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Beans - Diseases, Pests and Problems





Basic Information



Problem: Cutworms
Affected Area: Stem

Description: Cuts off young plant just above the soil; no other damage apparent. Lives in soil around roots.

Control: If troubled, place cardboard collars around seedlings. Extend collar 1" below soil and 1" above the soil.


Problem: Mexican Bean Beetle
Affected Area: Leaf

Description: Yellow with black markings about 1/3 inch long with spines; said to resemble a pincushion. Eats the surface at the leaf blade leaving leaf veins. Larvae and egg clusters on underside of leaf

Control: Hand pick when small. Crush eggs. Clean up debris in the fall * Rotenone, Pyrethrum and Sevin are registered for use. Sevin can be used to day of harvest. Allow at least 1 day between Rotenone application and harvest. * Pesticide use and recommendations for various areas are constantly changing. Check with your County agent for current recommendations.


Problem: Aphids
Affected Area: Leaf and Stem

Description: Small Insects found on new stems and the underside of the leaf. Usually green. They suck fluids from the plant leaving a honey dew substance behind. Leaves turn pale yellow.

Control: Insecticidal soaps, a strong stream of water, and most registered insecticides. * Pesticide use and recommendations for various areas are constantly changing. Check with your County agent for current recommendations.


Problem: Mites
Affected Area: Leaf

Description: Small, about 1/50" appear to be black, red, or green spots that move when placed on a white sheet of paper. Mites suck plant juices causing mottled, speckled, cupped, wilted, or dead leaves.

Control: Insecticidal soaps or a strong stream of water. Clean up debris in the fall. *Diazinon is registered but is ineffective. * Pesticide use and recommendations for various areas are constantly changing. Check with your County agent for current recommendations.


Problem: Common mosaic
Affected Area: Leaf

Description: Yellow/green mottled leaves may cup downward and veins discolor and die. Plants are dwarfed and spindly.

Control: Use resistant varieties. Control aphids


Problem: Damping Off
Affected Area: Seedling

Description: Young seedlings wilt and die

Control: Use treated seed and let soil dry out between waterings.


Problem: Stem and root rot
Affected Area: Leaf, Stem, and Root

Description: Stunted plant with yellow leaves that drop. The main root discolors (red to black) and rots. Other roots die.

Control: Let soil dry between waterings. Cultivate deeply before planting. Rotate placement from year to year.


Problem: White Mold
Affected Area: Entire plant

Description: Water soaked spots on leaves or stem. White fungal growth on plant. Plants wilt and die.

Control: Cultivate deeply before planting. Rotate placement from year to year.


Problem: Alternaria Leaf and Pod Spot
Affected Area: Leaf, Stem, and Pod

Description: This disease is characterized by small flecks or tiny water-soaked spots that appear on infected green leaves and pods. Lesions that develop on leaves appear as circular to irregular spots and flecks with a pale brown center and a dark brown margin surrounded by a yellow halo. The lesions may develop concentric rings, and diseased tissue may become dry and brittle and fall out, leaving a shot hole in the leaf.

Control: Control of the disease on snap bean pods involves the use of wider plant and row spacing, fungicides, resistant cultivars, and crop rotation.


Problem: Angular Leaf Spot
Affected Area: Leaf and Stem

Description: This disease is characterized by lesions that develop on the leaf that are gray or brown irregular spots that may be bordered by a yellow halo. As the disease progresses, these lesions may group together, the plant becomes yellow, and drying leaves may fall off prematurely.

Control: The best form of control includes using pathogen-free seed that has been treated with an effective fungicide, rotating the crop where possible, and using resistant cultivars where available.


Problem: Anthracnose
Affected Area: Leaf and Stem

Description: This disease is characterized by small, dark brown to black lesions that usually appear on leaf petioles and on the lower surfaces of leaves and leaf veins. The lesions are elongate, angular, and brick red to purple, becoming dark brown to black. Infected seeds are often discolored and may contain dark brown to black cankers.

Control: The best form of control is to use resistant cultivars where available and to apply seed treatments, including benomyl and thiophanate methyl.


Problem: Ascochyta Leaf Spot
Affected Area: Leaf and Stem

Description: This disease is characterized by brown to black lesions that develop on the leaves. These lesions may have concentric zones that are 10-30 mm in diameter and contain small, black pycnidia. Dark gray to black lesions may also appear on the branches, stems, nodes, and pods causing the plant to become girdled and die. Infected seeds turn brown to black.

Control: The best forms of control include using fungicide sprays and rotating the beans with nonhost crops such as cereal or corn.


