South America
Waterhyacinth (Pontederia crassipes)
Neochetina bruchi & N. eichhorniae are closely related and morphologically very similar. Eggs are white and oval. Larvae are C-shaped, white with yellow-orange heads, and up to 9 mm long. Pupae are white and enclosed in cocoons. Adults are somewhat rounded and have long snouts. Adult Neochetina bruchi are tan or brown and often have a lighter-colored V-shaped band on the lower parts of the elytra. Adult N. eichhorniae are usually a darker mottled gray and brown. Both species have two dark markings on their elytra. The markings are shorter for N. bruchi and located midway down the elytra while the markings for N. eichhorniae are longer and situated closer to the weevil’s head.
Both species are continuously brooded, creating frequent overlap of generations. In warm areas with temperatures above freezing, all stages of the beetles can overwinter. Adults may live longer than a year and can be found year-round. Adults feed on waterhyacinth leaves and stems, producing feeding scars 2–3 mm wide. Adults lay eggs (300–400 in a lifetime) embedded in waterhyacinth leaf and petiole tissue. Neochetina bruchi may deposit several eggs in the same site while N. eichhorniae deposits eggs singly. Larvae feed on plant tissue through three instars and mine the petioles towards the root crown. Neochetina bruchi larvae develop somewhat faster than N. eichhorniae larvae. Pupation occurs in cocoons attached to waterhyacinth roots below the water surface. Emerging adults climb on waterhyacinth tissue above the water surface to feed and mate.
Adult feeding causes characteristic feeding scars on leaves and petioles. Larval feeding produces mining tunnels in leaf petioles. Damage from adults and larvae stunts plant growth and reduces floral and vegetative reproduction. Heavy feeding and mining causes leaf petioles to become thin and brittle, and plants become waterlogged and gradually sink.
Smith, M.C., A.B.C. Goode, and N.E. Harms. 2022. Waterhyacinth 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-2022-16-WATERHYACINTH-A. https://bugwoodcloud.org/resource/files/25358.pdf