Yes, people may wonder: “Why don’t they just spray and kill all the mosquitoes?”
First, it’s impossible to kill all the mosquitoes. Any spraying, including from a truck as done by the County, kills only the portion of mosquitoes that happen to be flying around at the time and encounter toxic droplets. We have seen figures of up to an 80% kill rate (yes, this is a serious poison) but no really authoritative figure.
But suppose 20+% of adult mosquitoes survive (and any out of the spray zone, sheltered at the time in thick foliage, or in inaccessible areas like inside bulkheads or hollow trees, will not be affected). The females, at least, will be happily flying around the next day biting people and laying eggs as usual.
The hundreds of eggs that each female lays in stagnant water are affected by spray. Those eggs will become larvae, pupae, and adults, all within a week in hot weather like now.
And current larvae and pupae will not be affected by spray either.
And not all mosquitoes are created equal. Specifications require that spraying occur only in the evening, when honeybees are less active. Disaster for bees ensues if spraying occurs at other times.
Our home-grown mosquitoes, the ones that at least give us an auditory warning hum as they circle us looking for bare skin, tend to be active in the evening; however, the recently established “Asian Tiger” mosquitoes, the silent biters, tend to be active during the day and therefore are not much affected by spraying. Killing off some of the “regular” mosquitoes probably just opens the airways to more Asian Tigers.
Furthermore, anti-mosquito spray actually kills mosquito-eaters like dragonflies and toads, to say nothing of insects that we enjoy seeing or that are important to ecological balance like butterflies.
The County Health Department does not spray for the comfort of people who wish to be outside without the recommended bug repellents, long sleeves, and long pants. People outside need to weigh those nuisances against the nuisance of being bitten. The Health Department is not the Department of Outdoor Living.
Finally, proper public policy is to spray only, in the words of the Chesco Health Department, “after exhausting all other available mosquito control strategies.”
The prime non-toxic mosquito control strategy is larviciding suspect standing water. Individuals can larvicide on their own property but not on public property. We are glad to say that the Borough of West Chester is taking steps for two employees to receive the relatively simple licensing to do that, and we hope other municipalities will do the same.
Currently, the County does the larviciding but obviously needs to be informed where the problem areas are in such a large county. In West Chester, our Adopt A Drain program is clearing drain grills of plastics and other detritus and informing the Borough of drains that need cleaning below grill level or larvicing where they are holding standing water.
Example, as of Aug. 30, 2018: the storm drain at the NE corner of E. Nields and S. Matlack streets. If you check it out, you’ll see a water reflection at the bottom. After the dry last week in August, this drain could already have released swarms of adult mosquitoes to the neighborhood. In dry weather, mosquitoes could also be breeding in stagnant areas of Goose Creek and Plum Run, including water backing up in drainage pipes entering the stream. (Water samples are needed to check it out.)
If residents anywhere are aware of storm drains with standing water, they should inform their municipality. And of course, we should all patrol our own property, even for something as small as a bowl holding water under a potted plant, and put in a helpful word to neighbors who may not be addressing the issue. For some egregious “Case studies in what to avoid,” see here.