Problem: Ashy Stem Blight
Affected Area: Leaf and Stem

Description: This disease is characterized by wilting, yellowing, and death of the leaves that may only appear on one side of the plant. Lesions also develop on the seedling stem at the soil line during emergence and they are small, irregularly shaped, blackish, and sunken. Wilting, yellowing, and death of leaves may be more pronounced on one side of the plant.

Control: The best form of control is to use resistant cultivars where available, use pathogen-free seed, apply chemical treatment to the seed, and fumigate the soil.


Problem: Bacterial Brown Spot
Affected Area: Leaf and Pod

Description: This disease is characterized by lesions that develop on the leaves and are circular, brown, show areas of drying and are often surrounded by a bright yellow zone. Pods that become infected may be twisted or bent where the lesions develop.

Control: The best form of control includes using resistant cultivars and pathogen-free seed.


Problem: Bacterial Wilt
Affected Area: Leaf and Seed

Description: Soft, wilting leaves characterize this disease during warm, dry weather. Infected seeds may show purple or yellow discoloration and struggle to grow properly.

Control: If the disease is found, pathogen-free seed and control measures recommended for other bacterial diseases of bean should be used.


Problem: Bean Common Mosaic
Affected Area: Leaf, Tissue, and Growth

Description: This disease is characterized by light and dark green mosaic, leaf roll, malformation, yellow dots, and abnormally slow growth habits. The vascular tissues may dry out causing the plant to die if it is still young.

Control: The best form of control is the use of resistant cultivars.


Problem: Bean Golden Mosaic
Affected Area: Leaf

Description: This disease is characterized by fine, bright yellow lines that occur only in the veins of the leaves. The leaves curl and fail to expand properly and develop stiff and leathery surfaces. Leaves that may become completely yellow are usually distorted and may dry up.

Control: The best form of control is to use resistant cultivars and control whitefly vectors.


Problem: Bean Yellow Mosaic
Affected Area: Leaf and Growth

Description: This disease is characterized by either mild or diffuse yellow spotting with limited plant stunting, or coarse mosaic, rugosity, malformation, and severe stunting. Some cultivars may also develop dry spots, veinal and apical drying, wilting, and premature death.

Control: The best form of control is to use resistant cultivars.


Problem: Boron Deficiency
Affected Area: Entire Plant

Description: Boron deficiency is rare in beans, but may occur on coarse-textured soils with low organic matter content. Boron deficiency is characterized by crinkled, thickened, and leathery leaves. An early symptom is reduced growth or death of the apical meristem resulting in profuse lateral branches whose terminal buds die. Stems may be swollen near the nodes. Flowers and pods either do not form or they abort. The root system develops poorly.

Control: Boron deficiency is corrected by application of soluble boron salts. Beans are very sensitive to excess boron. Boron fertilizer rates are generally 0.5 lbs boron/acre or less. Because of potential toxicity, band applications are not recommended. Beans planted on soils with high boron may show toxicity symptoms which generally appear as firing of the leaf margins resembling salt injury.


Problem: Calcium Deficiency
Affected Area: Entire Plant

Description: Calcium deficiency is not commonly observed in beans. Most soils where beans are produced contain adequate calcium or are limed to raise soil pH. Deficiency symptoms include loss of turgor, death of growing points, and yellowing of young leaves. Pods may be soft and seeds may fail to develop. Calcium is a key component of cell walls and membranes.

Control: Deficiency is prevented by liming or application of soluble calcium salts such as gypsum.


Problem: Cercospora Leaf Spot
Affected Area: Leaf and Stem

Description: This disease is characterized by brown or rust colored lesions that develop on the leaves. These lesions may vary in shape from circular to angular and have a diameter of 2-10 mm depending on if the lesions group together. The lesions may also have a gray center with a slightly reddish border and severely affected leaves turn yellow.

Control: The best form of control is to use resistant cultivars.


Problem: Chaetoseptoria Leaf Spot
Affected Area: Leaf and Stem

Description: This disease is characterized by lesions that develop on the leaves that are irregular to circular, ash gray in color, medium to large in size and may have a diameter of approximately 10 mm with a reddish border and gray to black pycnidia in the center.

Control: The best form of control is to rotate the crop with nonhost crops for about 5 years.


Problem: Clover Yellow Vein
Affected Area: Leaf and Growth

Description: This disease is characterized by stunted plants that are malformed and have a yellow mosaic. Most plants also show apical drying, premature defoliate, and wilting that result in the death of the plant.

Control: The best form of control is the use of resistant cultivars.


