The immature/larval stage of the Argentine Stem Weevil is a legless, creamy-white, active larvae up to 4mm in length. When mature the adult appears as a dark grey to black weevil with mottled grey body markings and a distinctive protruding snout, up to 3mm in length.
Biology and Lifecycle
Populations of Argentine Stem Weevil will have 2-3 generations per year, with the second and third generation often overlapping resulting in a large population at various life stages. Adult weevils emerge from overwintering sites between September and November. After mating the female weevil deposits several eggs under the leaf sheath of the host plant. Once the eggs hatch the larvae begin to feed inside the plant stem until they reach the second or third instar at which point the burrow out of the plant and drop to the ground. Once outside the plant the larva begins to feed at the base of the turf plant, ingesting plant material from the stems and crown. After the fifth instar is reached the larva pupates within the upper soil profile and the adult soon emerges. Adults then mate and lay the next generation of eggs, or over winter to resume the lifecycle the following season.