Argentine Stem Weevil
Scientific Name:
Listronotus bonariensis
Order:
Coleoptera
How To Identify Argentine Stem Weevil
The presence of Argentine Stem Weevil can be identified by their larvae or mature / adult form:
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The immature/larval stage of the Argentine Stem Weevil is a legless, creamy-white, active larvae up to 4mm in length.
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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.
What is the biology and lifecycle of Argentine Stem Weevil?
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.
Damage Caused by Argentine Stem Weevil
Argentine Stem Weevil damage to turf typically occurs around November, and February when large numbers of later instar larvae are present. The larvae feed initially within the plant stem following hatching, and then drop from the stem to feed at the plant base and crown. The feeding habits of the larvae make it the most damaging stage of the pest’s lifecycle.
Symptoms of turf damage from Argentine Stem Weevil initially occur as the plant begins to yellow when larvae are feeding within the stem. The injured turf plants then turn straw colour, exhibiting symptoms similar to drought stress or localised dry spot, particularly in golf greens.
Management Tips for Argentine Stem Weevil
Early preventative treatment is paramount in successful season long control of Argentine Stem Weevil. If the initial generation of Argentine Stem Weevil is allowed to develop, subsequent generations will emerge and life stages will overlap creating a large, diverse population that is difficult to control.
