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Five Ways To Prevent Herbicide Resistance


No one likes to think about resistance. It’s all too easy to stick your head in the sand and believe it’s someone else’s problem. But the truth of the matter is that herbicide resistance is a fact of life that will likely impact every one of us at some stage in our farming careers. Despite that gloomy outlook, the good news is that there is a toolbox of products, techniques and best practices that farmers can employ to help stave off the onset of resistance. Good stewardship is our greatest ally in the fight against resistance.

Here are some tips I’ve put together to help you practice good stewardship, avoid resistance and maximize the effectiveness of your crop protection products.

1)Rotate herbicide mode of action or group chemistry

Resistance sets in when the same group chemistry or mode of action is used over several years on the same field. To avoid resistance, keep accurate records of past pesticide use, understand which herbicides are in which group, and always read and follow label recommendations for resistance avoidance.

For example a good herbicide- rotation strategy for spring wheat would be to alternate a Group 1 with a Group 2, to maintain control of wild oats while managing the risk of Group 1 resistance.

2)Avoid cutting application rates

Although it might seem tempting to cut costs by cutting application rates, the long-term pain of resistance will more than offset any short-term

A good crop

rotation strategy

makes it easier

to rotate

herbicides and

chemistry groups

gains. The rates are set precisely, at levels that maximize weed control and minimize the onset of pesticide tolerance. Using a lower rate can allow weeds that have a natural herbicide tolerance to flourish which quickly leads to the onset of full-blown resistance.

3)Introduce diversity through crop rotation

A good crop rotation strategy makes it easier to rotate herbicides and chemistry groups. For example, include herbicide-tolerant canola in the rotation with cereals, pulses and forages. Greater crop diversity, (such as three or more crop types over a six-year period) leads to greater herbicide diversity, which minimizes the threat of resistance.

4)Scout after application

It’s important to rogue escape patches. These patches can appear anywhere in the field, but are often found around the field perimeter. Clean up these weeds promptly — once seed matures and falls to the soil it is too late. Scout diligently and eliminate patches of suspected resistant plants before seed maturity.

5)Test if you suspect resistance

If you suspect resistance, send weed samples for immediate testing. Syngenta uses the AMA test (ACCase Mutation Analysis) to confirm the presence of genetic mutations that confer Group 1 herbicide resistance. Once you know what you’re dealing with it’s easier to make the correct herbicide, tillage and crop rotation choices to stop the spread of resistant weeds and maximize your in-crop weed control.

These techniques are easy to implement and don’t require much extra effort, but can be worth their weight in gold in terms of managing resistance and maximizing yield — both now and for future generations.

ByEdThiessenistechnicalcropmanager forSyngentaCropProtectionCanada

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