Lentil

Description

Lentil, Lens culinaris, is a a bushy, annual legume in the family Fabaceae grown for its edible seeds which are cooked and eaten. The lentil plant is slender and erect or sub-erect and has branching, hairy stems. The leaves of the plant are arranged alternately and are made up of 4–7 individual oval leaflets. The plant produces small blue, purple, white or pink flowers arranged on racemes with 1–4 flowers. The seeds, or lentils, are produced within rhomboidal pods and can range in size from 2-9 mm (0.1–0.3 in) in diameter depending on the variety and can be red-orange, yellow, green or black in color. There are generally 1–2 lentils per pod. Lentil plants can reach 15–75 cm (6–30 in) in height and as annuals, survive only one growing season. Lentil may also be referred to as red dhal or split pea and its origin is unknown although it is grown widely in Europe, Asia, and North Africa.


Uses

The lentil seeds can be eaten raw or are cooked and eaten in soups and other dishes. They are commonly eaten as dahl (lentils seeds which have had the husk removed and then split). Lentil seeds can be used as a source of starch for the textile industry or can be ground into flour. The youger pods are sometimes eaten as vegetables.


Propagation


Basic requirements
Lentils are adapted to grow in cool climates and are tolerant of some light frost. Lentil plants can be grown on a wide variety of soils from sandy soils to clay loams but will grow optimally in a sandy, well-draining soil with a pH of 4.5 to 8.2. A soil pH of close to 7 is ideal. Lentils will be killed by waterlogged soil so good drainage is very important. Growing lentils on a South or East facing slope will help to warm the crop early in the growing season. The optimum temperature for their growth is approximately 24°C (75°F). Lentils require and average rainfall of 10 to 12 inches per year but are fairly tolerant of drought although yield will be reduced. Yield will also be reduced by high humidity which promotes vegetative growth.

Propagation
Lentils are propagated by seed and are either sown by broadcasting or by drilling in rows. Seed should be sown in soil which is firm and which has been prepared to a fine tilth. Seeds should be planted planted at a depth of 2.5–5.0 cm (1–2 in), leaving 20–30 cm (7.8–12 in) between individual plants and 15–18 cm (6–7 in) between rows. Due to the small size of the seeds, seedlings struggle to emerge if planted too deep in the soil. Commercial fields are planted at a rates of between 30 and 80 kg of seed per acre, depending on the variety, when lentil is the sole crop being grown. The best yields are achieved when lentil is planted by drilling which ensures a uniform planting depth. In many countries where lentil is commercially produced, lentils are intercropped with crops such as rice or barley and seeding rates are reduced accordingly.

General care and maintenance
Lentil seeds are often inoculated with nitrogen-fixing bacteria prior to planting. These bacteria nodulate the plants, allowing them to fix atmospheric nitrogen. found in the soil. lentils should be inoculated with Rhizobium leguminosarum within 24 hours of planting if the planting field was not previously used to grow lentils or other legumes. If the nitrogen level in the soil is low at time of planting then an early nitrogen supplement should be applied at a rate of 30 to 40 lb per acre. This ensures that the seedlings have enough nitrogen while the root nodules develop. Lentils have high requirements for sulfur, potassium and phosphorous and a soil test should be used to establish the level on these nutrients in the soil and thus the rate at which they should be applied if the soil is found to be deficient. Optimum soil tests range 15 to 30 ppm (30 to 60 lb/acre) for P and 90 to 120 ppm (180 to 240 lb/acre) for K for most soils. Lentils do not compete well with weeds and the planting site should be cleared by hoeing prior to the seeds being planted. Lentils should be kept evenly moist and watering should be ceased when the pods have begun to dry out.

Harvesting
Lentils are ready to harvest when the plants turn yellow and the lower seed pods are yellow-brown in color. Plants should be watched carefully as this will happen over a period of a few days and the pods are easily shattered if left too long on the plants. Commercially grown lentil is harvested by swathing and the pods are threshed to collect the seeds. In the home garden, the pods can be picked from the plants or the whole plant can be gently pulled from the ground and set to dry on a rack for 1 to 2 weeks. The seeds can then be extracted from the dried pods by breaking them open and removing the seeds.


References

CABI Crop Protection Compendium. (2013). Lens culinaris subsp. culinaris (lentil) datasheet. Available at: http://www.cabi.org/cpc/datasheet/30274. [Accessed 11 February 15]. Paid subscription required.

Chen, W., Sharma, H. C. & Muehlbauer, F. J. (Eds.) (2011). Compendium of Chickpea and Lentil Diseases and Pests. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopap.... Available for purchase from APS Press.

Oplinger, E.S., Hardman, L. L., Kaminski, A. R., Kelling, K. A. & Doll, J. D. (1990). Alternative Field Crops Manual. University of Wisconsin-Extension, University of Minnesota Center for Alternative Plant and Animal Products and the University of Minnesota. Available at: https://www.hort.purdue.edu/newcrop/a.... [Accessed 11 February 15]. Free to access.




