Researchers explore new tools to combat herbicide resistance

Research by students from Stellenbosch University aimed at combatting herbicide resistance was highlighted during a recent technical trial information day hosted by the Western Cape Department of Agriculture.

- Glenneis Kriel reports on insights and findings shared at the event.

While conservation farming practices such as crop rotation and minimal soil disturbance have helped to improve the climate resilience of grain producers, these practices have been associated with rising herbicide resistance problems.

In the past, producers often burnt lands to destroy weeds and weed seeds, or used deep tillage to uproot or bury them. Under conservation farming systems, these practices are largely avoided, leaving producers with fewer mechanical options for managing weeds.

This has resulted in an increased reliance on herbicides, Stellenbosch University student Jade Hans explained at the technical information day held at Langgewens Research Farm in the Swartland.

The situation is further exacerbated by the limited number of active ingredients available for weed control. Environmental pressures are also leading to the removal of some active ingredients from the market, while the development of new ones is expensive and slow.

PLANTING DENSITY AND CULTIVAR CHOICE

To help address this challenge, Hans is investigating how cultivar choice and planting density can be used strategically to suppress weeds. Her trials are being conducted at Roodebloem Research Farm near Caledon and at Langgewens Research Farm between Malmesbury and Moorreesburg.

In the trials, she evaluated the wheat cultivars SST0166 and SST0187 at planting densities ranging from 50 plants/m² to 250 plants/m², with an inter-row spacing of about 30cm. However, the trials achieved a maximum establishment of about 150 plants/m², which she ascribed to fertiliser burn and competition between plants.

The entire trial site received a burndown herbicide application prior to planting, ensuring that all treatments were established on a weed-free field. For each cultivar planting density combination, two herbicide treatment factors were followed: one with herbicide applications, pre-emergent followed by post-emergent, and one without.