5 per acre. This expense is more than offset by the increase in tonnage secured in leaf-spot years. In addition, the sucrose percentage of the dusted plants was higher by approximately 2 per cent than that from undusted plants. There was also a corresponding improvement in the apparent coefficient of purity as a result of dusting. These
results have been reported in detail for the period from 1925-1928 (12). In the continuation of the work, confirmatory results have been obtained in the years when leaf spot has been a factor. But the low prices of recent years have, in
spite of the showing of efficacy, com-pletely militated against widespread adoption of the direct-control measure by the industry.
As it became apparent that control by direct measures would be taken up slowly and only as a last resort, the
emphasis placed on the breeding for
(12.) Coons, G. H .. Stewart, Dewey, and Larmer, F. G. Sugar-Beet Leaf-Spot Disease and Its Control by Direct Measures. U. S. Dept. Circ. 115; 20 pp. 1930.
(13.) Coons, G. H. Sugar-Beet Strains Resistant to Leaf Spot and Curly Top. Yearbook, U. S. Dept. Agr. 1931, 4 pp.
leaf-spot resistance has been increased. In this work notable results have now been obtained (13) and it is to be re-marked that the findings are at vari-ance with opinions expressed by some European investigators that the possi-bilities of attaining resistant lines are remote. The research which has been carried on has sought to secure basal stocks of resistant sugar beets satis-factory from the commercial point of view. After these stocks are secured as stabilized lines, these lines are to be combined in synthetic varieties. As a criterion in the testing, the resistant lines have been held to a standard of producing high sugar percentages and reasonably high tonnage under condi-tions of severe leaf spot, a standard commercial variety being used for com-parison. To induce the epidemic con-ditions, the experimental fields have been equipped with overhead sprinkler systems, thus making it possible to give the necessary artificial rain conditions to make leaf spot severe. The test fields are located at Fort Collins, Colo-rado; Rocky Ford, ColoColo-rado; and Ar-lington, Virginia.
We were fortunate to have made avail-able for the leaf-spot work the results of more than ten years of inbreeding of sugar beets carried on by the late W.W. Tracy, Jr. Several hundred selected lines of sugar beets which had had any-where .from 2 to 7 _generations of in-breeding were available in 1925 for in-tensive testing for resistance. By selec-tions under condiselec-tions of severe leaf spot, 14 outstanding resistant · lines were chosen, of which five were espe-cially promising, and with these and other new selections the breeding work has continued. As a result of this breeding work for leaf-spot resistance, we now have many lines of sugar beets possessing noteworthy degrees of leaf-spot resistance and the lines have been proved to be constant in this regard from year to year. As the inbreeding has been continued, not only has sta-bilization in disease reaction been ob-tained, but striking uniformity in foli -age and root characters as well. None of these lines are immune to leaf spot, but the more resistant ones retain their'
leaves without serious burning under serious epidemic conditions in which commercial brands are severely injured. With continued inbreeding the size and vigor of the lines have decreased sharply, but simple crossing between inbred lines has restored size and vigor in the hybrid plants. The first large-scale trials of the synthetic varieties obtained by putting together the lines selected for disease resistance will be made in 1934. In the meantime, the basic stocks of these lines are being increased.
In the experimental work a series of grades based on estimating extent of
leaf-spot damage in the plots have been employed. These have been based upon a scale of
lOt.
The grades take into account the extent of burning produced. With such a scale, with leaf-spot se-vere, a commercial variety such as R. and G. "Pioneer" will grade from 5 to 6; extremely susceptible types, such as some elites obtained from Europe, from 7 to 10. The resistant lines grade from 1 to 3 in such a test. The resistant plants have fewer spots, retain their foliage and stand out strongly in the field as green islands.Experience With Wild Beets Because of the renewed interest in
Beta maritima L. by European investi-gators, it will be of value to report our experiences. Seed from Beta maritima was collected in France and England in 1925 and some seed was also obtained from Krueger's collection of types. This material has been repeatedly tested. Some outstanding plants have been iso-lated and used as breeding material. The strongly varying response of the individuals in a single collection both to leaf spot and to the virus disease, curly top, has shown that in most wild beets to be found along the coast as great a divergence of types occurs as in the cultivated beet. Hence in all work, the individual has been taken as the starting point. Applying to in-dividual plants much the same system of grading as is used in the field tests with cultivated forms, outstanding in-dividuals have been found which would grade less than 1
(½
or less). In such resistant plants the spots on the leaves have been few in number, and reduced in size. The most resistant individuals have shown only flecking. Crosses of the resistant individuals have been ob-tained and from these breeding work has continued. From the outset, roots extremely low in sugar have been elim-inated, and the lines at present ap-proach the parent sugar beet lines int
Field grades for reactions of sugar beets to Cercospora beticola:0 Immune.
