Stormwater,
Mosquitoes and You
In Mississippi,
the joke is that mosquitoes come in two sizes:
small enough to slip through screen doors or
big enough to open them! But no matter where you live,
mosquitoes have one thing
in common—they need water to breed.
Stormwater
ponds are designed to collect and slowly release rainwater
to protect water quality and prevent urban flooding,
but they do hold water so concerns are natural. Properly
managed, these stormwater devices and other common yard
elements need not be bloodsucker
breeding grounds. Here’s how.
Keep it
Moving
The bad news is mosquitoes
only need a half-inch of standing water to breed.
Think bottoms of flowerpots, depressions in tarp, old
tires, birdbaths, even that
old wading pool you keep telling yourself to toss out.
The good news is they need four days of it to propagate.
Properly
constructed detention ponds stay dry until it rains.
Then, they slowly release water over a three-day period.
If the detention pond near you takes longer to drain,
it needs maintenance. Usually the problem is fixed by
clearing a clog of litter, silt or sediment. Rain
gardens are just the same. If they don’t
drain in three days, add
sand to the bottom to enhance drainage or adjust the slope
so water flows in sheets across the vegetation.
Ponds, Retention
Ponds and Wetlands Don’t Move—Now What?
If you have a pond, add fish. Most
fish love to eat mosquito larvae, but one in particular
excels at this task. Aptly called the
mosquito fish for its voracious
appetite, it is native to North Carolina,
but a word of caution is in order: These guys will eat
most anything—plants, beneficial insects, you name
it!
Fish can’t
eat what they can’t reach, so prevent pond plants
from forming a thick physical barrier. Vegetation
that falls into water and algae mats act like mosquito
maternity wards. Mow or manage plant growth and
skim algae mats.
About those
plants
Some plants are mosquito
friendly and some are not. Avoid wooded
overhangs and cat tails (hint: they won’t grow in
water over four feet deep), but
plant shrubs nearby for mosquito predators to roost in.
Dragonflies and purple martins take the day shift and
bats work at night, but who wants to commute? Bat
boxes and birdhouses keep these helpers near.
Mosquito
larvicide placed directly in the water works, too, but
not for free. Check your local extension
service to learn what works best in your area. Small sites
usually get results from Bacillus thuringiensis israelensis.
Death to mosquitoes, but
harmless to fish and other wildlife, it’s available
at retail stores in granules, floating disks or briquettes.
And while rain barrels
aren’t a true “pond,” they do hold water.
Cover them with a tightly fitting screen. If
you have a ditch in your yard, clear any debris that causes
pockets of stagnant water.
What Doesn’t
Work
Bug zappers, electronic
mosquito repellers, mosquito traps that use heat and/or
chemicals and various plants have all been touted as ways
to reduce or eliminate mosquitoes. To
date, no scientifically based tests support their claims.
Just tending to
your own business doesn’t work either. Mosquitoes
aren’t just frequent flyers; they go the distance.
The one that just bit you
probably doesn’t live in your back yard. So talk
to your neighbors and spread the word. Chances
are good they like mosquito control just as much as clean
water! Which brings us back to why the ponds,
wetlands, ditches, rain gardens and barrels got installed
in the first place. They do a great job of cleaning
and slowing down stormwater. With a bit of care—they’ll
do a job on mosquitoes, too.
Chrystal
Bartlett
currently
works
as
Stormwater
Awareness
&
Outreach
Coordinator
for
the
N.C.
Department
of
Environment
and
Natural
Resources
where
she
recently
launched
a
new
stormwater
Web
site,
www.ncstormwater.org.
She
is
also
a
freelance
voiceover
talent
and
image
management
consult.
Before
working
at
DENR,
she
worked
as
a
DJ,
news
reporter
and
at
several
ad
agencies.
Chrystal
graduated
from
N.C.
State
University
with
a
B.A.
in
Communication
and
an
M.A.
in
Public
Relations.