South America
Waterhyacinth (Pontederia crassipes)
Eggs are small, spherical, and creamy-white. First-instar larvae have a brown body with dark spots and a dark brown head. Later instars are cream-colored with scattered dark brown spots and a dark orange head and can be up to 2 cm long. Adults are variable in coloration, and females are often darker than males. Adult forewings range from golden to brown, while the hindwings are more consistently golden. Light-colored segments make their abdomens appear ringed. There is often a distinct white spot midway along the leading edge of the forewing and a distinct dark spot near the center of the hindwing. Adults are typically 6–10 mm long with wingspans of 17–25 mm.
This species is continuously brooded, creating frequent overlap of generations. In warm areas with temperatures above freezing, all stages can overwinter. Adults lay eggs (350–600 in a lifetime) singly or in small groups in leaf and petiole tissue, often in existing leaf injuries or feeding scars left by the Neochetina weevils. Larvae feed on leaf tissue through five instars, mining in petioles towards the root crown. Pupation occurs in cocoons within waterhyacinth petioles. Emerging adults are short-lived (up to 10 days), typically nocturnal, and can often be found resting on the undersides of waterhyacinth leaves. When adults emerge from leaf petioles, a glassy “window” is left covering the emergence tunnel.
Larval tunneling in leaf petioles causes a characteristic curling and browning of the affected leaf. Tunneling destroys shoot tips, preventing future growth. Attacked waterhyacinth stems often die or lose buoyancy and 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