Problem: Common Bacterial Blight
Affected Area: Leaf

Description: This disease is characterized by water-soaked spots that develop on the leaves. These spots gradually enlarge, becoming spongy and they dry out leaving a border of bright yellow tissue. Lesions can also be found at the margin and in areas between the veins of the leaf.

Control: The best forms of control include using resistant cultivars and spraying foliage with a copper-based bactericide.


Problem: Copper Deficiency/Toxicity
Affected Area: Entire Plant

Description: Copper deficiency, though rare, is most often observed in sandy, organic, or over-limed soils. Copper deficiency is characterized by stunted plants with shortened internodes and necrotic areas adjacent to the veins near the base of the leaflet. Leaves may show scorching, wilting, and senescence.

Control: Copper deficiency is prevented by application of soluble copper fertilizers, such as copper sulfate or copper EDTA. Fertilizer rates are generally about one lb Cu/acre. Rates of 2-3 lbs copper/acre may be effective for several years, but these rates should be broadcast not banded. Foliar sprays of copper sulfate or copper EDTA are also effective.


Problem: Cucumber Mosaic
Affected Area: Leaf and Pod

Description: This disease is characterized by curling, green or yellow spots, and blisters that develop on the leaves, and a dark green veinbanding, zipper-like appearance along the main veins. Plants that are flowering and become infected mostly show small, curved, spotted pods, but may also develop the other leaf symptoms in the apical leaves.

Control: The best form of control is to use virus-free seed and avoid planting in fields that may be infected or show signs of getting the disease.


Problem: Curly Top
Affected Area: Leaf and Bud

Description: This disease is characterized by a tight curl of the first trifoliate bud tips and yellowing of the trifoliolate leaf. As the disease progresses, the primary leaf also turns yellow and the plant dies.

Control: The best form of control is to use resistant cultivars.


Problem: Downy Mildew
Affected Area: Leaf and Stem

Description: This disease is characterized by lesions that develop on leaves and petioles and appear as white spots that enlarge and eventually cause the leaves to wilt and die. Major damage occurs as pods become infected and become covered by white, cottony patches of mycelium. Blossoms, buds, and other plant parts may also be killed if they are infected with the white mycelium.

Control: The best form of control is to use resistant cultivars, especially with lima beans, and applying a fungicide spray during flowering and pod formation.


Problem: Entyloma Leaf Smut
Affected Area: Leaf and Stem

Description: This disease is characterized by round or oval lesions that appear water-soaked and become gray-brown on the upper leaf surface and gray-blue on the lower leaf surface. Infected leaves exhibit a blister smut that appears as dark swellings on the upper leaf surface.

Control: The best form of control is to rotate the crop with non-host crops such as cereals and corn.


Problem: Floury Leaf Spot
Affected Area: Leaf and Stem

Description: This disease is characterized by light green to slightly yellow lesions that develop on the upper leaf surface. The lesions may be circular to angular and have a diameter of 10-15 mm. On the lower leaf surface, white, floury mats of conidiophores and conidia form and a heavy infection may cause defoliation.

Control: The best form of control is to apply chemical sprays such as benomyl and thiophanate methyl.


Problem: Fusarium Root Rot
Affected Area: Roots

Description: This disease is characterized by long, narrow, red to brown streaks that appear on hypocotyls and taproots of 7 to 10 day old seedlings. Plants that are established and become infected are usually stunted, vary in size and vigor creating an uneven top canopy, and depend on less important roots for survival.

Control: The best form of control is to practice good cultural control habits.


Problem: Fusarium Yellows
Affected Area: Leaf and Stem

Description: This disease is characterized by premature falling off of the lower leaves and yellowing of the leaves beginning just above the lowest leaves on the stem and progressing upward. As the disease progresses, the leaves become increasingly yellow until finally the plant is a bright yellow color. Plants become stunted if they become infected while they are still young.

Control: The best form of control is to use resistant cultivars where available.


Problem: Gray Leaf Spot
Affected Area: Leaf and Stem

Description: This disease is characterized by light green to yellow lesions that develop on the surface of the leaves. The lesions may be angular in shape, 2-5 mm in diameter on the upper leaf surface, and may group together and later become covered by the free, powdery, grayish white growth of the fungus.

Control: Resistant cultivars are the best form of control.


Problem: Grey Mold
Affected Area: Leaf and Stem

Description: This disease is characterized by lesions that are dark, water-soaked or translucent, soft and slimy and often develop zones of concentric rings. These lesions may girdle the stem or petiole in which case the distal parts of the plant are invaded and the plant collapses. As diseased tissues dry out, characteristic conidiophores and conidia are formed in a gray-brown, powdery mass, and sclerotia may be formed on bulky tissues, such as stems and pods.

