DEFY RESISTANCE
BEST PRACTICES & GUIDELINES

determine your long-term strategy

When faced with herbicide resistance the most important management strategy to remember is to give it time. Herbicide resistance isn’t a problem you will be able to solve in a season with one chemical application. Herbicide resistance management requires a strategy that your Defy Resistance Headquarters can help you develop and maintain until the premium level of health for your crop from year to year is obtained.

crop diversity and rotation

Typically weed resistance occurs in crop production systems that have not been diverse. Rotating crops with three to four different species allows for different herbicides to be used from year to year. The more years you give a field between the use of one specific herbicide,
the more likely you will rid the field of the weeds resistant to it, as well as prevent non-resistant weeds from building the resistance caused by overuse.

One thing that is sometimes overlooked is that canola tolerance allows the farmer to extend herbicide rotation to different modes of action by utilizing all three tolerance platforms - LibertyLink®, glyphosate tolerant and Clear field® Canola. Keep in mind though that a tight canola rotation can lead to disease issues that need to be carefully managed.

multi effective modes of action

When a plant develops resistance to a herbicide it is adapted in a way that makes that herbicide ineffective to it. Whether that means it is enhancing its cells to overpower the herbicide’s inhibitors or creating a new version of the cells all together, every plant adapts differently to different modes of action. Using multiple modes of action at once not only helps to prevent plants from being able to adapt as quickly, due to the number of ways it would have to adapt at once, but also can help with resistant weeds by adding multiple ways of inhibiting their growth, assuming they haven’t adapted to all, yet.

enhanced competitiveness of the crop

All weeds, included resistant ones, need the usual growing conditions that most plants need. Weeds are an issue for most crops because they reduce the value of those conditions for the crop, most importantly soil nutrients and space. Weeds would be less of a problem, however, if the crop, itself, was strong enough to compete for that space. To allow your plants to be strong enough, ensure you are planting the right varieties for your field, you are providing enough nutrients – soil testing will help you understand how much nutrients you have to provide – and you are ridding the plant of any other pests. (Did you know applying a fungicide will not only kill any pests or potential for pests but also enhance your crop’s competitiveness?)

pre- and post-harvest herbicide application

Any time a population of resistant weeds can be controlled prior to the crop being seeded,
or after the crop is harvested, the battle against resistance gets a boost. In spring, the early control ensures that weed growth doesn’t take important moisture and nutrients from the crop and lessens the weed pressure in crop. In fall, seeds can germinate and go to seed quickly and allow resistant weeds to get a strong foothold for years to come. This can be especially problematic in dryer years, when drought-resistant weeds can get a foothold. Out-of-crop control is a strong weed control strategy.

clean your equipment

Equipment can spread resistant biotypes from field to field. It is crucial to ensure all equipment is thoroughly cleaned before moving from one field to another to prevent the spread of herbicide-resistant weeds across your farm.

accurate record-keeping

Recording-keeping may not be the job you signed up for when deciding to farm, but it is now an essential part of the job. It’s important to keep track of what is planted, sprayed, applied, and yielded on every acre of your land to ensure that your rotations are managed properly and herbicides aren’t being over-used.