Hunt 365 July 2019-Herbicide Applications, Why and How
I got a call from a close friend the other night while I was watching You Tube videos about, what else, deer hunting. The phone conversation went something like, “Hey, I’m building a sprayer for my UTV. How do you know what kind of nozzles to buy? What about pump size? When I’m spraying, what strength solution do you use?” It had never occurred to me that he didn’t know these things. I had sprayed food plots with him for probably 15 years. Then it dawned on me that in all those years I had always mixed the tank, added the correct amount of herbicides, adjuvants, and AMS. I had previously calibrated one of my sprayers so I knew ahead of time just how much solution would be needed. After all this time, the details of spraying seemed second nature to me…I had just assumed it was for him as well.
When it comes to having really good food plots, the correct use of herbicides can make or break your work. I June’s article, I covered the use of my preferred herbicides like glyphosate and Raptor, but not in detail. In this article I’ll try to walk through a beginning food plotter on how to correctly spray herbicides, or help out someone who’s been doing it for years but maybe not correctly. Correctly applying herbicides will allow you to effectively kill target weeds and plants while using the least amount of chemicals. This will save you money and time.
Crop Oils, Adjuvants and Surfactants, and AMS
Before I get into figuring out your sprayer, I want to cover three common things you’ll see when reading herbicide labels. These things are known as additives to your herbicide solution and are meant to help the herbicide in performing its function of killing target plants. The first is the use of a crop oil. Many herbicide labels will say to use a crop oil or high surfactant oil concentration in your mixture. The goal of a crop oil is to allow for better coverage and penetration of the herbicide into the plants. The second additive/s are adjuvants and surfactants. Adjuvants and surfactants also allow for better performance of the herbicide by lowering the surface tension of the spray solution. The best way I can describe this is to picture spilling water on your countertop. It puddles right? The edge of the puddle of water doesn’t allow for the water to flow easily across the flat surface. Another example…when it starts to rain, notice how the droplets of water land on your vehicle. They are spread out and don’t flow or cover any more space than where they landed because of that surface tension. Crop oils, adjuvants, and surfactants all act to lower surface tension of spray solutions so that more of that solution makes contact with more of the plant surface. Without them, and you will have a greater chance of the solution running off and slower reaction times with the plants. These three additives allow the spray solution to spread out over the growing planting, something that is essential with a post-emergent application of herbicides.
AMS is an abbreviation for ammonium sulfate. On many herbicide labels it directs us to use crop oils or surfactants in combination with ammonium sulfate. Ammonium sulfate acts to help herbicides control weeds by making them more effective during periods of cold weather, or dry weather, droughts, excessive heat, in other words…if spraying during less than ideal periods the use of AMS will help your herbicide work better and faster. When using ammonium sulfate make sure to use either in liquid form or make sure that you are using soluble spray grade ammonium sulfate or your sprayer nozzles will plug.
Figuring Out Your Food Plot Sprayer
I have three sprayers. One was entirely manufactured in my shop intended for use on my Polaris Ranger as a quick attach unit. Another was a store-bought tank and pump with only a hand held wand in which I made a boom for it. And another sprayer that uses a boomless “boom” that allows me to drive down trails and in tight places without a boom extending out beyond my 4-wheeler. I also have a hand held 3-gallon sprayer with a hand pump, and a backpack sprayer. I use each sprayer almost every year for different applications around my farm.
Spot Spraying-When I only need to spray a smaller plot or one of my access trails where I can’t get an ATV, I’ll grab either my hand held or backpack sprayer. Years ago, I would actually spray entire soybean or corn plots with a hand held sprayer. When using a spot sprayer, follow the label instructions for your herbicide under the spot sprayer/hand held sprayer section. Most labels I’m familiar with will give you a simple chart to follow showing how much herbicide to add per gallon to get a desired % solution. Further reading under what weeds are controlled and under listed crops will give you options or ranges to follow when spot spraying. For example, I use my hand-held sprayer and run a 2% solution of glyphosate for general spraying around my apple trees, to burn down small plots, or touch up spraying around my electric fencing. There are 128 ounces in a gallon…so for every gallon you need to add 2% of 128 ounces (.02×128) to get the right solution. This would mean 2.56 ounces of chemical in each gallon. If your herbicide label has a chart, follow it and forget the math…many do.
