Agriculture Reference
In-Depth Information
Stalks of the loose leaf lettuce 'Lollo Rossa'
SELECTION CHARACTERISTICS
Propagating lettuce in a greenhouse, though often convenient, risks
unintentional selection for traits that are not useful for growing in outdoor gardens. Potential selection
criteria:
• robust plants
• typical or special leaf shape and size
• size and firmness of head
• health and disease resistance
• flavor
• color scheme of leaves
• anthocyanin content (the source of red color in leaves)
• drought, cold, or heat tolerance
• resistance to downy mildew and other diseases
• late bolting
• soft leaves for butterhead lettuce, crispy leaves for iceberg lettuce
• “self-closing” romaine lettuce heads
• hardiness of winter lettuce
DISEASES AND PESTS
The same diseases are of concern for lettuce whether growing for food or seed.
Mosaic virus, evidenced by light to dark green spotted leaves, is usually spread by aphids or is seed-
borne. Do not save seed from infected plants! Covering lettuce with fine-meshed netting can protect
plants from aphids. White mold (
Sclerotinia sclerotiorum
) is treacherous when it infects seed stalks.
Prevention: healthy soil, crop rotation. Treatment: soil can be treated with Contans
WG
, an organic bio-
fungicide.
CULTIVATION HISTORY
A direct ancestor of cultivated lettuce has never been satisfactorily identified.
It was long assumed that prickly lettuce (
Lactuca serriola
) was the species from which cultivated
