Cache mosquito numbers on the rise

With the Bear River Health District confirming its first human case of West Nile Virus has been detected in Box Elder County, Cache County officials say their testing indicates the mosquito numbers are peaking a week to 10 days earlier than normal.

Terrie Wierenga is administrative manager at the Cache Mosquito Abatement District, which includes most of the county except Logan, River Heights, Paradise and College-Young Ward.

“Our mosquito numbers, up until the last couple of weeks, have been fairly low compared with past seasons. The week of July 23 the numbers skyrocketed. It has held steady since then and based on the number of phone calls I got over this weekend they’re increasing even more.

“It’s a challenge trying to find all the pools where the mosquitoes are hatching and kill them before they get to adults.”

Wierenga said the majority of mosquitoes showing up in her traps are what are known as the floodwater mosquitoes and they like the irrigation runoff from fields. With the hot weather, irrigation cycles are in full swing and that is providing plenty of hatching places for them.

“We prefer to control the mosquitoes before they get to adult size so fogging is the last resort for us. We are now out in most areas of our district fogging at least once a week; Benson comes to mind as an area we hit twice a week because our field guys call it mosquito heaven right now.”

She expects to continue to see “high numbers” through the middle of August and then they will begin to taper off.

“Part of that is the crops are starting to be harvested so irrigation use goes down. That is true for irrigation use in the cities. It just reduces the places mosquitoes can breed.”

Even so, she said they are applying new larvicide that has a longer residual yet targets only the mosquito larvae.

Common practice is every Monday to put out 14 to 17 traps throughout the district.

“Those trap the female mosquitoes which are the ones that bite us. Tuesday morning we go out and collect the traps and bring them back to our office and five of us sit down and count every mosquito and identify the species.

“We have five species in Cache County and only one, the Culex species, carries the West Nile Virus. When those numbers go high, that’s when we step up our abatement program.”

Wierenga said the first line of defense against mosquitoes is to avoid going out between dusk and dawn when they are active, especially the ones carrying West Nile.

“If you have to go out wear long sleeves and pants, cover your skin as much as possible, and use one of the recommended repellants from the CDC, including those with DEET.”

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