1 Highly resistant-spots few, small. 2 Highly resistant-spots few, nor-mal size.
3 Fairly resistant-spots scattered, many, normal size, no coalescing of spots; no burning of leaves ...
4 Slightly resistant-spots many; slight burning of leaves; lesions on petioles.
5 Not resistant-spots many, coales-cing; leaves show burning.
6 Susceptible-spots many, coales
-cing; pronounced burning of leaves. 7 Susceptible-spots many, coales-cing; foliage reduced one-half.
8 Susceptible-spots many, coales-cing; foliage reduced three-fourths.
9-10 Susceptible-foliage completely burned; no living leaves, except center tuft.
quality, but usually are somewhat lower in sugar. The effect of crossing has usually led to pronounced increase in size in the F, generation-roots weigh-ing from 5 to 7 pounds not being un-common. Whether from this material desirable strains representing worth while improvement over present stocks can be obtained is as yet not clearly shown, but some seem extremely prom-ising.
In addition to the work with inbred lines and definite crosses, it has been found possible to make decisive advance in leaf-spot resistance by mass selec-tions. These have been made by select-ing roots, high in sucrose and large in size, from fields suffering from severe epidemics. From fields which would rate from 5 to 6 or higher, mass selec-tions based largely on field judgment, reinforced by rigid saccharimeter tests, have given progenies which maintain fairly closely a 3 to 3.5 reading. Under leaf-spot conditions these selections have been superior to the original stocks from which they were selected. Where, in the reselections from the first selections, groups of many roots have been put out to produce seed, root size has been maintained in the progenies. It is evident that some progress in beet improvement can be made by mass se-lection in which leaf-spot resistance is taken into account.
The JlOSsibilities QJ2e11e_d_ up by the demonstration that leaf-spot resistant lines can be obtained from cultivated beets, that in wild strains greater re-sistance exists than in cultivated strains, and the demonstration that the beet can be improved markedly in re-sistance by mass selections under con-ditions of leaf-spot epidemic should have
important bearing on future beet breeding work. It is not too sanguine a hope that leaf-spot resistant strains will become available to remove from the industry as a whole the great losses and uncertainties which this wasting disease now imposes.
Curly Top
In the study of the curly-top disease, intensive investigation of the nature of the virus has been carried on. It has been demonstrated that the virus is to be found chiefly, if not entirely, in the phloem. It seems likely that the virus moves only in this tissue, as Bennett
(14) has shown by girdling experi-ments with tobacco plants. After in-oculation, the movement is so rapid as to bring to question the commonly ac-cepted views of fluid movement in the phloem unless an independent move-ment of the virus is to be postulated.
(14.) Bennett, C. W. Plant Tissue Relations of the Sugar-Beet Curly-Top Virus. J our. Agr. Res., 47: ( in course of publication). 1934.
By securing phloem exudate, it has been possible to exclude the apparently in-hibiting or inactivating effects of the juices of other plant parts on the virus, thus opening up a field of experimenta-tion on the longevity of the virus, its
sensitiveness to chemical and to
physi-cal factors. Biochemical investigations
high leaf-hopper populations.
Ecologi-cal studies by Piemeisel (16) have
traced the successions of vegetation on
these lands and shown that if setbacks
such as those occasioned by continued
overgrazing, fires and replowing do not
occur, the original cover, such as
sage-brush and grass in Idaho, will return in
an attenuated virus can be restored by
passage through a susceptible host,
notably Stellaria media. It is probable
that other susceptible hosts may act
similarly, Many of the important
plants of the desert associations on
which the leaf hopper feeds have now
been tested and their reactions known.
Photo by courtesy of Hclly Sugar Corp. Grower-Test Planting of Beet Variety U. S. No. 1 (right) near Delta, Colorado. This Shows the Contrast of This Curly-Top Resistant Strain in an Infected ~rea With Ordinary Co11tmercial Beets (left) Attacked. by
Curly Top.
on the nature of curly-top resistance are beginning to reveal differences in
the curly-top-resistant strains as
con-trasted with the susceptible strains.
