Empirical and theoretical assessment of mechanical and injection cultivation methods to manage white grubs in turfgrass

Abstract

AbstractWhite grubs, or the larvae of scarab beetles, are widespread destructive pests of turfgrass systems around the world. We sought to determine if turfgrass cultivation machinery could reliably manage white grubs in turfgrass systems. Hollow‐tine aeration provided greater reductions in grub densities than solid‐vibratory tine and air/solid injection cultivation in field trials. In following studies, low to moderate reductions (0–53%) were observed with single hollow‐tine applications, though low grub densities encountered within field plots hindered the ability to detect statistical differences between cultivation treatments including tine diameter and tine spacing. Increasing aerification frequency on plots from one to two or more passes produced statistically significant reductions (>80% control) in both years of trials. To eliminate the variability observed in the field, a simulation model was constructed to determine the expected outcome of varying tine patterns have on increasing grub densities. Models suggests that expected mortality is likely to be minimal (<10%) in one‐time aerification events. In‐field simulations using templates overlaid on natural populations demonstrated two‐fold greater control than theoretical simulations. Differences in control between field studies and model simulation are likely caused by an over‐estimation of mortality when performing presence‐absence counts in field studies when grub densities are low. Although multiple aerification events will likely improve control, current cultivation practices are unlikely to achieve the level of control expected by turfgrass managers in intensely managed landscapes.