NON-CEREALS

Dry Edible Beans

Stem and Leaf Diseases � Fungal

RUST, Uromyces appendiculatus var. appendiculatus

Symptoms. Rusty-colored pustules erupt through the surface of the leaf. Rusty-colored summer spores can be brushed off the surface of the pustules. Pustules may also form on the pods. When rust is severe, leaves turn yellow, dry out, and drop prematurely. Late in the season the summer spores are replaced with dark-colored winter spores.
Survival and Spread. Survives on infected crop residue. Favored by cool (60-75°F) moist weather with long periods of dew or rain. It is most serious in late-planted beans or on beans delayed in maturity by weather damage (hail), high nitrogen fertility, etc.
Control. Bury infected bean residue by deep plowing. Avoid planting next to fields that had severe rust last year. Use a three- or four-year crop rotation. Monitor fields for rust. Use maneb or chlorothalonil fungicide when rust first appears. Early detection of rust and early application of fungicide is essential to rust management.
Remarks. Some varieties have shown resistance to the common races of rust, but races have changed recently (1996). Many rust races are present in North Dakota, and the dominant races may change from time to time, adversely affecting the resistance of certain varieties. Continued monitoring for rust is essential.

WHITE MOLD (SCLEROTINIA ROT), Sclerotinia sclerotiorum

Symptoms. A watery soft rot develops on pods, stems and foliage. First symptoms usually appear after flowering. The rotting areas develop a cottony white growth in wet weather or a bleached and shredded appearance in dry weather. Hard black fungus bodies, sclerotia, form on the surface of diseased tissues and inside diseased stems. Foliage of infected plants wilts, turns yellow and drops prematurely. Late season infections produce chalky-colored, lightweight bean seeds.
Survival and Spread. Sclerotia survive many years in the soil. Sclerotia near the soil surface germinate in wet weather to form tiny (1/8-3/16 inch) trumpet-shaped mushroom bodies called apothecia. The apothecia produce millions of airborne spores that usually infect dry bean plants through the dead blossoms but occasionally may infect through dead leaf tissue or wounds. Infection may occur over a wide range of temperatures (40-85°F), but moist weather and moderate temperatures (68-77°F) are most favorable for disease development. Fields may be infested through airborne spores infecting susceptible crops or weeds or through sclerotia mixed with seed.
Other Crops Affected. Sunflower, mustard, and canola (rapeseed) are very susceptible. Other susceptible crops include field peas, garbanzo beans (chickpeas), lentils, safflower and soybeans. Potatoes are infected occasionally. Flax and buckwheat are only rarely infected. Many broad-leaved weeds are also susceptible.
Control. Plow down infected crop refuse in the spring. Benomyl or thiophanate methyl fungicide may be used at early to 100% bloom. To be effective, plant coverage is important. The fungicide should be applied with adequate water and pressure (at least 40 psi); use drop nozzles to get spray on blossoms. Use crop rotation; avoid planting dry beans, mustard, canola (rapeseed), or sunflower more than once in four years. Avoid planting next to a field that had severe white mold in the past four or five years. Use upright varieties and wide (30 inch) row spacing. Control broad-leaved weeds.

ALTERNARIA BLIGHT, Alternaria sp.

Symptoms. Irregular brown lesions develop on the leaves. The spots often have light tan to whitish centers and dark purplish to black margins. After moist periods, the undersides of lesions are covered with a black fuzzy growth (the spores). The lesions tend to tear, giving severely affected leaves a tattered appearance.
Survival and Spread. Little is known, but the disease appears to be most severe after hailstorms or other wounding. Observations suggest that Alternaria may also infect the plant through bacterial brown spot lesions.
Control. Unknown.

Stem and Leaf Diseases � Bacterial

COMMON BLIGHT, Xanthomonas campestris pv. phaseoli

Symptoms. Large irregular patches of necrotic, brown tissue form, frequently at the edges of the leaves. Common blight lesions on young foliage often have a narrow lemon yellow border surrounding the dead tissue. Heavily infected plants appear scorched. Dark greasy-green water soaked spots form on the pods. In wet weather a yellow bacterial ooze forms on the spots; later this ooze dries to form a yellow flaky surface which glistens in the sunlight. As the pod lesions age, they become sunken and develop a brick red border. White bean seeds infected with common blight turn a butter-yellow color. Stem lesions are dark red; lesions may girdle the stems and cause the plant to break.
Survival and Spread. The common blight bacteria are seed-borne and survive in infected bean crop residue. Severely infected seeds are shriveled and often do not germinate. Lightly-infected seeds germinate to produce stunted, internally infected plants that can lead to rapid disease spread in wet weather. Spread occurs in splashing water and wind-blown aerosols. Spread is favored by warm, wet weather, driving rains, and windblown sand or hail followed by rain. Blight may also be spread by field cultivation when the plants are wet.
Control. Purchase certified seed. Certified seed is not blight-free but must meet certain standards. If possible, purchase seed that has been tested for blight using the dome test: a dome score of 4 is usually satisfactory (has a moderate blight risk); a 3 is preferable (lower risk), if available; a 5 has a moderately high risk and should be avoided, if possible. Seed with a test of 6 or 7 should not be used under any circumstance. Use a three- or four-year crop rotation. Treat seed with streptomycin to eliminate surface bacteria.