Such work may furnish a definite guide
in the breeding program, once the bases
of resistance are established.
The importance of desert plants
which harbor the curly-top virus, and
on which the beet leaf hopper feeds and
breeds, is recognized in the broad
in-\'estigational program dealing with
curly top. In the western area, the
seriousness of the curly-top problem
became acute when the original desert
vegetation, relatively unimportant in
maintaining the curly-top virus and
with which the leaf hopper population
was in equilibrium, was destroyed by
over-grazing, by breaking up of
semi-arid lands to permit grain growing and
by other types of denudation, thus
changing the plant cover of the desert
lands (15). These lands when the
cli-max desert vegetation was destroyed
be-came weedy areas which have favored
(15.) Carter, Walter. Ecological
Studies of the Beet Leaf Hopper. U. S.
Dept. Agr. Tech. Bui. 206: 115 pp. 1930.
a comparatively short time, thus
re-moving these areas as a source of large
leaf-hopper populations. These lands
have no place in an ordered agriculture
except for pastoral use, on which the
grazing is so controlled as to maintain
them always as a national asset.
Inas-much as the government policy seeks
to remove the submarginal and
mar-ginal agricultural lands from use in
crop growing, these studies are of
fun-damental value in throwing light on
what the successions of vegetation will
be when the periodic denudations are prevented.
Related studies on the relation of the
weeds of these desert lands to the
curly-top virus have revealed some
remark-able phenomena. Carsner (17) has
i"hown that certain refractory hosts
at-tenuate the curly-top virus. Lackey
(18) has shown that the virulence of
(16.) Piemeisel, R. L. Weedy
Abandoned Lands and Weed Hosts of
the Beet Leaf Hopper. U. S. Dept. Agr.
Circ. 229: 24 p., 1932.
(17.) Carsner, E. Attenuation of
the Virus of Sugar-Beet Curly Top.
Phytopath, 15: 745-757, 1925.
Thus certain mustards are extremely
susceptible; others are non-reactive, and
probably attenuate the virus. Tests
in-volving thousands of leaf hoppers
col-lected in the desert have revealed the
percentage viruliferous and thus
cap-able of inducing curly top. Such data
seek to show where the curly top comes
from in its annual flare-up in
culti-vated fields. Such tests may succeed in
localizing or accurately delineating the source areas of the leaf-hopper influx
from among the vast desert areas, each
with its leaf-hopper populations. Such
knowledge is of great importance if the
factors influencing the development to
epidemic proportions of curly top are
ever to be known. These studies, along
with those of the coordinated
en-tomological investigations dealing
di-rectly with the leaf hopper, are carried
on because it is recognized that a
prob-lem of this magnitude will yield to
successful solution only as all the
mani-(18.) Lackey, C. F. Restoration of
Virulence of Attenuated Curly-Top
Virus by Passage through Stellaria
media. Jour. Agr. Res., 44: 755-765, 1932.
fold threads are untangled and the at-tack approaches along a complete, un-broken front. While highly resistant lines of sugar beets are in sight, it is perhaps too much to expect that im-mune beets will be found. Nor is the beet the only crop affected by the leaf hopper. The damage done to a score of cultivated crops is, in proportion to their extent of cultivation, comparable to that done to the sugar beet. It has been the common experience in agri-cultural research that, as improved conditions in many regards are fur-nished, the ravages of disease become reduced to low proportions.
The results of the investigations to secure curly-top resistant lines are very gratifying, and economically very important. The first of these resistant lines, U. S. No. 1, has been announced and will be planted in 1934 on 37,000 acres, approximately half of the se-verely affected acreage. This release is essentially a synthetic variety. It is composed of a number of lines known to be curly-top resistant which were combined in 1929. By the coordinated activities of the division, it has been possible since the production of the seed in 1929 to test the variety in all the important curly-top areas and to increase the original small supply of seed to approximately 750,000 pounds. In the final increases to commercial quantities, interested sugar companies, working under cooperative agreement with the Division of Sugar Plant In-vestigations, have grown the seed under government supervision.
