NEWS
Wednesday, July 31, 2019
HeRMIsTOnHeRald.COM • A11
West Umatilla Mosquito Control District works to control pesky insects
By BEN LONERGAN
STAFF PHOTOGRAPHER
When Randy Gerard
started working as a seasonal
intern at the West Umatilla
Mosquito Control District
more than two decades ago,
he couldn’t walk through
parts of the district without
getting swarmed by mos-
quitoes. Now Gerard is the
manager of the district and
mosquito populations are
down to 20 to 25% of where
they were in the 1990s.
“In the 1990s it was not
uncommon to have to treat
some of these areas four to
five times per week; now we
can do them once or twice
a season and have a bet-
ter result,” Gerard said. “I
believe the decline in mos-
quito population is linked
directly with improvements
to technology and funding.”
The West Umatilla Mos-
quito Control District began
operations in 1972 and cov-
ers a 515-square-mile area
on the western edge of
Umatilla County. The pro-
gram operates on an approx-
imately $800,000 annual
budget funded through a
special property tax district.
Within the district, mos-
quito control can be bro-
ken down into four main
categories: the mosquito
surveillance
program,
which catches and moni-
tors sources and population
spikes; the larvicide pro-
gram, which aims to kill
mosquito larvae before they
become an issue; the lab
testing aspect, where dis-
ease testing occurs; and the
adulticide program, which
utilizes chemicals to kill off
adult mosquitoes.
“People are often most
familiar with the adulticide
program, the trucks driving
around city streets and your
property at night,” Gerard
said.” However, it is really
our last resort; our goal is to
use other programs to elim-
inate mosquitoes before it
gets to that point.”
staff photo by Ben lonergan
Rylie Smith checks a dip cup to see if he can find mosquito larvae. Dip cups are used to pull small amounts of water to more
easily inspect for mosquito larvae of different ages.
The West Umatilla Mos-
quito Control District moni-
tors approximately 980 doc-
umented larval habitat sites
and more than 1,200 catch
basins and storm drains on
a weekly basis to help catch
and kill mosquito larvae.
Rylie Smith has been
working for the district for
seven years in both the lar-
vicide and adulticide pro-
grams. During peak mos-
quito season Smith begins
work at about 5 a.m. to
maintain existing mosquito
sources and search out new
sources. Each day he checks
up on reported outbreaks
and treats infested areas
with a variety of chemicals.
“When I arrive for the
day, I try to find a place
where I can access as many
sites as possible. I’ll check
to see when I last sprayed
and check dip cups for lar-
vae,” Smith said. “Every-
one is pretty accepting of
us coming out to work;
the only real issues come
up when property changes
hands.”
One of the leading
sources of mosquito habitat
in the district is flood irriga-
tion. When landowners flood
fields it often leaves behind
standing water that can pro-
vide a perfect habitat for
mosquito larvae. While the
district makes some effort to
educate people about pres-
surized irrigation systems,
they lack the funding to help
secure or subsidize grants to
make improvements more
affordable.
“Being in the desert as we
are, the primary sources of
water are artificial sources,
flood irrigation, ponds, and
poorly maintained swim-
ming pools,” said Gerard.
“We use the results of our
surveillance program to
help find and treat out-
breaks before the mosqui-
toes become adults.”
The district utilizes a net-
work of about 100 mosquito
traps, 28 of which are set at
the same locations while the
other 72 rotate through the
coverage area on a weekly
basis. The traps consist of
blocks of dry ice in an insu-
lated container that vents
CO2 to attract mosqui-
toes. Mosquitoes are then
swept up by a small fan
into a collection container
to be tested. Traps are typ-
ically set and collected two
times per week in an effort
to monitor populations of
Culex mosquitoes.
Culex is a specific genus
of mosquito that, while
not usually the ones seen
swarming outside, are the
primary
disease-carrying
mosquitoes. By catching
Culex mosquitoes the dis-
trict can test them for West
Nile virus, St. Louis enceph-
alitis and Western Equine
encephalitis, as well as
monitor their prevalence in
a given area.
While the testing can be
done in house by the dis-
trict, or through Oregon
State University, positive
results must be sent to OSU
to be retested before a case
can be confirmed. The dis-
trict prefers to test in-house
so that results can be acted
on more quickly, with a 3-
to 5-day turnaround to send
to the lab. With this lead
time, the district can get a
jump on fogging or aerial
spraying to attempt to kill
off Culex mosquito popula-
tions in areas where a pos-
itive result has surfaced for
one of the diseases.
Although the district was
founded to deal with West-
ern Equine encephalitis,
they shifted their focus pri-
marily to the monitoring
and treatment of West Nile
virus in 2005. According
to Oregon Health Author-
ity, roughly one in five peo-
ple infected with West Nile
virus may show signs of
the disease, with the most
severe risk posed to individ-
uals over the age of 50 and
people with immune-com-
promising conditions.
Once an outbreak of
adult mosquitoes has been
established, fogger trucks
equipped with special-
ized spraying technology
are driven through affected
areas to spread a mosquito
control chemical called
Sumithrin.
Sumithrin,
paired with the spray tech-
nology run by the district,
is specifically targeted for
mosquitoes, however, pre-
cautions are taken to avoid
exposure for other animals,
according to field supervisor
Andrew Ross.
“We do our best to track
down organic farming oper-
ations and work with them
to establish management
plans,” said Ross. ”Addi-
tionally we do everything
we can do to avoid bees
and bee boxes by not spray-
ing near them and spraying
when bees are not active.”
Spraying typically starts
at sunset and takes into
account wind speed and
temperature to decide both
when and where trucks can
spray. The district has a fleet
of four trucks equipped with
the spray technology that
roam city streets, country
roads and farm property at
dusk.
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