Description
Basil, Ocimum basilicum, is a short lived annual or perennial plant in the family Lamiaceae grown for its leaves which are used as a herb. The basil plant grows from a thick taproot and has silky green opposite (paired) oval leaves which grow to be 3–11 cm (1.2–4.3 in) long and 1–6 cm (0.4–2.4 in), branching out from the central stem. The plant produces small white flowers which are clustered on a single spike at the top of the plant. Basil plants are often grown as annuals but may survive for several seasons with some care and can reach heights between 30 and 130 cm (11.8 and 51.2 in) depending on the variety. Basil may also be referred to as sweet basil, St. Joseph's wort, thai basil, lemon basil or holy basil depending on the variety and is native to India and other tropical regions of Asia.
Crop Details
Scientific Name: Ocimum basilicum
Common Name: basilico (Italian); basilic (Fr); तुलसी (Hindi); โหระพา (Thai)
Basil plant flowering
Close-up of basil flowers
Different basil varieties
Basil leaves
Basil
Uses & Benefits
Basil is an annual herb of the mint family (Lamiaceae), grown for its aromatic leaves. Basil is likely native to India and is widely grown as a kitchen herb. The leaves are used fresh or dried to flavour meats, fish, salads, and sauces; basil tea is a stimulantBasil is commonly used as a fresh or dried herb in cooking and is popularly used in beverages in Southeast Asia.
Essential oil can be extracted from the leaves and used in cosmetics, dental products and perfume.
Varieties
The following are some of the common basil varieties;
Thai basil: It is commonly used in Thai and Southeast Asian cuisine and adds a sweet licorice flavor to a dish)
Lemon basil: It has small leaves with a tangy lemon flavor.
Cinnamon basil: It is native to Mexico and adds a hint of cinnamon to a dish (typically paired with legumes or spicy stir-fried vegetables).
Sweet basil: It is commonly found in Italian dishes and is very popular. It has a unique taste that is similar to licorice and clove.
Propagation
Basic requirements
Basil is a warm season crop which will grow optimally in areas where daytime temperatures are consistently above 21°C (70°F) and nighttime temperatures stay above 10°C (50°F). Basil is very sensitive to frost and will need protected if a late cold snap is forecast. The plant will grow best in a fertile, moist soil with a pH between 6 and 7. Basil requires around 6–8 hours of sun every day and benefits from some shade in the afternoon.
Growing from Seed
Basil seeds should be sown indoors 6–8 weeks before planting outside. Sow seeds in a sterile seed starting mix in seed trays or pots 0.2–1.0 cm (0.08–0.4 in) deep and water gently. Ensure the temperature remains between 15.5 and 27°C (60–80°F). Seeds should germinate in about 5 days at 21°C (70°F).
General Care and Maintenance
Basil seedlings can be transplanted to the garden when they are between 6 and 8 weeks old, about 2 weeks after the last frost date. Plants should be spaced approximately 30 cm (12 in) apart, allowing 45 cm (18 in) between rows. Pinching back the growing tip of the plants after transplanting will encourage the growth of new shoots. Apply mulch to help retain soil moisture and minimizes weeds around the plants. Watering should be done more often if the crop is grown outdoors. To prevent downy mildew, water the base of the crop instead of the leaves and stems. Manual weeding is encouraged and should be done carefully. Weeds close to the plants should be cut off at ground level.
Harvesting
Basil leaves can begin to be harvested any time after the plants have reached a height of 15–20 cm (6–8 in). Harvest leaves by pinching the leaves from the tips of the stems to encourage the more branching. Leaves should be pinched regularly to keep the plants productive and prevent them from going to seed.
Young basil plants
Basil seedlings
References
CABI Crop Protection Compendium. (2008). Ocimum basilicum datasheet. Available at: http://www.cabi.org/cpc/datasheet/36858. [Accessed 06 November 14]. Paid subscription required.
Meyers, M. (2003). Basil: An Herb Society of America Guide. The Herb Society of America, Ohio, USA. Available at: http://www.herbsociety.org/factsheets/Basil%20Guide.pdf. [Accessed 06 November 14]. Free to access.
