Ask an Agronomist
What’s the difference between site of action and mode of action for weed control?
Jan 21, 2014
Question: What’s the difference between site of action for weed control and mode of action? I know figuring this out can help me address weed resistance.
Answer: This is a good question, and one I’m getting more often. Mode of action (MOA) tells us what effect the herbicide will have on the plant. Site of action (SOA) tells us what pathways the herbicide will use to inflict that damage. The goal in preventing weed resistance is to regularly change what pathways are being attacked within the plant by choosing herbicides with different SOAs. By choosing different SOAs, the mutated or resistant plants can be killed before they reproduce, stopping resistance from spreading. It is important to note that choosing products with different active ingredients is not enough; you must make sure that your rotation of products contains varying SOAs. One other consideration, in an attempt to change up the MOA or SOA, applicators and farmers are going to be using products that have not been all that common in the past decade. Be careful, in the process of using different products, that you don’t increase drift problems or carryover issues in the field, and follow all label recommendations.
Weed Warriors: Location, Location
Farmers who wrestle with tough-to-control weeds know all too well the importance of rotating herbicide chemistries, or using multiple modes of action. Multiple herbicide sites of action is also important to understand.
Using Cut Rates for Herbicide Application
Many farmers will be in the field hoping to control winter annual weeds this week. Use caution before turning to a cut-rate herbicide application.
Herbicides By the Numbers
Simplify the chore of herbicide rotation by using the numbers that are located on most herbicide labels.