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The Saskatchewan Department of Agriculture employed Mr. Edward G. Reekie, B.S.A. under a Youth Employment Service grant to review information concerning research which may be of special interest and assistance to persons wishing to carry on farming operations without, or with limited use of, chemicals. Mr. Reekie did an intensive and conscientious review of literature, covering the following:
He also visited research stations for additional information. The attached is a complete and unabridged summary as prepared by Mr. Reekie Only minor editorial changes have been made. The Department of Agriculture believes that the material is honestly and fairly presented but takes no responsibility for errors of content or interpretation. Further, while many of the practices discusses therein may form a part of normal departmental recommendations, neither the report nor any section thereof should be interpreted as official recommendations.
The best way to control stem rust is to use resistant varieties There are a number of wheat varieties with good resistance to stem rust (1).
Another method of controlling stem rust is to destroy barberry bushes (1). The barberry is the alternate host in the life cycle of the fungus which causes stem rust. The life cycle of this fungus starts with the black spores which are produced on infected wheat plants towards the fall. It is the black spores that are the overwintering stage of stem rust. The following spring these spores will germinate forming 4 smaller spores called sporidia which will then infect barberry bushes. The rust produced on the barberry bushes by the sporidia will produce more spores, these spores however can only infect grain crops and grasses. The rust produced on the grain crops and grasses will continue to produce more of the same type of spores spreading the infection throughout the summer. Once the crops start to ripen however, the summer spores will no longer be produced and the black spores, the overwintering stage of the rust, will be formed. Since the summer spores cannot survive the winter in Saskatchewan if the barberry was eradicated it would eliminate a source of infection of the crops. Eradication of the barberry would not completely eliminate stem rust however as each spring spores from southern Texas and Mexico, where the summer spores are able to overwinter, are blown northward infecting crops along the way, reaching southeastern Saskatchewan by early summer. Eradication of the barberry is useful for a second reason however, while the rust is on the barberry the different races of rust can interbreed to produce new races. These new races of rust may be able to infect previously resistant crop varieties.
The barberry is not a native plant, it was introduced from Europe and is now common in the eastern United States and in some parts of Eastern Canada (1). The barberry eradication program, which was initiated in 1918, has resulted in the destruction of most barberry bushes in the Mississippi Valley states and Western Canada.
Early seeding can also be used to reduce crop losses from stem rust (2). Since stem rust does not usually develop until early summer and the amount of infection increases as the season advances, early seeding will reduce rust losses as the crop will complete much of its development before it is infected by rust. Other practices which encourage the rapid development of the crop such as the use of early maturing varieties and proper seedbed preparation are also helpful.
As in the case of stem rust the use of resistant varieties is the best control measure for this disease (1).
Unlike other types of smut, bunt is not easily recognized in the field and low levels of infection may not be noticed. Therefore the use of what appears to be smut free seed will not give adequate protection against this disease (3). It is also true that although bunt, like the other smuts, is usually seed-borne, spring-sown crops can become infected from soil-borne spores, especially if there are infected heads lying on the surface (4). As a result, even if the seed used was free of bunt, in some cases the crop may still become infected.
The only effective, non-chemical control of this disease is to use resistant varieties. There are a number of wheat varieties which show resistance to bunt (3), but only those showing good resistance should be used. Varieties showing fair, poor or no resistance, require chemical seed treatments every 1 to 3 years depending upon their degree of resistance in order to give adequate protection against this disease.
Loose smut of wheat is very similar to loose smut of barley and since this disease is more prevalent in barley than in wheat, measures to control this disease in both crops are described in the section on be. ley diseases.
Common Root Rot
Crop rotations including summer fallow and non-susceptible crops such as flax, rapeseed, and legumes can be used to help reduce damage from common root rot (1). Although infection may arise from contaminated seed, more often it comes from spores on the surface of the soil and in crop residues, therefore when the land is fallowed or non-susceptible crops are grown many of the spores die reducing the infection of subsequent susceptible crops. The spores of common root rot however can survive in the soil for more than one year, therefore in order for crop rotations to be effective in controlling this disease the land must be kept free of susceptible crops for several years in succession (5). One method of doing this might be to plant a non-susceptible crop such as rape or flax after the summer fallow in the rotation. Oats should not be used in this respect however, contrary to what has been recommended in the past (5). Ledingham has found that even though common root rot is not a very conspicuous disease of oats, the oat crop will support the organisms which cause the disease sufficiently so that the infection of subsequent crops is not reduced. Another rotation which might be used is one in which a perennial forage crop is left down for several years. The forage crop may be either a legume, grass or a combination of the two. Legumes are non-susceptible crops while perennial grasses, even though they are susceptible to common root-rot, have been found to prevent sporulation of the disease fungus reducing the infection of subsequent crops (12).
