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New Dangers in the Woods

Industry Matters Newsletter 26 May 2022

Mark E. Jones, PhD

Morel mushroom hunting filled much of last week. The main reason for May camping in northern Michigan is morels. Trekking through the deep woods brought new appreciation for chemistry this year.

Morel mushrooms found in Michigan.

Dangers, at least in past years, were scarce in the morel woods. It is rare to see animals, with the occasional porcupine being the most dangerous looking, yet representing little real danger. I am now in my 32nd year walking in the Michigan woods. This is the first time I’ve found a tick.

There are over 860 species of ticks worldwide.   Only about 20 call Michigan home, but they are increasing.  Some have linked the increasing range to climate.  Cold keeps arthropod pests at bay, but the coldest temperatures are warming.  Pests now survive the milder winters.  Some link the growing deer and populations and other causes to increasing range.  Whatever the cause, we now have at least five problematic ticks in the Michigan woods. 

 The CDC lists 16 tick-borne diseases present in the U.S.  Mercifully, all aren’t yet in Michigan. .  All are scary.   A tick bite can also cause a potentially fatal allergy to meat.  An encounter with a tick can be a life-changing event.

 Ticks are an unwelcome addition to the menagerie of bloodsucking beasts found in the wilds of Michigan.  There are pesky mosquitos, annoying black flies, and blood-sucking leeches.  I hate them all.  Amber-encased ticks tell us they’ve been around since the time of the dinosaurs, just as Jurassic Park taught us about mosquitos feasting on dinosaurs.  The prevalence of both, success over eons, and expansion indicate it must be a ripe ecological niche.  It is unlikely they are going away.  We will have to adapt.   

 The adaptations available are decidedly chemical.  Chemophobic friends willingly spray themselves, spray their yards, ignite chemical-containing incense and, more recently, wear little chemical-spewing fans all in hopes of keeping the bloodsuckers away. 

 “They don’t bite, they don’t even light” was a memorable line in a TV commercial for insect repellents.  That commercial heralded the power of DEET, N,N-diethyl-meta-toluamide or N,N-Diethyl-3-methylbenzamide. It is the most widely used insect repellent, one I’ve used for years.  I’ve used Picaridin , or 1-methylpropyl 2-(2-hydroxyethyl)-1-piperidinecarboxylate.  DEET feels greasy.  Picaridin is non-greasy and odorless.  Both are proven to work on both mosquitos and ticks when applied to skin and clothing.  DEET can cause acute health effects, though it has never happened to me.  Seizures, uncoordinated movements, agitation, aggressive behavior, low blood pressure, and skin irritation have all been attributed to DEET use.  Picaridin has fewer  concerns.   Sadly, studies aren’t kind to the natural oils.  Studies and my experience indicate the synthetics work better. 

 Pyrethroids loom large in arthropod abeyance.  Synthetic pyrethroids are compounds with structures similar to compounds extracted from chrysanthemum flowers, pyrethrins.  They are rapidly absorbed and paralyze insect nervous systems.  The DoD preferred system for bug avoidance relies on application of DEET or Picaridin to skin and treating clothing and bed nets with Permethrin, (3-phenoxyphenyl)methyl 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate, a synthetic pyrethroid.  Pyrethroids aren't absorbed through human skin very well, but are not intended for direct skin application.  They do enter the body if eaten or inhaled.  Pyrethroids are generally considered safe for humans, but indiscriminately kill insects.  When used with DEET or Picaridin, Permethrin, on clothing is an effective contact poison for a broad range of biting arthropods.  Ticks and mosquitos are no match.

 Spatial repellents are things that keep bugs away.  Candles, incense and devices emit repellents to form a bug free zone making the campsite livable.  They make a cloud of pyrethroid vapor that serves to disorient or kill flying bloodsuckers.  Metofluthrin, [2,3,5,6-tetrafluoro-4-(methoxymethyl)phenyl]methyl 2,2-dimethyl-3-(1-propenyl)cyclopropanecarboxylate, or other pyrethroids are used in several of the most effective spatial repellants. 

 Volatilizing pyrethroids means breathing them.  They are rapidly absorbed through the lungs.  Measuring the metabolite 3-phenoxybenzoic acid shows the majority of us are already exposed to pyrethroids.  I am concerned, but, for now, willing to trade breathing the vapors for fewer bites.

 Some say the pyrethroids are safe, deemed natural or safe because their foundational structure comes from a flower. That perturbs me.  Pyrethroids are ubiquitous, having replaced several classes of insecticides deemed more problematic.  They kill all insects, including bees.  They are highly toxic to fish and other animals living in salt water or fresh water.  We are only beginning to understand the human health and environmental toll of that widespread use.  Metofluthrin has a tetrafluorinated aromatic ring.  Permethrin is dichlorinated.  These compounds are far from natural.  Permethrin is listed by the EPA as a “likely to be carcinogenic to humans”.   Exposure was recently linked to increased deaths by all causes.  If safe means incapable of causing harm, these compounds are far from safe, but they may be safer than going without 

My safety in the woods now depends on chemicals.  I will move to spraying my clothes with Permethrin to ward off ticks, in addition to using DEET or Picaridin on my skin.  I will trade chemical exposure for reduced risk of arthropod-borne disease, or at least for a reprieve from bloodsuckers.  As arthropod-spread diseases spike, I am trading risks.