Think Now About Herbicide Carryover and Planting Sensitive Crops in Spring 2013

Since it still looks like seeding will be a few weeks away, now is the time to think about what herbicides were applied in 2012 and if they could affect the your crops plans for 2013.

Summer and fall in 2013 for many areas of Manitoba was DRY! That looks to be over with all this snow, but it is has created the potential for higher risks of herbicide carryover in  spring 2013.   Due to little rainfall after herbicide applications and throughout the 2012 growing season, residues may still be present at damaging levels in late May and early June 2013.  To assess your risk, look at your 2012 herbicide records and check label restrictions for re-cropping periods.  You will find time interval recommended before planting the next intended crop, it will be listed in months or years.  High risk crops sensitive to residual herbicides can include alfalfa, canaryseed, canola, dry bean, fababean, field corn, flax, lentil, oat, soybean and sunflower. Please check the Manitoba Guide to Field Crop Protection 2013 for more details.  Information on Re-cropping Restrictions for Residual Herbicides can be found on page 61 and 62 in the paper guide or on-line at

Other risk factors identified by the Canola Council of Canada in the April 4, 2013 “Canola Watch”:

Applying residual products late in the season, at higher rates or repeatedly over time can increase the carryover risk. Soils with higher organic matter are at reduced risk of herbicide carryover because they tend to have more microbial activity and more moisture. Soil pH is also a factor, depending on the herbicide: certain Group 2 sulfonylureas and certain Group 5 herbicides breakdown slower in high pH (alkali) soils and Group 2 IMIs break down slower in low pH (acidic) soils.

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