Mustard

Description

Mustards, (Brassica spp.) are herbaceous annual plants in the family Brassicaceae grown for their seeds which are used as a spice. Mustard plants are thin herbaceous herbs with yellow flowers. The leaves of the plant are toothed, lobed, and occasionally have the larger terminal lobes. Plants can reach 16 cm (6.3 in) in length. The yellow flowers grow in spike like clusters of 2–12 flowers and individual flowers are 8 mm (0.3 in) in diameter. The seeds are red to brown in color and produced from each flower. Mustard can grow 1.2-2 m (4–6.6 ft) in height and as an annual plant, survives only one growing season. Mustard may also be referred to as mustard, brown mustard, red mustard, yellow mustard or wedlock and is believed to have originated in the temperate regions of Europe.


Uses

The leaves and shoots of the mustard plant are consumed as a vegetable in some countries. Mustard seed is incorporated into seasonings and dressings. Mustard may be grown as a cover crop in rotation with other vegetables.


Propagation


Basic requirements
Mustard grows very well in cool climates with short growing seasons, at temperatures as low as 4.4°C (40°F). Seedlings can tolerate some light frost but severe frost will kill the plants. The mustard plant can be grown in sandy, loamy or clay soils with a pH between 4.9 and 8.2 and prefers moist soil. The plant will tolerate partial shade.

Propagation
Mustards is propagated from seed and due to the small size of the seeds, should be planted in a well prepared seed bed which is firm and flat. Mustard seeds should be sown in Spring once soils have warmed to 4.4–7.2°C (40–45°F) and should be planted at a depth of 1.25–2.5 cm (0.5–1.0 in) at a density of 8–14 lbs of seeds per acre. The seed can be spread by broadcasting in the home garden or, in the case of commercial production, using a seed drill. Mustard generally matures in 80–85 days.

General care and maintenance
Weeds can cause huge losses in mustard cultivation as they quickly out compete seedlings and are difficult to eradicate once established. The best method of preventing weed growth in a mustard field is to plant seeds at the appropriate depth. Shallow planted seeds germinate rapidly, allowing the development of a uniform plant stand. Established plants are less susceptible to competition from weeds. soil should be tested to determine nutrient requirements prior to planting. Mustard will benefit from the addition of supplemental nitrogen and this is generally applied at a rate of 100–120 lb per acre.

Harvesting
Mustard is generally ready to harvest 80 to 85 days after planting. The crop should be harvested promptly to reduce losses to shattering. In commercially grown fields the recommended method of harvest is swathing. The plants should be cut just below the height of the lowest seed pods. In the home garden, mustard can be harvested by hand by cutting the plants. The seeds can then be recovered from the pods and dried for storage.


References

CABI Crop Protection Compendium. (2013). Brassica nigra (black mustard)datasheet. Available at: http://www.cabi.org/cpc/datasheet/10097. [Accessed 25 February 15]. Paid subscription required.

Oplinger, E. S., Oelke, E. A., Putnam, D. H., Kelling, K. A., Kaminsid, A. R., Teynor, T. M., Doll, J. D. & Durgan, B. R. (1991). Mustard. In: Alternative Field Crops Manual. University of Wisconsin Cooperative Extension. Available at: https://www.hort.purdue.edu/newcrop/a.... [Accessed 25 February 15]. Free to access.

Snapp, S., Date, K., Cichy, K. & O’Neil, K. (2006). Mustards – a Brassica cover crop for Michigan. Michigan State University, Department of Crop and Soil Sciences. Available at: http://forage.msu.edu/wp-content/uplo.... [Accessed 25 February 15]. Free to access.


Common Pests and Diseases

Bacterial black rot
Xanthomonas campestris

Symptoms
Irregularly shaped dull yellow areas along leaf margins which expand to leaf midrib and create a characterstic "V-shaped" lesion; lesions may coalesce along the leaf margin to give plant a scorched appearance
Cause
Bacterium
Comments
Pathogen is spread via infected seed or by splashing water and insect movement; disease emergence favored by warm and humid conditions
Management
Primary method of controlling black rot is through the use of good sanitation practices; rotate crops to non-cruciferous crops every 2 years; plant resistant varieties; control cruciferous weed species which may act as a reservoir for bacteria; plant pathogen-free seed

Alternaria leaf spot (Black spot, Gray spot)
Alternaria brassicae

Symptoms
Small dark spots on leaves which turn brown to gray; lesions may be round or angular and may possess a purple-black margin; lesions may form concentric rings, become brittle and crack in center; dark brown elongated lesions may develop on stems and petioles
Cause
Fungi
Comments
May become a problem on cabbage during cool, wet periods
Management
Plant only pathogen-free seed; rotate crops; applications of appropriate fungicides control disease when present

