| Leeks |
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Varieties
PlantingFor best results, leek seeds should be sown in the greenhouse about two and a half months before field setting. About 2 to 3 pounds of seed are needed to raise enough plants to set an acre at average spacing (1/4 to 1/2 oz per 100 feet of row). Before setting, clip plants to a height of 3” to reduce wind damage in the field. Set plants in the field from late April to late May depending on location and earliness desired. Plants can be set in late July for a late fall harvest, or in milder locations, growers may wish to try overwintering leeks using a straw mulch. Rows can be from 15” to 30” apart depending on equipment; plants should be about 3” to 6” apart (200 to 400 plants per 100 feet of row) CultureTo develop a long, white stem, leeks can be planted in a trench 3” to 4” deep. The trenches are gradually filled as the leeks grow and then soil is hilled around stems to a height of 3” to 4”. Soil particles have to be cleaned from the leeks when preparing for market. Self-blanching varieties are grown without trenching and hilling and require less cleaning. Lime and FertilizerSee the lime and fertilizer sections for Onions. Weed ControlNOTE: For the herbicides listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, days to harvest (dh), REI, and special instructions. In many cases there are other products available with the same active ingredient. Please see Table 17 and Alphabetical Listing by Trade Name for more information on products with the same active ingredients. See section on Soil Fumigation (page 59). Proper use of Vapam can provide control of most weed species. Stale SeedbedSee Page 45. glyphosate (Roundup 4S): 1 to 5 qt/A (REI 12h, Group 9). See Stale Seedbed Technique. Postemergencepelargonic acid (Scythe 4.2): 3% to 10% (REI 24h, Group 27). Use a 3-5% solution for annual weeds (4-6 oz/gal water), a 5-7% solution for biennial and perennial weeds (6-9 oz/gal water), and 7-10% solution for maximum burndown (9-13 oz/gal water). Delivery rate for boom applications should be 75 to 200 gal spray solution/A; complete coverage of weed foliage is essential. Use a DIRECTED/SHIELDED SPRAY; contact with crop will cause severe injury. For hand-held equipment, spray to completely wet all weed foliage but not to the point of runoff. Repeat applications as necessary. Tank mixes are allowed with this product. These include tank mixes with glyphosate (Roundup), sulfosate (Touchdown), and residual herbicides. See label for complete details. Insect ControlNOTE: For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, days to harvest (dh), REI, and special instructions. In many cases there are other products available with the same active ingredient. Please see Table 20 and Alphabetical Listing by Trade Name for more information on products with the same active ingredients. Onion ThripsThrips are favored by hot, dry weather. Heavy rain or overhead irrigation can lower populations quickly. Lacewing larvae, pirate bugs and predatory thrips are important natural enemies. Reduce populations by cleaning up crop residue after harvest to limit overwintering sites. Do not plant leeks near other Alliums (onion family) or alfalfa, clover, cucurbits or Brassica crops that can harbor large populations of thrips, which may migrate to leeks when these crops are cut or harvested. Begin applications when damage is first noticed. Repeat applications at 7 to 10 day intervals. Use a shorter interval in hot, dry weather. Use a spreader-sticker for better coverage. Apply in early evening, using high pressure and 100 gal water/A for best results. See onion thrips in the Onion section for more information. Beauveria bassiana (Mycotrol O): 8 to 32 oz/A (0 dh, REI 4h, Group 22). Thoroughly cover foliage. Takes 7 to 10 days after application to see control. OMRI listed. spinetoram (Radiant SC): 6 to 10 oz/A (1 dh, REI 4h,Group 5). spinosad (SpinTor 2SC): 4 to 8 oz/A (1 dh, REI 4h, Group 5). Suppression only. Disease ControlThe most common controls for leek and garlic diseases include the use of disease resistant cultivars and pathogen–free seed and bulbs, and cultural practices such as crop rotation and crop residue management that restrict the pathogen. NOTE: For the products for disease control listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, days to harvest (dh), REI, and special instructions. In many cases there are other products available with the same active ingredient. Please see Table 22 and Alphabetical Listing by Trade Name for more information on products with the same active ingredients. Damping-off and seed rot (Pythium and Rhizoctonia)Avoid excessive soil moisture by improving soil drainage or planting on raised beds. Seed and soil treatments with fungicides are a recommended practice. Downy Mildew (Peronospora destructor)During extended periods of cool, humid weather, this disease can be highly destructive causing losses in both yield and bulb quality. Practice a 3-4 year rotation. Plant on well-drained soil and orient rows in the same direction as prevailing winds. Avoid overhead irrigation. A regular program of fungicide spraying based on climatic conditions and disease forecasts should be followed. dimethomorph (Forum): 6 oz/A. (0 dh, REI12h, Group 15). Forum must be applied as a tank mix with another fungicide with a different mode of action. fenamidone (Reason SC): 5.5 fl oz/A. (7 dh, REI 12h, Group 11): Do not alternate with other Group 11 fungicides like Quadris or Cabrio. pyraclostrobin (Cabrio): 12 oz/A. (7 dh, REI 12h, Group 11).Do not make more than one application of Cabrio before alternating to a fungicide with a different mode of action. Do not rotate with Quadris or Cabrio. Purple Blotch (Alternaria porri) Practice long rotations with unrelated crops and practices that reduce hours of leaf wetness, i.e., plant spacing and good air drainage. Use of a single fungicide throughout the growing season is not recommended. azoxystrobin plus propiconazole (Quilt): 14-27.5 fl oz/A. (14 dh, REI12h, Groups 3 & 11). bocalid (Endura): 6.8 oz/A. (7 dh, REI 12h, Group 7). propiconazole (Tilt): 4-8 fl oz/A. (14 dh, REI 12h, Group 3). pyraclostrobin (Cabrio EG): 8 to 12 oz/A (7 dh, REI 12h, Group 11). Apply at the first sign of disease and alternate with chlorothalonil after 7-14 days. Do not exceed six applications or 72 oz/A. Do not rotate with other Group 11 fungicides (Quadris). pyraclostrobin plus boscalid (Pristine): 14.5-18.5 oz/A. (7 dh, REI 12h, Groups 11 & 7)/ White Rot (Sclerotium cepivorum)Avoid planting in infested fields. Destroy infected plants and spot treat the soil around the plants with fumigants. Warm season production of host crops may greatly reduce sclerotial inoculum. Practice crop rotation. Some fungicides (iprodione) provide protection for the establishment of garlic, but fungicide control is marginal for full-season crops. Soil fumigation may provide partial control. In general, neither fungicides nor fumigation have provided consistent, reliable, full-season control of white rot. Hot water treatment of garlic seed can reduce the potential to spread white rot sclerotia. Winter flooding and soil solarization can reduce the number of sclerotia. White rot symptoms are less severe on leeks. |
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