Weed Management
Herbicide Injury
Herbicides are a useful tool in weed management. Many herbicides are selective in their activity, injuring or killing weeds while being safe to use on a registered crop. From time to time, however, crop injury does occur. This generally happens when a crop is stressed beyond it's ability to adequately deal with a herbicide application.
Crop injury due to herbicides can arise from any of several factors or combination of factors. These include:
- Weather related factors
- Too much or too little rain
- Too cold and wet
- Too hot and humid
- Soil related factors
- Light textured soil with low organic matter
- High soil pH
- Soil crusting
- Application errors
- Excessive herbicide rate
- Incorrect application timing
- Spray drift
- Tank contamination
- Poor incorporation
- Incorrect adjuvant
- Time of day
- Planting problems
- Planting too shallow
- Planting too deep
- Interactions with other pesticides
- Herbicide residues
- Soil applied insecticides
- Herbicide tank mixes
- Sensitive crop varieties
There is often a pattern associated with herbicide injury in a field. This pattern can appear over the entire field (incorrect adjuvant or herbicide rate, sensitive crop variety) or just a portion of the field (overlap in spray boom tips, spray drift, different soil types).
Injury to a crop can also result from factors other than herbicides, such as drought, frost, nutrient deficiencies, insects, nematodes or diseases. The injury symptoms caused by these factors may look very similar to and be mistaken for herbicide damage.
The pages in this section contain information on herbicide injury to corn and soybeans. Injury symptoms are organized by crop, and within each crop, by herbicide. All herbicides are listed according to their currently registered Canadian trade name.
The herbicide list for each crop includes all products registered on that crop in Canada. As well, some of the products listed are not registered on that particular crop, but may still cause injury to the crop (drift, tank contamination or carryover of residues in the soil).