HALO BLIGHT, Pseudomonas syringae pv. phaseolicola

Symptoms. Small (1/16-1/8 inch) chocolate-brown spots form on leaves. In warm weather, these spots resemble bacterial brown spot. In cool weather, when temperatures are less than 70°F, the halo blight bacteria produce a toxin that causes a light green halo to form around each spot. These halos vary from 3/8 to 3/4 inch in diameter. Sometimes the toxin is transported to the upper parts of the plant, which turn greenish-yellow. Symptoms on stems and pods resemble those of common blight, except that any bacterial exudate which forms on the pods is cream-colored.
Survival and Spread. See common blight. Favored by cool rainy weather.
Control. See common blight. Copper fungicides will suppress spread of halo blight, but are of little value against common blight. Pinto and navy beans have some resistance to halo blight.

BROWN SPOT, Pseudomonas syringae pv. syringae

Symptoms. Small (1/16-1/8 inch) chocolate-brown spots form on leaves. The lesions are often surrounded by a narrow greenish yellow band and resemble warm-weather halo blight symptoms when no large halos form. Symptoms on stems and pods resemble those of common blight, except that any bacterial exudate which forms on the pods is cream-colored.
Survival and Spread. See common blight. Brown spot is more serious in protected areas where plants dry slowly.
Control. See common blight.

Stem and Leaf Diseases � Non-Infectious

ZINC DEFICIENCY

Symptoms. Older leaves turn yellow, especially between the veins, and dead areas may develop between the veins beginning at the margins and proceeding inward. New leaves may be small and mottled. Plants may be stunted. Zinc deficiency may occur on alkaline soils, especially on certain varieties of navy beans. High phosphate levels favor zinc deficiency.
Control. Apply 0.4 to 0.8 lbs actual zinc per acre in a chelated form, or 3 to 6 lbs in inorganic form, where soil tests are low in zinc. If zinc deficiency symptoms develop after emergence, the problem can be corrected by application of 0.2 lbs. actual zinc per acre as a foliar spray. Prompt detection and treatment are essential for satisfactory results.

BRONZING

Symptoms. Upper leaf surfaces are covered with small golden-brown spots which make the leaf appear bronze in color. Bronzing is caused by ozone from industrial or urban pollution or meteorological phenomena.
Control. None available.

Pod and Seed Diseases � Bacterial

COMMON BLIGHT, Xanthomonas campestris pv. phaseoli

See description under Dry Edible Beans -- Stem and Leaf Diseases.

HALO BLIGHT, Pseudomonas syringae pv. phaseolicola

See description under Dry Edible Beans -- Stem and Leaf Diseases.

BROWN SPOT, Pseudomonas syringae pv. syringae

See description under Dry Edible Beans -- Stem and Leaf Disease.

Root Diseases � Fungal

ROOT ROT, Fusarium spp., Rhizoctonia solani, and other fungi

Symptoms. Severely infected plants are stunted, wilted, and have yellow leaves. Seedlings may damp off. Rhizoctonia usually makes reddish-colored lesions on the roots. Heavily infected roots (hypocotyls) appear dry and rough and a chocolate-colored rot may progress up the pith. Fusarium causes elongated lesions without definite margins. Often the roots (hypocotyls) turn entirely brown in color. Fusarium seldom extends beyond the soil line.
Survival and Spread. Soil-borne. More common in soils that have been planted to dry edible beans for many years. Conditions such as drought or saline soils that prevent lateral root development intensify the symptom expression.
Control. Use long rotations. Hilling moist soil around the base of the plant can stimulate lateral root development. Avoid soil compaction. Plant tolerant varieties in fields with a history of root rot. Avoid short rotations of sugarbeets and dry beans, especially in fields with a history of Rhizoctonia root rot in dry beans or Rhizoctonia disease in sugarbeets.

