You Suspect Herbicide Drift – Now What?

Kristen Callow, OMAFRA Weed Management Program Lead – Horticulture; Leslie Huffman, OMAFRA Apple Specialist

Crop injury caused by herbicide drift is guaranteed to cause misery and confrontation, not to mention insurance claims and legal charges.  No one wins when herbicides drift – the applicator loses two ways: his herbicide misses the target, giving poor weed control, plus he is liable for damage; the “receiving” grower loses yield, crop health, perhaps timely markets plus his time. Sometimes our environment loses, and in general, agriculture loses in the public eye.

There Are a Number of Steps to Follow When you Suspect Herbicide Drift:

1.  Diagnose the problem:

• Is it really drift?  Eliminate other possible causes, such as: disease, insect, nutrient deficiency, herbicide carryover, environmental stress – may be similar to herbicide drift, etcetera.
• Are there patterns in the field?  Is the damage worse next to the spray source, with less damage occurring across the field?  Is the damage patchy? If it is, you need to check your soil pH. If your pH is considered high or low, test for herbicide carryover.
• Is there evidence of a spray application?  Look for wheel tracks, weed symptoms, boom patterns and overlap on the headlands.  Look for spray evidence in neighbouring fields, lawns, ditches, etcetera.

2.  Contact the appropriate people:

• Talk to your neighbour or sprayer operator. Ask what was sprayed, when it was applied and who did the application.
• Contact your regional Ministry of the Environment office (1-800-265-7672 Southwestern Region) – MOE officers can do a site visit, take samples of tissue and soil, and have them analyzed for the suspect herbicides. Where appropriate, the offending applicator may face charges under the Pesticide Act.
• Contact your insurance adjustor, and advise the applicator to contact theirs.

3.  Document all details of the problem:

• Collect spray records (yours – to prove it wasn’t your sprays) and the offending applicators’.
• Collect weather records (temperatures, wind speed, wind direction, rainfall – for the date of application).
• Take photos (many). Record date and location on each photo. Repeat photos several times through the season.
• Document yield loss from the damaged area and an undamaged area.  Choose a similar planting (same age, cultivar, rootstock, etcetera).  For perennial crops (e.g. vineyards, orchards, asparagus, berries) document the effects for several years after the damage occurred.

Every herbicide applicator needs to take all possible steps to avoid herbicide drift.  So what should an applicator do?

1. Work with the weather.  Avoid spraying when the weather is against you, e.g. when winds are above 11 km/hr or dead calm, when temperatures are above 30^oC, and/or when relative humidity (RH) is above 80%.
2. Identify vulnerable crops near your fields.  Choose a spray day when winds are blowing away from these sites.
3. Make your spray less prone to drift. Choose herbicides with a low risk of volatility. Avoid products like 2,4-D or dicamba near susceptible crops or greenhouses. Choose higher water volumes and lower pressures for larger  droplets.  Use the newest anti-drift nozzles.  There are many air-injection (AI) nozzles that will greatly reduce risk.
4. Work with your neighbours.  Let them know your intentions.  Maybe you can both make some buffer areas between vulnerable crops.  Greenhouse growers need to be notified to close vents during early morning spray times to avoid any possibility of drift.