A few weeks ago I wrote about ways we could get the upper hand on mosquito populations. Eliminating their habitat is the best option. However, living in a region with ubiquitous standing water, that can be difficult.
Many plants contain chemicals that repel mosquitoes. Citronella grass, lemon balm, lavender, catnip, rosemary, marigold and scented geraniums (what most people call citronella) are just a few. Several of these are either attractive ornamentals or useful cooking herbs.
The problem is that a little may not be enough. These plants must be planted in dense populations to be effective. One or two plants on the patio won’t cut it. That is unless we rub these plants on our skin.
Here’s where the herbs are promising, at least in the beginning. I seldom use insect repellants, so when I find myself in dense mosquito or yellow fly populations and have no fly dope or domestic herbs I reach for nature. Crushed dog fennel or wax myrtle leaves have natural insect repellant properties. The problem is that they need to be applied often as effectiveness is short-lived.
Unfortunately, that’s the same problem we have with the herbs I mentioned earlier. Numerous sources cite that catnip can be as much as ten times as effective as DEET, the most widely used commercial product. If we were only to be outside for a few minutes this would be true. Frequent reapplication is necessary though. DEET will last a few hours. Most herbals only last a few minutes without retreatment.
As chemicals go, DEET is generally considered safe. In fact it is labeled for infants as young as two months. Concentration should be less than 30%. It’s not quite that simple, so we must consider potential problems. DEET has an average dermal LD50 of about 3300 and an oral one of about 1100 depending upon the animal tested. LD50 is a measure of toxicity and it’s relatively low. That’s good.
Here’s the bad. Chemicals absorb into thinner less mature infant skin more quickly. Furthermore, babies and toddlers are more likely to lick their arms and hands and ingest the chemical than adults are. Children also don’t hold still, so we must be careful to keep spray from their eyes. Finally, kids are smaller, so doses are magnified.
Other chemicals are out there. When I was a kid my mother used a lot of Avon products. One was skin-so-soft. Mom often mixed this stuff with baby oil as many Maine woodsmen lathered their hardhats with baby oil to control blackflies. Hardhats went from bright yellow to black by day’s end.
All the research I found showed that this product far less effective than the old standby, DEET. You can bet companies are busy at work trying to develop herbals with DEET’s long-term effectiveness. In the meantime be prepared to apply natural products frequently.
Also, use netting where infants are exposed to mosquitoes and consider screening open porches. Above all, consult your medical professional if you or your children develop a rash you think may be the result of some insect repellant, natural or otherwise.
Ted Manzer teaches agriculture at Northeastern High School (firstname.lastname@example.org).