Lactuca

Lettuces
Genus:	Lactuca
Family:	Asteraceae
Type:	Annuals, Perennials, Biennials
Weediness:	Most species are weedy
Pollination:	Insect

Lactuca, commonly known as lettuce, is a genus of flowering plants in the Sunflower family Asteraceae. The genus includes about 100 species, distributed worldwide, but mainly in temperate Eurasia.

Description

Its best-known representative is the garden lettuce (Lactuca sativa), with its many varieties. But many are just common weeds. They are annuals or perennials. Their height can vary between 10-180 cm. They form heads or capitula in panicles of yellow, brown or purple flowers in ray florets.

The non-edible species may contain bitter elements. Others contain a milky juice.

Growing conditions

Species

• Lactuca biennis : Tall Blue Lettuce, Wild Blue Lettuce
• Lactuca canadensis : Canada Lettuce, Florida Blue Lettuce, Wild Lettuce (North America)
• Lactuca sativa : Garden Lettuce, Lettuce
• Lactuca serriola : Prickly Lettuce, China Lettuce, Wild Lettuce (Southern Europe)
• Lactuca tatarica : Blue Lettuce, Chickory Lettuce, Russian Blue Lettuce (Asia, India)

Uses

The garden lettuce is grown as a salad green, other species occur as weeds.

Pests and Diseases

Pests

Aphids

• Pea Aphid: Acyrthosiphon pisum
• Bean Aphid: Aphis fabae
• Brown Ambrosia Aphid: Dactynotus ambrosiae
• Potato Aphid: Macrosiphum euphorbiae
• Green Peach Aphid: Myzus persicae
• Red Lettuce Aphid: Uroleucon pseudambrosiae
• Cabbage Aphid: Brevicoryne brassicae
• Lettuce Aphid: Nasonovia ribisnigri
• Lettuce Root Aphid: Pemphigus bursarius

Hoppers

• Aster Leafhopper: Macrosteles facifrons
• Southern Garden Leafhopper: Empoasca solana

Whiteflies

• Silverleaf Whitefly: Bemisia argentifolii
• Greenhouse Whitefly: Trialeurodes vaporariorum

Bugs

• Pale Legume Bug: Lygus elisus
• Western Tarnished Plant Bug: Lygus hesperus
• Tarnished Plant Bug: Lygus lineolaris
• False Cinch Bug: Nysius raphanus
• Garden Fleahopper: Halticus bractatus

Thrips

• Western Flower Thrips: Frankliniella occidentalis

Flies

• American Serpentine Leafminer: Liriomyza trifolii
• Chrysanthemum Leafminer: Phytomyza syngenesiae

Beetles

• Banded Cucumber Beetle: Diabrotica balteata

Flea Beetles

• Palestriped Flea Beetle: Systena blanda
• Redheaded Flea Beetle: Systena frontalis

Caterpillars

• Zebra Caterpillar: Ceramica picta
• Corn Earworm: Helicoverpa/Heliothis zea
• Variegated Cutworm: Peridroma saucia
• Beet Armyworm: Spodoptera exigua
• Yellowstriped Armyworm: Spodoptera ornithogalli
• Cabbage Looper: Trichoplusia ni
• Celery Leaftier: Udea rubigalis
• Alfalfa Looper: Autographa californica Western US
• Celery Looper: Anagrapha falcifera
• Saltmarsh Caterpillar: Estigmene acrea
• Western Corn Rootworm: Diabrotica virgifera virgifera
• Western Yellowstriped Armyworm: Spodoptera praefica
• Angle Shades: Phlogophora meticulosa
• Autumnal Rustic: Eugnorisma glareosa
• Cabbage Moth: Mamestra brassicae
• Common Swift: Korscheltellus lupulina
• Garden Dart: Euxoa nigricans
• Ghost Moth: Hepialus humuli
• The Gothic: Naenia typica
• Grey Chi: Antitype chi
• Heart and Club: Agrotis clavis
• Heart and Dart: Agrotis exclamationis
• Ingrailed Clay: Diarsia mendica
• Large Yellow Underwing: Noctua pronuba
• The Nutmeg: Discestra trifolii
• Setaceous Hebrew Character: Xestia c-nigrum
• The Shark: Cucullia umbratica
• Small Angle Shades: Euplexia lucipara
• Turnip Moth: Agrotis segetum

Slugs and Snails

Diseases

Bottom Rot

• Rhizoctonia

Downy Mildew

Gray Mold

White Mold

• Sclerotinia

Other Problems

Calcium Deficiency

References

• Ann Fowler Rhoads and Timothy A. Block (2000). The Plants of Pennsylvania: An Illustrated Manual. Anna Anisko, illustrator. Morris Arboretum, University of Pennsylvania Press. pp. 225-227. 
• Staff of the L. H. Bailey Hortorium (1976). Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada. Cornell University Press. pp. 631. 
• Cranshaw, Whitney (2004). Garden Insects of North America: The Ultimate Guide to Backyard Bugs. Princeton University Press. pp. 602. 
• Pippa Greenwood, Andrew Halstead, A.R. Chase, Daniel Gilrein (2000). American Horticultural Society Pests & Diseases: The Complete Guide to Preventing, Identifying, and Treating Plant Problems (First Edition ed.). Dorling Kindersley (DK) Publishing, inc.. pp. 202.