Biology, Ecology, Distribution and Control of the Invasive Weed, Lactuca serriola L. (Wild Lettuce): A Global Review

Abstract

Lactuca serriola L. (wild lettuce) is a highly invasive C₃ weed in many countries, including Australia, Canada, and the USA. This weed is a severe threat to agricultural systems, especially in crops grown with reduced or no-tillage approaches, which commonly include wheat, cereals and pulses. Owing to the vertical orientation of its leaves in the north-south plane and its root architecture, L. serriola can maintain high water use efficiency under drought conditions, giving it the ability to expand its range under a drying climate. Each plant can produce up to 100,000 seeds which have no primary dormancy and form a short-term seedbank lasting up to three years. Most seedlings emerge in autumn and overwinter as a rosette, with a small flush of emergence in spring depicting staggered germination. Research into control methods for this weed has been performed, and these methods include chemical herbicides applied alone and in combination, the establishment of plant competition, tillage, mowing and bioherbicide. Herbicides can provide effective control when applied in the seedling or rosette stage; however, spring germination is difficult to control, as it skips the rosette stage. Some biotypes are now resistant to ALS inhibitor and synthetic auxins, causing concern regarding using herbicides. A dedicated integrated management plan for 3-4 years is recommended for the control of this troublesome species. This review will explore the biology, ecology, distribution, current control techniques and previous research on this weed, allowing us to make recommendations for its future research and management.

Keywords: invasive alien species; invasive species; prickly lettuce; wild lettuce.

Figure 1

Geographical distribution of Lactuca serriola.

Figure 2

Leaf of Lactuca serriola, showing spines on the underside of the midrib and on leaf margins (© Aakansha Chadha).

Figure 3

Lactuca serriola seed structure showing the brown seed colour, its longitudinal ribs, the bristles near the apex and the pappus (© Aakansha Chadha).