Low Energy Laser Treatments Control Annual Ryegrass (Lolium rigidum)

Abstract

Increasing concern for the ongoing availability and efficacy of herbicides is driving interest in the development of alternative physical and thermal weed control methods. Fortunately, improvements in weed detection through advancements in computing hardware and deep learning algorithms are creating an opportunity to use novel weed control tools, such as lasers, in large-scale cropping systems. For alternative control options, there are two key weed control timing opportunities, early and late post-crop emergence. Weed density for the early timing is typically higher, with a shorter window for control. Conversely, late post-emergent treatment of surviving and late-emerging weeds would occur in lower densities of larger and more variably sized weeds, given a prior weed control effort, but with a longer available weed control period. Research in laser weeding to date has primarily focused on early growth stage weeds and the ability of this approach to control larger weeds remains unknown. This study used a 25 W, 975 nm fiber-coupled diode laser to evaluate the opportunity for control of annual ryegrass (Lolium rigidum Gaudin) and the influence of four different growth stages (three-leaf, seven-leaf, mid-tillering, and late-tillering). Annual ryegrass plants at each growth stage were treated using a laser-focused to a 5 mm diameter with five different irradiation durations developing energy densities of 1.3, 2.5, 6.4, 19.1, and 76.4 J mm−2. At the three-leaf stage, all plants were controlled at 76.4 J mm−2 and 93.3% controlled at 19.1 J mm−2. Complete control of seven-leaf plants was only achieved at 76.4 J mm−2. Although laser treatments did not control mid-tillering stage plants, 76.4 J mm−2 reduced biomass by 60.2%. No similar reductions in biomass were recorded for the largest plants. This initial research assists in the development of novel weed control options in the context of large-scale conservation cropping systems. Future research should investigate the influence of laser treatments on additional weed species and the impact of increased laser power on larger weeds.

The Remarkable Journey of a Weed: Biology and Management of Annual Ryegrass (Lolium rigidum) in Conservation Cropping Systems of Australia

“…However, currently, the machinery is expensive to power and very slow. The use of low energy laser application has also shown promising results in controlling (up to 100% control) annual ryegrass plants at early growth stages [ 128 ]. Further research is needed to upscale and make this technology efficient and affordable.…”

Laser Weeding With Small Autonomous Vehicles: Friends or Foes?

“…Three laser types have been used for weed control experiments: The carbon dioxide laser (CO 2 laser) (e.g., Heisel et al, 2001Heisel et al, , 2002, the diode laser (e.g., Wöltjen et al, 2008), and the fiber laser (e.g., Kaierle et al, 2013;Coleman et al, 2021).…”

Laser weeding: opportunities and challenges for couch grass (Elymus repens (L.) Gould) control

“…Artificial intelligence has enabled rapid and precise identification and location of weeds and crops 13 , and mirrors can guide lasers to target the apical meristem of the weed plants 14 . Plants at the early stage of development can be severely harmed or killed when the apical meristem is exposed to the heat from a laser beam 15 , 16 . The advantage of using lasers is that only a tiny field area is exposed to the treatments.…”