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Plant NameTypeDescription 
Bacterial BlightsBeanDiseaseThree distinct bacterial blights may affect beans in the area: halo blight (Pseudomonas syringae pv. phaseolicola), common bacterial blight (Xanthomonas axonopodis pv. phaseoli) and bacterial brown-spot (Pseudomonas syringae pv. syringae). Bacteria pathogens require an opening to infect host plants. The bacteria can enter through natural openings, such as stomata, but also access wounds created by mechanical damage from contact or from hail. Bacterial pathogens can be found in other nearby hosts and weeds or may survive in debris in the soil but the most common source of the problems in the garden is the use of non-certified and/or contaminated seeds. Warm temperatures of at least 80oF coupled with humid conditions, including moisture retention in a crowded crop canopy, promote development of these bacterial infections. Halo bright can create greasy, water-soaked spots 1/16” in diameter on the underside of leaves or on pods. Leaves spots may be surrounded by greenish, yellow halos. Red waxy cankers can develop on stems and may girdle tissue. Common bacterial blight will look quite similar though leaf spots merge and darken and dry out with time. Bacterial brown spot, most commonly damaging to lima bean, starts with similar foliar symptoms followed by tissue dropping out leaving a shot-hole appearance while the pods may be distorted in shape.
Common and yellow mosaicsBeanDiseaseBean Common Mosaic and Bean Yellow Mosaic are virus diseases typically transmitted by aphids. The Bean Common Mosaic Virus is also seed-transmitted. Typical symptoms of these virus infections include blue-green, green, or yellowish mottling of leaves, downward curling or cupping of leaves, unusually glossy and brittle leaves, darkened leaf veins, and deformed pods which may be roughened or shiny. Leaves may also be distorted or stunted, and plants may grow poorly.
Curly top (Beet curly top virus)BeanDiseaseCurly top of bean is caused by Beet Curly Top Virus, a virus transmitted by beet leafhoppers. Many crops are affected, including tomato, bean, squash, cucumber, and pepper. Typical symptoms of the disease include puckering and downward curling of leaves, followed by a general yellowing of the plant. Young plants may be killed. Older plants are yellowed and dwarfed, with stunted pods. Leaves are thicker than normal and brittle in texture. The virus is also found in annual flowers and weeds. Beet Curly Top is not a problem in western Washington.
Damping-offBeanDiseaseDamping-off is caused by fungi that remain in the soil for long periods of time. Seeds may be rotted and seedlings may be infected and fail to emerge from the soil. Emerged seedlings are also attacked, causing them to wilt and topple over. Water-soaked or brownish lesions are often visible on the stem at the soil line. Plants become more resistant to attack as they mature. Damping-off fungi are more of a problem in cold soils with poor drainage, and in conjunction with overwatering.
Fusarium root rotBeanDiseaseRoot rot is a fungal disease which attacks the roots and underground stems of beans. Young infected plants show reddish-brown streaking on the stem or taproots. The streaks spread until the entire lower stem and taproot are discolored and decayed, and secondary roots may also be damaged. Plants with badly damaged root systems show aboveground symptoms of disease, including stunting and yellowing of the plants, premature leaf drop, reduced yield, and plant death. The fungus overwinters in the soil in diseased plant debris and can also survive in the soil for many years.
Gray moldBeanDiseaseGray mold of green beans is a fungal disease. It can affect any aboveground portion of the plant. Initial infections often occur on old flowers which remain on the plant. After initial infection, gray mold can spread into the adjacent healthy tissues. Water-soaked lesions appear and quickly become covered with a gray-brown mass of fungus and spores. The disease is strongly favored by cool, moist conditions and can survive on infected plant debris.
RustBeanDiseaseBean rust is a fungal disease which typically affects leaves, but can also be found on stems and pods. Small white blisters develop on the upper surface of infected leaves early in the summer. The underside of the leaf develops a pustule of white, powdery spores. Later in the summer leaves (undersides), petioles, stems, and pods develop reddish-brown, powdery pustules. Leaves often develop yellow halos around the pustules. Severely infected leaves drop, sometimes resulting in considerable defoliation and reduced yield. The brown pustules may later turn dark or black. Disease development is favored by cool, cloudy, humid weather.
