LETTUCE
	Butterhead (Boston)		Romaine (Cos)
		Ermosa (48)¹		Dark Green Cos (70)
		Nancy (52)		Green Towers (70)
		Buttercrunch (60)		Ideal Cos (75)
		Summer Bibb (65)		Parris Island Cos (76)
		Tania (65)
		Esmerelda (68)
		Dark Green Boston (75)	Leaf
				Grand Rapids (45)
	Crisphead (Iceberg)			Red Sails (45)
		Great Lakes		Tierra (46)
		Ithaca		New Red Fire (48)
		Onondaga		Sierra (red, 50)
		Raleigh		Slobolt (50)
		South Bay		Waldmann’s Green (50)

ENDIVE
		Florida Deep Heart		Green Curled Ruffle
		Full Heart Batavia		Salad King

¹Approximate days to harvest

19.2 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.

19.3 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 19.3.1 for the recommended rates of nitrogen, phosphorus, and potassium.

19.4 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 19.3.1 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*	80	40	*150*	*100*	50	*Total recommended*
40	90	50	0	120	70	50	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 soils.

Table 19.4.1 Nonpathogenic disorders

Disorder	Cause
Tipburn	Poor water management/calcium deficiency. Plant tipurn resistant varieties during warmer parts of growing season.
Poor stand	Thermodormancy due to soil temperatures >80F. Irrigate when seeding in hot weather.
Bolting	High night temperatures during early summer
Russetting	Ethylene exposure during postharvest

19.5 Disease Management

19.5.1 Anthracnose, Microdochium panattonianum

Time for concern: The fungus is favored by cool, wet weather, which are normal conditions for the early-spring crop.

Key characteristics: Water-soaked, circular spots first appear on the undersides of leaves. If bounded by large leaf veins, these spots may be angular in shape. Later, the lesion centers dry up and may fray or fall out giving a shot hole appearance. Lesions on the midrib begin as water-soaked spots, but become markedly sunken. The fungus survives in the soil and on crop debris. See Reference 1.

Management Option

Recommendation

Pest Management Guidelines A Cornell Cooperative Extension Publication	Cornell Guide for Pest Management of Vegetables
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