Basil nc state extension publications electricity generation by state

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All basils are tender annuals which are easy to grow, but are very susceptible to cold weather. They should be planted in late spring after all danger of frost is past. To produce high quality basil, grow it in full sun in warm, well-drained soil. Raised beds are highly recommended because they promote good drainage and warm quickly in the spring. A light sand to silt loam with a pH of 6.4 is best.

Basil may be grown in the field from seed or transplants. For a direct-seeded crop, sow seed thinly (8-10 seeds per inch) in a well-prepared seedbed. About 6 lbs. of seed are required to seed one acre. A small, manual seeder, or a commercial onion seeder, will provide an even seeding rate. To prevent the soil from crusting, cover with a fine layer of soil (approx. 1⁄ 8 inch) mixed with vermiculite or peat and keep the soil surface moist. Plants should emerge in 8-14 days.

Basil may also be grown from transplants started in the greenhouse in late March to early April for the piedmont and coastal counties and mid-April to early May for the mountains. Trim transplants to encourage branching and plant into the field when about 6 inches tall (4-6 weeks old). Basil also roots readily from cuttings.

Space plants 2-3 feet between rows, depending on cultivation equipment, and 6-12 inches within the row. Double-row plantings on 2-4 foot wide beds increase yields per acre and help to shade out weeds. Large producers growing for oil plant 30,000 to 35,000 plants per acre. Planting dates may be staggered to provide a continuous supply of fresh leaves throughout the growing season.

For fresh-cut basil production, the use of mulch is highly recommended. Mulch conserves moisture, reduces weed growth, and keeps the basil leaves clean. Highest yields have been obtained with black, polyethylene mulch. Hardwood bark and straw also are good choices.

There are no pesticides registered for disease control on basil. Prevention of disease through good cultural practices is the most effective means for healthy crop production. To help prevent foliar fungal diseases, keep foliage as dry as possible by watering early in the day so foliage dries quickly, or by using drip irrigation. To reduce soil borne diseases, rotate herbs to different parts of the field each year and remove and destroy all plant debris after final harvest.

A devastating basil wilt disease caused by a soilborne pathogenic fungus, Fusarium oxysporum f. sp. basilicum, was first discovered in the U.S. in 1991 and identified in North Carolina in 1992. Plants infected with this disease usually grow normally until they are six to twelve inches tall, then they become stunted and suddenly wilt. Initial symptoms usually include brown streaks on the stems, discoloration of the internal stem tissue, and sudden leaf drop. Interestingly, only sweet basil is affected. Some of the specialty basils, such as lemon basil and purple basil, show some resistance to the disease.

The disease is introduced into fields, hydroponic systems, and greenhouse culture primarily through contaminated seed. Growers should only buy basil seed that has been tested for the fusarium wilt fungus. Currently, these tests involve growing out a large number of seed and looking for disease symptoms. This does not guarantee that the seed will be free of infection, but it greatly reduces the risk. If it is not possible to obtain tested seed, the seed should be soaked in cold water for four hours followed by a heat treatment of 20 minutes in 133 to 136°F water. Seed germination rates will probably be reduced by the hot water treatment, so a germination test should be conducted on a small lot of the treated seed to determine how much seeding rates need to be adjusted. Also, the hot water treatment causes a sticky layer to develop on the outer surface of seed making it difficult to handle.

Once a field has become infested with the fusarium wilt pathogen, infective propagules may persist in the soil for 8-12 years. During that time, growers should avoid growing sweet basil or members of the mint family. Mints will not exhibit symptoms of the disease but may carry over the inoculum from year to year. There are currently no products registered to help control this disease.