Snap Bean, Phaseolus vulgaris, is a tender, warm season crop belonging to the Leguminosae or pea family. The seed are planted when the soil temperature is above 62 degrees F in spring, summer, and fall. Spring crop snap beans are planted 1 to 1 1/2 inches deep after the beginning of the frost-free period. Fall crop snap beans are planted early enough in the summer for harvest to be completed before the first killing frost. Row spacing for bush beans is 2-3 inches in the row and 18 to 36 inches between rows. The optimum temperature for plant growth is 60 to 70 degrees F. Snap beans require moist soil for germination. Water availability at pod fill is also critical to ensure high yields. Because of the relatively shallow root system of the snap bean the water requirement is high.
Snap beans are adaptable to a wide variety of soil types but have difficulty emerging in crusted soils. The use of a rotary hoe is sometimes necessary on heavy soils to break the crust. Uniform emergence is particularly important for bush type beans that will be mechanically harvested. For this reason, all areas of the field must be well drained and prepared with no crusted, cold or wet areas.
Snap beans prefer a well-drained, fertile soil with a pH of 5.8 to 7.0. Beans are particularly sensitive to boron and may experience toxicity problems in fields where boron is naturally high. Snap beans will nodulate and form symbiotic associations with nitrogen-fixing bacteria in the soil even without artificial inoculation. Modern cultivars require fertilizer nitrogen for best performance; however, plants fixing their own nitrogen often get off to a slower start in the cool spring weather and are less uniform in bloom time and subsequent number of days to harvest.
Green beans are normally planted in the spring (March 25 to May 5) into prepared fields. Approximately 99% of the planting is by mechanical means.
Preemergent herbicide applications are applied to the beds. These applications are made in early spring, primarily with tractor mounted spray equipment. Postemergence herbicide applications are made to the beds of traditionally grown beans primarily with tractor mounted sprayers, although backpack sprayers are occasionally used.
Insecticides and fungicides are applied from early spring up to harvest primarily with airblast sprayers, aerial or boom sprayers.Virtually the entire bean crop is mechanically harvested (June - July).
Bean Leaf Beetle (Ceratoma trifurcate)
Potato Leafhopper (Empoasca fabae)
European Corn Borer (Ostrinia nubilalis)
The European corn borer overwinters as a mature larvae in the stem of the plant on which it fed in the fall, usually field corn. The larvae ¾ to 1 inch long and grayish pink in color with a dark head and rows of small brown spots on their backs. The larvae pupate in late spring and the adults emerge to begin mating and laying eggs. The eggs are laid in groups of 5 to 50 resembling overlapping fish scales. They will hatch in approximately 5 days. The young larvae do the most damage to green bean. They feed on leaves, buds, or flowers for 4-6 days before boring into stem or the beans when the temperature reaches 70˚F. If the temperature is higher the larvae will enter the stems and beans more quickly. There are usually 2-3 generations of European corn borers in Arkansas.
Corn Earworm (Helicoverpa zea)
Seedcorn Maggot (Delia platura)
The insect overwinters as small, brown pupae in the soil. Adult flies emerge late in April to May. They are attracted for egg laying to soils that are high in decomposing organic matter, including plowed-down cover crops and animal manure. Eggs are laid on or beneath the soil surface. Larvae feed on decomposing plant material in the soil and especially on seeds of corn, beans and cucurbits. Seeds may be attacked before or shortly after germination. Planting under cool, moist soil conditions favor the development of this pest.
Chemical Insect Controls:
Carbaryl (Sevin)
Acephate (Orthene)
Phorate (Thimet)
Dimethoate
Bacillus thuringiensis (Dipel, XenTari)
Fonophos (Difonate)
Esfenvalerate (Asana)
Bifenthrin (Capture)
Methomyl (Lannate)
Disulfoton (Di-Syston)
Cultural Controls:
Most growers plant when the soil is warmer so that seeds can germinate more quickly and produce earlier crops that helps avoid insect problems. Some cultivars have a lower susceptibility to insect damage and are used by growers when available. European corn borer and corn earworm populations are monitored using scouting or blacklight traps so that chemicals can be applied when the insects are the most vulnerable. Insecticides with action against multiple pests are often recommended and utilized.
