Common Pests and Diseases That Affect Broccoli Farming In Kenya
Broccoli, Brassica oleracea, is an herbaceous annual or biennial grown for its edible flower heads which are used as a vegetable. The broccoli plant has a thick green stalk, or stem, which gives rise to thick, leathery, oblong leaves which are gray-blue to green in color. The plant produces large branching green flower heads covered with numerous white or yellow flowers. Broccoli can be annual or biennial depending on the variety and can grow to 1 m (3.3 ft) in height. Broccoli may also be referred to as sprouting broccoli and likely originates from the Mediterranean although the exact location has not been determined.
Broccoli is a cool-season vegetable that can be grown in Kenya during the spring and fall. It is a relatively easy crop to grow, and it can be harvested in about 70-80 days.
Choose a planting site
Broccoli prefers full sun and well-drained soil. It is important to avoid planting broccoli in areas where water tends to pool. If your soil is heavy clay, you may need to amend it with sand or compost to improve drainage.
Prepare the soil
Before planting, loosen the soil to a depth of 12-20 inches. Add a 2-3 inch layer of compost or manure to the soil. You can also add a balanced fertilizer, such as 10-10-10.
Plant the broccoli
Broccoli can be planted from seed or from transplants. If you are planting from seed, sow the seeds directly in the ground 4-6 weeks before the last frost date. If you are planting from transplants, plant them 2-3 weeks before the last frost date.
Space the broccoli plants 12-18 inches apart in rows that are 24-36 inches apart.
Water and fertilize the broccoli
Broccoli needs regular watering, especially during hot weather. Water the broccoli deeply once a week, or more often if the weather is hot and dry.
Fertilize the broccoli every 2-3 weeks with a balanced fertilizer, such as 10-10-10. You can also use a fertilizer that is specifically designed for broccoli.
Harvest the broccoli
Broccoli is ready to harvest when the heads are tightly closed and firm. The heads should be about 6-8 inches in diameter.
To harvest the broccoli, cut the head off of the plant with a sharp knife. Be sure to leave about 2 inches of stem attached to the head.
Harvesting broccoli multiple times
Some broccoli varieties can be harvested multiple times. To do this, harvest the outer heads of the plant as they mature. This will encourage the plant to produce more side shoots.
Problems Faced By Broccoli Farmers
There are two basic types of problems with any vegetable, including Broccoli: pest problems and health problems. Broccoli is no exception. If you are losing plants at any growth stage, it is good to find out whether the problem is a pest or a problem with the plant’s health. A lot of pests visit the Brassicas. Humans have been growing Broccoli, Cabbage, and other members of the Brassicas family for thousands of years.
Some pests have become as attached to these hearty, nutritious vegetables. Some fungi and diseases can destroy the Broccoli crop as well. But if you are paying attention and taking preventive measures, it will be easy to keep your Broccoli crop healthy and grow stronger.
Common Pests and Diseases of broccoli
Diseases
Category : Fungal
Alternaria leaf spot Alternaria brassicae
Symptoms
Cause
Comments
Management
Plant only pathogen-free seed; rotate crops; applications of appropriate fungicides control disease when present
Black rot Xanthomonas campestris
Symptoms
Cause
Comments
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
Clubroot Plasmodiophora brassicae
Symptoms
Cause
Comments
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
Powdery mildew Erysiphe cruciferarum
Symptoms
Cause
Comments
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
Cause
Comments
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
Cause
Comments
Management
Rotate crops; plant only disease-free seed; apply appropriate fungicide if disease becomes a problem
Category : Bacterial
Black leg Phoma lingam
Symptoms
Cause
Comments
Management
Use disease free seed or treat with hot water to remove fungus prior to planting; remove and destroy crop debris after harvest or plow deeply into soil
Category : Fungal, Oomycete
Downy mildew Hyaloperonospora parasitica
Symptoms
Cause
Comments
Management
Remove all crop debris after harvest; rotate with non-brassicas; it is possible to control downy mildew with the application of an appropriate fungicide
Wirestem (Damping-off) Rhizoctonia solani
Symptoms
Cause
Comments
Management
Plant pathogen-free seed or transplants that have been produced in sterilized soil; apply fungicide to seed to kill off any fungi; shallow plant seeds or delay planting until soil warms
Category : Viral
Ring spot Mycosphaerella brassicicola
Symptoms
Cause
Comments
Management
Refrain from planting in areas known to have had disease previously; rotate crop to non-brassicas; sanitize tools and equipment regularly; apply appropriate fungicide if disease is identified in crop
Pests
Category : Insects
Diamondback moth Plutella xylostella
Symptoms
Cause
Comments
Management
Larvae can be controlled organically by applications of Bacillus thurengiensis or Entrust; application of appropriate chemical insecticide is only necessary if larvae are damaging the growing tips of the plants
Flea beetle (Crucifer flea beetle) Phyllotreta cruciferae
Symptoms
Cause
Comments
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
Large cabbage white (Cabbageworm) Pieres rapae
Symptoms
Cause
Comments
Management
Hand pick caterpillars from plants and destroy; scrape eggs from leaves prior to hatching; apply appropriate insecticide if infestation is very heavy
Thrips (Western flower thrips, Onion thrips, etc.) Frankliniella occidentalis
Thrips tabaci
Symptoms
Cause
Comments
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
Category : Nematodes
Root knot nematode Meloidogyne spp.
Symptoms
Cause
Comments
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
Reference: https://plantvillage.psu.edu/topics/broccoli/infos