Keeping toxic weeds out of your baby leaf salad – with lasers

Baby leaf salad – the spinach, lettuce and rocket that make up a summer salad - is highly sensitive to weed contamination, including by weeds that can be toxic to humans.

Because these crops are harvested for direct consumption, growers have very limited herbicide options, and manual weeding is slow and expensive. Contamination can lead to entire crops being rejected by processors.

For example, in December 2022, over 190 people across four states became seriously ill after eating baby spinach contaminated with thornapple, a toxic weed that caused hallucinations and hospitalisations.

Research team leads Dr Ali Bajwa and Dr Hoang Thanh Nguyen Nguyen from La Trobe’s Institute for Sustainable Agriculture & Food are working in collaboration with industry partners, including Tripod Farmers in Bacchus Marsh, on a project focused on evaluating innovative non-chemical weed control methods - including lasers.

Tripod Farmers have been using a laser weeding unit, attached to a tractor which uses image-based detection to identify and zap weeds.

The La Trobe researchers have run field trials using the lasers to compare results with pre-emergent herbicides and conventional practices.

Results from spinach and wild rocket show that going over a field twice with the laser provided stronger weed control and reduced contamination at harvest, while causing minimal crop injury. These findings demonstrate the potential of laser weeding to contribute to integrated weed management approaches.

Angela Candeloro, Director at Tripod Farmers Group says the collaboration with La Trobe has marked an important step forward in helping growers adopt practical, science‑backed solutions to reduce weed contamination in baby leaf crops.

"This partnership brings together rigorous academic research and the day-to-day realities of production, creating insights that neither group could achieve alone. The field trials at our farms have already shown that laser weeding can deliver meaningful contamination control with minimal crop impact, offering growers an additional nonchemical tool at a time when options are increasingly limited."

She adds that the project has provided an important commercial context for testing new weed management strategies, and that the impacts of the partnership will be ongoing.

"Overall, the project has built a strong foundation for ongoing innovation in baby leaf production. We're proud to support research that directly benefits growers, enhances product safety, and contributes to more sustainable weed management across the industry. The research team's work to understand toxic weed species and their risks has also been invaluable for strengthening industry-wide food safety."

Earlier in 2025, the researchers surveyed weeds in Queensland and Victoria to identify species most likely to contaminate baby leaf crops and highlighted how contamination risks vary across the year.

This information was previously unknown to growers, and the findings help predict periods of higher weed pressure and support more proactive farm planning.

They are also analysing the chemicals produced by major weed species to understand their potential toxic effects. This will help identify risks associated with specific weeds and support effective risk assessment to safeguard the industry.

This research is part of a broader applied horticulture research initiative supported by Hort Innovation.

The project team is also developing practical tools for growers, including a weed identification guide, designed to help producers recognise key weed species at different growth stages.

By combining early-stage field research, new technology testing and strong industry collaboration, the project is building an evidence base that will help Australian baby leaf growers reduce contamination risks and improve the sustainability of weed management.