Weed Resistance

Weed resistance to herbicides has been around for a number of years now. With glyphosate resistance being confirmed in Alberta it seems a lot more people are starting to really take notice. I hope to see a lot more guys throwing in some extra groups with their pre burn, putting down a soil applied herbicide or alternating groups between years. We have already lost a lot of control with our group 2 products due to resistance, would hate to see group 9 be lost in Canada on more problem weeds such as wild oats or cleavers.

A lot of the time simply upping the rate of glyphosate may be the most economical and most effective way to control those target weeds in a pre burn, but we have to take a pro active approach and spend a few extra dollars an acre now rather than lose glyphosate as an effective chemical all together. In front of canola for example the only registered option to add to glyphosate is a group 14 product known as AIM (in Cleanstart). While this product is not the most potent and in a lot of cases it may be cheaper and more effective to add another 0.5L equiv. to get those tougher to kill weeds, adding Aim can help fight resistance. Especially if that field is going into Round Up Ready Canola. If a producer uses glyphosate pre burn, 2 in crops apps and then a fall applied glyphosate app, that’s 4 straight applications with ONLY glyphosate, not to mention probably using glyphosate again the following growing season as a pre burn. It is scenarios like that where you begin to increase your resistance risk significantly.

When it comes to group 1 wild oat resistance it should be approached the same, you know you are going to spray a grassy herbicide essentially every year. To help combat resistance there are a number of options from applying granular herbicides with activity on wild oats (Avadex or Edge) or alternating between group 2 and group 1 grassy herbicides. Bayer just released their gr2 grassy herbicide as stand alone product giving you another option for the 2012 growing season. Dow’s Simplicity, Arysta and Syngenta’s flucarbazone products have been around for a number of years now giving you options in your cereal fields. If you want to go even farther you can begin to recognize different chemical families within the group 1 chemical classification and begin to alternate between the ‘dim’, ‘den’ and ‘fop’ families (the actives will end in one of those three 3 letter words. Axial is in the ‘den’ classification with its active being pinoxaDEN). There has been research from AAFC’s Dr. Hugh Beckie showing that different families within group 1 have different levels of resistance to a wild oats resistance mutation.

Pulses rely heavily on group 2 herbicides, one reason there may such high levels of gr 2 resistance in some areas across the prairies. With the registration of a gr 14 in Authority in front of peas, there is another option in your weed control arsenal. The group 3 product of Edge is also something that has been used effectively for a while in front of pulses. On top of this using a product such as Reglone (gr 22) or Heat (gr 14) as a desiccant can further diversify the chemical spectrum on a pulse field in a given season.

Acknowledging the problem at hand starting now will allow us to lengthen the life time of many different chemicals, ensuring high efficacy weed control well into the future.