Pigeon pea

Description

Pigeonpea, Cajanus cajan, is a perennial shrub in the family Fabaceae grown for its edible pods and seeds. Pigeonpea is a highly branched shrub with a woody base, slender stems and trifoliate leaves. The plant leaflets are oblong or elliptical in shape and the leaves are alternate and arranged spirally on the stems. The plant usually produces yellow flowers, but they can be yellow with streaks of purple or red. The flowers are produced on racemes of 5–10 flowers. The seed pods are flat and either straight or sickle shaped and measure 5–9 cm (2–3.5 in) in length. Each pod can contain between 2 and 9 seeds which can be white, cream, brown, yellow, purple or black or mottled with any combination of these colors. Pigeonpea can reach 0.5–4.0 m (1.6–13.1 ft) in height and is usually grown as an annual, harvested after one season. It may also be referred to as red gram or congo pea and originates from India.


Uses

Pigeon pea is one of the most important legumes grown in semi-arid tropical regions and young seeds are consumed fresh as a vegetable or can be allowed to mature before drying and eating as a pulse. The seed pods are also edible and are eaten as a vegetable. The leaves and seed husks of the plant can be used as an animal feed.


Propagation


Basic requirements
Pigeon pea grows best in hot humid climates where temperatures are between 18 and 38°C (64.4–100.4°F). The plants will grow in a wide range of soils, from sandy soil to clay and also in soils with low fertility. Pigeon pea will grow optimally in a well drained soil with a pH between 5.0 and 7.0. Once established, pigeon pea is relatively tolerant to drought conditions and can survive for long periods with little irrigation.

Propagation
Pigeon pea is propagated directly from seed which should be sown in a prepared seed bed. Seeds should be planted to a depth of 2.5–10 cm (1–4 in) leaving 30–50 cm (12–20) between plants and 150 cm (60 in) between rows. Higher seeding rates should be used if the pant is being grown for use as a green manure. Pigeon pea is commonly intercropped with millets, cotton, sorghum or groundnut.

General care and maintenance
All weeds should be eliminated from the seed bed to prevent competition with the initially slow growing seedlings. Generally, pigeon pea does not require irrigation or fertilization. An application of phosphate at a rate of 20–100 kg per hectare is recommended and irrigation may be necessary if the plants are intensively grown.

Harvesting
Pigeon pea is commonly harvested by hand. Machine harvesting by combine is possible if a variety is grown where pods ripen uniformly. The plant is cut at the ground when the majority of pods have reached maturity. The plants are air dried and then threshed to remove the seeds.


References

CABI Crop Protection Compendium. (2008). Cajanus cajan (pigeon pea) datasheet. Available at: http://www.cabi.org/cpc/datasheet/10794. [Accessed 27 March 15]. Paid subscription required.

Sheahan, C. M. (2012). Plant guide for pigeonpea (Cajanus cajan). USDA-Natural Resources Conservation Service, Cape May Plant Materials Center. Cape May, NJ. 08210. Available at: https://plants.usda.gov/plantguide/pd.... [Accessed 27 March 15]. Free to access.

Valenzuela, H. & Smith, J. (2002). Pigeonpea. University of Hawaii Cooperative Extension Service. Available at: http://www.ctahr.hawaii.edu/oc/freepu.... [Accessed 27 March 15]. Free to access.


Common Pests and Diseases

Alternaria blight
Alternaria alternata

Symptoms
Small irregular brown lesions on leaves which expand and turn gray-brown or dark brown with concentric zones; older areas of lesions may dry out and drop from leaves causing shot hole; lesions coalesce to form large necrotic patches
Cause
Fungus
Comments
Disease emergence favored by high humidity and warm temperatures; plants grown in nitrogen and potassium deficient soils are more susceptible
Management
Plant beans in fertile soil; foliar fungicide application may be required in order to control the disease

Wilt
Fusarium udum

Symptoms
Sudden yellowing of leaves; death of leaves; plant death; blackened tissue at base of stem; symptoms may be present on only one side of plant
Cause
Fungus
Comments
Fungus can survive in soil for several years
Management
Practice long term crop rotation; avoid over or under watering plants

Cercospora leaf spot
Cercospora cajani

Symptoms
Small light brown lesions on upper surfaces of leaves; angula brown spots on leaves; leaf death; lesions on stems and petioles
Cause
Fungus
Comments

Anthracnose
Colletotrichum spp.

