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Continuation of Validation and Implementation of a Control Decision Rule for Scarab Grubs in Turfgrass 1997

Project Leaders: M. G. Villani & J. P Nyrop

Objectives:

1. Determine whether our control decision rule for European chafer has general applicability for monitoring this pest in turf by

a. ascertaining whether the pattern we observed among mean density, maximum patch size, and density in the patch and the risk rating system apply to various locations, times, and spatial scales

b. verifying that samples taken 3m apart capture the spatial structure of scarab larvae populations and determining the spatial resolution required for samples taken when estimating density for use in the decision rule.

2. Determine the applicability of our European chafer control decision rule to the Japanese beetle.

3. Disseminate the information generated by this work through hands-on training, demonstration, educational meetings, and newsletters.

Results:

The pattern of patch size in relation to average grub density was found to be quite robust and can therefore serve as a basis for the protocol for deciding on the need for control. The risk rating system was also found to be robust. Patterns of grub abundance were found to be correlated in time but not so much as to obviate the need for sampling. The European chafer decision guide can be depended upon to provide reliable decisions on the need for scarab grub control in home lawns. Use of the decision protocol should reduce the need for insecticide applications by 50-80% when compared with prophylactic treatments.