Adult Control

Even the most rigorous larviciding program may not be able to keep adult mosquito populations at acceptable levels.

For instance, Saginaw County has a species of mosquito which is very difficult to control in its aquatic stages; larvae of the cattail marsh mosquito Coquillettidia perturbans attach to aquatic plant roots to obtain oxygen.

Another factor is Saginaw County has State and Federal Wildlife lands located in the center of the County which are not accessible to larviciding during the summer.

Each ULV unit is carefully calibrated monthly to dispense only 0.05 ounces of active ingredient per acre. In order to be effective against mosquitoes it is important for these machines to break down insecticides into proper droplet sizes, which is 12-25 microns.

Insecticides that the Commission utilizes are a contact spray. This means a certain number of droplets must come into contact with the mosquito in order for it to be absorbed into its body resulting in mortality. Monthly tests are conducted to determine the mass median diameter (MMD) droplet size of the ULV equipment. MMD is defined as the diameter of the drop which divides the spray volume into 2 equal parts. Fifty percent of the volume of droplets are below the MMD and 50% are above. MMD’s are also completed on all repaired ULV equipment before it is returned to service. By determining the MMD’s, the biology staff knows if the equipment is producing droplets within the optimal range, and meeting adulticide label requirements.

ULV applications are less effective at temperatures below 56 degrees, if winds are greater than 10 mph, or in heavy rain. Due to these factors, ULV operations cannot be performed every evening.

Our principal adulticiding material is a 4% permethrin ULV formulation.

SCMAC is continuously aware of the presence and importance of pollinators and works with the Saginaw Valley Beekeepers Association to follow the best management practices for bee colony/pollinator health in Saginaw County. With this in mind our control efforts are designed around Pollinator Best Management Practices, using an Integrated Mosquito Management Program.

In order to adequately protect honey bee colonies and other pollinators from possible pesticide exposure, there must be effective communication and cooperation from those involved. It may be necessary to control adult mosquitoes in areas known to have bee colonies. Bees and many pollinators are most active from sunrise to sunset. Our treatment schedule in these areas begins after sunset, which is after the time most bees have returned to their hives. A major portion of the insecticide budget is for larvicide (Bti) that is applied directly to the water and does not affect pollinators.

Spray equipment is carefully calibrated to dispense proper droplet size to impact mosquito sized insects, not the larger insects like butterflies, bees, or beetles. The spray is a contact insecticide, once released it breaks down rapidly. The treatment has a short range, 300 feet from the treatment path, depending on wind direction and speed.