Resistant Ryegrass Getting Tougher To Beat

It’s confirmed. Australian annual ryegrass populations are now resistant to three different pre-emergent herbicide groups. Last August, the national weed resistance surveys of grower’s paddocks identified complex resistance patterns.

Annual ryegrass now has resistance to;
Group D (trifluralin),
Group J (Avadex Xtra & Arcade) and
Group K (Butisan & Sakura) herbicides, along with combinations of these herbicides (Group J-K – Boxer Gold).

Generally, there hasn’t been any resistance to Group D (propyzamide). However, there has been found some low-level resistance to Group D in areas that had resistance to multiple pre-emergent herbicides.

With the patterns of resistance across the pre-emergent herbicides being so variable, even across single paddocks, it is essential to know what resistance you have in your crops so you can make informed management decisions. Speak to a local agronomist, they’ll know what resistance is like in your area. Or, if you really want to break it down, ask us about resistance testing for your paddocks. By knowing what your resistance is like, we can work out the best strategies for your ryegrass management. Such as what the best mixtures and rotations of pre-emergent herbicides will be. Also remember to implement other seed reducing tactics as well. Crop topping and harvest weed seed control are also options to delay the onset of more resistance issues.

It’s important to note that not all pre-emergent herbicide failures will be due to resistance. Environmental conditions will play a big part in the equation. Insufficient moisture, high stubble loads or later germinating weeds will have the biggest effects on performance.
For more information, get in contact with one of our agronomists today.