Some in-crop conditions can mimic the same sort of damage caused by drift
Everyone likes gifts, but farmers aren’t likely to welcome extra herbicide drifting in.
Manitoba’s spray season has already hit its height, and sprayers have commonly been seen trundling down the provincial highways and grid roads for weeks.
But while farmers are already watching for insect damage, stand counts and weed issues, this time of year also has them watching for damage from pesticides applied nearby.
Spray drift dangers are well known, and provincially reportable, but Manitoba Agriculture weed specialist Tammy Jones says damage might be hard to pin as a drift issue with the naked eye.
“Sometimes what you’re seeing in the field is something else,” she said during a June 20 Crop Talk webinar. “Chlorosis can be caused by a bunch of different stresses and there’s three different types of chlorosis, or yellowing. It can be a general yellowing of the leaf, it can be only interveinal or it can be mottled.”
Jones pointed to corn as an example. Purpling on the leaves is a common sign of herbicide injury, she said, but it might also be a fertility issue. Phosphorus deficiency also causes the distinctive colouring. Likewise, yellow spotting, dead tissue and even stem dieback could mimic spray damage.
Sprayers101, the blog run by western Canadian “Spray Guys,” Tom Wolf and Jason Deveau, has a similar message.
“Many other factors can cause symptoms that appear to be herbicide drift,” the blog warns on a list of how to deal with suspected drift issues.
The Saskatchewan experts advise looking for weed damage, evidence of nearby spraying and damage patterns that might signal drift.
Jones also warned that symptoms might look very different, depending on what group was used, how close the plant is to the source of the spray, the rate it was applied, the wind at the time, and even which product was sprayed within a herbicide group.
Group 1, which hits the growing point in grasses, will cause yellowing and easily stripped leaves, but diagnosing within Group 2 might be harder, Jones said. Chlorosis and crown proliferation might be a sign of either sulfonylurea or imidazolinone, while plants that don’t flower might be caused by the latter chemistry.
“The imidazolinones, instead, you see the chlorosis of the new leaves, but there tends to be a little more crinkling and cupping with that leaf growth stopping,” she said. “Again, that crown growth, it sort of bunches up there, but it’s not as red or as yellow.”
On the other hand, a farmer might be fighting dicamba drift if damage is only on new growth, Jones said.
Manitoba Agriculture noted a jump in dicamba drift issues in the Red River Valley last year, pointing to the spread of dicamba-tolerant soybean varieties and drift to non-tolerant fields.
Depending on the severity, dicamba drift damage might be isolated to a few leaves or haunt a crop for the rest of the season, webinar attendees heard, although farmers will have to be patient for a diagnosis. Damage may take up to two weeks to show up, stretching to three in poor growing conditions.
Farmers should watch for puckering or leaf cupping, provincial farm production adviser Lionel Kaskiw said last year in an interview with the Manitoba Co-operator.
Rapid growth might mimic dicamba damage, he said at that time, although plants will outgrow the abnormal leaves.
When the damage is done
Documenting drift will not fix a crop, but it’s key for the followup, said Pratisara Bajracharya, pesticide minor use and regulatory specialist with Manitoba Agriculture.
She urged farmers to mark the time and date, details of the suspected damage and follow that up with time-stamped pictures and samples.
The province’s crop diagnostic lab can do a visual analysis, she said, but farmers must turn to a private lab for residue testing to confirm drift injury.
That chemical analysis will be key if the producer reports the incident, although both Jones and Bajracharya warned that the clock is ticking on those samples as residue starts to degrade.
“What you can do is collect samples and maybe store them in the fridge if you are sending it to (the) crop diagnostic lab and freeze the samples if you are sending it to residue testing,” Bajracharya said. “I often recommend people to take a large sample and split it into two and freeze half of it just in case they intend to send it to residue testing later on.”
Further response will depend on what got accidentally sprayed, she added.
If it’s a person or animal, Bajracharya suggested an immediate call to the doctor or a veterinarian, and a possible followup with Health Canada’s online reporting tool. An environmental impact might also draw in Health Canada’s involvement, as well as the regional environment officer or emergency line, she added.
Crop impact, on the other hand, should be reported and followed up by Manitoba Agriculture.
The same Sprayers101 “how-to” list urges farmers to record yields both in the damaged and undamaged area come harvest, and for several years in the case of a perennial crop.
Jones, meanwhile, suggests that farmers are familiar with formulation, not just chemical names, since that will impact volatility and that, in turn, might help farmers deal with a drift complaint.
— Alexis Stockford is a reporter for the Manitoba Co-operator at Brandon, Man. Follow her at @AlexisStockford on Twitter. This article originally appeared in the June 28, 2018 edition of the Manitoba Co-operator (page 17).