Scott Larzelere
Mosquito Control, Program Manager (Acting)
- [email protected]
- Main
- 410-841-5870
Black Fly Monitoring & Control
In response to black fly concerns from citizens in Washington County, the Maryland Department of Agriculture in partnership with the Maryland Department of Natural Resources (DNR) and the University of Maryland Department of Entomology handle black fly monitoring and control on the Potomac River in Washington County.
What are black flies?
While black flies are small (2-5 mm length), they can have a big impact on outdoor activities. Some black flies (Diptera: Simuliidae) can impact outdoor recreation and tourism with their persistent biting and swarming behavior.
The black fly life cycle has four stages: egg, larva, pupa, and adult. All are aquatic except the adults, which leave the water to search for food and mates. Larval growth is very temperature dependent, with relatively slow growth during the cold winter months and very rapid growth during warm summer water temperatures.
The aquatic stages of black flies are often abundant organisms in river ecosystems, where the larvae filter and eat fine food particles from the water column. The immature stages of black flies are aquatic and exclusively inhabit flowing waters. However, black flies are not found in lakes, ponds, swamps, and other standing water habitats. Stream flow is essential for transporting food and oxygen to the immature stages.
Black flies can play in important role in local food chains where they are preyed upon by many insect predators, fish, amphibians and birds.
Get tips for avoiding bug bites.
Treatment
Bacillus thuringiensis israelensis (Bti) - PDF will be applied by helicopter. Maryland’s program is modeled heavily on Pennsylvania’s program, which has been in effect since the 1980s.
Treatment will focus on portions of the Potomac River in Washington County near Williamsport and from Harpers Ferry to Brunswick.
Is BtiSafe?
Bti is a naturally occurring soil bacterium that has been demonstrated to be non-toxic to humans, mammals, birds, fish and most invertebrates.
The pesticide, Vectobac 12 AS was chosen because of its effectiveness for this use and because it is harmful to a very limited variety of aquatic organisms that only includes midge larvae, black fly larvae, mosquito larvae and a few other aquatic Dipteran (flies) insects. It is not harmful to fish, crabs or other aquatic invertebrates.
Stay informed about spraying
The Maryland Department of Agriculture will manage the aerial spray contract and issue spray notifications. Sign up for program updates and spray notifications. For more information, email: [email protected]
Monitoring
Maryland Department of Natural Resources biologists will conduct biomonitoring of aquatic macroinvertebrates and fish in selected streams to ensure there is no impact on the environment and review the effectiveness of the spraying. For more information, email [email protected].
Resources
- North American Black Fly Association
- Metropolitan Mosquito Control District (Minnesota) Black Fly Control Page
Black Fly FAQs
Bacillus thuringiensis subsp. israelensis (Bti) is a naturally occurring soil bacteria used as a microbial insecticide to control the spread of vector-borne diseases, protect public health, and manage insect pest species.
Bti was first discovered in a stagnant pond in Israel in 1976 (Margalit and Dean 1985).
Initial testing of Bti revealed acute toxicity to mosquitoes (Goldberg and Margalit 1977) and black flies (Undeen and Nagel 1978). Further research demonstrated that Bti is nontoxic to humans, mammals, birds, beneficial insects, fish, plants, and most aquatic organisms (EPA 1998 Bti EG2215 Factsheet).
Bti is an ideal pesticide with greatly reduced environmental impacts in comparison to man-made chemical insecticides. In addition, Bti is species specific, breaks down rapidly, limited non-target impacts (de Barjac and Sutherland 1990).
There are 26 Bti products in the United States with some of the following trade names: Vectobac, Teknar, Aquabac, Bactimos, LarvX, etc.
Bti is applied by via aerial spraying or boat spraying at a safe rate specified by the United States Environmental Protection Agency in the form of liquid.
Bti is currently being used in several states to control black flies and mosquitos. Both Pennsylvania and West Virginia have large black fly suppression programs and use Bti as the treatment.
Bti is also currently being used to suppress mosquito populations throughout Maryland.
Black flies must actively ingest Bti in order for the material to be effective. Bti is a spore-forming bacterium that produces protoxins in the form of parasporal protein crystals. Bti works best in black flies with alkaline guts because the protoxins become activated into highly toxic delta-endotoxins. The endotoxins cause a rapid breakdown in the lining of the midgut and necrosis of skeletal muscles, resulting in paralysis and mortality of target insect pests. Bti is nontoxic to other non-target species due to their acidic digestive system.
Research has demonstrated that Bti is nontoxic to humans, mammals, birds, fish (trout and bluegill), and most invertebrates when properly applied (EPA 1998 Reregistration Eligibility Decision). Data from a large number of studies indicate that Bti can be used in a carefully managed treatment program to selectively control insect pest and vector species with minimal adverse environmental impacts (Jackson et al. 2002), (Laird et al. 1990).