Infested bean straw and cull beans contaminated with sclerotia should not be fed to animals if the manure is to be used on land where beans may soon be planted.

When possible, infested bean fields should be planted for 2 years or more to crops including small grains, corn, and hay that are not susceptible to sclerotinia wilt. That practice is not likely to eliminate the trouble entirely, but it will reduce losses.

COMMON BEAN MOSAIC has been known for more than 50 years and is world-wide. Since 1930 several other mosaics of bean have been reported.

Because the different mosaics generally produce similar field symptoms, they are discussed here more or less as one disease. Many growers underestimate the importance of bean mosaics because infected plants are rarely killed. The mosaics reduce yield and quality of the product. The annual losses from these diseases total several million dollars in the United States.

The important mosaic diseases of bean are common bean mosaic, a variant of that disease called New York 15 mosaic, and yellow bean mosaic. Two other bean mosaics, southern bean mosaic and pod mottle, have been found, and may become of economic importance if they become widespread. Several strains of yellow bean mosaic have been identified. In some years they have caused considerable damage.

Common bean mosaic is the most widespread of the bean mosaics. The New York 15 mosaic virus, which produces much the same symptoms, is less serious. Yellow bean mosaic, which is primarily a disease of sweet-clover and is found also on crimson clover, red clover, and gladiolus, has entirely different symptoms. Plant lice spread it from those crops to beans.

The bean mosaics cause mottling and malformation of leaves and stunting of the plants. The symptoms are more intense at high temperatures. Symptoms are not noticed on stems or seeds. The patterns made by the mottled yellow and green areas may vary. Dark-green areas frequently develop near the veins and veinlets of infected leaves. Leaves of very susceptible varieties may be considerably puckered and may develop areas that look like blisters And warts. On less susceptible varieties, the leaves are ruffled, crinkled, or cupped downward.

With yellow bean mosaic, the contrast between the yellow and green areas of the leaves usually is more intense than it is with common mosaic. On solve resistant varieties the common mosaic virus may produce occasionally a necrosis of the leaves, pods, stems, and roots. This symptom has been observed only rarely in the field.

Pods from infected plants are sometimes mottled, deformed, and rough. Some may be very shiny. Yellow mosaic (especially the pod-distorting strain), southern bean mosaic, and pod mottle viruses produce the worst symptoms on pods.

Each of the bean mosaics is caused by a different virus. Plant lice usually spread the viruses from diseased to healthy plants.

The viruses of the important mosaic diseases are not spread from infected to healthy plants by cultivation or picking, but the viruses of southern bean mosaic and pod mottle can be spread thus.

The virus of common bean mosaic and its variant are seed-borne. The infected seeds look normal, but they carry the virus and produce diseased plants. None of the viruses causing the other mosaic diseases is carried in the seed.

The only satisfactory way to prevent mosaic is to use resistant varieties. None resists all viruses. Some of the bush snap beans that resist common bean mosaic and its variant are Contender, Florida Belle, Logan, Improved New Stringless, Idagreen, Puregold, Rival, Idaho Refugee, Sensation Refugee 1066, Sensation Refugee 1071, U. S. 5 Refugee, Tender-long 15, Ranger, Toperop, and Wade. The resistant pole varieties include Blue Lake, Kentucky Wonder, and U. S. No. 4 Kentucky Wonder.

Dry beans resistant to common bean mosaic are Michelite, Robust, Great Northern U. I. Nos. 16, 31, 81, and 123, Montana Nos. 1 and 5, Red Mexican U. I. Nos. 3 and 34, Pinto U. I. Nos. 72, 78, and 111. Only the Great Northern strains are resistant to the New York 15 variant strain.

No variety has yet been developed that resists yellow bean mosaic.

In sections where yellow bean mosaic is widespread it is a good practice to avoid planting beans too close to fields of sweetclover, red clover crimson clover, and gladiolus. Fence rows and ditch banks should be kept free of sweetclover, which commonly grows "wild" in many Western States.