Control: The best form of control is to use resistant cultivars.


Problem: Hail Injury
Affected Area: Entire Plant above ground

Description: Plants that suffer from hail injury usually have tattered leaves, broken or crushed stems and branches, and long, whitish, bruised areas on stems, branches, petioles, and leaves.

Control: NA


Problem: Halo Blight
Affected Area: Leaf, Stem, and Pod

Description: This disease is characterized by small, water-soaked spots that appear on the lower leaf surface and may develop a zone of yellow-green tissue around the point of infection. Stems and pods are also infected with pods developing red or brown, water-soaked lesions. If these lesions develop on mature, yellow pods, they may be green but exhibit crusty bacterial ooze on the surface.

Control: The best forms of control are to use resistant cultivars and apply bactericidal sprays containing fixed copper to reduce epiphytic populations and to control secondary disease spread.


Problem: Iron Chlorosis
Affected Area: Entire Plant

Description: Iron chlorosis, the name given to iron deficiency symptoms, occurs frequently in beans grown on high pH soils containing free calcium carbonate. Iron availability declines rapidly as soil pH increases. Water-logging of the soil worsens the symptoms, but the effect may be temporary and disappear as the soil dries. Iron chlorosis typically occurs on the new leaves as a distinctive yellowing of the tissue between veins while the veins remain green. Severely chlorotic leaves may be almost white and have necrotic areas.

Control: The best method of prevention is variety selection. So-called iron-efficient cultivars are less susceptible to chlorosis and should be planted if chlorosis has been observed previously and soil conditions are conducive to development of deficiency. Soil applications of iron fertilizers are generally ineffective in correcting iron deficiency. The most effective corrective treatment is foliar sprays of soluble iron materials, such as iron chelates or ferrous sulfate. A 0.5 to 1.0% solution of ferrous sulfate with a surfactant sprayed in enough water to wet the leaves (about 20 gals/acre) is effective. Multiple applications at 7-14 day intervals may be necessary.


Problem: Peanut Stunt
Affected Area: Leaf, Pod, and Growth

Description: This disease is characterized by mosaic, drying of plant tissues, rugged leaf edges, deformation, and stunting. Pods rarely develop and if they do they are small and malformed with only a few seeds being produced.

Control: There are no control measures available at this time for this disease.


Problem: Powdery Mildew
Affected Area: Leaf and Stem

Description: This disease is characterized by spots that are slightly darkened, about 10 mm in diameter, and develop on the upper surfaces of leaves. These areas become covered by a circular growth of white, superficial, powdery mycelium which may spread on the entire leaf and plant causing the plant to become distorted and yellow.

Control: The best form of control is the use of resistant cultivars.


Problem: Pythium Diseases
Affected Area: Roots

Description: This disease is characterized by plants that show a lesion, initially water-soaked but becoming dry, extending from the roots up the hypocotyl and sometimes reaching the growing point. This disease often affects seeds or seedlings which may become mushy and discolored, fail to emerge, or wilt and die within the first few weeks of growth.

Control: There are a few resistant varieties available and should be used. There are no other control measures for the disease.


Problem: Red Node
Affected Area: Leaf and Stem

Description: This disease is characterized by a reddening of nodes of the stem and a cushion-like swelling at the base of leaves and leaflets. These symptoms may also be accompanied by drying and reddening of veins of primary and trifoliolate leaves.

Control: There are no control measures available because of the minor importance of the disease.


Problem: Rhizoctonia Root Rot
Affected Area: Roots

Description: This disease is characterized by small, elongated, sunken, reddish brown lesions that appear on hypocotyls and roots in the early development of the disease. As these lesions grow and become more sunken, they become cankerous, and the red color may take over until the cankers are old. These cankers may girdle the hypocotyls if they group together which may result in preemergence or postemergence damping-off.

Control: The best form of control is to apply a heavy application of fungicides as a seed treatment of soil drench.


Problem: Rust
Affected Area: Leaf and Stem

Description: This disease is characterized by reddish brown, circular pustules on leaves or pods, which rupture the epidermis to produce abundant, powdery urediniospores.

Control: The best form of control is to use resistant cultivars where available. Not all cultivars are resistant to all forms of rust disease.


Problem: Southern Blight
Affected Area: Roots

Description: This disease is characterized by a slight yellowing of the lower leaves, water-soaking and slight darkening of the stem just below the soil line, followed by a yellowing of upper leaves and leaf drop. The fungus grows downward in the stem and roots, destroying the cortex.

Control: The best form of control is to use resistant cultivars.


