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By Dr Brian de Villiers
March 2021
We often still think of adjuvants as efficacy enhancing products. This is an incorrect perception as we should regard them as efficacy restoring products. All crop protection products (CPP) have a certain potential that they could reach under optimal environmental conditions. Unfortunately, environmental conditions are seldom optimal, therefore CPP never reach their true potential. Adjuvants are used to ensure that CPP reach more of their potential to enable adequate control In the ensuing paragraphs two growers with different strategies about adjuvants with glyphosate will be discussed.
Grower 1
Grower 1 understands that glyphosate is antagonised by hard and brackish water
and that ammonium sulphate is beneficial to glyphosate, even in low salt content water. Therefore, he uses a quality ammonium sulphate adjuvant. He is also aware that coverage is vital, and he uses the correct water volume and a deposition agent.
Furthermore, he understands that some oil adjuvants are antagonistic to glyphosate and he therefore only uses surfactants if needed for additional coverage, spreading and absorption. By choosing his adjuvants wisely, Grower 1 ensures that glyphosate reaches most of its potential and he gets effective weed control.
Grower 2
Grower 2 decides not to use an ammonium sulphate adjuvant to address antagonistic salts in water and he may lose 7% of the efficacy.
He doesn’t use a deposition agent and also chooses to use an antagonistic oil adjuvant for retention, spreading and absorption.
Because of these incorrect decisions, he may lose another 8% efficacy Grower 2 has therefore lost a total of 15% of the glyphosate potential 15% may not sound that much, but it could be the difference between acceptable and unacceptable control.
It could also warrant a re application with all the additional costs involved. The 15% loss in efficacy is a theoretical number to try and illustrate a point.
Under harsh environmental conditions, this number can be much worse!
Conditions
These differences in efficacy because of adjuvant choice are sometimes not as evident under optimal conditions. This is because glyphosate is more forgiving under optimal conditions and the effect of incorrect adjuvant choice is not as visible. However, when environmental conditions and water quality are poor, incorrect adjuvant choice is exposed. This often leads to poor weed control and a re-application.
Villa’s stance
The use of the correct adjuvants with glyphosate is crucial Incorrect adjuvant choice will be exposed under sub optimal conditions, leading to poor weed control. Use the registered Villa adjuvants to help glyphosate to reach its true potential. Small differences with adjuvant choice could have a huge impact on weed control.
