County gets new tool to com­bat mos­qui­toes

Traps added to mon­i­tor pests

Maryland Independent - - News - By TA­MARA WARD tward@somd­ Twit­ter: @CalRecTAMARA

See Some­thing. Say Some­thing. Many peo­ple are fa­mil­iar with the na­tional cam­paign to raise pub­lic aware­ness of in­di­ca­tors of ter­ror­ism and to re­port sus­pi­cious ac­tiv­i­ties and pack­ages to state and lo­cal en­force­ment. How­ever, the Calvert County Mos­quito Con­trol Divi­sion does not want residents to be alarmed by the new spe­cial­ized mos­quito traps sprin­kled through­out county neigh­bor­hoods.

The omi­nous-look­ing, can­is­ter-shaped trap, with wires and a bat­tery at­tached, is white or black and roughly the size of a 5-gal­lon bucket. Each trap is la­beled “Calvert County Mos­quito Con­trol (410) 535-6924.” The trap, which poses no health threat to hu­mans, is used to mon­i­tor adult mos­quito pop­u­la­tions.

“We have an in­te­grated pest man­age­ment pro­gram in place in the county to re­duce the pop­u­la­tion of mos­qui­toes through ed­u­ca­tion, bi­o­log­i­cal and in­sec­ti­cide ap­pli­ca­tions,” said Mos­quito Con­trol Su­per­vi­sor William “Bill” Clay.

The pro­gram is con­sis­tently run the same way year af­ter year, ac­cord­ing to Clay, stress­ing the Zika virus has noth­ing to do with how the pro­gram op­er­ates. Zika has be­come a prom­i­nent threat in South Amer­ica and can lead to birth de­fects in ba­bies born to women who have been in­fected with the virus.

“We haven’t changed how we run it and there will be no diver­sion from the nor­mal pro­gram un­til Zika is found in the county,” said Clay, who ac­knowl­edged the in­tro­duc­tion of this new trap into his arse­nal of mon­i­tor­ing tools to de­tect mos­qui­toes that could pos­si­bly carry the virus.

Clay said the most likely sce­nario for Zika in Calvert County is a travel case where some­one goes out of the coun­try, con­tracts the dis­ease and then comes back. To date, there are no re­ported cases in Calvert County. How­ever, ac­cord­ing to the Cen­ters for Dis­ease Con­trol and Pre­ven­tion, as of June 22, there were 820 cases of Zika in the United States; 819 were travel cases. The other was lab-ac­quired.

While there are no known mos­qui­toes with the Zika virus in the U.S., the new traps, called the BG-Sentinel Bio­gents, are spe­cially de­signed to catch two va­ri­eties of mos­qui­toes in Calverty County that are ca­pa­ble of car­ry­ing the Zika: Aedes ae­gypti and Aedes al­bopic­tus.

“They are con­tainer breed­ers. They came from south­east Asia orig­i­nally and breed in bam­boo stalks,” said Clay. “Once they came to this coun­try they re­ally adapted. They came into the coun­try in used tires [with stand­ing wa­ter in them].”

Tra­di­tion­ally used for re­search, the new traps lure those species of mos­qui­toes with three dif­fer­ent types of bait to in­clude chemicals, such as car­bon diox­ide, and the emis­sion of non-toxic sub­stances that mimic those re­leased from the hu­man body. A fan pulls the mos­qui­toes into a col­lec­tion bag once they are near the trap.

Clay’s team will set up a trap af­ter they have done a sur­vey of a prop­erty, at the owner’s re­quest, where they have found a lot of breed­ing sites. The trap is set nor­mally for overnight. The next day, the team col­lects and an­a­lyzes the mos­qui­toes in the trap to de­ter­mine their species.

“If we catch an ae­gypti, we have to turn that in to the state health depart­ment for test­ing for the [Zika] virus. We have not caught any ae­gypti this year,” said Clay. Any mos­qui­toes iden­ti­fied as a pos­si­ble car­rier of Zika must be re­ported and sent to the CDC.

In ad­di­tion to ae­gypti and al­bopic­tus, there are 58 other species of mos­qui­toes in Calvert County. Most mos­qui­toes lay their eggs on or in wa­ter, in the form of a raft con­tain­ing 100 to 400 eggs. Over the course of seven to 10 days, the eggs be­come lar­vae and then pu­pae before be­com­ing adult mos­qui­toes.