CURLY TOP is a virus disease of beans and several other crops. It commonly is found in Utah, Idaho, Washington, Oregon, and California, and sometimes in other Western States. In some localities it is not serious every year, although when there are many beet leafhoppers, which transmit the virus, the bean crop may be ruined. In some parts of Idaho, Washington, and Oregon, the disease has been so serious every year that only resistant varieties survive.

Young plants infected with curly top are decidedly dwarfed. The symptoms are most pronounced on the trifoliate leaves which pucker, curl downward, and show a clearing of the veins. The young leaves cease to develop, turn yellow, and curl downward. They are thick and brittle and readily break off from the stem. Frequently they are cupped; sometimes they resemble small green balls. Plants infected when very young usually die; plants that are infected later do not die, and typical symptoms do not always develop. The pods produced on infected plants are usually stunted. The disease is not seed-borne.

Curly top is spread from plant to plant only by the beet leafhopper, usually called whitefly in the West. Before being able to infect beans, it must feed on some plant that is infected with curly top. It overwinters in desert areas where many weeds carry the curly top virus. In the spring the leafhoppers migrate to cultivated fields of beans, beets, tomatoes, and other crops and spread the disease. The symptoms appear about 10 to 14 days after infection. Within a few weeks after that an infected plant may die.

Because curly top is transmitted only by leafhoppers, the disease is prevalent only where that insect thrives. The severity of the disease reflects the population of the leafhoppers and the percentage carrying the virus.

Curly top can be best controlled by growing resistant varieties. Unfortunately, no commercially suitable resistant variety of snap bean has been developed, but progress is being made in obtaining such beans, notably in developing several resistant Blue Lake types.

Resistant varieties of dry beans are Great Northern U. 1. Nos. 16 and 31, Red Mexican U. I. Nos. 3 and 34, and Pinto U. 1. Nos. 72, 78, and III, Pink, and Pioneer. Pioneer can also be used as a snap bean in home gardens in regions where curly top is prevalent, although as such it is only fair.

DOWNY MILDEW was first reported in the United States about 60 years ago. In later years it has caused considerable damage to lima beans in some of the Middle Atlantic and North Atlantic States. It is of minor importance elsewhere. The fungus that causes it develops best during periods of wet weather with cool nights, heavy dews, and fairly warm days.

The disease is recognized by the white, cottony growth that forms in large, irregular patches on the pods. Each patch may have a purplish border. When young pods are attacked and when older ones are covered with fungus growth they shrivel, wilt, and die. Downy mildew less frequently attacks young leaves, shoots, and flower parts. Infected leaves may show irregular spots, particularly near the veins, without much visible fungus growth.

Downy mildew is caused by a fungus, Phytophthora phaseoli, which attacks only lima beans. The organism may penetrate the seeds and live in them over winter. It can also survive in debris which may be a source of infection of the new crop. During the growing season, the fungus may be spread to healthy plants by insects that visit infected flowers. Rapid natural spread depends on ideal weather conditions favoring the fungus.

Seed from an infected crop should not be used for planting. Seed produced in the far West where downy mildew is not found should be used. A 2- or 3-year crop rotation is wise. When the disease is first noted the crop should be dusted with a copper dust containing 5 to 7 percent actual copper, such as tribasic copper, at the rate of about 40 pounds of dust to the acre for each application. Dustings should be made at weekly intervals as long as the weather favors the development of the disease.

No commercial variety of lima beans is resistant. Several resistant noncommercial types have been found. A breeding program has been started to incorporate that resistance into suitable varieties.

W. J. ZAUMEYER, a graduate of the University of Wisconsin, is principal pathologist in charge of bean and pea disease investigations in the division of vegetable crops and diseases of the Bureau of Plant Industry, Soils, and Agricultural Engineering. Since he joined the Department in 1928, his work has dealt particularly with the diseases of beans and peas. At present much of his time is spent in developing bean varieties that are disease-resistant and in determining other ways of controlling bean diseases.

H. REX THOMAS, a graduate of the University of California, is a plant pathologist in the division of vegetable crops and diseases of the Bureau of Plant Industry, Soils, and Agricultural Engineering. He joined the Department in 1937 and specializes in the diseases of beans and peas.