In the past it has been claimed that one year of fallow is enough to reduce damage from common mot rot (6). According to Ledingham and his co-workers, however, the reduction in damage following the fallow year noticed by the early researchers was more the result of the fact the moldboard plow was still used to work the fallow rather than to the absence of susceptible crops during the fallow year (7). Deep plowing is effective in reducing the damage from common mot rot because it buries the trash and surface soil where the spores of this disease are found. Deep plowing to a depth of 4 inches or greater in the spring before the crop is sown has been recommended as a control measure in itself (1). The detrimental effects of deep plowing on soil conservation however may outweigh any benefit it might have in regards to root rot control.
The incorporation of straw and crop residues with shallow tillage may be of some use in common root rot control. Ledingham in a recent study found that if shallow tillage is used to incorporate straw and stubble immediately prior to or during seeding there is a slight reduction in the severity of the disease (8). The incorporation of the crop residue normally produced on the land, on average, resulted in a reduction in the disease rating while the incorporation of 3 times as much residue as was produced on the land resulted in an average reduction of 16% in the disease rating. The reason for the beneficial effect of the incorporated straw on the severity of the disease is not known but it is possible that the microorganisms that are associated with the decomposition of the straw have a detrimental effect on the microorganisms which cause the root rot. The incorporation of the straw however)did not result in any significant yield increases. Ledingham attributed this lack of yield response to the smallness of the reduction in the disease rating caused by the straw.
Even though Ledingham did not obtain any significant yield increases by incorporating the straw, the conservation of the straw and stubble on the surface of the soil until seeding time will help prevent soil erosion and may be of at least some use in reducing losses due to root rot. If this practice is used it is important that the straw only be incorporated immediately before seeding, Ledingham found that a delay of even a week between the incorporation of the straw and seeding caused a substantial reduction in the usefulness of this practice.
It has been found that the time, rate and depth of seeding will affect the intensity of a root rot infection (9). It can be seen from Table 1 that the earlier a wheat crop is planted the lower its root rot rating will be and the higher its yield will be. Table 2 shows that the thinner the crop is planted the less root rot there will be. The thicker plantings however)tended to have higher yields. Deep seeding increases the root rot infection. Both early and shallow seeding therefore appear to be good methods to decrease damage due to root rot. According to Greaney, the researcher who conducted these studies, any agronomic practice which favors the rapid, vigorous growth of a crop will tend to reduce the intensity of the root rot infection.
Although soil borne spores are the main source of root rot infection, seeds can also carry the disease and give rise to blighted seedlings. (1) Since smudge or black-point in the seed indicates that the seed may be infected, it has been recommended that such seed be treated before it is used (1). If chemical seed treatments are not to be used however; it may be advisable that such seed not be used at all.
Resistant varieties can also be used to help control common root rot. Although there are no wheat varieties that are completely resistant to root rot, some varieties show more resistance than others (3).
Take-all Root Rot
Take-all root rot is a soil borne disease which is often found to be a problem when wheat is grown continuously. This disease can be controlled however by summer fallowing or growing non-susceptible crops for a year or two to reduce the infestation, after which any recommended rotation can be used. Although it is not known how many years it takes to starve out the microorganism which causes take-all from land which is not producing any of its hosts, it has been found that 1 or 2 years is sufficient to reduce the infestation to such an extent that it no longer causes appreciable injury to wheat unless wheat is again sown for several years in succession (10).
Non-susceptible crops which can be used to help reduce the take-all _ infestation include: oats, flax, rape, sunflowers and legumes. Barley and rye, although not as severely attacked by take-all as wheat, are susceptible to the disease. It is not considered safe to sow wheat after barley or rye if the land has recently been infested but the injury is not as severe as if following a diseased crop of wheat (10). Grasses, especially wheat grasses, are also attacked by take-all and wheat following grasses in the rotation is often severely damaged (11). When sod is being broken in districts where take-all is prevalent, it is advisable to use a rotation such as wheat, oats, wheat, fallow (10). After one cycle of this rotation any other good rotation can be used.
