Question of the Week
Thank you for your question about managing white grubs. Please see ATTRA's Sustainable Turf Care publication. This publication has information about managing white grubs on pages 18 and 33. I would also recommend that you visit the ATTRA webpage to access the new Biorationals Database tool, described in more detail below.
White grubs are the larval stage of many species of scarab beetle, including Japanese beetles, European chafers, Oriental beetles and Asiatic garden beetles.
The beetles spend the winter as a grubs, buried in the soil. There they feed first on decaying vegetation and later on plant roots. The adults emerge in July and August. “They prefer to feed on parts of the plant exposed to the sun. As a rule, there is one generation annually, but the grubs may take 2 years to develop in wet cold soils” (1). Adults are strong fliers, able to travel up to 5 miles. They feed and fly during the day.
Adult beetles feed on more than 350 kinds of plants, so crop rotation or elimination of hosts would be almost impossible. However, some older research (1963) indicated that Japanese beetle grubs do not do well in red, white, sweet or alsike clovers, alfalfa, soybean, buckwheat, or orchardgrass. Using one or more of these as a cover crop or green manure might lessen the incidence of Japanese beetles in your fields.
It is important to keep fields free of weeds and turf, since these are the places where beetles prefer to lay their eggs. A recent study that examined beetle populations in nursery fields found that Japanese beetles were far more abundant in grassy areas bordering fields than in the field itself (2). Weedy fields supported more than 10 times as many larvae as clean fields.
Some of the most promising research in biological control focuses on using the nematodes Heterorhabditis bacteriophora and Steinernema glaseri to kill beetle grubs in the soil. You can get more detailed information if you go to the ATTRA website homepage, click on the “Biorationals Database” (right hand column) or simply go to:
and then use the database by selecting “Insect” in the “Pest Category” box, and under that, selecting “white grub” in the “Pest Name” box, then click on “search treatment options” box just below the “pest name” box. The table generated by this search provides hotlinks to more details about each product, including labels, active ingredients, pests controlled and manufacturer contact information.
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