Pea

Description

Pea, Pisum sativum, is an annual herbaceous legume in the family Fabaceae grown for its edible seeds and seedpods. The pea plant can be bushy or climbing, with slender stems which attach to a substrate using tendrils. Each leaf has 1–3 pairs of oval leaflets and can reach 1–6 cm in length. The plant produces white, red or purple flowers and swollen or compressed green seedpods which can be straight or curved. The pods can range in size from 4 to 15 cm long and 1.5–2.5 cm wide. Each pod contains between 2 and 10 seeds, or peas. The pea plant is an annual plant, surviving only one growing season and can reach 30–150 cm in height. Pea may also be referred to as garden pea, English pea or green pea and likely originates from Southwest Asia.


Uses

Young green seeds and pods can be eaten fresh or cooked as a vegetable.


Propagation


Basic requirements
Peas are cool-season crops and should be grown in early Spring or late summer to avoid high summer temperatures. Peas grow best at temperatures between 15 and 24°C (60–75°F) and are tolerant of frost down to -6.5°C (20°F) although they are generally less sensitive to Spring frost. Pea plants will grow best in soils rich in organic matter with a pH between 5.5 and 7. They should be planted in a well draining soil or raised bed as they do not tolerate too much moisture. Peas perform best in full sunlight although they are also tolerant of partial shade.

Sowing seeds
Peas should be direct seeded in the garden in Spring as soon as soil is workable and its temperature is above 4.4°C (40°F), or in late summer 8–10 weeks before the first frost date. The optimum soil temperature for germination is 10–25°C(50–77°F), lower temperatures will slow germination. Seeds should be planted 2.5–5.0 cm (1–2 in) with shallow planting beneficial in soils which are cool and wet. Seeds should be sown 2.5–10.0 cm (1–4 in) apart allowing 45 cm (~18 in) between rows. Seedling should emerge in 9–13 days at a soil temperature of 15.5°C (60°F) and do not require thinning.

General care and maintenance
Tall, vining pea varieties require a trellis to support their growth. Trellises can be made easily out of chicken wire or lengths of string and the plants will begin to grow around them, using tendrils to grip around the support. If growing a variety that requires trellising then the row spacing should be adjusted accordingly. Cool season crops are often attacked by powdery mildew and where the disease is known to be problematic, resistant varieties should be planted.



References

CABI Crop Protection Compendium. (2014). Pisum sativum (pea) datasheet. Available at: http://www.cabi.org/cpc/datasheet/41042. [Accessed 05 March 15]. Paid subscription required.

Coolong, T. (2012). English and edible pod peas. University of Kentucky College of Agriculture Cooperative Extension Service. Available at: http://www.uky.edu/Ag/NewCrops/intros.... [Accessed 05 March 15]. Free to access.

Drost, D. (2010). Peas in the garden. Utah State University Cooperative Extension. Available at: http://extension.usu.edu/files/public.... [Accessed 05 March 15]. Free to access.

Kraft, J. M. & Pfleger, F. L. (2001). Compendium of pea diseases and pests. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopap.... Available for purchase from APS Press.

Muehlbauer, F. J. & Tullu, A. (1997). Pisum sativum L.. Purdue University Center for New Crops and Plant Products. Available at: http://www.hort.purdue.edu/newcrop/cr.... [Accessed 05 March 15]. Free to access.

Myers, J. R., Colt, W. M. & Swanson, M. A. Peas and beans. University of Idaho Cooperative Extension System, the Oregon State University Extension Service, Washington State University Cooperative Extension, and the U.S. Department of Agriculture . Available at: http://www.cals.uidaho.edu/edcomm/pdf.... [Accessed 05 March 15]. Free to access.


Common Pests and Diseases

Spider mites (Two-spotted spider mite)
Tetranychus urticae

Symptoms
Leaves stippled with yellow; leaves may appear bronzed; webbing covering leaves; mites may be visible as tiny moving dots on the webs or underside of leaves, best viewed using a hand lens; usually not spotted until there are visible symptoms on the plant; leaves turn yellow and may drop from plant
Cause
Arachnid
Comments
Spider mites thrive in dusty conditions; water-stressed plants are more susceptible to attack
Management
In the home garden, spraying plants with a strong jet of water can help reduce buildup of spider mite populations; if mites become problematic apply insecticidal soap to plants; certain chemical insecticides may actually increase mite populations by killing off natural enemies and promoting mite reproduction

