Adjuvants for Post-Emergence Herbicide Applications in Corn

Sithin Mathew, Weed Science Graduate Student, Eric Yu, UMN Extension Crops Educator, and Debalin Sarangi, Extension Weed Scientist

Herbicides often require the use of adjuvants to maximize weed control efficacy and minimize application-related risks. Although some herbicide formulations contain built-in adjuvant packages, few are designed to optimize performance across the wide range of environmental and application conditions. Therefore, the applicator often needs additional adjuvants to optimize the herbicide application for the specific conditions of the area being treated.

The most commonly used adjuvants can be grouped into four categories: 1) activator adjuvants [e.g., nonionic surfactant (NIS), crop oil concentrate (COC), and methylated seed oil (MSO), etc.], 2) water conditioners [e.g., ammonium sulfate (AMS), and volatility reduction agent (VRA), etc.], 3) spray solution modifiers [e.g., antifoam agents, and drift reduction agents (DRA)], and 4) adjuvant mixtures. Adjuvants can enhance herbicide activity by improving spray retention, spreading, penetration, absorption, and overall weed control. For more information on adjuvant use and function in herbicide applications, see the following Crop Protection Network article. Additional information on the history of adjuvants and best management practices can be found in this Crop News article.

Correctly using adjuvants is important because using an incorrect type or rate can result in poor weed control and/or crop injury. The appropriate use of an adjuvant, including adjuvant selection and the amount required, may vary by herbicide and environment. The herbicide label should be the first place to look to determine if an adjuvant is required, the correct type needed, and the recommended rate. If multiple herbicides are being applied, consult the label of each product, paying particular attention to guidance on adjuvants, tank mix partners, and any restrictions or “do not” statements. When label directions differ among products, follow the most restrictive label requirements to ensure compliance and minimize the risk. In this article, we summarize adjuvants commonly recommended for widely used post-emergence herbicides in corn (Table 1). ALWAYS CONSULT HERBICIDE LABELS BEFORE APPLICATION TO ENSURE COMPLIANCE!

Table 1. Adjuvants (NIS/COC/MSO with UAN/AMS) for commonly used post-emergence herbicides in corn

