Euhrychiopsis lecontei, also known as the milfoil weevil, is a type of weevil that has been investigated as a potential biocontrol agent for Eurasian water milfoil. ^[1] It is found in the eastern and central United States and western Canada. ^[2]

Life cycle

E. lecontei is a holometabolous insect, undergoing true metamorphosis. Development is temperature dependent, but the time to develop from eggs to larvae is about 4 days, from larvae to pupae 13 days, and from pupae to adults 13 days. Larvae are stem borers and damage plant tissue from about 7 cm from the tip of the plant.

Use as a Biocontrol

Milfoil weevils occur in natural populations in much of North America on their native host, Northern watermilfoil ( Myriophyllum sibiricum). They often reach sufficient densities to suppress invasive Eurasian watermilfoil ( Myriophyllum spicatum) infestations after a prolonged infestation or artificial augmentation. Studies indicate that for effective control a density of about 1 weevil per two stems of milfoil (0.5 weevils per stem) is necessary. ^[3] There are mixed reviews that fish such as bluegills can reduce weevil populations as research has only been conducted in very limited settings. ^[4] Augmenting native weevil populations as a biological control is effective as long as there is a small amount of milfoil to sustain the population. Milfoil weevils are commercially available as a management option for Eurasian water milfoil by a firm based in the United States and Canada. ^{[5] [6]}

References