Growing grub-tolerant home lawns

Grub damage to lawns spurs homeowners to apply millions of dollars worth of insecticide each year. In Michigan, European chafer causes more lawn damage than all other turf pests combined. For more than 30 years turf scientists have searched for types of turfgrass that are resistant to white grubs, without any success. In our own research at Michigan State University we found that some turf types were more tolerant of European chafer grubs than other types. In greenhouse and field experiments with three cultivars each of four species of cool-season turfgrass,European chafer grubs were added to turf cylinders to evaluate grub-tolerance levels. By washing, drying and weighing root masses of all treatments along with the non-grub controls, we were able to conclude that the grub tolerance was highly correlated with the density or mass of turf roots in the control treatments. The historical body of research on turf management, including Beard's original work, 'Turfgrass: Science and Culture',indicate that fertility, soil moisture, and mowing height are important factors that influence root mass,with mowing height being the most critical. Based on previous research in entomology and turf managment we are now investigating how much of the European chafer damage to home lawns could be avoided by raising mowing heights from 2.5 to 3.5 inches.