Basil

Introduction

Basil (Ocimum spp.) is a member of the mint family. There are several species and numerous interspecific hybrids. The most common culinary type is sweet basil, O. basilicum, which also has purple and lemon-scented cultivars. Specialty types include Thai (O. tenuiflorum), lemon (O. americanum x O. citridorum) and small-leaved bush types of various species and crosses. Basil seed is not always true to type. Try to obtain high-quality seed that is uniform with a high germination percentage.

Types and Varieties

Basil Varieties
Sweet/Pesto Purple
Amazel - BDM Red Rubin - BDM
Aroma 2 - F Dark Opal
Elidia - F (intermediate) Amethyst Improved
Everleaf - BDM, F (intermediate) Purple Ruffles
Eleonora  - BDM  
Genovese Bush
Italian Large Leaf Spicy Bush
Newton - F Spicy Globe
Nufar - F  
Prospera - BDM Scented
Rutgers Devotion - BDM Sweet Dani (lemon) - BDM
Rutgers Obsession - BDM, F Lime Basil - BDM
Rutgers Passion - BDM Holy Basil (medicinal)
Rutgers Thunderstruck - BDM Cinnamon Basil
   
Thai  
Sweet Thai  
F: Some resistance to Fusarium wilt, BDM: Some resistance to basil downy mildew.

NOTE:  Basil downy mildew (Peronospora belbarhii) was first reported in the United States 2007. Eleonora and Everleaf (aka Pesto Party) were the first downy mildew resistant sweet basil cultivars available in the US. Varieties with stronger resistance have since been released: Prospera, Amazel, and the Rutgers varieties Obsession, Devotion, Passion, and Thunderstruck. In trials conducted in NY in 2018, Amazel and Prospera showed the strongest disease resistance, followed by Thunderstruck, Passion, Devotion, and Obsession. None of these varieties are fully resistant to the disease but all will develop disease more slowly than fully susceptible varieties. Thai, lemon, and spice basil varieties are generally less susceptible than sweet basil varieties.

Soil Fertility

Basil grows well in a warm, well-drained soil in a wide pH range, although the typical vegetable crop range of pH 6.0-6.8 is ideal. Although adequate fertility is required (see Table below), excess nitrogen applications can cause post-harvest discoloration and reduce flavor. Basil benefits from a sidedress application of nitrogen after the first or second cutting.

PLANT NUTRIENT RECOMMENDATION ACCORDING TO SOIL TEST RESULTS FOR BASIL

BASIL

NITROGEN (N)* LBS PER ACRE

   PHOSPHORUS (P) LBS P2O5   PER ACRE

   POTASSIUM (K) LBS K2O      PER ACRE

SOIL TEST RESULTS

 

VERY LOW

LOW

OPTIMUM

ABOVE OPTIMUM

VERY LOW

LOW

OPTIMUM

ABOVE OPTIMUM

Broadcast and Incorporate

100

120

60

30

0

100

50

25-50

0

Sidedress after 1st or 2nd cutting

15-30

0

0

0

0

0

0

0

0

TOTAL RECOMMENDED

115-130

120

60

30

0

100

50

25-50

0

*SEE PLANT NUTRIENTS FOR INFORMATION ON NUTRIENT MANAGEMENT AND APPLICATION.

Planting

In New England, basil is most commonly transplanted, but because it is highly sensitive to cold (low 40s), it should not be set out until after danger of frost. Seeds will germinate within 4-8 days at temperatures of 68-74ºF. Transplant at approximately 6 weeks old. Topping when plants are 5-6 in. tall encourages branching. Basil is often spaced at 6-12 in. between plants in double rows. Tighter spacing will promote longer shoots for bunching.

If field soils are warm enough, basil can be direct-seeded in a well-prepared seedbed at a spacing of 8-10 seeds per foot and later thinned. Basil can be direct sown using an onion seeder. Pelleted seeds are also available to facilitate outdoor seeding.

Field Culture

Because of the lack of herbicides for weed control and the need for warm temperatures, basil is well suited to growing in raised beds covered with black plastic mulch. Drip irrigation allows consistent application of water while also reducing foliar diseases. Cultural management of insects, diseases and weeds is necessary because few pesticides are registered for use on basil.  Summer weight row covers can help to exclude insect pests and create a more humid, tropical environment that is reminiscent of basil's native South Asian habitat. Some growers say that basil is more fragrant when grown in a wind-protected environment. However, high humidity is conducive to downy mildew, the most important pest of basil in recent years.