Weed control is especially important when trying to control take-all. This disease can live over on grassy weeds and on volunteer wheat. Padwir and Henry have found that in Alberta, wheat fields which are severely infected with take-all are usually also infested with couchgrass, a common weed (11). Therefore if a field is infested with both take-all and weeds it is best to use summer fallow in the rotation to control both the weeds and take-all rather than using non-susceptible crops (10).
The maintenance of good soil fertility has also been recommended -as a practice which will help control take-all root-m t (1).
Browning root rot occurs when the soil nutrients are unbalanced (13). This is the reason why this disease is usually only found on land summer fallowed the previous year. Decomposition of organic matter during the fa] low year releases nitrates changing the balance between the available phosphorus and nitrogen in the soil. This situation can be corrected by supplying extra phosphate with phosphatic fertilizers to correct the nutrient imbalance. Farm manure however applied before fallowing, has also been found to give adequate control (14). Manure, which is high in phosphorus, not only helps to correct the nutrient imbalance but it also increases the activities of the soil microorganisms which may have an inhibitive effect on the disease causing organisms. The practice of working the straw and crop residues into the soil will have an effect similar to that of manure but is less effective (14). Burning the stubble will add the phosphorus back to the soil more rapidly and will be of use in the respect but this practice will destroy the organic matter. Turning the stubble under has been found to give a longer lasting effect (14). The inclusion of a forage crop in the rotation is also useful as it will add organic matter to the soil (14). If a grass species is used as the forage crop however, wheat should not be sown immediately after the grass as browning root rot can use the grass as a host and the damage to the wheat crop will be increased (14). Flax can be grown after the forage crop.
A firm seed bed has also been found to decrease damage from browning root rot (14). The reason the decrease in the root rot is not known but it is possible that the compact soil inhibits the spread of the fungal mycelium through the soil.
Although this disease does attack wheat ergot is most prevalent in rye and control measures for this disease are described in the section on rye diseases.
This viral disease which is spread by a mite, cannot survive in ripe seeds, in mature or dead plants, or in the soil, a crop can only become infected if it is grown beside infected living plants (1). As a result this disease is most prevalent in areas where winter wheat is grown. Winter wheat becomes infested in the fall, carries the virus and mites over the winter and then next spring the mites, which are blown about by the wind, infect nearby spring wheat fields and volunteer wheat. The wheat infected in the spring then carries the disease over the summer and is a source of infection for winter wheat fields sown in the fall. Barley may also become infected if grown beside an infested wheat field but it does not suffer serious damage. As well~a number of cultivated and wild grasses may become infected with the virus but none are seriously injured and do not appear to be important in spreading the disease.
This disease can be controlled by ensuring that the land is free from all disease-carrying plants for a week or more before sowing wheat there or in adjacent fields (1). This means that winter wheat should not be sown beside spring wheat until the latter is completely ripe. SyIkbuis and his co-workers have found that in southern Alberta the best time to seed winter wheat next to infected fields is in the first part of Sept. (15). Seeding at an earlier date increases the likelihood that the winter wheat will become infected while if the seeding is delayed even more, the crop will mature late and the losses due to rust will be severe.
It is also important that spring wheat not be sown next to winter wheat that is diseased and all volunteer winter wheat should be destroyed before planting spring wheat on the same land (1). If winter wheat is so severely diseased with mosaic that it must be destroyed in the spring, it is not safe to sow spring in the same field until all of the diseased plants have been destroyed (1). It has been found that one operation with a moldboard plow will destroy the mosaic infection in immature wheat but if either a one-way disk or subsurface cultivation is used, one operation is insufficient (15). It is safer to reseed the land to some crop other than wheat (1).
Speckled Leaf Blotch
This is a fungal disease which is fairly common in eastern Saskatchewan but does not cause serious damage (1). The fungus overwinters of the dead leaves and stems of the wheat plants, therefore rotation with crops other than wheat such as flax and oats and deep plowing to bury the crop residues have been recommended as control measures (3). These practices will help reduce the disease incidence.