Soybeans

Stem and Leaf Diseases � Fungal

SCLEROTINIA STEM ROT (WHITE MOLD), Sclerotinia sclerotiorum

Symptoms. Often occurs as patches of plants that appear dead or slightly shorter due to lodging. Base of stem on affected plants may be rotted or the upper stem can be infected. Tufts of white mold are common on stems and later turn into hard black fungus bodies (sclerotia). Sclerotia form inside and outside the stem. Leaves wilt or else are covered with white mold. This is an increasingly common disease.
Survival and Spread. Sclerotia survive many years in soil and also can be spread with seed. In wet weather, over-wintered sclerotia produce wind-borne spores that infect dead blossoms.
Other Crops Affected. Dry edible beans, field peas, garbanzo beans (chickpeas), lentils, mustard, potatoes, rapeseed (Canola), safflower, and sunflower. Flax and buckwheat are only rarely attacked. Cabbage, cucumbers, melons and tomatoes also are susceptible.
Control. Crop rotation -- avoid highly susceptible crops in the rotation. Some cultivars are less susceptible than others. Use clean seed free of sclerotia. Solid seeding favors disease. Reduce overhead irrigation during flowering.

STEM CANKER, Diaporthe phaseolorum var. caulivora

Symptoms. Seldom found in North Dakota. Brown canker forms above the soil line. Plants may be girdled before leaves mature. Leaves dry up and remain attached. Symptoms appear late in season as the crop approaches maturity.
Survival and Spread. Seed-borne. Survives in soybean crop residue, producing wind-borne spores that infect new crop.
Control. Use disease-free seed and crop rotation. Plow residue after harvest.

POD AND STEM BLIGHT, Diaporthe phaseolorum var. sojae

Symptoms. Rows of dark fruiting bodies occur on stems and are scattered on pods. Develops late in season on senescent or dead tissue. Infected seed is cracked, often with a white fungal growth.
Survival and Spread. Seed-borne. Survives on soybean crop refuse. Spores can infect through wounds. Favored by warm wet weather in late summer.
Control. Use fungicidal seed treatment, disease-free seed and crop rotation. Bury infected soybean stubble by tillage.

BROWN STEM ROT, Phialophora gregata ( = Cephalosporium gregatum)

Symptoms. A rare disease in North Dakota. Red-brown discoloration develops in the stem pith, at first near the soil line and at the nodes. Infected plants turn brown just before maturing (normally maturing plants turn yellow-green). Infected plants may lodge. On leaves, brown areas occasionally develop between the veins.
Survival and Spread. Survives in soil and soybean crop refuse. Occasionally seed-borne. Fungus invades through roots. Favored by cool weather.
Control. Crop rotation: avoid alfalfa, red clover or soybeans for three years.

BROWN SPOT, Septoria glycines

Symptoms. Angular reddish-brown spots develop, starting on lower leaves; affected leaves turn yellow and drop off. A common disease in North Dakota but losses are seldom significant.
Survival and Spread. Overwinters in soybean crop residue. Seed-borne. Spread by wind and splashing rain. Develops during warm wet weather.
Control. Plant disease-free seed. Use crop rotation. Use tillage to bury crop refuse.

DOWNY MILDEW, Peronospora manshurica

Symptoms. This disease is fairly common in North Dakota when summers are humid but is rarely serious. First symptoms are indefinite yellowish-green areas on the upper leaf surface. Later, the spots turn gray-brown with yellow-green margins; a downy gray growth forms on the under surface of lesions. A whitish crust develops on seed.
Survival and Spread. Seed-borne. Overwinters in soybean crop refuse. Spread by wind-borne spores. Favored by cool, humid weather. Early infection from seed produces systemic invasion.
Control. Plant disease-free seed. Use fungicidal seed treatment. Use crop rotation -- one or more years out of soybeans. Use tillage to bury crop refuse. Varieties differ
in resistance.

Stem and Leaf Diseases � Bacterial

BACTERIAL BLIGHT, Pseudomonas syringae pv. glycinea

Symptoms. The most common leaf disease in North Dakota, but of minor importance. Leaves develop small, angular water-soaked spots that become brown with a yellow border. Portions of the leaf tissue drop out. Black lesions develop on the stem. Small water-soaked spots develop on pods; the spots enlarge and become black; seeds are shriveled.
Survival and Spread. Seed-borne. Overwinters in crop residue. Spread by driving, splashing rain. Favored by cool temperatures and windy rain storms. Attacks only soybean.
Control. Plant high quality seed. Use crop rotation. Use tillage to bury crop refuse when feasible. Do not cultivate plants when wet.

Stem and Leaf Diseases � Virus

SOYBEAN MOSAIC, Soybean Mosaic virus

Symptoms. Not common in North Dakota. Leaves are mottled green and yellow; small veins turn yellow. Leaves become crinkled in cool weather. Entire plant becomes stunted and yellow. Seed hilums may "bleed" and entire seeds may be mottled brown or black. Some leaf symptoms may be mistaken for 2,4-D injury.
Survival and Spread. Seed-borne. May overwinter in perennial weeds. Transmitted by aphids and by mechanical contact.
Other Crops Affected. Some other legumes, weeds.
Control. Plant disease-free seed. Control weeds and aphids. Rogue out infected plants from seed fields.

