Modeling the Impact of Harvest Weed Seed Control on Herbicide-Resistance Evolution

The modelling in this paper was a component of the PhD research of AHRI PhD student Gayle Somerville, who is now a postdoc at Arhus University in Denmark.

Harvest weed seed control (HWSC) is a term that describes a range of techniques to capture and destroy weed seed on standing weed plants infesting crops at the time of grain harvest. HWSC techniques have become adopted by many Australian grain growers, with AHRI research in HWSC led by Michael Walsh (now at University of Sydney). HWSC is currently being evaluated in other parts of the world. The objective of HWSC is to target weed seed at grain harvest to minimise weed seed injection into soil seedbanks and reduce weed densities over time.

It is well understood that herbicide resistance evolution in weeds would be much slower if any herbicide-resistant individuals were annually prevented from injecting seed back onto crop fields. There are examples of small farms where hand-weeding of weed individuals surviving herbicide treatments has greatly delayed or prevented herbicide resistance evolution. HWSC is for very large farms. In this modeling work, Gayle Somerville evaluated the value of HWSC in minimising the rate of herbicide resistance evolution. The modeling clearly showed the benefit of HWSC in minimising resistance evolution. There is a real benefit in having the diversity tactic of the non-chemical HWSC in minimising the rate of resistance evolution. HWSC reduces weed numbers over time and helps achieve greater sustainability and longevity of important herbicide resources.