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Chapter 20: Lettuce and Endive

20.1 Varieties

Tables of Disease Resistant Varieties, including Boston, butterhead, green leaf, and red leaf lettuces.

20.2 Planting Methods

Lettuce is a cool-season crop, and high temperatures (particularly at night) in midsummer are very damaging, promoting such disorders as premature bolting, tipburn, and brown rib. Crisphead (iceberg) lettuce is especially sensitive to heat, although some new varieties are more tolerant.

Once-over harvesting is done on most large commercial acreage, so every effort must be made to promote uniform maturity. Although lettuce can be transplanted readily, most lettuce in New York is direct seeded, usually with pelleted seed in precision seeders. Irrigation immediately following seeding promotes uniform emergence. Where irrigation is not possible, deep plowing followed immediately by fitting and seeding is helpful. Rows generally are spaced about 15 inches apart, and in-row spacing is determined by variety and desired size of marketed lettuce. Uniform spacing is important for achieving uniform maturity.

Growers are encouraged to rotate lettuce with another crop whenever possible. This aids in the management of many pests that affect lettuce. Double-cropping lettuce on the same field may greatly increase problems such as Sclerotinia drop, corky root rot, root knot nematode, and virus diseases in the second planting.

20.3 Fertility

Maintain a pH of 6.0 to 6.2 on mineral soils. Consider liming if pH falls below 5.5 on muck soil. If mucks require lime for lettuce production, avoid turning up more than one inch of new muck in any one plowing. Liming to a pH higher than 5.6 is not advisable on muck. See Table 20.3.1, below, for the recommended rates of nitrogen, phosphorus, and potassium.

Table 20.3.1 Recommended nutrients based on soil tests

N pounds/acre
P2O5 pounds/acre
 
K2O pounds/acre
Comments
  Soil Phosphorus Level   Soil Potassium Level  
  low med. high   low med. high  
100 (50-100 on muck) 120 60 30   150 100 50 Total recommended.
40 90 50 0   20 70 0 Broadcast and disk-in.
30 30 30 40   30 30 50 Apply in band at planting or drill deep after plowing.
30 0 0 0   0 0 0 Apply 3 weeks after thinning or setting. Not needed on muck soil.

20.4 Harvesting

Care in harvesting and handling is important for these crops since they are easily damaged. Noncrisphead varieties are more susceptible to damage during harvest and transit and therefore have a shorter shelf life than crisphead varieties. Vacuum cooling and/or contact icing to remove field heat will improve market quality and shelf life. The use of top ice when packaging acts to supply moisture and remove heat. Optimum storage conditions are 32°F and at least 95 percent relative humidity. Good air flow through and around boxes is essential.

Table 20.4.1 Nonpathogenic disorders

Disorder Cause
Tipburn Poor water management/calcium deficiency. Plant tipburn resistant varieties during warmer parts of growing season.
Poor stand Thermodormancy. Irrigate after seeding during periods of very hot weather.
Bolting High night temperatures during midsummer
Russetting Ethylene exposure during postharvest

20.5 Disease Management

20.5.1 Anthracnose
20.5.2 Botrytis Gray Mold
20.5.3 Bottom Rot
20.5.4 Damping-Off
20.5.5 Downy Mildew
20.5.6 Drop
20.5.7 Northern Root-Knot Nematode
20.5.8 Lettuce Viruses
20.5.9 Aster Yellows

 

20.6 Insect Management

20.6.1 Aster Leafhopper
20.6.2 Aphids
20.6.3 Slugs

20.6.4 Leafminers

20.6.5 Cabbage Looper

20.6.6 Tarnished Plant Bug

 

20.7 Weed Management

 

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Maintained by Abby Seaman, New York State IPM Program. Last modified 2019.