I have been holding back writing about lateral movement of flumioxazin, aka Sureguard, on to a bentgrass putting green. I wanted to see if other movement scenarios would happen of in an incident in Alabama was a freak occurrence. Since an incident happened in December 2013 in Alabama I have heard of other situations of movement in the Carolinas. Considering it is the summer it seems like an opportune time to discuss the potential for movement of herbicides applied normally for Poa annua control in the green surrounds to damage bentgrass if the herbicide moves onto the green.
Sureguard is a single active ingredient herbicide containing flumioxazin, a protox inhibiting herbicide that is primarily used as a preemergence herbicide but also can be used for postemergence burndown in dormant to semi-dormant warm-season turfgrass. In my evaluations it is an excellent preemergence herbicide for annual bluegrass and crabgrasses. The problem is that if one applies Sureguard to green bermudagrass, “chemical induced dormancy” will quickly occur. In other words it will turn the bermudagrass brown. This is not a problem if it is late fall and bermudagrass would be going dormant anyway. In fact, I see it as a positive because Sureguard causes the bermudagrass to develop a lighter, blonde coloration to the turfgrass instead of a normal darker brown.
But the topic at hand is lateral movement. Lateral movement is the movement via surface water, foot traffic, or machine traffic from a treated area to an adjacent non-treated area. Sulfonylurea herbicides, atrazine, simazine, and Kerb (pronamide) are well known for their ability to be move with surface water or tracked to non-treated areas.
Let me set up a typical scenario for lateral movement. In the vast majority of cases it is the movement of a herbicide applied to warm-season turfgrass such as bermudagrass or zoysiagrass on to a cool-season bentgrass putting green, perennial ryegrass overseeded into a fairway, or a tall fescue rough area. Very simply, lateral movement most often occurs when herbicides are applied to warm-season turf and move on to cool-season turf. Golf courses are the ideal situation for movement because of multiple different turfgrass species. Of course movement can occur in other turfgrass situations, but if a sensitive species is not close by then the injury will not be observed.
I’m going to make a broad statement about lateral movement in turfgrass– any herbicide can move laterally short distances in a turfgrass environment. Most information regarding the potential for lateral movement is based on the potential for herbicide soil binding and water solubility. If a herbicide binds to soil and is not water soluble, it is thought that it will not move laterally. To the contrary, if a herbicide does not bind tightly to soil and is water water soluble, it is thought that it can move laterally. This is true in an agricultural environment where the herbicides are applied to the crop and directly to the soil surface. But in a turfgrass environment the herbicide is first captured by the turfgrass leaf material and then the undegraded turfgrass mat layer which lies above the soil or constructed rootzone. Leaf material and undegraded organic material have very low binding compared to degraded organic material and soil.
Consider the application of a herbicide, or any pesticide for that matter, to the turfgrass surface. If the herbicide is allowed to stay on the surface and a large rain event or irrigation event occurs, the material can be “washed” from the leaf surface and move laterally along the turfgrass surface before it has time to percolate into the soil. The infiltration rate would be an obvious factor influencing potential lateral movement with factors such as saturated soils, smaller particle size, and hydrophobic soils increasing the likely hood of lateral movement.
Tracking is another possibility in a turfgrass environment. Herbicides can be picked up after a herbicide application by foot traffic or equipment tires. Allowing the herbicide to dry on the surface can decrease the potential for tracking. But the herbicide can be redissolved by dew allowing for tracking days after application.
Based on these standards for gauging a herbicide lateral movement and tracking, Sureguard seems to have low potential for movement. In addition, creeping bentgrass is more tolerant to Sureguard than sulfonylurea herbicides like Monument, Revolver, Tranxit, or Katana and it is a contact herbicide with minimal translocation throughout the plant. Based on all these factors, Sureguard would be considered to have low movement potential. But the fact remains that this is a turfgrass environment and in my opinion, in turfgrass, anything can move.
And that is exactly what happened at a golf course in Alabama. Sureguard moved laterally following a heavy rainfall and damaged a bentgrass putting green (see images). To make matters worse, herbicide was picked up by foot traffic and damaged the green in footprint patterns.
The key to reducing the potential for lateral movement and tracking is to not apply herbicides that can injure bentgrass above the putting green and do not apply within 15-20 feet of the green. But if applications must me made, to reducing lateral movement and tracking is light, successive irrigations following application can aid to move the herbicide off the leaf surface and into the soil. The majority of herbicides need only 1 to 2 hours on the leaf surface to have an adequate amount absorbed in. Following this, two light irrigations can aid to first wash the herbicide from the leaf surface and second push the herbicide into the soil surface where it will be degraded, bound, or remain available for plant uptake.
These best management practices are the best way to prevent lateral movement. But in the Sureguard movement case in Alabama, these irrigation practices were followed and the herbicide still tracked and moved. So the best practice is to keep a safe distance and do not apply up slope.