Rapid increase of the seed has been made possible by the utilization of the overwintering in the field method of seed increase, in which advantage is taken of the mild winter conditions of the southwestern United States. The widespread tests under moderate to se-vere curly-top conditions in 1931 have shown clearly that this new variety has a greater resistance to curly top than commercial brands grown in compari -son, and that under all but the most severe conditions of curly top it will give a high degree of relief. The aver-age superiority, as shown by 42 tests in 1931, was between 4 and 5 tons per acre. In sucrose percentage it was equal to the commercial brands. These results are reported in detail in a re-cent technical bulletin (19). The tests in 1932 and 1933 were largely under conditions in which curly top was a minor factor. In these tests the com-mercial brands on the average slightly out-yielded U. S. No. 1, but were lower in sucrose percentage. It is doubtful if the two sorts differ significantly in
(19.) Carsner, E., and others. Curly-Top Resistance in Sugar Beets and Tests of the Resistant Variety, U. S. No. 1. U. S. Dept. Agr. Tech. Bui. 360: 68 pp. 1933.
sugar produced per acre. Apparently the use of the variety should cause no drop in returns in non-curly-top years, while giving great superiority in curly-top years.
The announcement of a curly-top re-sistant variety is, of course, likely to be misunderstood and assumption made that curly top forthwith ceases to be a factor in the stricken areas. Such assumption goes widely beyond any of the statements of the division that the new introduction should give a bene-ficial reduction in curly-top losses. Be-cause of the emergency situation, it was not advisable to withhold the re-lease of the U. S. No. 1 variety until the breeding work was completed and the variety stabilized. The results given in the bulletin referred to show that the variety as now constituted is far from being perfected. It is not curly-top immune, and, under California con-ditions, in which seed is planted in December or early January, it has a tendency to bolt. All in all, the variety can profitably be reselected repeatedly to improve its resistance. It is a com-bination of strains which were known to have resistant or slightly reacting individuals predominating. Under se-vere curly-top conditions as many as 40 per cent of the plants may be killed by curly top or severely injured. At least a third of the remainder grow vigorously in spite of curly top, and the balance are only moderately affected. It
is the predominance of the resistant and disease-tolerant individuals which accounts for the gains in yields con-sistently found.
Additional promising sugar beet strains, some representing selections from the original component lines used in making the U. S. No. 1, now exist. These appear to be superior in resis-tance and in other qualities. Exten-sive field testing of these remains to be done, and the most satisfactory will be substituted as basic seed stocks in a program of seed production continued along the lines of the one previously followed. Thus, the industry, cooperat-ing with the Department, may quickly put to use the results of the experi-mental work.
Agronomic Investigations
TESTS OF PROMISING STRAINS AND SEED-PRODUCTION STUDIES. - The De-partment of Agriculture is not author-ized by law to carry on tests of im-ported commercial brands to attempt officially to grade, certify, or classify them as to quality or productiveness. No such regulatory service is in opera-tion in the United States. The testing of varieties which is carried on is en-tirely of the nature of evaluating the products of beet breeding researches for special conditions of the various areas of the United States.
As seed stocks promising for one reason or another are developed, in-tensive field tests at appropriate sta-tions are being carried on to determine the performance to be expected from such seed lots. Thus, in the case of the U. S. No. 1 variety, as soon as prelim-inary tests in 1930 showed promise, in-tensive field tests at all the field sta-tions in the curly-top area were under-taken and, in addition, grower-test plantings in all important curly-top areas. Thus in one year a body of in -formation was forthcoming to guide the use, on a large scale, of the variety by growers. During the two-year period when seed was being increased to required commercial quantities, ad-ditional tests have continued. At the time when the seed will be released for grower test in 1934, repeated tests will have given what appears to be a safe indication of the performance to be expected.
When basic seed stocks are found to be disease resistant and otherwise im-proved, there is involved at once the questi'on of ways and means of multi-plication of the desirable stocks to pro-portions adequate for commercial utili-zation. The Department of Agricul-ture has therefore for many years studied problems underlying successful sugar beet seed production. It guided the domestic seed production program during the world war when customary seed supplies were cut off. Within the last ten years the method of seed pro-duction from plants overwintered in the field has been developed to a high point of efficiency by the efforts of this divi-sion (20, 21) by cooperative work in New Mexico and by tests in California and Utah.
Interesting new results are now forthcoming from the continued experi-ments with this method of seed produc-tion. These experiments have dealt with the factors which influence seed yields and seed quality. As important as any are the findings as to fertilizer requirements for maximum seed pro-duction. Experiments in New Mexico, California, and Utah have consistently shown that even with highly fertile fields nitrogen applications are exceed-ingly beneficial, the sugar beet respond-ing strongly to such applications both in seed quantity and, where the appli-cations are early, in improved seed quality.
