Protect Yield with Prickly Lettuce Management

Prickly lettuce seed
Prickly lettuce seeds can survive one to three years in the soil, and most seeds germinate immediately.The plants overwinter as rosettes, which develop a long taproot. (c) AgStock Images/Joe DiTomaso

Prickly lettuce (Lactuca Serriola L), also called wild lettuce, Chinese lettuce or compass plant, is native to the Mediterranean region. Prickly lettuce spread to North America in the late 1800s.

Prickly lettuce didn’t pose a problem to U.S. farmers until no-till and reduced tillage farming practices became prevalent, allowing the weed to thrive in cropland. Prickly lettuce is drought tolerant and most commonly found in dryland crops such as wheat grown in western states under reduced tillage systems.

Identifying Prickly Lettuce

Prickly lettuce is a winter annual or, occasionally, a biennial weed. It’s sometimes called a compass plant because its leaves grow vertically from the main stem. A distinguishing characteristic of prickly lettuce is that leaves will have spines on the undersides. Without fall or spring cultivation or herbicide application, prickly lettuce can overwinter as rosettes, which develop a long taproot.

Prickly lettuce may grow as tall as 6 to 6 ½ feet. The roots, stems and flowers produce a sticky, white-colored substance.

Favorable Conditions for Weed Seed Production

Prickly lettuce begins flowering in late spring to early summer. A single plant can produce from 35 to 2,300 flowers, each containing an average of 20 seeds and producing an estimated 700 to 46,000 seeds per plant, according to Washington State University scientists.

Most seeds germinate immediately and can survive one to three years in the soil. Prickly lettuce seeds spread through wind dispersal. Light plumes similar to dandelion seeds help prickly lettuce seeds easily become airborne. Drought tolerance also aids proliferation of prickly lettuce, allowing it to thrive and compete with crops for valuable moisture.

Prickly lettuce
Prickly lettuce may grow as tall as 6 ½ feet. The roots, stems and flowers produce a sticky, milky looking substance.

Potential Damage and Economic Impact

Because prickly lettuce is drought tolerant, it competes with the crop for water, which can significantly reduce wheat yield. 

Prickly lettuce can also reduce grain quality if the weed is flowering during harvest because the buds are not easy to separate from the grain. Farmers then must be concerned about discounted prices at the grain elevator. Further complications from prickly lettuce flowers include increased moisture content and the production of a sticky, white substance that can interfere with proper operation of harvesting equipment.

Known Resistance in Prickly Lettuce

Some prickly lettuce populations can become resistant to herbicides after repeated years of applying chemistry with the same mode of action. Prickly lettuce resistance to ALS herbicides (Group 2), dicamba and 2,4-D (Group 4) has been documented.

It’s sometimes a challenge for farmers to keep track of the many factors that contribute to the management and proliferation of herbicide-resistant weeds; therefore, the best approach to manage resistance is to use best management practices (BMPs) to keep tough-to-control and resistant weeds from going to seed and entering the soil seedbank, where they can remain viable and cause problems in future crops.

For more information on prickly lettuce and other confirmed resistant weeds by state, refer to the International Survey of Herbicide Resistant Weeds.

Prickly Lettuce Control

The most effective management strategies for prickly lettuce in wheat should focus on preventing seed production throughout the year. Prickly lettuce is most susceptible to herbicide application prior to emergence and before weeds exceed 2 to 3 inches in height. The first weeds to emerge will be the most competitive and difficult to control.

  • Consider pre- and postharvest spraying where dense populations of prickly lettuce exist in your field. Farmers benefit from a preharvest application because it helps speed dry-down of prickly lettuce, improves harvest efficiency and lessens residue difficulties during fall tillage. At postharvest, control prickly lettuce with appropriate herbicides to reduce crop residue and preserve soil moisture, or with tillage two weeks after harvest. Tillage eliminates most prickly lettuce but will result in less residue and overwintering water storage than herbicide control.

  • Do not plant into existing stands of prickly lettuce. Start weed-free at planting using a burndown tankmixed with a preemergence residual herbicide just prior to or at planting.

  • If prickly lettuce-infested fields are not treated with a fall herbicide application or not cultivated in the fall, weeds may overwinter. In these situations, prickly lettuce should be controlled early in the spring to ensure effective burndown. Farmers may want to apply burndown herbicides with some of the residual herbicide in early spring and then apply the remainder of the residual herbicide at planting. Remember to practice herbicide diversity to manage resistance by choosing products with different modes of actions from different classes of chemistry.

  • Two important cultural practices for managing prickly lettuce in wheat include crop rotation and crop competitiveness. Managing crop residue, controlling weeds and planting high-quality, uninfested seed helps establish a vigorous crop that can compete more effectively with emerging weeds for space, nutrients, light and water. Depending upon geography, farmers may want to consider crop rotation.

Crop Science Solutions

Crop Science has a broad portfolio to combat tough-to-control and resistant weeds, including prickly lettuce. A well-thought-out herbicide program, using multiple modes of action, should be implemented to sustainably manage weeds. Before applying any herbicide, please read the entire label for the best possible results and to confirm that the product is effective on the weeds you wish to control. Not every product is suitable for every situation, and use of the correct application technique will ensure the best results.

The following Crop Science solutions are valuable tools to consider for your program.

Huskie® herbicide (6, 27) is available to wheat growers in 40 states and includes a unique chemistry for use in cereals with multiple modes of action (MOA). Huskie controls many broadleaf weeds such as kochia, Russian thistle, prickly lettuce and wild buckwheat—including ALS- and glyphosate-resistant biotypes. Huskie® Complete herbicide (2, 27, 6) is available to wheat growers in Colorado, North Dakota, South Dakota, Minnesota, Montana, Wisconsin and Wyoming. This all-in-one wheat herbicide is a combination of Huskie plus thiencarbazone that provides grass control. Together, these modes of action provide good control of green and yellow foxtail along with 50 grass and broadleaf weeds.

Because Crop Science continuously provides growers with new solutions to weed management problems, the company recently introduced Wolverine® Advanced (1, 6, 27) which controls 69 grass and broadleaf weeds in wheat, thanks to three modes of action in a single product. Wolverine Advanced provides the same unique broadleaf control found in Huskie with the addition of ACCase grass chemistry to control green and yellow foxtail and barnyardgrass. This wheat herbicide is an excellent tool to consider as grass chemistry rotation partner to manage weed resistance

Visit the cereals section for information on additional herbicide products Bayer offers as part of an integrated weed management program for wheat.

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