Europe, Mediterranean
Rush skeletonweed (Chondrilla juncea)
Eggs are tiny, flattened, and initially white but turn a darker red with age. Newly hatched larvae are tannish-orange with brown heads. Late-instar larvae are robust, 20–25 mm long, off-white, and have brown head capsules. Pupae are tan and up to 25 mm long. Adults are up to 13 mm long, cream-colored, and have three light brown horizontal bands on their front wings. They have wingspans up to 28 mm.
Although two generations per year have been reported in southern Europe, it appears most Bradyrrhoa gilveolella in North America have one generation per year. In North America, adults emerge throughout summer as rush skeletonweed is bolting and flowering. Females lay eggs (up to 250 each) on rush skeletonweed stems or soil near plants. Once in contact with the plant, larvae feed into the stem base, and move downward to attach themselves to the root. Several larvae may feed on the same root simultaneously. Larvae develop through five instars, feeding on the root cortex and spinning feeding tubes made of silk, sand, and frass as they travel. Larvae overwinter in feeding tubes, and pupation occurs in the tubes throughout spring and summer. Tubes (also referred to as exit chimneys) are 7 cm long on average, extend to the soil surface, and are used by the moths to reach the soil surface.
Adults do not feed on any plant material. Heavy larval feeding results in diminished root reserves and decreased plant vigor of attacked rush skeletonweed plants. The attack on roots reduces plant density and can lead to decreased plant populations over time.
Milan, J., J. Littlefield, C.B. Randall, and J.E. Andreas. 2022. Rush Skeletonweed Biocontrol Agents: History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2022-13-RUSH SKELETONWEED-A. https://bugwoodcloud.org/resource/files/25241.pdf