In addition to the specific work of testing varieties and strains for
adapt-(20.) Overpeck, J. C. Seed Produc-tion from Sugar Beets Overwintered in the Field. U. S. Dept. Agr. Circ. 20: 7 pp. 1928.
(21.) Overpeck, J. C. and H. A. Elcock. Methods of Seed Production from Sugar Beets Overwintered in the Field. U. S. Dept. Agr. Circ. 153: 21 pp. 1931.
ability in the various sugar beet re-gions, a general agronomic-research
program to serve all important sugar beet growing districts of the United States is in operation. Because of a limited personnel, stations can not be maintained in all states, but the loca
-tion of field operations has been so chosen that regions, rather than state
entities, are served and the problems undertaken have regional rather than local applicability. The tests con-ducted seek to cover the range of lead-ing soil types of a region, thus
broad-ening the scope of utilization of the findings. From one station investiga-tions may be conducted in three
con-tiguous states, whereas in other cases the wide divergence of soils, climatic
conditions, elevation, or crop practices,
as well as the mere fact of great dis-tances between beet areas, may make
two stations in a state desirable. With the particular needs of each
re-gion being taken into account, the in-vestigations seek to determine by ex-periment the proper methods of sugar beet growing. Planting methods, types
of soil preparation, and other cultural practices are compared. The place of
sugar beets in the rotation, the fer
-tilizer to apply, the kind of seed to use, irrigation practices, when and how to harvest, and the space relations as they affect quality and quantity of the crop
are studied. Throughout the program,
those fundamental methods of crop
production which are essential to
uni-formity of crop production from year to year are sought. The sugar beet
crop, apart from the fluctuations brought about by the disease factors already discussed, has shown wide fluctuations in yield and quality, due to lack of proper understanding of how to adjust the methods of production to the great climatic and environmental variations. The yield and quality of the
crop have also suffered because
un-suited soil types have been pressed into use for beet growing, and because fer-tilizer applications have been omitted
or improper combinations used. In general, the sugar beet, which is
essentially an intensive crop, has been grown by farmers as if it were an ex
-tensive or ordinary field crop. This
situation is the one which impresses European observers whenever they have critically viewed American methods of production. It must be obvious that
a crop which has from. $35 to $45 per
acre spent upon it in labor costs differs from a field crop such as wheat or corn, and requires a building up and
appli-cation of specific information as to
ef-ficient crop handling.
Without particularizing for each sta-tion engaged in this general agronomic program, it can be said that as a result
of the three or more years of
experi-mental work which has been carried on,
a start has been made in the estab-lishment of pertinent facts as to when
and how to plant, what soil to use, what fertilizers are necessary with a
given soil type, and what methods of crop handling are most economical or productive for all beet areas in the United States. These results, when
put in practice, may confidently be ex-pected, year in and year out, to raise the average production of beets in each
section one or two tons per acre and at the same time improve the quality of the sugar beet. It must be recog-nized that the tonnage and sugar pro-duction obtained in the United States are far below those obtained in Euro-pean agriculture. In our opinion, it
should be possible to reach the splendid
returns of European agriculture, not on isolated farms, but as a general na-tional average, if sound agronomic practices become generally adopted, and disease losses are controlled.
The above prediction is not based upon mere speculation but seems fully warranted from the results from many of our stations. A few specific examples
may be cited. At the Michigan station,
in cooperative experiments, the use of fertilizers rich in phosphate, applied with the seed, at the rate of 125 pounds per acre, has shown on the average a
3½
ton increase in yield over sugarbeets not so fertilized. This experience is not unique but has been duplicated
at practically all of our other field sta
-tions where, by exact experimentation, the fertilizer needs of the soil and the crop have been determined. Time-of-planting experiments in Nebraska have shown that seasonably early planting, because of the longer growing period given, has increased the average yield
of sugar beets
1½
tons with an eleva-tion of sucrose percentage by at least one per cent over the sucrose percent-age of the late-planted beets.Mechani-cal blocking and cross cultivation
ex-periments in Minnesota and at other
stations have shown that the laborious, time consuming processes of blocking and thinning beets can be safely speeded up so as to take advantage of the gains from early planting (22). It
has commonly been necessary to stag
-ger the planting of beets to distribute the labor load, but by using machines to block the beets practically the total acreage may now be planted at the proper time for maximum production. The labor savings effected, together with the gains from weed control which come from the subseqeunt cross
culti-vations made possible by the mechanical blocking, greatly reduce production
costs. More than 40,000 acres of sugar beets in Iowa, Minnesota, and North
(22.) Mervine, E. M., and Skuderna, A. W. Cross-Blocking Sugar Beets by Machine. U. S. Dept. Agr. Leaflet 97: 6 pp. 1933.