Clubroot
Plasmodiophora brassicae

Symptoms
Slow growing, stunted plants; yellowish leaves which wilt during day and rejuvenate in part at night; swollen, distorted roots; extensive gall formation
Cause
Fungus
Comments
Can be difficult to distinguish from nematode damage; fungus can survive in soil for periods in excess of 10 years; can be spread by movement of contaminated soil and irrigation water to uninfected areas
Management
Once the pathogen is present in the soil it can survive for many years, elimination of the pathogen is economically unfeasible; rotating crops generally does not provide effective control; plant only certified seed and avoid field grown transplants unless produced in a fumigated bed; applying lime to the soil can reduce fungus sporulation

Downy mildew
Peronospora parasitica

Symptoms
Irregular yellow patches on leaves which turn light brown in color; fluffy gray growth on the undersides of the leaves
Cause
Fungus
Comments
Disease emergence favored by cool, moist conditions
Management
Remove all crop debris after harvest; rotate with non-brassicas; application of appropriate fungicides may be required if symptoms of disease are present

Powdery mildew
Erysiphe cruciferarum

Symptoms
Small white patches on upper and lower leaf surfaces which may also show purple blotching; patch3es coalesce to form a dense powdery layer which coats the leaves; leaves become chlorotic and drop from plant
Cause
Fungus
Comments
Disease emergence favored by dry season, moderate temperatures, low humidity and low levels of rainfall
Management
Plant resistant varieties; rotate crops; remove all crop debris after harvest; remove weeds; avoid excessive application of nitrogen fertilizer which encourages powdery mildew growth; powdery mildew can be controled by application of sulfur sprays, dusts or vapors

Sclerotinia stem rot (White mold)
Sclerotinia sclerotiorum

Symptoms
Irregular, necrotic gray lesions on leaves; white-gray leions on stems; reduced pod set; shattering seed pods
Cause
Fungus
Comments
Disease emergence favors moderate to cool temperatures and high humidity
Management
Rotate crop to non-hosts (e.g. cereals) for at least 3 years; control weeds; avoid dense growth by planting in adequately spaced rows; apply appropriate foliar fungicides

White rust
Albugo candida

Symptoms
White pustules on cotyledons, leaves, stems and/or flowers which coalesce to form large areas of infection; leaves may roll and thicken
Cause
Fungus
Comments
Fungus can survive for long periods of time in dry conditions; disease spread by wind
Management
Rotate crops; plant only disease-free seed; apply appropriate fungicide if disease becomes a problem

White leaf spot
Mycospaerella capsellae

Symptoms
Small, necrotic, brown spots on leaf tips or margins that matures to light gray or white with the original dark spot in center; margins of lesions may be darker; lesions may coalesce to form large chlorotic areas and cause defoliation
Cause
Fungus
Comments
Symptoms easily confused with downy mildew; disease emergence favored by wet leaves and cool temperatures
Management
No known plant resistance to white leaf spot so control relies on cultural practices such as rotating crops and removing weeds; application of appropriate fungicide may help control the disease

Flea beetles
Phyllotreta spp.

Symptoms
Small holes or pits in leaves that give the foliage a characteristic “shothole” appearance; young plants and seedlings are particularly susceptible; plant growth may be reduced; if damage is severe the plant may be killed; the pest responsible for the damage is a small (1.5–3.0 mm) dark colored beetle which jumps when disturbed; the beetles are often shiny in appearance
Cause
Insect
Comments
Younger plants are more susceptible to flea beetle damage than older ones; older plants can tolerate infestation; flea beetles may overwinter on nearby weed species, in plant debris or in the soil; insects may go through a second or third generation in one year
Management
In areas where flea beetles are a problem, floating row covers may have to be used prior to the emergence of the beetles to provide a physical barrier to protect young plants; plant seeds early to allow establishment before the beetles become a problem - mature plants are less susceptible to damage; trap crops may provide a measure of control - cruciferous plants are best; application of a thick layer of mulch may help prevent beetles reaching surface; application on diamotecoeus earth or oils such as neem oil are effective control methods for organic growers; application of insecticides containing carbaryl, spinosad, bifenthrin and permethrin can provide adequate control of beetles for up to a week but will need reapplied

Cabbage aphid
Brevicoryne brassicaea

Symptoms
Large populations can cause stunted growth or even plant death; insects may be visible on the plant leaves and are small, grey-green in color and soft bodied and are covered with a white waxy coating
Cause
Insect
Comments
Cabbage aphids feed only on cruciferous plants but may survive on related weed species
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

Cabbage aphid
Brevicoryne brassicaea

Symptoms
Large populations can cause stunted growth or even plant death; insects may be visible on the plant leaves and are small, grey-green in color and soft bodied and are covered with a white waxy coating
Cause
Insect
Comments
Cabbage aphids feed only on cruciferous plants but may survive on related weed species
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

Mosaic
Turnip mosaic virus (TuMV)

Symptoms
Mottled pattern on leaves; veinclearing; downward rolling of leaves;
Cause
Virus
Comments
Virus transmitted by many species of aphid, including the peach aphid and cabbage aphid
Management
Adjust planting date to avoid peak aphid activity; reflective mulches may deter aphids from crop; application of appropriate insecticides may help control secondary spread of virus but will not help plants already infected