Common Pests and Diseases

Damping-off
Pythium ultimum
Rhizoctonia solani

Symptoms
Failure of seedling to emerge; light brown, seedlings with light brown to redwater-soaked roots and stems; collapse of plants; plant dry up and die; stunted plant growth; rotting taproot with few lateral roots
Cause
Fungi
Comments
Occurs more often in cold temperatures when growth of seedlings is slow and in moist soil
Management
Treat seeds with fungicide prior to planting

Anthracnose
Colletotrichum truncatum

Symptoms
Tan lesions with darker borders on leaves which often appear prior to flowering or shortly after bloom; diseased leaves may drop from the plant prematurely; tan to light brown lesions appear on lower stems and begin to spread upwards, appearing higher on the plant; lesions may contain numerous black dots; as plant matures, the lesions expand and may cover large areas of the stem; lesions may also be present on pods and are light to tan brown with a dark margin; diseased pods often produced discolored seeds; disease can cause severe losses in yield
Cause
Fungus
Comments
Disease emergence is favored by wet conditions; fungus is spread by splashing water; faba beans and filed peas are alternate hosts for the fungus
Management
There are no varieties of lentil which are completely resistant to the disease but some are less susceptible than others and can be planted in areas where disease is prevalent; a well-timed application of an appropriate fungicide may be enough to control the disease but should be reapplied in the event of persistent wet weather

Ascochyta blight
Ascochyta pinodella

Symptoms
Tan to light brown lesions with a dark border can appear an any aerial part of the plant (leaves, stems, pods, petioles, peduncles); during periods of high humidity, numerous black dots may be visible in the center of the lesions; diseased plants may abort flowers and/or fruits; seeds may be discolored
Cause
Fungus
Comments
Disease can be transmitted to seedlings from infected seeds; foliar transmission is favored by cool, moist soils
Management
Plant only disease-free seed or seed treated with a fungicide prior to planting; rotate crop away from lentil for a period of three years; remove and destroy all lentil crop residue after harvest to reduce the levels of inoculum the following growing season; a single application of an appropriate foliar fungicide is usually enough to control the disease but should be reapplied during persistent wet weather

Gray mold
Botrytis cinerea

Symptoms
Plants turning yellow and wilting; diseased tissue covered with fuzzy gray fungal growth during periods of high humidity; lesions may girdle the stem and cause the upper canopy to die; if the disease does not girdle the stem, the upper leaves remain green and the lower canopy becomes necrotic
Cause
Fungus
Comments
Disease emergence is favored by cool, wet conditions and dense canopies which pro,mote high humidity in the lower canopy; disease can be transmitted by infected seed or from infested crop debris from the previos year
Management
Plant only pathogen-free seed or seed treated with an appropriate fungicide prior to planting; avoid planting lentils in fields or areas adjacent to fields which had an outbreak of gray mold the previous year; remove and destroy lentil crop residue after harvest; applications of appropriate fungicides can be helpful for controlling the disease

Fusarium wilt
Fusarium oxysporum

Symptoms
Weak and wilting leaf stems, leaves and flowers; lower leaves drying out and dying; leaves turning brown or pale yellow; splitting the stem reveals discoloration of the inner tissue; leaves turn dull yellow in color and collapse; disease appears in fields in patches
Cause
Fungus
Comments
Disease emergence favors warm, moist soils; disease can be spread by water splash, movement of infected soil and plants and by infected seed
Management
The primary method of controlling the disease is to use resistant varieties; damage can be reduced by application of appropriate fungicides; crop debris should be removed or plowed deeply into the soil after harvest; if disease is present in the soil then a rotation to a non-host for a period of three years can reduce the levels of inoculum in the soil

Sclerotinia rot
Sclerotinia rolfsii

Symptoms
Lesions girdle stem causing upper plant parts to become chlorotic and wilted; plants become necrotic after they die; disease often causes a patchwork of symptomatic plants throughout a field with plants initially becoming chlorotic and finally dying; fungus causes characteristic white lesions on stems which may be covered in a fluffy white growth during periods of wet weather
Cause
Fungus
Comments
Disease emergence is favored by cool, wet conditions and a dense canopy which promotes high humidity
Management
A long rotation to small grains can help to reduce the levels of inoculum in the soil; control of the disease using appropriate fungicides can be difficult to achieve as the disease is favored by dense plant canopies which can be hard to penetrate with chemicals

Powdery mildew
Erysiphe pisi

Symptoms
Yellow spots on upper surface of leaves; powdery gray-white areas which coalesce to cover entire plant; if plant is heavily infected it may appear light blue or gray in color
Cause
Fungus
Comments
Fungus overwinters on plant debris or alternate host; disease emergence is favored by warm, dry weather with cool nights that result in dew formation
Management
Plant resistant varieties, particularly if sowing late; use overhead irrigation (washes fungus from leaves and reduces viability); plant crop as early as possible; frequent applications of sulfur may be required to control heavy infestations

Cutworms
Agrotis spp.

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
Insects
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

Mosaic
Alfalfa mosaic virus (AMV)
Bean yellow mosaic virus (BYMV)
Pea enation mosaic virus (PEMV)

Symptoms
Mottled dark and light green patterns on leaves; leaves may be distorted; yellow dots may be present on leaves; growth of plant may be reduced
Cause
Virus
Comments
Viruses are transmitted by aphids
Management
Plant virus-free seed; plant resistant varieties