Egg                                             Larva                                              Pupa                                                Adult

(Click on images to enlarge)

Professional Lake Management is always looking for new and innovative management techniques for the control of exotic species.  Biological control is used as a natural integrated tool of a management program for controlling unwanted pests.

What is Biological Control?

Biological control is the use of one organism (the control) to manage another (the pest).  Under most circumstances the “pest” is an exotic plant or animal introduced into a new area where it lacks any native control boundaries.  Freed from ecological context in which it evolved, it tends to take over the community where it is found.  To counteract this, another exotic organism is introduced to control the first pest.  The long-term goal of a biological control is not eradication of the pest, but rather to provide a controlled, low density of both the weed and the control agent.

The Middfoil™ process is a biological control that utilizes an insect that specifically feeds on Eurasian Watermilfoil.  This insect, a native aquatic weevil, is intentionally introduced in to the water body where Eurasian Watermilfoil is a problem.  The weevil has proved to be an effective control agent in extensive field trials.  Depending on specific lake characteristics the weevils take from two to five years to produce expected results.

Life Cycle of the Weevil

The adult weevil is small, only about 2-3 millimeters or slightly smaller than a grain of rice.  The adult weevil lays eggs on the growing tips of milfoil.  These eggs hatch within a week and the larvae begin to feed upon the plant.  Eventually the larvae form puparia in the lower stem of the plant.  Adults hatch out, swim to the top of the plants and begin the life cycle again.  In the Midwest, the weevil goes through about 3 generations a summer.  In autumn, the adult weevils move to plant litter at the lake margin where they over-winter.  The following spring, the adults fly back to the plants in the lake.

While the adults and larvae both feed on the milfoil leaves, the larvae do the most destruction by eating the conductive tissue inside the stem.  Eventually, damaged plants lose buoyancy and the stems fall to the bottom of the water body and slowly decay.

As Eurasian Watermilfoil decreases in a managed lake, the weevil population gradually declines to a self-sustaining level.

Inquire to see if this is an option for your lake. (Click here to request more information)