Chapter 19 Lettuce and Endive
Contents
19.5.1 Anthracnose, Microdochium panattonianum
19.5.2 Botrytis gray mold, Botrytis cinerea
19.5.3 Bottom rot, Rhizoctonia solani
19.5.4 Damping-off, Pythium spp
19.5.5 Downy mildew, Bremia lactucae
19.5.6 Drop, Sclerotinia sclerotiorum, S. minor
19.5.7 Northern root-knot nematode,
Meloidogyne hapla
19.5.8 Lettuce mosaic virus (LMV)
transmitted by aphids
19.5.9 Cucumber mosaic virus (CMV)
transmitted by aphids
19.5.10 Broadbean wilt virus (BBWV)
transmitted by aphids
19.5.11 Aster yellows (AY)
phytoplasma transmitted by aster leafhoppers
19.6.2 Aphids, primarily the green
peach aphid, Myzus persicae
19.1
Recommended Varieties
Table 19.1.1 Recommended lettuce and endive varieties.
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LETTUCE |
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Butterhead (Boston) |
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Romaine (Cos) |
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Ermosa (48)1 |
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Dark Green Cos (70) |
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Nancy (52) |
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Green Towers (70) |
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Buttercrunch (60) |
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Ideal Cos (75) |
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Summer Bibb (65) |
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Parris Island Cos (76) |
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Tania (65) |
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Esmerelda (68) |
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Dark Green Boston (75) |
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Leaf |
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Grand Rapids (45) |
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Crisphead (Iceberg) |
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Red Sails (45) |
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Great Lakes |
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Tierra (46) |
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Ithaca |
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New Red Fire (48) |
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Onondaga |
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Sierra (red, 50) |
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Raleigh |
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Slobolt (50) |
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South Bay |
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Waldmann’s Green (50) |
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ENDIVE |
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Florida Deep Heart |
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Green Curled Ruffle |
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Full Heart Batavia |
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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.
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Table 19.3.1 Recommended nutrients based on soil tests. |
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N pounds/acre |
P2O5
pounds/acre |
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K2O pounds/acre |
Comments |
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Soil Phosphorus
Level |
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Soil Potassium
Level |
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low |
med. |
high |
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low |
med. |
high |
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100 (50-100 on muck) |
120 |
80 |
40 |
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150 |
100 |
50 |
Total recommended |
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40 |
90 |
50 |
0 |
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120 |
70 |
50 |
Broadcast and disk-in. |
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30 |
30 |
30 |
40 |
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30 |
30 |
50 |
Apply in band at planting or drill deep after plowing |
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30 |
0 |
0 |
0 |
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0 |
0 |
0 |
Apply 3 weeks after thinning or setting. Not needed on muck soils. |
Table 19.4.1 Nonpathogenic disorders
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Disorder |
Cause |
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Tipburn |
Poor water management/calcium deficiency. Plant tipurn resistant varieties during warmer parts of growing season. |
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Poor stand |
Thermodormancy due to soil temperatures >80F. Irrigate when seeding in hot weather. |
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Bolting |
High night temperatures during early summer |
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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.
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Management
Option |
Recommendation |
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