Herbicide	NISa or	COCa or	MSOa	With UANa, b or	With AMSa, b
AAtrex 4L	-	1 qts/A	1 qts/A	DO NOT MIX	DO NOT MIX
Accent Q	0.25%	1%	0.5%	2-4 qts/A	2-4 lb/A
Acuron	0.25%	DO NOT MIX	DO NOT MIX	DO NOT MIX	8.5-17 lb/100 gal
Acuron Flexi	0.25%	Not to exceed 1% or not more than the equivalent of 1 qt/A	DO NOT MIX	DO NOT MIX	DO NOT MIX
Acuron GT (only Roundup Ready corn)	0.25-0.5%	DO NOT MIX	DO NOT MIX	DO NOT MIX	8.5-17 lb/100 gal
Aim EC	0.25%	1-2%	1-2%	2-4%	2-4lb/A
Anthem Maxx	0.25%	1-2 pts/A and concentration must not exceed 2.5%	1-2 pts/A and concentration must not exceed 2.5%	1-2 qts/A	8.5-17 lb/100 gal
Anthem Flex	0.25%	1-2 pts/A and concentration must not exceed 2.5%	1-2 pts/A and concentration must not exceed 2.5%	1-2 qts/A	8.5-17 lb/100 gal
Armezon PRO	0.25-0.5%	0.5-1%	0.5-1%	1.25-2.5%	8.5-17 lb/100 gal
Basis Blend	0.25%	1-2%	1-2%	2 qts/A	2 lb/A
Bicep II Magnum	1-2 qts/100 gal	-	-	-	-
Cadet	0.25%	1-2 pts/A and concentration must not exceed 2.5%	-	1-2 qts/A	8.5-17 lb/100 gal
Calibra	0.25%	-	DO NOT MIX	DO NOT MIX	8.5-17 lb/100 gal
Callisto	0.25%	1%	DO NOT MIX	2.5%	8.5 lb/100 gal
Callisto Xtra	0.25%	1%	DO NOT MIX	DO NOT MIX	8.5-17 lb/100 gal
Calibra	0.25%	DO NOT MIX	DO NOT MIX	DO NOT MIX	8.5-17 lb/100 gal
Capreno	-	1%	0.5%	1.5 qts/A	8.5 lb/100 gal
Clarity, Banvel	1-2 pts/100 gal	1 qts/A	1 qts/A	2-4 qts/A	2.5 lb/A
DiFlexx	0.25%	1%	1%	-	8.5-17 lb/100 gal-
DiFlexx Duo	-	1%	1%	-	-
Enlist Duo/Enlist One (for Enlist corn)	0.25%	-	-	DO NOT MIX	8.5-17 lb/100 gal
Halex GT (for Roundup Ready corn)	0.25-0.5%	-	-	DO NOT MIX	8.5-17 lb/100 gal
Harness Max	0.25%	1%	DO NOT MIX	-	8.5-17 lb/100 gal
Hornet	0.25%	1%	1%	2.5%	2-4 lb/A
Impact/Impact Z	In tank mixtures that prohibit use of MSO, can use at 0.25%	In tank mixtures that prohibit use of MSO, can use at 1%	1-1.5%	2.5%	2-3 lb/A
Katagon	0.25%	0.5-1%	0.5-1%	2.5%	8.5 lb/100 gal
Kyro	0.25-0.5%	0.5-1%	0.5-1%	1.25-2.5%	8.5-17 lb/100 gal
Laudis	-	-	1%	1.5 qts/A	8.5 lb/100 gal
Liberty Ultra (for Liberty Link corn)	-	-	-	-	1.5-3 lb/A
Maverick	0.25%	Do not exceed 1%	DO NOT MIX	DO NOT MIX	DO NOT MIX
Perpetuo	-	1 pt/A	-	1-2 qts/A	2-2.5 lb/A
Realm Q	0.25%	1-2%	DO NOT MIX	2 qts/A	2 lb/A
Resicore REV	0.25%	Do not exceed 1%	DO NOT MIX	DO NOT MIX	DO NOT MIX
Resolve Q	0.25%	1-2%	1-2%; 0.5% if noted on adjuvant product labeling	2 qts/A	2 lb/A
Resource	-	1 pts/A for bradcast; 1 qts/A for drop-nozzle application	1 pts/A for bradcast; 1 qts/A for drop-nozzle application	1-2 qts/A	2-2.5 lb/A
Revulin Q	0.25%	1-2%	DO NOT MIX	2 qts/A	2 lb/A
Roundup PowerMax3 (for Roundup Ready corn)	0.25-0.5%	-	-	-	8.5-17 lb/100 gal
Shieldex 400SC	0.25%	1%	0.5%	2.5%	8.5 lb/100 gal
Sequence (for Roundup Ready corn)	-	-	-	-	8.5-17 lb/100 gal
Sinate (for LibertyLink corn)	-	1%	1%	-	3 lb/A
Status	0.25%	1-2 pts/A	1-2 pts/A	1.25%	5-17 lb/100 gal
Stinger	0.25%	-	-	-	8.5-17 lb/100 gal
Storen	0.25%	DO NOT MIX	DO NOT MIX	DO NOT MIX	8.5-17 lb/100 gal
Surestart II	-	-	-	DO NOT MIX	DO NOT MIX
Surtain	0.25% with AMS (optional)	-	-	-	8.5-17 lb/100 gal (optional)
Tough 5EC	0.25%	Do not exceed 2.5%	DO NOT MIX	2-4 qts/A	2-4 lb/A
WideMatch	-	-	-	-	-
Yukon	0.25-0.5%	1%	1%	2-4 qts/A	2-4 lb/A

^aAbbreviations: NIS is nonionic surfactant (% v/v or dose specified), COC is crop oil concentrate (% v/v or dose specified), MSO is methylated seed oil (% v/v or dose specified), UAN is urea ammonium nitrate, and AMS is spray grade ammonium sulfate.

^b Whenever the label states “at recommended rates” or “specified use rates” for AMS they are referring to this rate of 8.5 - 17 pounds per 100 gallons. DO NOT MIX if not specified in the label.