Planned Treatment MethodBacillus thuringiensis israelensis (Bti) will be applied by
boat using an apparatus designed specifically for midge control. Bti is a naturally occurring soil
bacterium that has been demonstrated to be non-toxic to humans, mammals, birds,
fish and most invertebrates. While the schedule is subject to change, the
preliminary schedule is for five monthly treatments: August-October 2017,
and May-June 2018.
Treatment AreasStaff from MDA and DNR have worked together to
identify a 260-acre section of the Back River in Essex where midge populations
have become a major nuisance.
What product will be used?The insecticide that
will be used for this project is Bactimos WG. The
active ingredient is Bti.
Is Bti safe?The pesticide,
Bactimos WG, was chosen because of its effectiveness for this use and
because it is only harmful to a very limited variety of organisms including midge
larvae, black fly larvae, mosquito larvae and a few other aquatic Dipteran
(flies) insects. It is not harmful to humans, fish, crabs or other aquatic
MonitoringMaryland Department of Natural Resources biologists will conduct larval sampling
and continuous adult sampling using light traps. DNR will also track midge
complaints in the area. For more information, contact Maryland Department of
Natural Resources (Access.DNR@maryland.gov).
Spray NotificationThe Maryland Department of
Agriculture will manage the aquatic spray contract and issue spray
Background Information: Midges & Back River
Midge population sampling by Baltimore County Department of Environmental Protection and Sustainability in 2009-2010 confirmed a large nuisance midge population in the Back River (Baltimore County) with over several thousand midge larvae per square meter (up to 12,000 per square meter). Nuisance levels are counts of midge larvae over 500 per square meter (Baltimore County Department of Environmental Protection & Sustainability (draft), 2010.)
Midges are not a health risk or a vector of human disease. However, in some situations, midges result in severe nuisance and economic problems to nearby residents and businesses.
They are common in shallow, nutrient-rich waters with muddy, sandy substrate
Phytoplankton is a major food source for midge larvae
Peak midge populations occurs during the warm months of May through October
Midge life cycle - Females drop between 5-1000 eggs in egg masses on water surfaces. Eggs hatch with 3-5 days and feed on egg case jelly then move to bottom to burrow in sediment of make tubes. Larvae molt four times over 7-10 days, increasing in size to pupa. Pupa travel to the surface. Adults live 3-5 days. Total life cycle is 10 -15 days in warm water, and one month in winter (Ali, A.,1978).
50 Harry S. Truman Parkway, Annapolis, MD 21401