Mosquito Board Pressured to Spray
Paonia is seeing an unseasonably intense attack by mosquitoes. The North Fork Mosquito Abatement District reports receiving many calls from citizens asking or demanding that the District “Do something!” about the mosquito problem.
According to Parks, “Callers seem to generally assume that what is needed is that the District spray poison to kill the mosquitoes. Most callers have seen spray operations in the past, and have the idea that spraying is the reasonable response to this problem. Our board members have felt tremendous pressure to go along with this idea – to even go against their own judgment – just to relieve some of the pressure being placed on them.”
So far, the board has resisted the pressure to “go along to get along”. From their evaluation of the pros and cons of spraying, they are convinced that spraying would actually, unquestionably, do more harm than good.
This is not what most callers want to hear, according to Parks. They just want the problem to go away, and it is clear to them that spraying is the answer.
Operations manager, Elizabeth Collins, explains that spraying’s most effective benefit is perceptual. Spraying gives the appearance that the taxpayers are getting some protective action by the District because you can see the fog, you can hear the truck coming for blocks, and it leaves a residual smell. This gives people the false impression that they are protected. However, that’s really misleading.
“In 2006, our area had the highest per-capita incidence of West Nile Virus in the state of Colorado. During this outbreak, the district sprayed weekly. What happens is people become complacent because they believe they are safe. Yet the most effective protection is that which you give yourself.
“Fogging has been shown to be not very effective. The problem is that for a mosquito to be killed by the spray, the mosquito has to actually come into physical contact with a droplet of the poison while flying.
“In the laboratory, under perfect conditions – that is, with the mosquitoes sealed into a box – the effective kill rate is only about 50%. When you add trees, walls, or any other obstacle, the kill rate drops dramatically. Around our houses and gardens, and even in our pastures, the mosquitoes have countless places to hide. We’re lucky if even a very small percentage of mosquitoes are killed by spraying.
“On the other hand, bees will be killed by the residual pesticides on flowers. Bees’ bodies are designed to pick up pollen. They’re covered in little hairs. You can see how they would pick up the leftover pesticide. The pesticide residue on plants takes days to break down. Meanwhile, the bees are very vulnerable. It’s rather frustrating because that same pesticide residue won’t kill any mosquitoes.”
Another consequence of spraying is that the poison kills off natural predators, which are of tremendous help in controlling mosquito populations. The slight beneficial effect that might be seen from spraying would be more than offset by the reduction of the help we get from natural predators.
Since 2008, the district has used a comprehensive methodology called IPM. Since then, the district has experienced no human cases of West Nile Virus (WNV), according to the State Health Department definition. IPM requires more diligence, time and money, but the results have clearly been worth it.
The district’s technicians visit over 500 known mosquito breeding sites each week. They take many samples at each site, and when mosquito larvae are found, they treat the area with corn kernels that are coated with bacteria that kills mosquito and blackfly larvae, but is harmless to anything else. The bacteria kill all of the mosquito larvae and prevent them from becoming biting adult mosquitoes.
A team of dedicated local citizens regularly set and collect mosquito traps placed around the 50 square miles of the district. Other volunteers sort and count the mosquitoes caught in the traps, then send those that can potentially carry disease to by the State Health Department for WNV testing.
This season, several of these tests have indicated that the virus is already in the mosquito population. Without the trapping, there would have been no report of WNV in the area until a person came down with the disease.
You may ask, “If IPM is so effective, why do we still have so many mosquitoes right now?”
One reason is that the river level has dropped far below normal for this time of year. This has created many pools of shallow, stagnant water in unpredictable places. These pools are perfect places for what are called flood-plain mosquitoes to hatch. Although these mosquitoes do not carry WNV, they are aggressive biters. Technicians search the river and creeks as part of their weekly routes, and are continuing to find new breeding sites.
Another reason is that the hot weather makes mosquitoes go through their life cycle, from egg to adult, much more quickly. Since district technicians can get to each site only once a week, sometimes adult mosquitoes can emerge between visits.
Of course, a major issue is that some places that are irrigated have standing water for more days at a time than it takes for mosquitoes to go from egg to adult. Unless irrigated areas are allowed to dry out every few days, it’s a serious challenge for the district to keep up with the mosquitoes breeding in irrigated fields and gardens. Any help that you can give in allowing irrigated land to dry out regularly will make a difference.
The North Fork Mosquito Abatement District is eager and committed to choosing the response that will be of the greatest benefit to the health of the community. The board members take seriously the trust placed in them to do not just what will put the least pressure on them personally, but what will be the most responsible way to honor the trust placed in them when they were placed on the board.