Problem: Temperature Stress
Affected Area: Entire Plant

Description: Plants that are exposed to low temperatures may produce chilling or frost damage that appears as dark, water-soaked areas on wilted leaves or plants. If these low temperatures persist for an extended period of time, they may cause the plant to become stunted. High temperatures may cause flowers to abort, increase the rate of evapotranspiration causing leaf wilting or drying if there is an insufficient supply of soil moisture or if root growth is limited due to root rot, mechanical damage, or soil compaction.

Control: NA


Problem: Web Blight
Affected Area: Leaf and Stem

Description: This disease is characterized by small, dry spots on the leaves that are 5-10 mm in diameter with brown centers and olive green margins, originating from sclerotia. Infections caused by basidiospores appear as distinct, small, dry, circular lesions 2-3 mm in diameter that are light brown or brick red with a lighter center. Symptoms on pods are similar to those produced on foliage by sclerotia or basidiospores.

Control: The best forms of control are to apply chemical sprays with benomyl, carbendazim, and captafol and rotate with nonhost crops, such as cereals and corn.


Problem: White Leaf Spot
Affected Area: Leaf and Stem

Description: This disease is characterized by spots that develop on the lower leaf surface and appear as white, angular areas that are 2-5 mm in diameter and found only on the veins. These spots may become slightly gray with age and are pale green to yellow on the opposite, upper leaf surface.

Control: The best form of control is to apply benomyl sprays and use resistant cultivars where available.


Problem: White Mold
Affected Area: Leaf and Stem

Description: This disease is characterized by Infected flowers may develop a white, cottony appearance as mycelium grows on the surface. Lesions on pods, leaves, branches, and stems are initially small, circular, dark green, and water-soaked but rapidly increase in size, become slimy, and may eventually encompass and kill the entire organ.

Control: The best form of control is to use resistant cultivars where available, apply a fungicide spray, such as benomyl, during the flowering period, and rotate the crop with non-host crops, such as cereals and corn.


Problem: Zinc Deficiency
Affected Area: Entire Plant

Description: Beans are among the crops most sensitive to zinc deficiency. Symptoms are frequently observed in beans grown in high pH soils of low zinc content. Yield reductions and delayed maturity may occur without accompanying symptoms. Low soil organic matter, cold soil temperatures, high nitrogen and phosphorus levels, poor root growth, and compaction can all induce deficiencies. Deficient plants develop dwarfed or deformed leaves with a mottled interveinal chlorosis. Chlorosis progresses to necrosis as severity increases. Plants may be stunted with shortened internodes. Delayed maturity is a frequent result of zinc deficiency.

Control: Zinc deficiency can be prevented by soil application of water-soluble zinc sources such as zinc sulfate. Zinc EDTA is also effective, but costs significantly more. Insoluble zinc sources such as zinc oxide in granular form are ineffective. Band applications of 1-5 lbs Zn/acre are most effective. Banding of nitrogen and zinc together improves zinc uptake efficiency. Broadcast applications can also be used, but higher rates of 5-10 lbs Zn/acre are normally required for high pH soils. These rates may be effective for several years. Foliar application of soluble zinc fertilizers is also effective. A 0.5 to 1% zinc sulfate solution applied with a surfactant in enough water to wet foliage is an effective treatment. Repeated applications at 7-14 day intervals may be necessary.


Problem: Mites
Affected Area: Stem and Leaf

Description: Small, about 1/50" appear to be black, red, or green spots that move when placed on a white sheet of paper. Mites suck plant juices causing mottled, speckled, cupped, wilted, or dead leaves.

Control: Insecticidal soaps or a strong stream of water. Clean up debris in the fall. *Diazinon is registered but is ineffective. * Pesticide use and recommendations for various areas are constantly changing. Check with your County agent for current recommendations.


Problem: Common mosaic
Affected Area: Stem and Leaf

Description: Yellow/green mottled leaves may cup downward and veins discolor and die. Plants are dwarfed and spindly.

Control: Use resistant varieties. Control aphids


Problem: Damping Off
Affected Area: Seed

Description: Young seedlings wilt and die

Control: Use treated seed and let soil dry out between waterings.


Problem: Stem and root rot
Affected Area: Stem and Root

Description: Stunted plant with yellow leaves that drop. The main root discolors (red to black) and rots. Other roots die.

Control: Let soil dry between waterings. Cultivate deeply before planting. Rotate placement from year to year.


Problem: White Mold
Affected Area: Stem and Leaf

Description: Water soaked spots on leaves or stem. White fungal growth on plant. Plants wilt and die.

Control: Cultivate deeply before planting. Rotate placement from year to year.






Beans

Tips

Increase watering after plants bloom.

 

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