Ascochyta Leaf Spot
Wheat varieties differ in their resistance to this disease, the sown y resistant wheats in particular being susceptible (1). In areas where this disease is severe resistant varieties of wheat can be grown.
Splotch is a nutritional disorder which occurs when the soil is deficient in nitrogen (1). The application of nitrogen fertilizer has been recommended as a means of reducing the severity of the disease (1). Presumably, maintaining the fertility of the soil with manures and crop rotations including legumes would achieve similar results.
It has also been noted that durum wheats are more susceptible to this disease than the bread wheats are (1).
Rotation with crops other than wheat, such as flax and oats and the turning under of crop residues are measures that have been recommended as helping to reduce the disease incidence (3). As wheat grasses are also attacked by this disease these crops should not be used in the rotation (3).
The most effective control measure for ergot is to cut the grass along the borders of grain fields (1). Grasses are also infected by ergot and if they are allowed to head out they will produce ergot bodies which can spread the infection into the grain fields.
Crops should be rotated to avoid having diseased crops on the land two years in succession (18). Rye is the most susceptible crop, but durum and common wheat are also infected and barley is occasionally infected. Oats however are seldom infected while non-cereal crops are immune although they may sometimes bear sclerotia which resemble ergot bodies. Therefore rye, wheat and barley should only be sown after fallow, oats or non-cereal crops. Forage grasses can also be used in the rotation place of the fallow or resistant crops so long as the grasses are cut or grazed often enough to prevent them from heading out.
In fields which are infested with ergot the ground should be tilled so as to bury the ergot bodies to a depth of at least two inches (1). This will help prevent the infection of subsequent crops. It is also important not to drop combine screenings containing ergot bodies on the ground (1). The screenings containing the ergot should be destroyed.
Seed which contains ergot should be thoroughly cleaned before seeding to remove the ergot bodies which can infect the new crop (1). Seed which has been stored one year however can be used without cleaning (18). Storage for one year has been found to reduce the viability of the ergot to almost zero.
Although the bacteria which cause this disease can be carried by the seed, the bacteria can also overwinter on the crop remains and this is the usual source of infection (1). Therefore crop rotations in which rye does not follow rye or wheat will help to reduce the major source of infection. Wheat is not a good preceding crop as it is also infected by the bacterium which causes this disease. If possible only seed from uninfected fields should be sown to eliminate the seed-borne infection.
This disease can also be spread from infected grass next to a field. Therefore when planting fall rye the grass should be burned at the time of sowing to destroy the bacterium (1).
Leaf and Stem Rust
There are no varieties of rye resistant to either leaf or stem rust but since rust infections do not usually develop until early summer, fall rye escapes much of the damage because of its early maturity (1). Early seeding will help control the diseases in spring rye (1).
There are several fall rye varieties which show good resistance to this disease and can be used as a control measure (3). As this smut produces spores which can overwinter in the soil it is also helpful to use crop rotation to prevent the build-up of spores in the soil (3). It has been found that the spores can survive in the soil for more than one year therefore several years should elapse between successive rye crops in the rotation (3).
Stem rust of oats can be controlled by using resistant varieties (1).
Crown rust, like other rust diseases can be controlled by using resistant varieties (1). Early seeding is also a useful practice however (1). This disease does not develop until the summer months, therefore by seeding early the crop can complete much of its development before becoming infected.
Buckthorn is the usual alternate host for the crown rest fungus. Buckthorn like the barebarry, the alternate host for stem rust of wheat, is not a native plant but was introduced from Europe. Eradication of the buckthorn would not only eliminate a source of infection of this disease, (actually the main source of infection of this disease in the Prairie Provinces are spores blown northward each spring from the southern United States where the disease can overwinter on crops) but it would also prevent the different races of crown rust from interbreeding to produce new races which may be able to infect previously resistant varieties of oats. It is therefore recommended that the buckthorn be destroyed wherever it is found (3).
Covered Smut and Loose Smut
These two diseases of oats are very similar and the control recommendations for them are the same (1). Although there are several varieties of oats which show resistance to these diseases, none of the varieties has complete resistance (3). Therefore whether using seed of resistant or susceptible varieties only seed from crops free of smut should be used as these diseases, like most smuts are seed-borne (3).
Both halo blight and stripe blight are bacterial diseases of oats. Both diseases are seed-borne but they can also overwinter on crop residues. The most effective control measure is to use resistant varieties (1).