Harvest and Storage

Basil can be lightly harvested by pruning as early as 6 weeks after planting, with regular harvests starting a few weeks after that. Harvests should take place in the morning after the dew has left the plants. Depending on the intended use and market, individual leaves or entire stems may be harvested. Basil grown for culinary use should be harvested before flowering. Flavor will be adversely affected if allowed to flower. If grown for essential oil production, it should be harvested at full bloom. Plants will set seed if flower spikes are not removed as they appear. Sequential plantings can help ensure continuous production of quality shoots and leaves. However, harvesting basil by mid-summer can often prevent crop destruction from downy mildew.

Damage can be caused by rough handling, desiccation and chilling (<40°F). Cooling can be accomplished by rinsing in 55°F water, but foliage should be dried completely prior to packing. Maintenance of clean growing conditions, free from mud splash, enables some growers to avoid contact with water. Basil should then be stored at temperatures above 54°F.

Disease Control

NOTE: For the disease control products listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same active ingredient. Please see Table 25 and Fungicides and Bactericides Alphabetical Listing by Trade Name for more information on products with the same active ingredients.

The symbol OG   indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

PESTICIDE USE IN GREENHOUSES AND HIGH TUNNELS:

Pesticides can be used on high tunnel and greenhouse crops if: 1) the crop and pest/disease is on the label, AND the products specifically says it can be used in the greenhouse; OR 2) the crop and pest/disease is on the label, AND the product is ‘silent’ about use in the greenhouse in the greenhouse. Products that specifically prohibit greenhouse use cannot be used in greenhouses or high tunnels regardless of the crops or pests/diseases listed on the label.

Purchase disease-free seed. Use resistant varieties where feasible. Promptly remove any stock plants that are diseased or low in vigor. Use separate greenhouses for herb production and keep stock plants separate from production areas. There are few fungicides or bactericides registered for herbs.

Bacterial Leaf Spot (Pseudomonas cichorii )

Disinfect all benches, equipment, and pots. Purchase culture-indexed plants and disease-free seed. Avoid overhead irrigation. Discard infected plants. Clean production areas thoroughly after harvest as bacteria can survive in dead leaves.

Botrytis blight and stem canker (Botrytis cinerea)

Management of environmental conditions such as temperature, relative humidity and duration of leaf wetness is vital to Botrytis control. Control weeds and remove plant debris between crops and during production. Provide good air circulation and reduce humidity within the plant canopy by proper plant spacing, plant height, and fertility. Water in the morning, never late in the day.

Bacillus amyloliquefaciens F727 (StargusOG): 2.0 to 4.0 qt/A; PHI 0d, REI 4h, Group BM02. Apply preventatively in a minimum of 50.0 gallons of water/A.

cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 7d, REI 12h, Groups 9 & 12. Do not make more than 2 consecutive applications.

potassium bicarbonate (PB 133, AKA MilStopOG): 2.5 to 5.0 lb/100.0 gal; PHI 0d, REI 1h, Group NC. See label for small volume application rates.

Ulocladium oudemansii U3 strain (BotryStopOG): 2.0 to 4.0 lbs/A; REI 4h, Group NC. Begin application when conditions are conducive to disease development.

Damping-off, Crown and Root Rot (Pythium spp., Rhizoctonia spp., Fusarium spp. & Phytophthora spp.)

Use pasteurized soil or soil-less mixes for transplant production. Disinfect all flats, pots, and tools. Use bottom heat to promote rapid seed germination. Avoid over-watering, over-fertilizing, and overcrowding. Promptly rogue out infected plants. Manage fungus gnats and shoreflies. 

Bacillus amyloliquefaciens F727 (StargusOG): 2.0 to 4.0 qt/A; PHI 0d, REI 4h, Group BM02. Apply preventatively in a minimum of 50.0 gallons of water/A.

mefenoxam (Ridomil Gold SL): 0.5 to 1.0 pt/A; PHI 21d, REI 48h, Group 4. Pythium and Phytophthora ONLY.

fludioxonil (Maxim 4FS): 0.08 to 0.16 oz/100 lb seed; REI 12h, Group 12. For protection against seed-borne and soil-borne fungi. Does not control Pythium or Phytophthora.

potassium phosphite (K-Phite): 1.0 to 4.0 qt/A; PHI 0d, REI 4h, Group NC. Apply in a minimum of 20.0 gal water/A.