Dakota, where the method was first tried out, were mechanically blocked in 1932.
Radical change in irrigation practice from the "feast and famine" system commonly in vogue in the western beet
growing areas may be expected as a result of experiments in Nebraska, South Dakota, and Colorado. It has
been shown that frequent light irriga-tions, by which the beet is kept
grow-ing uniformly and steadily, result in
tcnnage gains and increased sugar pro-duction. Efficiency in the use of irriga-tion water is a definite need in the parched western areas (23). West of
tlie Rocky Mountains, all problems of beet growing have in the past been largely overshadowed by the curly-top
menace, but even in these areas, as demonstrated by tests carried on in Utah, Idaho and California, fields in which curly top is prevalent can often be made to return the cost of produc-tion by proper handling of the beets that still remain functioning in the field. Further, it has been shown in Idaho under curly-top conditions that early planting, long known as beneficial against curly top, when combined with use of fertilizers and the resistant U. S. No. 1 variety, gives striking yield in
-creases (24).
These results have been obtained in experimental plots. Their translation to field experiences depends upon the
adequacy of the field experimentation
reliably to assign the gains in due pro-portion to the contributing factors. For this reason, at the Minnesota field
sta-tion in the humid area, and at the
northern Colorado field station for the irrigated area, plot-technic studies
have been carried on. From these
sta-tions, the size of plot and the number of replications requisite to secure the desired precision have been determined
(25, 26). In general, plots from 4 to
fi rows wide, at least 60 feet long, repli-cated five or more times, have been found most efficient. The plot arrange-ment has been random, and in the an-alysis of results the accepted methods of R. A. Fisher have been commonly
used. As application has been made of the results from the intensive field
(23.) Brewbaker, H. E. Sugar-Beet Irrigation Studies. FACTS ABOUT SUGAR, 28: 93-94, 1933.
(24.) Skuderna, A. W., Cormany,
C. E., and Hurst, L. A. Effect of Time
of Planting and Fertilizer Mixtures on
the Curly-Top Resistant Sugar Beet Variety, U. S. No. 1, in Idaho. U. S. Dept. Agr. Circ. 273: 16 pp. 1933.
(25). Immer, F. R. A Study of Sam-pling Technic with Sugar Beets. Jour. Agr. Res., 44: 633-647. 1932.
(26.) Immer, F. R. Size and Shape
of Plot in Relation to Field Experi-ments with Sugar Beets. J our. Agr. Res., 44: 649-668. 1932.
experiments in practical field tests, the concordance in the actual results with those predictable has been entirely con-firmatory of the experimental method. Thus, by basic and by applied re-search, closely coordinated, the prob-lems of the beet industry are receiving attention in the United States.
Thoughtful consideration of the problems of the industry will show that so far as the fabrication of the crop into sugar is concerned, the factories are being made technically efficient and capable of making sugar with loss
re-duced to a mrn1mum. The uncertain factor in all sugar production is the agricultural factor. The hazards of soil, climate, disease, and faulty farm operations have made for the variable production which is strikingly shown in the average figures for even so large a geographical area as a state. The farmer must be put in a position to secure a dependable yield of beets sat-isfactory in quality. Means of adjust-ing farmadjust-ing methods to fit conditions must be discovered and means of pro-tection from serious disease losses
Reprinted from
FACTS ABOUT SUGAR,Volume 29, Nos. 3-4;
March-April,1934
found. From the standpoint of the factory, a reasonably stable acreage from year to year, producing a de-pendable crop, is necessary so that the factory may always have adequate ton-nage for efficient operation. Thus grow-ers and factories have a common inter-est in the agricultural problems. As the significance of the dependence of the industry on the outcome of scien-tific research is more fully recognized, we may expect that even greater em-phasis will be placed on research pro-grams for sugar beet improvement.
