Bradyrrhoa gilveolella
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Common Name
Skeletonweed root moth
Weed Impacted
Larvae feed on roots and root buds of rush skeletonweed, destroying vascular tissue and diminishing plant energy reserves. Damage from several larvae can result in the death of above-ground plant parts and may also weaken the plant’s ability to survive the winter.
Insect Description
When mature, larvae are 20 to 26 mm (approximately 3/4 to 1 inch) long, white caterpillars with brown head capsules and are found in protective tubes (30 to 60 mm or approximately 1 to 2 inch) around skeletonweed roots. Adults are slender, light-grayish moths with three horizontal bands on the front wings. The moth's wingspan is 25 to 28 mm (approximately 1 to 1 1/16 inch).
Life Cycle
This moth completes two generations per year. In its native range (south central/eastern Europe), first generation adults appear in May and June, and second generation adults emerge from late August to October. Females lay eggs either in the rosette crown or in the soil near the plant. Eggs hatch in 6 to 10 days, and the new larvae move down through the soil to begin feeding on roots. Larvae use roots, latex, sand grains, and digested plant material to construct protective tubes in which they continue to feed both on and within root tissues. Mature larvae extend the tubes to the soil surface to form exit chimneys made of silk and digested plant material. The larvae pupates within the tube after closing the entrance with silk. Complete development from egg to adult takes from 2 to 3 months.
Field Identification
Presence of B. gilveolella in the field can be determined by distinctive larval shelter tubes encasing the roots.
Availability
Currently, B. gilveolella has not established in the United States. Research is underway at the University of Idaho to determine whether B. gilveolella can establish and be an effective agent for controlling rush skeletonweed. These insects are currently unavailable for general distribution.
References
Coombs, E. M., J. K. Clark, G. L. Piper, and A. F. Cofrancesco, Jr. 2004. Biological Control of Invasive Plants in the United States. Western Society of Weed Science, Oregon State Univ. Press, Corvallis.
Photo Credits
Bradyrrhoa gilveolella adult - Mark Schwarzlaender, University of Idaho
Bradyrrhoa gilveolella larva - Mark Schwarzlaender, University of Idaho
Bradyrrhoa gilveolella tube - Mark Schwarzlaender, University of Idaho
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