Bacterial blight
Pseudomonas syrngae

Symptoms
Small, water-soaked spots on leaves steam and pods which coalesce and turn brown and necrotic; lesions on leaves are angular and develop translucent centers; lesions on stem may enlarge and girdle stem, killing plant parts above; lesions on pods may cause seeds to be covered in slime
Cause
Bacterium
Comments
Disease is spread both in and on seed and can survive like this for 3 years; if infected seed is used, the whole pea crop can be lost if conditions are favorable to the bacterium
Management
Plant resistant varieties; plant only disease-free seed; disinfect all tools and equipment regularly; avoid sprinkler irrigation

Brown spot
Psuedomonas syringae

Symptoms
Water-soaked spots on leaves, stems and pods identical to those caused by bacterial blight; after several days lesions turn tan, lose their water-soaked appearance and resemble a scorch or burn; stem lesions are sunken and elongated and spread upwards; symptomatic leaves dry and drop from plant
Cause
Bacterium
Comments
Disease is spread by infected seed; bacterium survives in soil for several months; brown spot more common on plants injured by wind, frost and hail or by mechanical means
Management
Plant only disease-free seed; continuously rotate crops; avoid planting peas in fall when they are more likely to be injured by inclement weather

Ascochyta disease
Mycosphaerella pinodes
Phoma medicaginis
Ascochyta pisi

Symptoms
Tan or purple lesions on leaves, stems and pods which may expand and produce a concentric ring pattern; blossoms or pods may drop or become distorted if lesions girdle sepals
Cause
Fungi
Comments
Disease emergence favors high moisture
Management
Grow peas in dry areas; use an appropriate fungicide to treat seeds prior to planting; discard any seed which is known to be heavily infected

Aphanomyces root rot (Common root rot)
Aphanomyces euteiches

Symptoms
Leaves turning yellow starting from bottom of plant and moving upwards; pod production reduced; soft dark lesions on roots; plants may be severely stunted
Cause
Fungus
Comments
Disease emergence favors high soil moisture; currently a problem in the midwest and northeast US
Management
No fungicides effectively control this disease and no pea varieties with high resistance, control therefore relies on avoiding planting in infested fields; rotate crops to avoid build up of disease in soil

Fusarium root rot
Fusarium solani

Symptoms
Stunted plant growth; yellowing, necrotic basal leaves; brown-red or black streaks on roots that coalesce as they mature; lesions may spread above the soil line
Cause
Fungus
Comments
Damage caused by the emergence of the disease is worsened by warm, compacted soils, limited soil moisture and poor soil fertility
Management
There are currently no pea varieties with resistance to Fusarium root rot so control relies on cultural practices e.g. do not plant peas in same area more than once in any 5 year span or treating seeds with an appropriate fungicide prior to planting

Gray mold (Botrytis mold)
Botrytis cinerea

Symptoms
Fuzzy gray elongated lesions whoch girdle stem causing wilting of upper parts of plant; lower leaves may be covered in fuzzy gray growth which causes them to dry out and shrivel; small, oval, water-soaked lesions on pods which are tan in color; pod lesions spread irregularly and become gray and sunken; young pods may shrivel and become covered in fuzzy, gray mycelial growth
Cause
Fungus
Comments
Fungus survives in or on crop debris in soil; disease spreads by splashing water and on equipment under favorable conditions
Management
There is no reported resistance to gray mold in pea; potassium deficiency may make plants more susceptible and should be supplemented in deficient soils; the fungus causing gray mold has developed resistance to many systemic fungicides and control relies on the application of an appropriate protective fungicides if flowering and pod set coincides with wet weather

Downy mildew
Peronospora viciae

Symptoms
Yellow-brown blotches on upper surface of leaves; angular patches of fluffy white-gray fungus on lower side of leaves; plant growth may be stunted or distorted and whole plant may die before flowering; plant may produce
Cause
Fungus
Comments
Fungus overwinters in soil and on crop debris; fungus can survive in soil for 10-15 years
Management
Rotate crops for at least 5 years; till crop debris deeply; avoid sowing pea in late Autumn at greater soil depths as this can promote severe infections

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

Rhizoctonia seedling blight
Rhizoctonia solani

Symptoms
Water-soaked sunken, red-brown lesions on hypocotyls (germinating shoot below seed leaves) and epicotyls (shoot above seed leaves); death of growing tip as it emerges from soil; new shoots may emerge from a node at seed but may also be killed
Cause
Fungus
Comments
Fungus can survive in soil for long periods; disease most damaging in warm conditions; fungus spreads by wind, contaminated water, equipment and movement of people and animals in plantation
Management
Crop rotation helps to reduce the build up of the fungus in the soil; reduce soil compaction; do not plant seeds too deep

