Horseradish

Imported crucifer weevil adults are metallic blue-black and only about 1/10 inch long. Their mouthparts are at the end of an obvious, elongate "snout" that protrudes forward and down from the head. The adults use this snout to chew egg-laying holes in the roots. The resulting larvae are stout, legless, white larvae that tunnel along the root surface. The larvae pupate in these tunnels and emerge as adults. There are two generations per year.

Larval tunneling can be extensive enough to reduce yield or even kill sets. These surface tunnels reduce the market value of the roots.

Imported crucifer weevils have been in Illinois and the mid-west for more than 35 years. The adults overwinter in unharvested roots and sets that are in cold storage. Since the adults cannot fly (most weevils have fused wings that make them flightless), they walk to the new plants to feed or are carried through human movement of plant material.. Eggs are laid in the spring. Legless larvae emerge and feed on plant roots. These weevils pupate in the roots before emerging as adults. There are two generations per year in the mid-west.

Crop rotation, along with the control of volunteer horseradish, is effective. Although imported crucifer weevil has fully developed wings, it primarily walks to new hosts or is carried through human movement of plant material. At planting, treat sets with an insecticide if they are infested or the fields have a history of weevil damage. Examine crowns in early August and apply foliar sprays if adult weevil populations exceed one to three per ten plants, or use the field's weevil history to determine the potential for damage.

Home, Yard & Garden Pest Guide
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Illinois Commercial Landscape and Turfgrass Pest Management Handbook
The Illinois Commercial Landscape and Turfgrass Pest Management Handbook (ICLT) is written for professional applicators and provides nonchemical and current chemical recommendations as well as application timing information for all major pests of turf, woody ornamentals and herbaceous ornamentals. This publication may be purchased at your local University of Illinois Extension Unit office, or by calling 800-345-6087, or by placing an order online (search for "ICLT").
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U of IL - Distance Diagnosis through Digital Imaging
A free plant, weed, insect and disease identification service available through your local University of Illinois Extension office. Center Educators or State Specialists review & respond to information and digital images submitted by local Extension office personnel. Some samples may require further examination or culture work (nominal fee involved) at the U of IL Plant Clinic.
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U of IL - Plant Clinic
Services include plant and insect identification, diagnosis of disease, insect, weed and chemical injury (chemical injury on field crops only), nematode assays, and help with nutrient related problems, as well as recommendations involving these diagnoses. Microscopic examinations, laboratory culturing, virus assays, and nematode assays are some of the techniques used in the clinic.
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