Confirmed findings of wild oats resistant to certain herbicides is a good news, bad news story for southern Alberta farmers.
The discovery of these hardy weeds confirms what many farmers in the County of Wheatland suspected, even though they thought they were getting good coverage from their herbicides, say Alberta Agriculture agrologists.
“The good news is that we caught these fields at very low levels,” said agrologist Scott Meers, who works at Strathmore.
Finding the weeds early provides a good chance to manage the problem before it grows.
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The survey focuses on the county east of Calgary where about one third of the 705 eligible farmers will be approached over the next four years about their spraying practices and weed problems.
The survey ends in 2000. In the final year, the group studied in 1997 will be surveyed again to determine whether they had any success in cleaning out weeds.
The study started last year with a written, confidential questionnaire about farming practices and weed infestations.
Following that, agrologists gathered 33 samples of wild oat seeds from areas that appeared to be at risk.
While resistance appeared in 23 samples, the percentage of resistance was generally low so the problem can be combatted before the weeds take over the fields, said Meers.
The affected samples showed resistance from three percent to a few samples that registered 65 percent. However, even at low levels, once those resistant weeds survive, they can increase their numbers.
The study showed the wild oat seed is resistant to herbicides categorized as groups one, two and eight.
“The majority was in the group one area,” said Meers.
In addition, group one herbicides have subsets of different types of chemistry with names like diclofop-methyl and clethodim, nicknamed fops and dims by researchers.
“Most of the samples were resistant to the fops but not to the dims. That is very important when you are selecting herbicides. It gives us some wiggle room,” said Meers.
Armed with this information, Meers expects herbicide use among farmers will change.
All producers involved received a letter explaining the program and went through their herbicide risks and problems.
Wild oats is the most common weed for the area, but kochia, Russian thistle and green foxtail could be trouble makers later.
“It’s a problem we have to deal with and we have to deal with it now,” said Meers.
Avoid resistance:
- Rotate chemical groups and keep records of use.
- Rotate crops.
- Plant vigorous, quality seed.
- Band nitrogen near the seed to give the crop an advantage over the weeds.
- If a resistance problem develops, consider a short-term forage crop.
- Combine resistant weed patches separately to reduce spread.