Tank mixing for boomless or boomed sprayers-The first thing anybody should do when using a tank sprayer is to figure out or calibrate the sprayer so that you know exactly how much spray volume you will be using. If you have a sprayer, simply fill the sprayer with water only. I’ll use my 25-gallon tank sprayer on my ATV for example since this seems to be a popular choice out there. Once filled with water only, spray an acre of ground. Choose a speed that results in total coverage of any plants you are spraying but not so slow that water would run off. The plants need to be covered by not necessarily soaked. Once you’ve finished spraying the acre, simply see how much water you’ve used up. For my sprayer, if I cover 1 acre, I will use 20 gallons of water. I now know that as long as I’m going roughly the same speed, I will always be using 20 gallons on every acre. For tank mixing (other than a hand held sprayer) you will be applying your given herbicide at a rate per acre…say 2 quarts per acre taken from the label instructions. If you want to spray 2 quarts per acre, and you know 20 gallons of water will spray 1 acre, you simply add 2 quarts of glyphosate to 20 gallons of water and go spray. If you have only ½ acre to spray, add one quart of chemical to 10 gallons…etc. Raptor herbicide calls for 5 oz/acre when spraying soybeans. Simply add 5 ounces to every 20 gallons and go spray.
Let’s say, for example, your label instructions say to use a rate of 1.5 quarts per acre of glyphosate, and you want to tank mix Raptor as well for use in soybeans. Raptor label calls for 3-5 ounces per acre…you decide on 3. Raptor also says to use 1 quart of surfactant per 100 gallons of water and 2.5 gallons of AMS per 100 gallons. What would be the total combination?
First, if you want to mix for 1 acre, start with your 20 gallons of water. Then add 1.5 quarts of glyphosate. Now add the 3 ounces of Raptor. Your solution is only 20 gallons, not 100, so you only need 1/5 of the surfactant and AMS. So that’s 1/5 of 1-quart surfactant and 1/5 of 2.5 gallons AMS, or 6.4 oz and 64 oz respectively. Your tank mix for this example would then look like this: 20 gallons water, 1.5 quarts glyphosate, 3 ounces Raptor, 6.4 ounces of surfactants, and 64 ounces of ammonium sulfate. Make sense? I hope so. Once you figure it all out for any given solution, use a black permanent marker and write notes for yourself right on your sprayer tank making things easy the next time. Never spray with reduced strengths of herbicides or you risk making resistant weeds…although spraying without or with reduced levels of additives like surfactants and ammonium is ok. I’ve already sprayed without additives at all on days that were great for spraying like warm, no wind, plenty of ground moisture, young weeds, etc. and had great control.
Final Spraying Tips-There are some things to watch for to make your spraying the most effective. Spray on calm days to avoid drift and to ensure the best solution to weed contact. Spray during the day after the morning dew has burned off but before evening dew sets in. Spraying in the middle of the day with low winds is best. Young plants kill easier than older tall ones so don’t let things get out of control before you spray. Spraying works best when plants are actively growing (for contact herbicides like glyphosate), so avoid spraying during periods of super high stress like cold or hot conditions or periods of drought.
Setting up a sprayer and knowing how to correctly calculate herbicide levels and mixes is one of those topics that quite frankly isn’t very entertaining. Many food plotters I suspect have just gone out and winged it and had some luck. But I also know of food plotters that grossly over-used chemicals and killed off acres of corn and soybeans; or conversely didn’t understand mixes or solutions and didn’t kill anything at all. Many food plotters spray during adverse conditions like windy days, or don’t use additives during times of stress leading to weed consumed plots bearing very little yield. I guess my point is simply this; understanding herbicides and their correct application will save you time and money and will yield you the best possible food plots.