Midge Pilot Program


Why is Maryland treating Baltimore County for Midges?
In response to concerns from citizens and businesses in the Back River area, Governor Larry Hogan issued an Executive Order​ creating a midge supression pilot program directed by the Maryland Department of Agriculture (MDA) in conjunction with Maryland Department of Natural Resources (DNR). The pilot program will be implemented this summer (2017) on the Back River in Baltimore County. 

Program Objectives
The objective of this pilot program is to test the feasibility of Back River midge control and determine the impact of Bacillus thuringiensis israelensis (Bti)​​ in controlling midge populations in the area. The pilot program will also aim to determine the most cost effective dosage and frequency of ​Bti treatments in the area.

Planned Treatment Method
Bacillus 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 Areas
Staff 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 invertebrates. More Information​

Maryland 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 Notification
The Maryland Department of Agriculture will manage the aquatic spray contract and issue spray notifications

Additional Resources


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).​