Environmentally Responsible Gardening & Landscaping in the Low Desert Masked Chafer Beetle/Annual White Grub (Cyclocephala spp.) in the Low Desert
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Description:
Grubs: The grubs are light colored (white or cream), C shaped, up to one inch long. They have dark translucent dorsal stripes, brown head capsules and legs, and the bristles on the underside of the posterior end of the abdomen (the raster) are scattered rather than parallel as are those of the May or June Beetle. Masked Chafer Beetle grubs have a slight constriction at the forward portion of the abdomen, which helps distinguish them from other grubs. Beetles: Adult beetles are golden brown, hairy on the underside of the thorax, and have a darker brown head "mask". Lifecycle: Masked Chafer Beetles complete one generation per year overwintering as mature larvae, which form earthen cells in soil where they pupate. In late spring or early summer Masked Chafer Beetles emerge from the soil to mate. Then females burrow back into the soil to lay their eggs. In just two to three weeks the small, first instar grubs (Annual White Grubs) emerge and feed on the roots of grass throughout the summer. They grow rapidly (doing most of their damage at this time) and will have matured by mid to late September. They continue to feed until cool weather begins in late October, when they burrow deeper into the soil and remain dormant for the winter. As soil temperatures warm in the spring, the grubs become active and move up in the soil to just below the grass root zone. These full sized grubs do little damage. In May grubs pupate and the beetles emerge two to three weeks later to repeat the life cycle. Adult males are attracted to lights at night, mostly from mid-June through July.
Damage:If large populations build up, Masked Chafer Beetles can be a problem on turf. As the grub matures it does more and more damage. By late summer early fall damage becomes noticeable. The turf turns brown in irregular patches and comes up easily. Symptoms of drought stress persist even after the turf has been watered. In areas with heavy infestations the turf may roll back like a rug, because the roots have been destroyed. Digging by vertebrate predators, such as crows, raccoons, skunks, and coyotes, is a common indication of high grub populations. The damage is more severe on turf that is stressed due to improper watering, improper fertilization, competition with weeds, or improper mowing heights.
Monitoring:Unless there are more than six grubs per square foot there is no need for treatment.
Management:Cultural: Spike-aeration of turf may kill significant portions of white grub populations when they are feeding close to the soil surface (approximately 45 days after beetles appear). Chemical: Treat with insecticides labeled for use on grubs 45 days after adult beetles appear. This is when the immature forms are closest to the surface and most vulnerable. Ariefication or dethatching prior to application will improve the success of using an insecticide to treat grubs. In addition, you will need to water adequately ahead of time to bring the grubs to the surface. |
Photograph from Department of Entomology, University of Nebraska-Lincoln
Photograph from Department of Entomology, University of Nebraska-Lincoln
Photograph from Department of Entomology, University of Nebraska-Lincoln Photograph from Department of Entomology, University of Nebraska-Lincoln |
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