Stem and Leaf Diseases � Non-Infectious

IRON CHLOROSIS, Iron deficiency

Symptoms. This extremely common problem is most prevalent in early to midseason. Plants are stunted with yellow leaves and green veins. A few scattered plants may be affected or large circular patches may develop. Appears on highly alkaline soils; it is more common when cool, wet weather follows seedling emergence.
Control. Plants generally recover naturally. Sprays with an iron chelate can overcome the deficiency. Varieties differ in sensitivity to iron chlorosis. Check current variety recommendations for variety sensitivity.

Pod and Seed Diseases � Fungal

POD AND STEM BLIGHT, Diaporthe phaseolorum var. sojae

See description under Soybeans -- Stem and Leaf Disease.

PURPLE STAIN, Cercospora kikuchii

Symptoms. A rare disease in North Dakota. Seed is discolored pink to purple, in small spots or on the entire seed. Infected leaves have angular, crusty, dark spots.
Survival and Spread. Survives in crop refuse and in seed. Spores are wind blown and splashed from infected seedlings. Favored by warm, humid weather.
Control. Crop rotation. Plant high quality seed. Fungicidal seed treatment helps prevent seedling loss.

Pod and Seed Diseases � Virus

SOYBEAN MOSAIC, Soybean Mosaic Virus

See description under Soybeans -- Stem and Leaf Diseases.

Root Diseases � Fungal

FUSARIUM ROOT ROT, Fusarium spp.

Symptoms. A common disease. Seedlings are stunted or damp off; adult plants show root rot. Dark brown to black lesions form on root and lower stem; plants may wilt in dry weather.
Survival and Spread. Soil-borne.
Control. Plant in warm, well drained soil. Do not cultivate affected seedlings until adequate moisture is available. Ridge soil up around base of plant to promote feeder roots from stem base.
Reduce soil compaction to promote root growth.

PHYTOPHTHORA ROOT ROT, Phytophthora sojae

Symptoms. Leaves turn yellow and wilt. Few lateral roots form and a dark discoloration extends several inches up the stem from the root. Disease develops most rapidly on water-logged soils in warm weather. Symptoms appear in seedlings and adult plants.
Survival and Spread. Soil-borne, mostly associated with heavy soils and low spots in the field. Attacks throughout the season. Survives many years in soil.
Control. Resistant varieties. Determine the Phytophthora race present before selecting a resistant variety. Use seed treatment with metalaxyl when planting resistant varieties in high risk situations; metalaxy protects the seedling until mature-plant resistance is expressed. Plant in warm well-drained soil.

PYTHIUM ROOT ROT, Pythium spp.

Symptoms. Seedling decays before or after emergence (called "damping off"). Seed may decay in soil. Roots develop a brown wet rot, causing the plant to wilt. This is a common disease problem.
Survival and Spread. Soil-borne. Usually occurs in low areas of the field. Favored by cold, wet soil.
Other Crops Affected. Many.
Control. Fungicidal seed treatments, especially those with metalaxyl, aid against seed decay and damping off. Use high quality seed and plant in warm, well drained soil.

RHIZOCTONIA ROOT ROT, Rhizoctonia solani

Symptoms. A common and sometimes severe fungus disease, especially on seedlings. Causes a reddish-brown decay of the root and stem tissues. Plants are often attacked early and can be girdled or killed. Usually occurs on a few scattered plants or groups of plants.
Survival and Spread. Soil-borne. Pathogen attacks a large number of broadleaved plants including soybeans, dry beans, flax, lentils, sugarbeet, and canola.
Control. Ridge soil up around base of plant to promote feeder roots from stem base. Fungicidal seed treatments reduce seedling losses.

Root Diseases � Nematodal

SOYBEAN CYST NEMATODE, Heterodera glycines

Symptoms. Not observed in North Dakota as of 1996, but spreading in Minnesota and could develop in North Dakota within a few years. A potentially serious disease, plants are stunted and may have small pin-head sized cysts on roots. The cysts are white, later turning brown. Stunted plants develop in elliptic or lens-shaped areas in the field with the long axis parallel to the direction of major tillage.
Survival and Spread. Soil-borne. Nematodes build up in soil when susceptible crops are grown. Survives as cysts which live four to seven years in soil. Seed-borne as small bits of soil mixed with seed. Can also be carried in soil on farm machinery.
Other Crops Affected. Dry edible beans.
Control. Do not plant seed imported from infested regions. Do not import used farm machinery from infested regions or regions near those infested, or else thoroughly wash all soil from machinery. Where nematode is established, crop rotation involving at least two or three years between host crops will help avoid serious buildup of the nematode. Resistance is not currently available in varieties adapted to North Dakota.