Choosing the right adjuvant for the job

Anything that prevents a herbicide from reaching its target, deactivates a herbicide or reduces exposure to the target weed is a hur­dle to effective pest control. Often, these hurdles seem daunting. While matching applications to proper en­vironmental conditions is critical for highly effective weed control, there are tools we can use to overcome threats to herbicide performance— even in optimum circumstances. Among these are properly selected, high-quality adjuvants.

Adjuvants are often one of the least understood but most effective tools to enhance crop protection performance. Depending on the product, a properly selected adjuvant can prove invaluable to increasing the likelihood of plant uptake. Adjuvants condition water to prevent herbicide deactivation, reduce drift fines and make mixing and tank cleanout easier. The key to successful adjuvant use is knowing the right product for the job.

Adjuvants typically fall under three basic categories: activators, spray modifiers and utility products.

Activators

These include non-ionic surfactants (NIS) such as MFA’s Astute, crop oil concentrates (COC) such as MFA’s Relay, and methylated seed oils (MSO) such as MFA’s SoyPlus. NIS, often called “wetters” or “spreaders,” are designed to reduce surface ten­sion of a water droplet. This action causes a droplet to flatten out and spread across a leaf surface, increas­ing the surface area in contact with the leaf. NIS products contain ingre­dients such as organosilicones that have some penetrative properties, but typically oils (COC and MSO) are considered true penetrants. While oils provide less reduction in surface tension than NIS, they increase penetration through barriers such as waxy leaf cuticles.

Selecting the proper activator is a balance of increasing weed control without adversely affecting crop safety. For example, oils can add to weed control, especially in unfavor­able conditions, but can have nega­tive effects with certain herbicides.

More and more products such as Xpond, a high-surfactant oil con­centrate (HSOC), are being used be­cause of their combined effects as a spreader and oil. Lower oil use rates makes them safer on crops without sacrificing weed control.

Spray modifiers

These products vary in utility and include fertilizers, water condition­ers, humectants and deposition and retention aids (DRA). Fertilizers such as ammonium sulfate (AMS) are of­ten used as a water conditioner. AMS can neutralize hard water ions that deactivate herbicides such as glypho­sate but can also improve uptake of herbicides by introducing ammo­nium to the solution. Problems with use of ammonium-containing fertilizers include high volume re­quirements and incompatibility with newer dicamba formulations due to increased volatility. Low-use alter­natives are available. Some contain ammonium, such as Waypoint, and some don’t, such as Impetro II.

Humectants aid weed control by increasing a droplet’s drying time. Extending the time a herbicide remains in liquid form can improve uptake by weeds, increasing control. In MFA’s Crop Advantage lineup, humectants have been added to Impetro II and AMS Advantage.

DRAs are used to control drift and minimize droplet bounce to reduce off-target movement and leaf retention. Compatibility and consid­erations with tank-mix partners are important, so choose DRA products wisely. PowerShot and SoyPlus HD contain both penetrants and DRAs, and MFA’s Impetro products contain DRAs in addition to humectants and water conditioners.

Utility products

This broad category of adjuvants covers several products that mostly work to increase the ease of handling pesticides. Included in this group are defoamers, tank cleaners such as Evict and compatibility agents such as Convert that can prevent or even remedy certain tank-mix issues.

With such a wide array of func­tions and compatibility, adjuvant selection is challenging. To compli­cate matters further, adjuvants are not regulated like pesticides, and the market is full of untested, inferior products claiming to be of equal quality. For example, you would assume an NIS labeled 90/10 would contain 90 percent surfactant. In fact, the label only implies 90 per­cent active ingredient, which could be any number of things and make a typical rate ineffective.

The uncertainty in the market is why MFA developed its Crop Advan­tage line of adjuvants. We subject our products to third-party testing by the Council of Producers and Distributors of Agrotechnology to ensure the highest quality. Growers can be assured that products with a Crop Advantage label adhere to MFA values of honesty, integrity, account­ability, innovation, technology, cus­tomer partnering and stewardship. For more information, visit with your local MFA crop specialist.