Just above Violettes Lock, the waterway in the C&O Canal comes to a tranquil end — perhaps too tranquil.
Most of the locks in the 22 miles of the canal below Violettes have bypass flumes that keep water flowing. Violettes, however, is the end of the continuously watered section of the canal. Just above the lock, a pool of still water lies enveloped in a film of algae growth. Sheltered from the wind and other disturbances to the surface, it fits the description of mosquito breeding habitat.
The water just above Violettes Lock, as well as a swampy stretch above Rileys Lock, is a reminder that not all bodies of still water can be eliminated. After a summer when mosquitoes in the area have tested positive for West Nile and malaria viruses, some breeding grounds cannot be eliminated.
"THAT HAPPENS in some of the lift locks," said Doug Faris, superintendent of C&O Canal National Historic Park, who said the wood of the locks is protected by remaining underwater.
The National Park Service (NPS) has a plan to address West Nile virus and mosquito control, but Faris says that the drought has minimized the issue in the park.
"Because of the nature of the weather this year, there has been little standing water in the park," said Faris. "Because the river has been so low, we have more standing water along the river bank."
Faris said the park also provides information to visitors about avoiding mosquitoes, and rangers have patrolled the park for tires, buckets and other containers that may have standing water.
WHILE CONSTRUCTION to alter or create water flow is unlikely, Faris said the park has experimented with a commercial substance to treat standing water and eliminate mosquito larvae. The park is considering this as a regular course of action, but has not made a final decision about its implementation.
To treat some bodies of standing water that could not be eliminated, Maryland has used bacillus thuringiensis israelensis (BTI) products, said Cy Lesser of the Maryland Department of the Environment.
BTI is one of the least toxic pesticides available for treating mosquito larvae, said Lesser. Larvacide is another option, a pesticide that prevents larvae from becoming adults, leaving them in a transitional 'pupil' growth stage.
ELSEWHERE IN THE county, the drought conditions have created breeding environments for mosquitoes.
“With the drought, we’ve got a lot of standing bodies of water that aren’t supposed to be standing bodies of water,” said Marilyn Piety, program manager for Montgomery County Public Health Services.
Jeannine Dorothy, entomologist for the Maryland Department of Agriculture, agreed, “It’s been a really dry year, and there are some creek beds that have dried up and are breeding mosquitoes.”
County health officials now consider West Nile virus endemic to the area. Over 100 dead birds have tested positive for the virus this year, and the county's first West Nile death occurred when Elise Karo of Bethesda died in August.
Along the canal, said Faris, mosquitoes have been tested for West Nile throughout the summer, with none testing positive. The health department has stopped picking up dead birds reported in most of the towns along the canal in Montgomery County, however, because enough birds testing positive have already been collected to confirm the presence of the virus.
THE PRESENCE of West Nile virus in the county is not cause for alarm, but rather for precaution, say health officials. Mosquitoes can be managed, even if they can't be eliminated.
"People shouldn't be panicked about it, but they should be concerned about it. It's a concern for any older person" especially, said Lesser. "You should take prudent personal protective measures to prevent yourself from being bitten by mosquitoes [but] it's not something you should alter your habits about."
Protection, not avoidance, may be the best course for those visiting the C&O Canal near Violettes.
“If they’re biking through, it’s probably not going to be a problem,” said Dorothy.
Those enjoying the outdoors can take precautions against mosquito bites, including using insect repellent.
Piety recommends “Three L’s” for dressing for outdoor activity: light colored, loose-fitting and long.