White mold (Sclerotinia rot)BeanDiseaseWhite mold is a fungal disease which may attack stems, leaves, and pods of beans. Water-soaked spots appear on the lower portions of the plant. These spots soon show the white, cottony fungal mats characteristic of the disease. The fungus also forms hard, round, black bodies in the white mats. These variously-sized fungal structures may be internal or external on living or dead diseased tissues. They serve as an overwintering source of fungus for future infections. Diseased plants turn yellow and wilt. Diseased tissues die and turn white to beige in color. White mold development is favored by moist conditions and overfertilization. The fungus has a wide host range, including many vegetables (beans, lettuce, carrot, parsnip, cucumber, tomato, etc.).
Bean aphidsBeanInsectBean aphids are small, pear-shaped, dark green to black insects. These soft-bodied insects often feed in clusters on the shoot tips and leaves of new growth. Severe infestations can result in curled or deformed leaves and shoot tips. Aphid feeding can produce large amounts of honeydew, a sweet, sticky material that may attract ants or become covered with a dark growth of sooty mold. The summer form of the aphids may be found on various hosts including many vegetables, flowers, and ornamentals. The aphids typically overwinter on hosts such as euonymus and viburnum.
Brown marmorated stink bugBeanInsectThe brown marmorated stink bug (BMSB) is an introduced pest species from Asia that is spreading quickly across the United States. Nymphs and adults feed on a wide variety of plant hosts. BMSB prefers to feed on fruit, seeds, and seed pods, but will also feed on stems and leaves of some hosts. Both adults and nymphs have piercing-sucking mouthparts and inject digestive enzymes into plant tissues to aid in feeding. On beans, BMSB damage can appear as discolored, sunken lesions or as warty or pimple-like growths on the pod surface. Inside the pod, whitish or brown spots develop and seeds may be deformed, shriveled or fail to develop. Secondary damage from rot may occur at the feeding site. Other known vegetable hosts of BMSB include tomatoes, peppers, corn, and cucumbers. One or two generations of BMSB per year are expected in the Pacific Northwest. Adults overwinter in sheltered locations (including houses, where they can become a significant nuisance pest). In the spring, light green to white eggs are laid in groups of about 20 to 30 on the underside of leaves. Young stink bugs, or nymphs, are black with a red-and-black striped abdomen. Nymphs often feed in groups when young. Older nymphs are dark with white bands on body, legs, and antennae. They may feed in groups or singly. Adults are a little over 1/2 inch long, with a shield-shaped body. Body color on adults is mottled gray and brown, while the legs and antennae have alternating dark and light bands. The abdomen also has dark and light bands which are visible at the edge of the wings. NOTE: BMSB adults closely resemble other stink bugs found in WA and OR. For more information on BMSB identification, see FS079E, Pest Watch: Brown Marmorated Stink Bug, available at
Cutworms and armywormsBeanInsectCutworms and armyworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration. The greenish, grayish, or tan caterpillars are hairless, nocturnal, and generally spotted, striped, or otherwise marked. They may be 1/4" to 1" in length and tend to curl up when disturbed. Cutworms may feed by cutting through stems of young plants an inch or less above ground level. Several plants may be damaged in one night. They may also climb into the plant and feed on foliage and chew holes in developing pods and seeds. While armyworms typically feed during the day, cutworms spend the day just beneath the soil surface or under debris near the host. They usually feed at night, so it is advisable to search for them with a flashlight in the dark. Weeds are their primary food source.
Spider mitesBeanInsectSpider mites are tiny, eight-legged mites which may range in color from yellowish to green or red. Several species may occur on beans. They typically feed on the underside of leaves, causing a yellowish stippling or speckling of the leaf. Severe infestations can cause entire leaves to turn yellow and drop, sometimes resulting in considerable leaf loss and reduced yield. Spider mite feeding is usually accompanied by webbing on the underside of leaves and between leaves and stems. Mites are worse in hot, dry, dusty conditions.
ThripsBeanInsectThrips are tiny (1/20" or less), elongate, yellowish to dark insects. They typically feed in flower buds and blossoms. Thrips feeding can cause buds to fail to open. Blossom drop may also occur. Thrips can often be found by firmly tapping flowers into the palm of the hand and looking for the tiny yellowish insects. They are seldom a serious problem on beans.