Grey speck is a nutritional disorder which results when there is a shortage of manganese in the soil. Other crops are more tolerant of manganese deficiency and these can be substituted for oats in the rotation (1).
Common Root Rot
Common root rot of oats is similar to common root rot of wheat and the control measures recommended for control of this disease in wheat can be applied to oats (1).
Speckled Leaf Blotch
This is a fungal disease which can overwinter on both the seed and the crop residues. If this disease is a problem a variety which shows some resistance can be used (1).
This disease is caused by the same virus which causes barley yellow dwarf (1). The control measures recommended for the control of this disease in barley can be applied to oats.
Blast is a nutritional disorder which occurs when growing conditions change suddenly for the worse (1). Early sowing of oats results in the formation of large panicles so that even if there is a large amount of blast yields will still be favorable (1).
Both wheat stem rust and rye stem rust attack barley plants but the former rust variety is by far the most common one found attacking barley in the Prairie Provinces (1). As with stem rust in wheat, resistant varieties are the best control measure for this disease in barley, but the other control measures for stem rust described in the section on diseases of wheat may also be useful (1).
Covered and False Loose Smut
The control measures for both of these diseases are the same; the use of resistant varieties (3). There are several varieties of barley which show varying degrees of resistance to both of these diseases. If a variety showing good resistance is not used, then only seed from a crop free of smut should be sown as these diseases are seed-borne. Varieties with only fair or poor resistance can still be infected by smut.
Loose smut like most smut diseases is seed-borne and can be controlled by using seed from crops free from smut (3). There are varieties of barley which show some resistance to loose smut but none of these varieties have good resistance and may still become infected with this disease (3). Therefore even when using resistant varieties care should be taken to ensure that only seed from crops free of smut be used.
It is also possible to control loose smut by treating the seed from crops infected with smut before sowing (16). There are two types of non-chemical treatments which can be used to destroy the loose smut in the seed; the water-soak treatment and the hot-water treatment. The water-soak treatment consists of soaking the seed in water that is maintained at a temperature of 70-75 degrees F for 65 hours. It is important that the seed is completely covered by the water. The temperature of the water can be brought up to the required temperature by adding warm water. If the hot-water treatment is used the seed must first be soaked in water at 70 degrees F for 5 hours. The seed is then placed in water maintained at 126 degrees F for 11 minutes followed by a dip in cool water. In both treatments it is important that the seed be dried as quickly as possible to prevent the seed from sprouting or spoiling after the treatment is finished. If the seed is spread out thinly on a warm, windy day the seed will dry satisfactorily.
In order to minimize the amount of seed to be treated by either of the above methods, only enough seed should be treated to seed a small plot. The seed from this plot can then be used next year for the main planting. The seed plot should be isolated from other fields of wheat Ana barley to prevent re-infection.
Although both the water-soak and hot-water treatments are effective if the directions are followed carefully, these treatments are time consuming and will damage the seed reducing the percentage germination. The amount of damage to the seed varies with the quality of the aced; sound healthy seed suffers less damage. In view of the disadvantages of these treatments however it is probably preferable to use smut-free seed of a variety showing some resistance rather than trying to treat infected seed.
Common Root Rot
There are no varieties of barley completely resistant to common root rot but some barley varieties show more resistance than others. Other measures used to control common root rot in barley are the same as those used to control this disease in wheat and will be found in the section on diseases of wheat.
The organism which causes spot blotch is the same organism which causes common root rot (1). Measures to control this disease in barley will be found under "Common Root Rot" in the section on diseases of wheat.
The organism which causes this disease can overwinter on both the seed and the remains of an infected crop (17). Therefore turning under the crop residues and crop rotations in which barley does not follow barley will help reduce one source of infection. It is also recommended that seed disinfectants be used to prevent the disease from being introduced to uninfected fields and to reduce the damage to the seedlings (3) If chemical seed treatments are not to be used however it may be beneficial to avoid using seed from infected fields.
There are no varieties of barley which are resistant to this disease but in general the six-rowed barleys show less damage from this disease than do the two-rowed varieties (3).
Speckled Leaf Blotch
The fungus which causes this disease overwinters in crop remains in the soil (1). Crop rotations which include other crops besides barley and deep plowing to bury the crop residues will help to reduce the infection (3).