Downy Mildew (Peronospora belbarhii)

Downy Mildew of basil can be serious in both field and greenhouse production. Start with certified, disease-free seed. Scout crops regularly and promptly remove and destroy infected plants. Reduce leaf wetness duration by plant spacing, improving air circulation, and watering when plants will dry quickly. In the greenhouse, use a combination of heating and venting to reduce humidity and condensation, especially when warm days are followed by cool nights. Varieties with some resistance to downy mildew are available (see varieties).

azoxystrobin (Heritage): 0.18 oz/A; PHI 0d, REI 4h, Group 11. See label for instructions.

Bacillus amyloliquefaciens F727 (StargusOG): 2 to 4 qt/A; PHI 0d, REI 4h, Group BM02. Apply preventatively in a minimum of 50.0 gallons of water/A.

copper (Cueva): 16.8 gal/A; PHI 0d, REI 4h, Group M01. Begin applications when environmental conditions favor disease development. 

cyazofamid (Ranman): 2.75 to 3.0 fl oz/A; PHI 0d, REI 12h, Group 21. Registered for greenhouse use.

fenamidone (Reason SC): 6.0 fl. oz/A; PHI 2d, REI 12h Group 11. Greenhouse and field. Do not alternate with other Group 11 fungicides.

fluopicolide (Presidio): 4.0 fl oz/A; PHI 1d, REI 12h, Group 43. Field use only. Must be tank mixed with a fungicide with a different mode of action. 

hydrogen peroxide and peroxyacetic acid (Oxidate 2.0OG): 1:2 to 1:4 dilution; PHI 0d, REI 0h. Do not tank mix with copper. 

mandipropamid (Micora): 8.0 fl oz/A; PHI 1d, REI 4h, Group 40. NOTE: greenhouses use limited to structures with permanent flooring ONLY. Not labeled for field use.

mandipropamid (Revus): 8.0 fl oz/A; PHI 1d, REI 4h, Group 40. Labeled for field use.

mefenoxam (Subdue): 2.0 pt/A; PHI 21d, REI 48h, Group 4. Tank mix with fungicides from other groups. 

oxathiapiprolin (Segovis): 1.1 to 2.4 fl.oz/A; PHI 0d, REI 4h, Group 49. Begin foliar application prior to disease development. Use the higher rate when disease is present. 

potassium bicarbonate (PB 133 AKA MilStopOG): 2.5 lb/100 gal; PHI 0d, REI 1h, Group NC. Thorough coverage is essential. Registered for greenhouse and field use. See label for small volume application rates.

phosphorous acid (Fosphite): 1.0 to 3.0 qt/100.0 gal; PHI 0d, REI 4h, Group P07. Do not apply to plants that are heat or moisture stressed.

Streptomyces lydicus (ActinovateOG): 6.0 to 12.0 oz/A; PHI 0d, REI 1h, Group NC.

Fusarium Wilt (Fusarium oxysporum f.sp. basilici)

Fusarium wilt is very difficult to manage as it can persist in the soil or hydroponic system for many years. Practice strict sanitation. Begin with disease-free seed or treat seed with hot water or dilute bleach. The basil varieties Aroma 2, Nufar, Newton and Rutgers Obsession have some resistance to Fusarium wilt. Fusarium is a soil inhabitant that can become established in the field. Promptly remove and destroy all infected plants, infested soil, and plant debris. Rotate crops, excluding members of the mint family, which can be symptomless carriers of Fusarium.

Insect Control

NOTES:  For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (AI) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same AI. Please see Table 26 and Insecticides Alphabetical Listing by Trade Name for more information on these insecticides.

The designation (Bee: L, M, or H) indicates a bee toxicity rating of low, moderate, or high. See the Protecting Honeybees and Native Pollinators section for more details.

The symbol * indicates a product is a restricted use pesticide. See Pesticide Safety and Use for more details.

The symbol OG   indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details

Aphids

For more information on biology, see aphids in the pepper section.

azadirachtin (Azatin OOG): 4 to 16 oz/A foliar or drench, 4 to 16 oz/100 gal in greenhouses; PHI 0d, REI 4h, Bee: L, Group un. When using lower rates, combine with adjuvant for improved spray coverage and translaminar uptake.