One of the bi­o­log­i­cal con­trols used by the pest man­age­ment pro­gram is the in­tro­duc­tion of the gam­bu­sia, or mosquitofish, into stand­ing wa­ter, such as stormwa­ter ponds or or­na­men­tal ponds. One adult mosquitofish will eat 100 mos­quito lar­vae and pu­pae a day, before they have an op­por­tu­nity to turn into adult mos­qui­toes, re­ported Clay. Mos­quito Con­trol Pro­gram of­fers the ser­vice free of charge to residents who re­quest the fish.

An al­ter­na­tive method to cur­tail the mos­quito pop­u­la­tion is the in­tro­duc­tion of the chem­i­cal methro­prene into wa­ter. The hor­mone kills mos­qui­toes in the wa­ter as they reach adult­hood.

Another trap com­monly used is the New Jer­sey Light Trap, which uses a 25-watt light­bulb and a fan to at­tract mos­qui­toes with no bait. In part­ner­ship with com­mu­ni­ties that re­quest pest con­trol ser­vices, the pro­gram runs an Ul­tra Low Vol­ume Pro­gram, where vol­un­teers run the tra­di­tional trap ev­ery week, which the team also col­lects and in­spects to also de­ter­mine species.

“Species tells us where to look,” said pest man­age­ment tech­ni­cian Sonja Gat­ton. “If it is al­bopic­tus, we know we are look­ing for a con­tainer. If its a vexan, we know that’s gotta be down in a mud pud­dle in the woods.”

Gat­ton said ed­u­ca­tion is part of the in­spec­tions the team con­ducts and that they make a point to let the prop­erty own­ers know the source of the mos­qui­toes and how to best mit­i­gate the prob­lem. Phys­i­cal con­trols used by the pro­gram in­clude elim­i­nat­ing breed- ing sites by sim­ply re­mov­ing the wa­ter.

“The wa­ter goes away — the lar­vae die and the adults that are left in the area are look­ing for that con­tainer to breed in,” Clay said.

The team also sprays com­mu­ni­ties af­ter test­ing is done. Test­ing in­cludes set­ting up the non-baited light trap. The num­ber of fe­male mos­qui­toes cap­tured dic­tates whether spray­ing should be done.

Of­fice as­sis­tant Bar­bara Car­lough said there are 80 com­mu­ni­ties that cur­rently pay for mos­quito spray­ing ser­vices at an hourly rate through an agree­ment.

While mos­qui­toes are usu­ally a prob­lem in the county from late April to Oc­to­ber, Clay and Car­lough work year round to con­trol the county’s mos­quito pop­u­la­tion. Dur­ing peak sea­son, up to seven ad­di­tional em­ploy­ees are added to the staff to do field in­spec­tions, set up traps, re­spond and mit­i­gate mos­quito in­fes­ta­tion com­plaints and drive spray trucks.

County pub­lic in­for­ma­tion of­fi­cer An­gela Wal­ters shared that pub­lic mes­sages have gone out to residents to en­sure the new traps are not per­ceived to be sus­pi­cious pack­ages and to dis­cour­age residents from touch­ing or dis­turb­ing the traps if they see them.


Pest man­age­ment tech­ni­cian Sonja Gat­ton in­spects un­der a mi­cro­scope a frozen mos­quito col­lected from traps set by the Calvert County Mos­quito Con­trol Pro­gram.


BG-Sentinel Bio­gents is the county Mos­quito Con­trol Divi­sion’s new spe­cial­ized mos­quito trap. The black and white can­is­ter-shaped trap is the size of a 5-gal­lon bucket, and has wires and a bat­tery at­tached to run a fan. Each trap has three dif­fer­ent types of bait specif­i­cally de­signed to catch the two va­ri­eties of mos­qui­toes in Calverty County that are ca­pa­ble of car­ry­ing the Zika virus: Aedes ae­gypti and Aedes al­bopic­tus. Each trap is la­beled “Calvert County Mos­quito Con­trol (410) 535-6924.”

Dozens of mos­quito lar­vae were scooped out of a stand­ing bucket of wa­ter. The lar­vae will ma­ture to be­come adult mos­qui­toes in a mat­ter of days.

Mos­qui­toes lay on a freeze plate prior to ex­am­i­na­tion in the Mos­quito Con­trol Pro­gram lab area. By de­ter­min­ing the species, the pro­gram can de­ter­mine the best way to abate them.

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