It’s amazing how many things in life seem complex when we try to figure them out for ourselves but then we end up smacking ourselves on the forehead when someone shows us how simple it really is. The infield fly rule comes to mind. Some colleagues of mine here at Michigan State may be on their way to such a solution for the problem of white grubs in lawns. Drs. Dave Smitley (Entomology), Kurt Steinke, and Trey Rogers (Crop and Soil Science) are investigating the effect of mower height on turf damage from grubs.
European chafer grub. Photo: David Smitley
The premise is simple: White grubs damage turf when they consume about 75% of the turf roots present. Raising the mowing height of most standard mowers from 2” to the highest setting (usually 3 ½”) also results in more root growth; often by more than double. Since there’s a limit to how much root mass grubs can consume, increasing the amount of roots ensures the damage threshold is never reached. The working hypothesis has been confirmed by greenhouse tests and now the researchers are taking to the field.
Chafer grub damage. Photo: David Smitley
This may turn out to be another example of how raising mower height and not trying to make your lawn look like a golf course fairway can reduce inputs and keep your turf healthier.