MacKenzie, J. (Ed) (2007). Growing basil. University of Minnesota Extension. Available at: http://www.extension.umn.edu/garden/yard-garden/vegetables/growing-basil/index.html. [Accessed 06 November 14]. Free to access.
Tran, T. (2011). Basil Diseases. Cornell University Department of Plant Pathology and Plant-Microbe Biology. Available at: http://plantclinic.cornell.edu/factsheets/basildiseases.pdf. [Accessed 06 November 14]. Free to access.
Common Pests and Diseases
Diseases
Category : Fungal
Cercospora leaf spot
Cercospora ocimicola
Cercospora leaf spot symptoms on basil
Cercospora leaf spot symptoms on basil
Cercospora leaf spot symptoms on basil
Cercospora leaf spot symptoms on basil
Symptoms
Circular to irregular dark spots on leaves with light centers
Cause
Fungus
Comments
Management
Avoid overhead irrigation and splashing plants with water, instead water plants from the base and apply a layer of mulch around the plants to reduce water splash; remove and destroy any symptomatic leaves; minor infections can be controlled by spraying weekly with a fungicide containing potassium bicarbonate
Downy mildew
Peronospora belbahrii
Masses of purplish sporangia on the undersurface of a leaf.
Chlorotic (yellow) patches (symptoms) on the upper surface of a basil leaf with downy mildew
Downy mildew symptoms on basil
Downy mildew symptoms on basil foliage
Heavy spore production on the undersurface of the leaf may look like dust or dirt on the tissue.
Dark-colored fungal growth (sign) on the bottom surface of a basil leaf opposite the chlorotic (yellow) patches (symptoms) on the upper surface of a leaf with downy mildew
Downy mildew symptoms on basil foliage
Downy mildew symptoms on basil foliage
Fruiting Bodies (sporangia) on lower surface of leaf
Downy mildew symptoms on basil foliage
Downy mildew symptoms on basil foliage
Downy mildew symptoms on basil foliage
Symptoms
Yellowing leaves; discoloration often begins around middle vein and spreads outwards; gray fuzzy or downy growth on lower surface of the leaves; brown to black angular necrotic patches on the plant.
Cause
Fungus
Comments
Management
Grow tolerant varieties; apply protective fungicide; ensure good air circulation around greenhouse grown plants; use drip irrigation to avoid wetting foliage.
Fusarium wilt
Fusarium oxysporum
Symptoms
Yellow, wilting leaves; brown streaks on lower surface of leaves; stunted growth; death of plant.
Cause
Fungus
Comments
Management
Use only disease free seed; treat seeds with hot water to kill fungi prior to planting; if present in field, rotate crop every 2-3 years with crop other than basil or mint.
Gray mold
Botrytis cinerea
Conidiophores with whitish conidial heads
Gray mold infected basil stem
Conidiophores with conidia
Conidiophores with conidia arising from infected tissue
Wilted foliage on cankered stem at left due to grey mold infection
Symptoms
Dense, brown to gray fuzzy growth on stems and leaves and fallen plant debris; leaves dying and dropping from plant; severe lesions on stem may cause plant death.
Cause
Fungus
Comments
Management
No chemical treatment available; avoid working in field in rainy conditions; remove infested leaves and/or plants; avoid overhead irrigation.
Leaf spot
Pseudomonas cichorii
Colletotrichum spp.
Infected stem
bacterial leaf spot infected leaves
Symptoms of bacterial leaf spot (Pseudomonas cichorii) on basil leaves
Symptoms on leaf
bacterial leaf spot (Pseudomonas cichorii) symptom
Symptoms on leaves and stem
Infected plant
Symptoms on stem
Symptoms of bacterial leaf spot on basil foliage
Symptoms
Angular or irregular brown or black water-soaked spots on leaves; streaks on stems.
Cause
Bacteria
Comments
Management
No treatment when present; use disease free seed and/or transplants; use wide field spacing to promote air circulation around plants; remove diseased leaves from plant and soil surface immediately.
Root rot
Rhizoctonia solani
Pythium spp.
Symptoms
Failure of seeds to germinate; germinated seedlings collapsing; brown, shriveled area at base of stem; roots brown and water-soaked.
Cause
Fungus
Comments
Management
Plant seeds in sterile soil; plant basil in well-draining soils.
