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United States Department of Agriculture

Agricultural Research Service

Title: Late Fall Rescue Treatments Against European Chafer Grubs Infesting Rhododendrons in An Ohio Nursery

Authors
item Reding, Michael
item Klein, Michael
item Brazee, Ross

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 26, 2002
Publication Date: N/A

Technical Abstract: In October 2001, European chafer (EC) larvae (grubs) were infesting young (planted late May 2001) PJM rhododendrons in a nursery in northern OH. The EC grubs were causing severe damage and plant death by feeding on the plant roots. Dying plants were wilted and upon further inspection the fibrous roots had been removed and the stems were often girdled. No grubs were found beneath dead plants, but examination of plants containing fibrous roots detected grubs in almost all cases. This suggested that when the fibrous roots of a plant were gone the grubs moved to a new plant. There was no other vegetation in the block, thus, the rhododendrons were the only food source available to the grubs. Some type of rescue treatment was needed to prevent further loss of plants. Insecticides were applied directly to the root ball of each plant. Three different applicators were tested: 1) a nozzle produced by the grower which screwed on to a handgun sprayer (high-pressure car washer); 2) a high-pressure spray nozzle with a rubber splash guard that attached to the same handgun sprayer as applicator 1; 3) a LESCO root feeder (#013873) with a flow meter added. The LESCO feeder and grower nozzle applicators were able to saturate most of the root-zone. Insecticides applied by all three applicators significantly reduced numbers of EC compared to the untreated plants. There was no difference in EC numbers among the applicator treatments. Healthy EC grubs were found in all untreated plants except one. Almost all grubs in the insecticide treated plants were sick or dead. These data indicate that applying insecticide directly to where the grubs are located can provide acceptable control. This application technology warrants further investigation.

Last Modified: 10/22/2014
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