I have been getting a lot of suggestions for articles and they are always welcomed. The most recent was to write a “knucklehead” article. The comment was “these knuckleheads around here are spraying burndown herbicides in 15- to 20-mph winds with wheat everywhere!”
This call has been followed with several calls about glyphosate injury to wheat. What can I say? A lot of decisions go into spraying, but drift prevention is just common sense and treating someone else like you wish to be treated.
I like the calls such as “Doc, I need to spray a burndown and I have wheat a quarter mile away with a wind of such and such blowing right toward it — will it drift that far?” He really knew the answer before he called, but at least he did call.
Common sense says if in doubt, don’t spray.
Another good one is “the wind was below the 10 mph cut-off — it was only 9.” Yes, but the wheat was right across the turn row — down wind.
More and more, things in agriculture happen in very compressed time frames. It is reality, but it also results in poor decision-making sometimes. I hear statements like, “I didn’t have any choice but to spray because they are calling for rain tomorrow.” The question is would you have sprayed if it was your wheat down wind?
Perhaps a better question is would you have wanted your neighbor to have sprayed in the same situation with your wheat down wind?
There seems to be a continuing misconception that ground sprayers are bullet proof when it comes to drift. Better yet, “I used hoods so it couldn’t have drifted.”
I cannot tell you how many times I have been told by both pilots and ground applicators, “It couldn’t have been me —- my setup will paint a line in a 10-mph wind!” While you might paint a line on the target weeds, you can also have fines blowing downwind that will injure a crop that may be 10 or more times more sensitive than what you are spraying.
There are things that can be done to reduce drift. However, preventing drift usually comes down to the common sense of not spraying when it is too windy and not spraying when there are susceptible crops down wind. It also comes down to asking your self, “Would I want my neighbor spraying if the situation was reversed?”
A lot of growers have lots of bushels of wheat booked at high prices, hoping to help recover from a bad year in 2010. Going from a crop that looks good to one with short flag leaves and blank heads in definite drift patterns is a bummer.
While I am on the topic of drift, I have had to bite my lip several times in meetings when I have heard well-meaning folks making blanket recommendations not to use air induction spray tips when applying the contact-type herbicides such as Ignite or Flexstar. I am sure on the opposite end of the spectrum since I rarely recommend anything but air induction nozzles.
The objective with the contact-type herbicides is to get a spray droplet size in the medium category — 250 to 300 microns in diameter. This is in contrast to the large droplets you can use with a translocated herbicide like glyphosate.
A lot of folks associate air induction tips with large spray droplets. Well, the large air induction tips normally used with glyphosate do produce large spray droplets — especially on the low end of the recommended pressure range.
However, just as with any other type of tip, smaller air induction nozzles produce smaller droplets. By going to smaller air induction tips and operating them in the recommended pressure range, you can easily select a tip that will produce a 250- to 300-micron spray droplet at your desired speed and spray volume.
All spray tips produce a range of droplet sizes. When you get a 250- to 300-micron volume mean diameter (VMD) droplet, there will be a portion of the volume with larger droplets and a portion with smaller droplets, and the smaller ones are normally those that drift. The advantage of the air induction tip is it produces a much more consistent droplet size, resulting in a smaller number of fines compared to a conventional flat fan nozzle delivering the same 250- to 300-micron VMD.
With properly sized air induction tips, you can deliver more of the droplets in the size range you desire to the target. This can actually increase efficacy while reducing the drift potential.