Category : Other
Slugs & snails (Gray garden slug, Spotted garden slug, Brown garden snail, European garden snail , etc.)
Decoratus reticulatum
Limax maximus
Helix aspersa
Cornu aspersum
dusky slug (Arion subfuscus)
Cartusian snail (Monacha cartusiana) feeding on leaves
amber snails adult
European brown snail
Banded wood snail
Gray garden slug
Symptoms
Irregularly shaped holes in leaves and stems; flowers and fruit may also be damaged if present; if infestation is severe, leaves may be shredded; slime trails present on rocks, walkways, soil and plant foliage; several slug and snail species are common garden pests; slugs are dark gray to black in color and can range in size from 2.5 to 10 cm (1-4 in); garden snails are generally smaller and possess a rounded or spiral shell.
Cause
Mollusc
Comments
Management
Practice good garden sanitation by removing garden trash, weeds and plant debris to promote good air circulation and reduce moist habitat for slugs and snails; handpick slugs at night to decrease population; spread wood ashes or eggshells around plants; attract molluscs by leaving out organic matter such as lettuce or grapefruit skins, destroy any found feeding on lure; sink shallow dishes filled with beer into the soil to attract and drown the molluscs; chemical controls include ferrous phosphate for organic gardens and metaldehyde (e.g. Buggeta) and carbaryl (e.g Sevin bait) for non-organic growers.
Pests
Category : Insects
Aphids (Various spp.)
Various
Aphid on basil
Praying Mantis feeding on basil aphid
Winged adult aphid
Aphid feeding on basil
Aphid
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
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.
Cutworms, loopers, owlet moths, and underwings
Spodoptera exigua
Trichoplusia ni
and others
Larave on basil leaf
Loopers
Cutworm damage
Larva
Larvae feeding on basil leaf
Larave
Symptoms
The early stage larvae feeds on terminal clusters. Later stage larvae skeletonize the leaves. Also, they will cut the seedling stem near the base resulting in heavy loss.
Cause
Insect
Comments
Management
Hand pick the larvae and kill them. Remove and destroy weeds and crop residue. Spray biocontrol agent (bacteria/virus) to kill insects. If infestation is severe, spray suitable insecticide.
Flea beetle
Phylotreta spp.
Flea beetle on basil
Flea beetle and damage on basil leaf
Adult flea beetle on a leaf.
Flea beetle damage to leaves
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
Insects
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.
Grasshoppers
Various sp.
Grasshopper feeding on basil leaf
Grasshopper feeding on soybean leaves
Grasshopper on basil
Initial stage grasshopper nymphs damage
Symptoms
Both adult and nymphs feed on foliage, buds, and tender stems. The first stage nymphs feed on leaves by forming circular holes. As the insect develops it feeds on entire foliage. Grasshoppers are very eager feeders.
Cause
Insect
Comments
Management
Encourage birds in the field. If population is severe, spray suitable insecticide.
Japanese beetle
Popillia japonica
Japanese beetle adult
Adult Japanese beetle
Japanese beetle (Popillia japonica) larvae
Adult Japanese beetle on basil leaf
Symptoms
Leaves skeletonized (only veins remaining); flowers and buds damaged; plant damage may be extensive; adult insect is a metallic green-bronze beetle with tufts of white hair protruding from under wing covers on each side of the body; adult beetles are approximately 13 mm in length; larvae are cream-white grubs which develop in the soil.
Cause
Insect
Comments
Management
If beetles were a problem in the previous year, use floating row covers to protect plants or spray kaolin clay; adult beetles can be hand picked from plants and destroyed by placing in soapy water; parasitic nematodes can be applied to soil to reduce the number of overwintering grubs; insecticidal soaps or neem oil can help reduce beetle populations.
Leafminers
Liriomyza spp.
Leafminer larave
Larvae still with in leaf mine
Leafminer fly
Leafminer damage
Leafminer pupae
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; larave hatch and feed on leaf interior.
Cause
Insects
Comments
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.
Category : Nematodes
Root knot nematode
Meloidogyne spp.
Galls or nodules associated with the root system caused by root-knot nematodes. May be small or large.
Galls on a bean root infested with the root knot nematode Meloidogyne spp. in the field.
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
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.