HPIPM:Prickly lettuce

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Asteranae
Order	Asterales
Family	Asteraceae
Subfamily	Cichorioideae
Tribe	Cichorieae
Genus	Lactuca

Scientific Name

Lactuca serriola

Scientific Name Synonyms

Lactuca scariola

Common Name

prickly lettuce

Prickly lettuce (Lactuca serriola)

Compiled by Terry Angvick, Montana State University, Sheridan County Extension

and Marjolein Schat, Montana State University from the following sources:

http://plants.usda.gov/java/profile?symbol=LASE

http://www.whitman.wsu.edu/weeds/pricklylettuce.html

http://www.ppws.vt.edu/scott/weed_id/lacse.htm

Identification and Life Cycle

Prickly lettuce (Lactuca serriola) is an annual or rarely a biennial in the sunflower family (Asteraceae). Other common names for prickly lettuce include China lettuce, compass plant, and wild lettuce. Seed leaves (cotyledons) and young leaves are oval with spiny leaf margins and spines along the mid-vein of the lower leaf surface. The leaves form in a basal rosette. Prickly lettuce has a deep tap root which will exude a milky sap. Prickly lettuce will produce an upright stem 1 to 5 feet tall. The leaves are alternate, clasp the stem, and are deeply lobed with spiny margins and a row of spines along the mid-vein of the lower surface. The leaves will twist vertical to the stem. The flowers of prickly lettuce are yellow in color and approximately one third of an inch in diameter. Seeds are small, grayish brown and have an attached pappus. Prickly lettuce is similar in appearance to dandelion at the rosette stage and sowthistles at any stage, but may be distinguished from other plants by the row of spines along the mid-vein of the lower leaf surface.

Habitats

Prickly lettuce grows in waste areas, along roadsides, in nurseries, orchards, and agronomic crops and is found throughout the United States.

Impacts

Prickly lettuce can reduce crop value and can reduce efficiency of wheat harvest. Flower buds can be difficult to screen out of grain. The latex in stems can clog harvesting equipment and raise the moisture content of the grain.

Biology and Ecology

Prickly lettuce reproduces only by seed. A rosette of leaves forms after emergence, usually in autumn, and develops a long taproot. It overwinters as a rosette, and then produces one or more flowering stems in early summer. Each plant produces 35 to 2,300 flowers in early summer. Each flower head contains an average of 20 seeds. The seeds are wind dispersed and most seeds are viable and ready to germinate immediately after dispersal. Seeds in the soil survive 1 to 3 years.

Biological Control

Sheep and goats readily feed on prickly lettuce and can consume entire fields of the weeds.

Mechanical and Cultural Control

Seedlings and rosettes of prickly lettuce are easily controlled by cultivation. Mowing is ineffective. Rosette leaves lay close to the soil surface and mowing after stem elongation causes the plant to produce new flowering stems.

Chemical Control

The best results are obtained when the plant is treated at the rosette stage. There have been numerous reports of ALS inhibitor resistance in Australia, Idaho, Washington, and Oregon. In 2007 Synthetic auxin resistant populations were reported in Washington. For more information on each of these reports please see http://www.weedscience.org/Summary/USpeciesCountry.asp?lstWeedID=102&FmSpecies=Go

For herbicide recommendations for specific grain rotations and weeds in Montana, please see the MSU Herbicide Chooser Tool.

Examples of herbicides that can be used to manage prickly lettuce

Consult herbicide labels for additional rate, application, and safety information. Additional herbicide information can be found at http://www.greenbook.net.

Herbicide Active Ingredient trade name	Mode of Action	Product per Acre	Application Time or Growth Stage
Alfalfa
Hexazinone; diuron	hotosynthesis inhibitor (Photosystem II)
*Velpar AlfaMax		3 - 4.3 pounds	Make a single application during winter months when alfalfa plants are in the least active stage of growth.
Lentils
Paraquat	Membrane disruptor
*Gramoxone Inteon		1.5 - 2 pints	Apply when crop is mature and at least 80% of the pods are yellowing and ripe and no more than 30% of the leaves still green.
Wheat and Barley
Chlorsulfuron; metsulfuron	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Finesse		0.2 - 0.3 ounce	Preplant and pre-emergence applications recommended for winter wheat only. Post-emergence applications should be applied after the crop reaches the 1 leaf stage, but before the boot stage.
Wheat, (Except for Durum and Wampum varieties of spring wheat) Barley, and Triticale
Thifensulfuron; tribenuron; metsulfuron	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Ally Extra		0.2 – 0.4 ounce	Apply after crop reaches 2-leaf stage but before the flag leaf is visible. For best results against resistant biotypes of prickly lettuce, apply in a tank mix with “Starane”, “Starane+Salvo”, “Starane+Sword”, bromoxynil containing products, or dicamba.
Durum and Wampum varieties of spring Wheat
Thifensulfuron; tribenuron; metsulfuron	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Ally Extra		0.2 – 0.4 ounce	Apply after crop is tillering but before the boot stage. Apply in combination with 2,4-D. For best results against resistant biotypes of prickly lettuce, apply in a tank mix with “Starane”, “Starane+Salvo”, “Starane+Sword”, bromoxynil containing products, or dicamba.
Wheat, Barley, and Triticale
Tribenuron	Inhibition of acetolacetate synthase ALS (acetohydroxyacid synthase AHAS)
*Express		0.25 - 0.5 ounce	For best results use in a tank mix with dicamba and 2,4-D or MCP. Apply in spring when prickly lettuce rosettes are less than 2 inches across and are actively growing. See label for tank mix rates. Apply when crop is in the 2-leaf satage but before flag leaf is visible. Do not harvest within 45 days of last application.
Wheat, Barley, and Oats
Dicamba	Action like indole acetic acid (synthetic auxins)
*Banvel		2 – 4 ounces	Use 2 to 4 ounces in wheat, and fall seeded oats and barley, and 2 to 3 ounces in spring seeded barley. Apply, before, during, or after planting when weeds are in the 2-3 leaf stage.
Clopyralid	Action like indole acetic acid (synthetic auxins)
*Stinger		0.25 – 0.33 pint	Apply before prickly lettuce reaches 5-leaf stage and crop is in the 3-leaf to early boot stage of growth.
Fluroxypyr	Action like indole acetic acid (synthetic auxins)
*Starane		0.5 – 0.66 pint	Apply as a broadcast post-emergence treatment to actively growing wheat, barley, or oats from the 2-leaf stage up to and including flag leaf emergence stages of growth. Apply before weeds reach 8 inches tall.
Clopyralid; fluroxypyr	Action like indole acetic acid (synthetic auxins)
*WideMatch		1 – 1.33 pints	Apply broadcast post-emergence to actively growing crops from the 3-leaf stage up to and including flag leaf emergence stage. Apply when weeds are actively growing and less than 8 inches tall.
Rangeland and Permanent Grass Pastures
Picloram	Action like indole acetic acid (synthetic auxins)
*Tordon 22K		1 pint	Treat in spring when weeds are small and actively growing.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

References

For more information and images please visit IPM Bugwood. http://www.ipmimages.org/search/action.cfm?q=Lactuca%20serriola&Start=1&results=78