|
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
 |
|
|
|
 |
|||
|
You Can Solve Most of the World’s problems With a Good Adjuvant OK, maybe that’s a stretch. But at the very least, improve performance of your post emergence herbicides, which are getting more specific to their required adjuvants. By Jason Hanson With the upcoming post emergence weed control season Most of today’s post emerge products require some sort of adjuvant to enhance their performance or improve their consistency. But there is much confusion about adjuvants in general, and almost all companies marketing them claim that theirs are better than the next guy’s stuff. In order to separate out the differences, we need to look at what an adjuvant is, and the types used with certain products. What is an adjuvant? An adjuvant is any additive used in conjunction with a pesticide to increase biological activity and/or to modify various physical properties of a spray solution. That is a pretty broad explanation, but for effective weed control, herbicides must adequately contact the leaves, be absorbed in sufficient quantities, move within that weed to its “site-of-action” and reach toxic levels at its “site-of-action” to effectively destroy that weed. There are many physical variables that affect spray application, such as solubility, compatibility, foaming, droplet size, drift, surface tension, volatilization, coverage, adherence and penetration. Adjuvants play a key role in helping to control those variables. Adjuvants are classified into four categories:
Let’s look a bit closer, beginning with the two categories that generally cause the most confusion, activators and spray modifiers. There are certain fits for each adjuvant, just as there is for each post applied chemical. So it is very important to know the difference and where they are to be used. Let’s break down the activators into each product. I use Agriliance adjuvants as examples. Non-Ionic Surfactants The purpose of a surfactant like Preference is to increase spray retention, allowing the pesticide to cover more area of the leaf and have a better chance of being absorbed. Some weeds have very hairy leaf surfaces, and a surfactant aids in making sure that a spray mix droplet doesn’t get hung up on the leaf hairs and evaporate. Be aware that when doing a tank mix with Puma, Bison, and Tilt, adding more/increasing the rate of surfactant might cause some crop response, as there are solvents and formulations that get “hotter” when more is added to the tank, under certain weather conditions. Common use rates for non-ionic surfactants are 1-2 quarts/100 gallon. Crop Oils Crop oil use rates are usually from 1 pint per acre up to 1 gallon per 100 gallons, depending on chemical being used. The difference between crop oils and methylated seed oil (MSO) isn’t that large, until you get into specific herbicide types and environmental conditions . Products like Raptor, Steadfast, Option, FirstRate, and Upbeet really like to have an MSO in the tank. Notice that these chemicals are in the ALS class. That is because an MSO like Destiny has even greater activity than crop oils when it comes to cuticle penetration and ultra violet degradation. When the weeds get taller than you would like them to be or the weather is drier and hotter, then the switch from a crop oil to an MSO is warranted. Most of the time MSOs are recommended at 1% v/v basis (1 gal/100 gal of spray solution). Basic pH blends Fertilizers Almost all glyphosate needs AMS, as it helps to condition water from things like calcium, magnesium, and iron, and also helps reduce antagonism that may occur on the leaf surface. Products can vary. Some are promoted as water conditioning agents. Some contain straight rates of AMS, like Alliance or Class Act Next Generation, while others like Arrow Four have reduced rates of AMS but are mainly built for convenient handling. Some contain additional surfactants along with the AMS. With all products, you have to weigh performance with convenience, as weather conditions change and weed species are in need of different rates of AMS. Spray modifiers When it comes to drift control, there are two classes- the encapsulators (or droplet modifiers) and the thickeners. The thickeners will make the spray solution get a latex look and makes the droplets a larger size, thus reducing the amount of fines that come out of your sprayer. These work very effectively in visual reduction of drift, but can also reduce your spray pattern. A thickener will take a 110-degree pattern and bring it down quite considerably, to like an 80 degree. Corral AMS Dry is an example of a thickener. Thickeners come in liquid or dry forms and usually contain some amount of AMS in them. The early polymer products were referenced to as “snot in a jug” as they were sticky and not real pleasant to handle. Encapsultors are invert emulsions that put chemical into certain size droplets for drift control. Even though it sounds like magic pixi dust, dealers that have used products like Placement and Placement Propak have had great luck in managing off-target drift. These products manage the chemical, and do not affect the spray pattern. The newest introduction to this group is Interlock, and has some encapsulation properties but mainly is a droplet modifier. Getting most of your droplets into a 200-400 micron size helps with keeping product where it is needed. Interlock also has very good deposition qualities, making it have great fits with fungicides and insecticides. Drift products fit into situations where liability and headaches are not wanted. They are a tool, but the main thing to consider when drift is a concern is the product being used, wind speed and direction, pressure used, and common sense. Use What’s Recommended Always read the label and match up your herbicide with the right adjuvant. Sometimes that additional cost of the additive is very small when it can improve your performance, by 10% or more in some cases. All post emergence pesticides are getting more specific to their required adjuvants, so keep up to speed on the best fit for your spraying needs. Hanson is a certified crop advisor near Devils Lake, N.D. Agriliance adjuvant web site: www.agriliance.com/1crop_protection/adjuvants .asp . ------------------------------------------------ NDSU Tips on Choosing Adjuvants With Herbicides Some herbicide labels restrict use of oil adjuvants and recommend only the use of NIS alone or combined with nitrogen based fertilizer solutions. Follow label directions for adjuvant selection. Where labels allow use of oil additives, a petroleum oil based adjuvant referred to as crop oil concentrates (COC) or methylated seed oil (MSO) adjuvants may be used. The term crop oil concentrate is misleading and incorrect. The base substance in COC is petroleum oil based ingredients, not crop oil based. NDSU research has shown wide difference in adjuvant enhancement of herbicides. However, in many studies, no or small differences occur depending on environmental conditions at application, growing conditions of weeds, rate of herbicide used, and size of weeds. For example, under warm , humid conditions with actively growing weeds, NIS + nitrogen fertilizer may enhance weed control the same as oil additives. The following are conditions where MSO type additives may give greater weed control than other adjuvant types: Conditions That Favor Use of MSO Type Adjuvants
– NDSU Extension Service NDSU list of adjuvant products and approximate prices: |
|||
upon us, it is time
to get the calculator out and start thinking ounces and pints per acre, gallons per 100, pressures and water volumes, anti-foam, tank cleaner and adjuvants.