Beauveria bassiana (Mycotrol ESO): 8 to 32 oz/A; PHI 0d, REI 4h, Bee: L, Group UN. Treat when populations are low and thoroughly cover foliage. Takes 7 to 10 days after application to see control.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M. Group UN.

imidacloprid (Admire Pro): 7 to 10.5 oz/A soil, 1.2 oz/A foliar; PHI 14d soil, 7d foliar, REI 12h, Bee: H, Group 4A.

insecticidal soap (M-PedeOG): 1.25 to 2.5 oz/gal water; PHI 0d, REI 12h, Bee: L. Spray to wet all infested plant surfaces. Repeat application every 2 to 3 days until pest is under control. For enhanced and residual control apply with companion labeled aphicide.

Isaria fumosorosea Apopka Strain 97 (PFR-97 20% WDGOG): 1 to 2 lb/A (foliar or soil drench); PHI 0d, REI 4h, Bee: M, Group UN.

pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

Japanese and Oriental Beetles

Beetles move into basil after emerging from soil in turf, pastures or fallow areas, starting in late June and peaking in July.  Adult beetles skeletonize leaves as they feed. Row covers can prevent feeding, but watch for build-up of aphids due to exclusion of natural enemies. The basil variety Nufar is very attractive to Japanese beetles and can be used for a trap crop.

azadirachtin (Azatin OOG): 4 to 16 oz/A foliar or drench, 4 to 16 oz/100 gal in greenhouses; PHI 0d, REI 4h, Bee:L, Group un. When using lower rates, combine with adjuvant for improved spray coverage and translaminar uptake. 

Isaria fumosorosea Apopka Strain 97 (PFR-97 20% WDGOG): 1 to 2 lb/A (soil applications only); PHI 0d, REI 4h, Bee: M, Group un.

pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

Weed Control

Suggestions for weed management in basil include use of the Stale Seedbed Technique and use of plasticulture. Both glyphosate (Roundup) and pelargonic acid (Scythe) are registered for stale seedbed use. Flaming can also be used. Stale seed beds can be used between plastic mulch (be careful with flaming as it melts the plastic). Basil usually grows quickly and shades the planting hole in plasticulture, out-competing weed growth. Apply the plastic at least 2 to 3 weeks prior to planting and kill the weeds between the mulch prior to setting the basil plants on the plastic. On bare ground culture, keep cultivations shallow to protect crop roots. Do not move soil into the crop row as basil plants may be more susceptible to diseases when soil is mounded against the stems of the crop.

Herbicides Used Preemergence to Weeds

napropamide (Devrinol 2-XT): REI 12h, Group 0.  Apply 2 to 4 qt/A as a preplant/preemergence application to weed-free soil surface.  Apply with ground spray equipment only, in 20 to100 gallons of water per acre. Apply to a weed free surface. Shallow incorporate no deeper than seeding depth or sprinkler irrigate within 24 to 72 hours using sufficient water to wet the soil to a depth of 2 to 4 inches. Use the lower rate on light soil (coarse textured - sandy) and the higher rate on heavy soil (fine textured - clay).

Herbicides Used Postemergence to Weeds

carfentrazone (Aim EC): REI 12h, Group 14.  Aim is a burndown herbicide and will injure any foliage it comes into contact with. Apply Aim to row middles of emerged crops with hooded sprayers to control emerged weeds, including crops grown on mulch or plastic.  Prevent any spray from contacting the crop, or injury will occur.  For best results, make application to actively growing weeds up to 4 inches tall and rosettes less than 3 inches across. Good coverage is essential for good control.  Apply up to 2 oz/A per application, and do not exceed a total of 6.1 oz/ per season. 

clethodim (Select Max): PHI 14d, REI 24h, Group 1.  Has not been tested on all varieties.  Crop tolerance should be verified on a small area of the crop at the desired rate. If no crop response is evident seven days after treatment, Select Max Herbicide may be used on the entire field at the rate tested. Will control grass weeds only. Apply to actively growing grasses.  See label for rate selection.  Multiple applications permitted of 9 to 16 oz/A per application, minimum 14 days between applications, not to exceed 64 oz/A per year.  Add 0.25% v:v nonionic surfactant (1 qt per 100 gal of spray).  Can also be used as a spot-spray by mixing 1/3% to 2/3% (0.44 to 0.85 oz per gallon) Select Max and 0.25% v:v nonionic surfactant (0.33 oz per gallon).  Spray to wet, but do not allow runoff of spray solution.