Broadleaves and Grasses:
Weeds compete with green bean plants for water, sunlight, and nutrients. Significant yield losses (>50%) can occur if weeds are not controlled. Early season control of weeds is critical for good yield potential. Most herbicide applications are made with ground equipment (boom and airblast sprayers) with the occasional use of backpack sprayers.
Key weeds that are common problems for Arkansas producers are Barnyardgrass (Echinochloa crus-galli), Bermudagrass (Cynodon dactylon), Crabgrass (Digitaria spp.), Johnsongrass (Sorghum halepense), Morningglory (Ipomea spp.), Smooth pigweed (Amaranthus hybridus), Nutsedge (Cyperus spp.), Pale smartweed (Polygonum lapathifolium), Common ragweed (Ambrosia artemisiifolia), Lambsquarter (Chenopodium album), Common cocklebur (Xanthium strumarium), Velvetleaf (Abutilon theophrasti), Purslane (Portulaca oleracea) and Carpetweed (Mollugo verticillata).
Chemical Controls:
Metolachlor (Dual)
Dimethenamid (Basagran)
EPTC (Eptam)
Trifluralin (Treflan, Trifluralin)
Clomozone (Command)
Cultural Controls:
Shallow mechanical weed cultivation can be used to manage weed in the rows until there is a potential for plant damage by the cultivation equipment. Most producers utilize this practice.
White Mold:
White mold is caused by the fungus Sclerotinia sclerotiorium that overwinters in residues from diseased plants in and near bean fields. During wet spring weather fungal spores are produced and then carried by wind to the bean plants. The fungus commonly colonizes senescent petals and injured tissues. Infection occurs after prolonged periods of wet conditions. Symptoms of the disease first appear as watery rot on stems, leaves and pods. White cottony growth appears on the infected pods and stems. The affected tissue dries quickly and bleaches to a pale tan or white color. Entire branches or stems may be killed but if the main stem is infected near the soil line, the entire plant may be killed.
Gray Mold:
Gray mold is caused by the fungus Botrytis cinerea. The fungus is commonly present in most any dead organic matter in fields. It is spread by wind and promoted in wet weather. Gray mold primarily infects the pods of bean plants where it causes a distinctive grayish powdery mold to develop. Pods resting on the soil or touching another decaying pod or leaf are most easily infected.
Rust:
The fungus Uromyces phaseoli var. typica causes the disease rust in beans. The fungus overwinters on residues from diseased plants. The underside of leaves are usually first infected with the fungus. They develop small spots that enlarge, turn red and develop a blister-like appearance. Eventually the pustules rupture and release millions of brick red spores that can be transported long distances by wind. Severely infected leaves turn yellow, begin to dry and then drop from the plant. Rust attacks when the weather is cool and wet with frequent and prolonged dew or rain.
Bacterial Blight:
There are several types of bacteria that cause disease in green beans in Arkansas. The most common causal bacteria is Xanthamonas campestris pv. phaseoli. The bacteria overwinter in infected seed and in the residues of diseased plants left in the field. Infection of bean foliage is favored by conditions of high humidity and moisture. Symptoms of the disease appear as water-soaked spots on the underside of the leaves. The spots enlarge and the tissue in the centers dies and turns brown. A characteristic lemon-yellow ring develops around the irregular shaped spots. The spots can grow together, causing the death of the entire leaf and the defoliation of the plant. Infected pods also show small watersoaked spots that develop into large, dark irregular spots but under moist conditions a yellow ooze is produced by these spots.
Chemical Disease Controls:
Chlorthalanil (Bravo)
Fixed Copper
Benomyl (Benlate)
Thiophanate-methyl (Topsin)
Cultural Controls:
It is recommended that green beans be planted in well-drained soil not recently planted with beans, potatoes, tomatoes, lettuce or cabbage (serve as host plants for many pathogens). If possible, growers orient the rows parallel to the prevailing winds with wide row spacing to help keep low levels of moisture in the plant canopy. Planting in shaded field, fields bordered on two or more sides by trees or fields that drain poorly should be avoided. Disease free seeds and disease resistant cultivars are utilized many growers when available. Two to three-year rotations and deeply plowing infested debris will help control diseases.
Profile Compiled By:
Contact Personnel:
Ples Spradley
Pesticide Assessment Specialist
Cooperative Extension Service
University of Arkansas
P.O. Box 391
Little Rock, AR 72203
Phone: 501-671-2234
Fax: 501-671-2303
E-mail: pspradley@uaex.edu