Symptoms
Small, dark brown to black lesions on cotyledons; oval or eye-shaped lesions on stems which turn sunken and brown with purple to red margins; stems may break if cankers weaken stem; pods drying and shrinking above areas of visible symptoms; reddish brown spots on pods which become circular and sunken with rust colored margin
Cause
Fungus
Comments
Disease transmitted through infected seed; fungus can survive in crop debris in soil and reinfect crop the following season
Management
Plant resistant varieties; use certified disease free seed; avoid sprinkler irrigation, water plants at base; plow bean crop debris into soil

White mold (Sclerotinia rot)
Sclerotinia sclerotum

Symptoms
Flowers covered in white, cottony fungal growth; small, circular, dark green, water-soaked lesions on pods leaves and branches which enlarge and become slimy; cottony white growth may be visible on lesions during periods of high humidity; death of branches and/or entire plant
Cause
Fungus
Comments
Fungus can survive in soil for in excess of 5 years; disease can be spread by wind, contaminated irrigation water and by infected seeds
Management
Rotate crops with non-hosts like cereals and corn; plant rows parallel to direction of prevailing winds to prevent spread of disease from secondary hosts nearby; avoid excessive nitrogen fertilizer; use a wide row spacing

Aphids (Cowpea aphid, Pea aphid, etc.)
Aphis craccivora
Acyrthosiphon pisum

Symptoms
Small soft bodied insects on underside of leaves and/or stems of plant; usually green or yellow in color, but may be pink, brown, red or black depending on species and host plant; if aphid infestation is heavy it may cause leaves to yellow and/or distorted, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants
Cause
Insect
Comments
Distinguishing features include the presence of cornicles (tubular structures) which project backwards from the body of the aphid; will generally not move very quickly when disturbed
Management
If aphid population is limited to just a few leaves or shoots then the infestation can be pruned out to provide control; check transplants for aphids before planting; use tolerant varieties if available; reflective mulches such as silver colored plastic can deter aphids from feeding on plants; sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves; insecticides are generally only required to treat aphids if the infestation is very high - plants generally tolerate low and medium level infestation; insecticidal soaps or oils such as neem or canola oil are usually the best method of control; always check the labels of the products for specific usage guidelines prior to use

Armyworms (Beet armyworm, Western striped armyworm)
Spodoptera exigua
Spodoptera praefica

Symptoms
Singular, or closely grouped circular to irregularly shaped holes in foliage; heavy feeding by young larvae leads to skeletonized leaves; shallow, dry wounds on fruit; egg clusters of 50-150 eggs may be present on the leaves; egg clusters are covered in a whitish scale which gives the cluster a cottony or fuzzy appearance; young larvae are pale green to yellow in color while older larvae are generally darker green with a dark and light line running along the side of their body and a pink or yellow underside
Cause
Insect
Comments
Insect can go through 3–5 generations a year
Management
Organic methods of controlling armyworms include biological control by natural enemies which parasitize the larvae and the application of Bacillus thuringiensis; there are chemicals available for commercial control but many that are available for the home garden do not provide adequate control of the larvae

Corn earworm
Helicoverpa zea

Symptoms
Larvae damage leaves, buds, flowers, pods and beans; young caterpillars are cream-white in color with a black head and black hairs; older larvae may be yellow-green to almost black in color with fine white lines along their body and black spots at the base of hairs; eggs are laid singly on both upper and lower leaf surfaces and are initially creamy white but develop a brown-red ring after 24 hours and darken prior to hatching
Cause
Insect
Comments
Adult insect is a pale green to tan, medium sized moth; insect is also very damaging pests of corn; insect overwinters as pupae in the soil
Management
Monitor plants for eggs and young larvae and also natural enemies that could be damaged by chemicals; Bacillus thuringiensis or Entrust SC may be applied to control insects on organically grown plants; appropriate chemical treatment may be required for control in commercial plantations

Cutworms
Agrotis spp.
Peridroma saucia
Nephelodes minians
and others

Symptoms
Stems of young transplants or seedlings may be severed at soil line; if infection occurs later, irregular holes are eaten into the surface of fruits; larvae causing the damage are usually active at night and hide during the day in the soil at the base of the plants or in plant debris of toppled plant; larvae are 2.5–5.0 cm (1–2 in) in length; larvae may exhibit a variety of patterns and coloration but will usually curl up into a C-shape when disturbed
Cause
Insect
Comments
Cutworms have a wide host range and attack vegetables including asparagus, bean, cabbage and other crucifers, carrot, celery, corn, lettuce, pea, pepper, potato and tomato
Management
Remove all plant residue from soil after harvest or at least two weeks before planting, this is especially important if the previous crop was another host such as alfalfa, beans or a leguminous cover crop; plastic or foil collars fitted around plant stems to cover the bottom 3 inches above the soil line and extending a couple of inches into the soil can prevent larvae severing plants; hand-pick larvae after dark; spread diatomaceous earth around the base of the plants (this creates a sharp barrier that will cut the insects if they try and crawl over it); apply appropriate insecticides to infested areas of garden or field if not growing organically

Leafminers
Lyriomyza spp

Symptoms
Thin, white, winding trails on leaves; heavy mining can result in white blotches on leaves and leaves dropping from the plant prematurely; early infestation can cause fruit yield to be reduced; adult leafminer is a small black and yellow fly which lays its eggs in the leaf; larvae hatch and feed on leaf interior
Cause
Insects
Comments
Mature larvae drop from leaves into soil to pupate; entire lifecycle can take as little as 2 weeks in warm weather; insect may go through 7 to 10 generations per year
Management
Check transplants for signs of leafminer damage prior to planting; remove plants from soil immediately after harvest; only use insecticides when leafminer damage has been identified as unnecessary spraying will also reduce populations of their natural enemies