At the present time there is one barley variety, Galt, which appears to be resistant to this disease (3). Its performance has not been completely evaluated as yet however.
The fungus which causes this disease overwinters on crop debris (1). Therefore a rotation in which barley does not follow barley and turning under the crop remains will be useful reducing the infection (3). It has been noted that bromegrass may be susceptible to this disease and it is recommended that bromegrass not be used in the rotation (3).
This disease is usually transmitted by the seed but a crop can also become infected from last year's crop residues (1). Seed from uninfected fields and crop rotations where barley doesn't follow barley will help to control this disease (1).
This viral disease is carried by infected seeds. Only seed from uninfected fields should be sown (1). The virus is rare or absent in pedigreed seed and this seed can be used safely (3).
This is a viral disease which is transmitted by grass-and-grain infesting aphids (1). By sowing the crop early it is possible to avoid some of the damage (1). The aphids which transmit the disease don't usually become numerous until midsummer or later. If the crop is sown early it will have passed its most susceptible stage by the time it becomes infected.
There are no barley varieties resistant to this disease but some are more susceptible than others (3).
Aster yellows is another viral disease. This disease is carried by leaf hoppers which migrate into the Canadian prairies each spring from the United States, By sowing the crops early it is possible to avoid some of the damage (1).
This is a seed-borne disease. It can be controlled by using resistant varieties (3).
1. Diseases of Field Crops in the Prairie Provinces. Agriculture Canada, Publ. 1008, Revised 1967.
2. Craigie, J.H., 1940, Studies In Cereal Diseases XII Stem Rust of Cereals. Agriculture Canada, Publ. 6 .
3. Cereal Subcommittee Report of the Western Committee on Plant Disease Control. Revised 1977.
4. Eanna, W.F. and W. opp, 1934. Bunt Infection of Spring Wheat By Soil-borne Spores. Sci. dgr. 14 ~
5. Ledingham, R.J., 1961. Crop Rotations And Common Root Rot in Wheat. Can. J. Plant Sci. 41:479-486.
6. Broadfoot, W.C., 1934. Studies On Foot And Root Rot of Wheat. Can J. of Res. 10:115-124.
7. Ledingham, R.J., B.J. Sallans, and A. Wenhart, 1960. Influence of Cultural Practices On The Incidence of Common Root Rot of Wheat In Saskatchewan. Can. J. Plant Sci. 40:310-316.
8. Ledingham, R.J., 1970. Effects of Straw and Nitrogen On Common Root Rot of Wheat. Can. J. Plant Sci. 50:175-179.
9. Greaney, F.J., 1946. Influence of Time, Rate and Depth of Seeding On the Incidence of Root Rot in Wheat. Phytopathology 36:252-263.
10. Russell, R.C., 1930. Field Studies of Take-all In Saskatchewan. Sci. Agr. 10: 654-668.
11. Padwick, G.W. and A.W. Henry, 1933. The Relation of Species of Agropyron and Certain Other Grasses to the Foot-rot Problem of Weat in Alberta. Can. J. Res. 8:349-36
12. Ledingham, R.J. and S.H.F. Chinn, 1964. Effect of Grasses On Helminthosporium Saturum in Soil. Can. J. Plant Sci. 44:47-52.
13. Vanterpool, T.C., 1935. Studies on Browning Root Rot of Cereals. III. Phosphorus-nitrogen relations of Infested Fields. IV. Effects of Fertilizer Amendments. V. Preliminary Plant Analysis.
14. Vanterpool, T.C., 1940. Present Knowledge of Browning Root Rot of Wheat With Special Reference to Its Control. Sci. Agr. 20:735-749.
15. Sylkbuis, J.T., J.E. Andreld3, and IJ.J. Pittman, 1957. Relation of Date of Seeding Winter Wheat in Southern Alberta to Losses From Wheat Streak Mosaic, Root Rot, and Rust. Can. J. Plant Sci. 37:113-127.
16. Diseases of Field Crops in the Prairie Provinces. Agriculture Canada, Publ. 1008, published 1957.
17. Piening, L., 1968. Development of Barley Net Blotch From Infested Straw and Seed. Can. J. Plant Sci. 48:623-625. 18. Champlin, M., 1925. Ergot Control. University of Saskatchewan Field Husbandry Dept., Circular No. 513.
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