Septoria blotch
Septoria pisi

Symptoms
Irregular yellow lesions on leaves and pods with no definitive margin that coalesce to form large yellow patches; large patches may dry out and become covered in black fungal fruiting bodies
Cause
Fungus
Comments
Disease emergence favors high humidity and moderate temperatures; disease is common but rarely causes economic damage as it occurs mainly on old leaves and pods
Management
Rotating crops regularly prevents disease build-up in soil

Mexican bean beetle
Epilachna varivestis

Symptoms
Irregular patches of feeding damage on underside of leaves which causes the top surface of the leaf to dry out, giving the leaves a lacy appearance; insect will also damage flowers and small pods; pods may be damaged so badly that they drop from the plant; adult insect is an orange-brown beetle with black spots; larvae are fat-bodied grubs which taper at the end and are in rows of conspicuous spines
Cause
Insect
Comments
Beetles can decimate bean crops; beetles overwinter as adults and undergo 2-3 generations per year
Management
Some bean varieties may be less attractive hosts for the beetle, e.g. snapbeans are preferred hosts over lima beans; early varieties may escape damage form beetles beetle populations can be reduced by remove overwintering sites such as brush and leaves on the ground; handpick larvae and adults; brush eggs from leaves and destroy; apply insecticidal soap to leaf undersides if infestation is heavy

Thrips (Western flower thrips, Onion thrips, etc.)
Frankliniella occidentalis
Thrips tabaci

Symptoms
If population is high leaves may be distorted; leaves are covered in coarse stippling and may appear silvery; leaves speckled with black feces; insect is small (1.5 mm) and slender and best viewed using a hand lens; adult thrips are pale yellow to light brown and the nymphs are smaller and lighter in color
Cause
Insect
Comments
Transmit viruses such as Tomato spotted wilt virus; once acquired, the insect retains the ability to transmit the virus for the remainder of its life
Management
Avoid planting next to onions, garlic or cereals where very large numbers of thrips can build up; use reflective mulches early in growing season to deter thrips; apply appropriate insecticide if thrips become problematic

Aphids (Pea aphid, Bean aphid, Cowpea aphid, Melon aphid, Peach aphid, etc.)
Acyrthosiphon pisum
Aphis
spp.
Myzus persicae

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 plant
Cause
Insects
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

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 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

Root knot nematode
Meloidogyne spp.

Symptoms
Galls on roots which can be up to 3.3 cm (1 in) in diameter but are usually smaller; reduction in plant vigor; yellowing plants which wilt in hot weather
Cause
Nematode
Comments
Galls can appear as quickly as a month prior to planting; nematodes prefer sandy soils and damage in areas of field or garden with this type of soil is most likely
Management
Plant resistant varieties if nematodes are known to be present in the soil ;check roots of plants mid-season or sooner if symptoms indicate nematodes; solarizing soil can reduce nematode populations in the soil and levels of inoculum of many other pathogens

Enation mosaic
Pea enation mosaic virus (PEMV)

Symptoms
Blister-like outgrowths (enations) on underside of leaves and on pods; leaves with translucent areas; severely deformed plants
Cause
Virus
Comments
Virus is transmitted by several species of aphid
Management
In areas where virus is a problem, early planting may allow plants to mature before virus becomes severley damaging; control of aphid populations and hosts plants which act as reservoirs can help control spread of virus

Mosaic
Red clover vein mosaic virus (RCVMV)

Symptoms
Mottled patterns on leaves; yellow leaf veins; distorted leaves; stunted plants which often die
Cause
Virus
Comments
Virus transmitted by aphids; aphids acquire virus from perennial hosts such as clover and alfalfa and spread to peas
Management
No known resistance to virus, control depends on control of aphid populations; apply appropriate insecticide if aphid populations are significant

Streak
Pea streak virus (PSV)

Symptoms
Purple or brown necrotic streaks on stems and petioles; small brown necrotic lesions on leaves; brown, sunken lesions on pods; pods fail to fill properly or do not fill at all; pods discolored; dieback of growing tips; chlorosis of leaves
Cause
Virus
Comments
Transmitted by pea aphids; alfalfa most important perennial virus reservoir
Management
No resistance to virus; avoid planting peas close to established alfalfa; insecticide application of little benefit due to short time aphid requires to transmit virus but can help control secondary spread