Wednesday, January 17, 2018

Will Our Extreme Winter Cold Wipe Out Ticks?

Deer TickI’ve been asked on four different occasions, recently, how tick populations will be impacted by the December/January below-zero cold. Some of those asking had heard reports, apparently claiming that tick populations would be decimated, if not eradicated, by the prolonged period of extremely cold weather.

We’d all certainly welcome that. It’s probable that you or someone you know has been affected by ticks and/or by Lyme disease. And any downward pressure on tick populations is welcome. But, the answer isn’t that simple.

Extremely cold temperatures do have an impact on overwintering insects and insect-like critters. (Technically, ticks are not insects. They’re arachnids, like spiders.) But determining mortality rates based on winter weather conditions is anything but certain. The mechanisms that allow their survival are varied and complicated. So different groups will have different rates of survival.

Some ticks survive as eggs deposited before winter. Depending on the species, a single female tick may lay 3,000 – 8,000 eggs, after which she dies. Ticks in other stages of development also overwinter in the shelter and relative comfort of the soil or within leaf litter and ground clutter, where snow cover can actually provide additional protection from extremely cold temperatures and wind.

Even when the air temperature lingers in the double digits below zero F, things that are covered with an insulating blanket of snow will remain much nearer to 32°F. In fact, the temperature beneath the snow, in many cases, will keep the soil from freezing. I’ve been told that just one foot of snow cover will completely protect the soil, and any organisms living within the soil, from the subzero air temperatures above the snow surface. And many experts believe that, even without snow, it takes a long period of bitterly cold weather to even have a chance of knocking tick populations back.

The rate of mortality greatly increases, however, with the combination of extremely cold conditions and liquid water. Overwintering insects and non-insects alike (i.e. ticks), must remain dry; insulated by the surrounding ice and snow; but not touching it.

A 2012 study co-authored by Rick Ostfeld; an ecologist at the Cary Institute of Ecosystem Studies in Millbrook, NY (Dutchess County), examined the probability of tick mortality in winter conditions in both Millbrook and Syracuse. The study found that exposure to subzero temperatures increased mortality “only at super-cold temperatures. And it wasn’t a clear die-off; just an increased probability of dying.” Regardless of winter conditions, more than 80 percent of the ticks survived at both sites.

According to Peter Jentsch, an entomologist and Senior Extension Associate with Cornell Cooperative Extension’s Hudson Valley Lab in Highland, NY, “most living things are able to survive environmental extremes if they have enough time to transition and acclimate to change.”

It’s interesting to note, too, that a 2010 study from the Journal of Clinical Investigation showed that some ticks developed a type of glycoprotein, a compound produced within their bodies, which works to help them survive the cold.

Some tick species overwinter on warm mammalian hosts; often moose or deer, but also black bears, dogs, and occasionally horses or cattle. They attach themselves to the animals’ fur. Then, during the winter months, to the hosts themselves; feeding and molting until spring arrives, at which time they drop to the ground, where the females lay their eggs.

NYS Integrated Pest Management (IPM) Program Extension Support Specialist, Joellen Lampman, first looks at how extremely harsh weather conditions may impact mammals; small mammals, like mice, when considering the question of the recent frigid weather and how it will impact tick populations.

In a recent IPM news article she writes, “Animals that have a harder time finding food are more likely to (in order of lessening consequences) die of starvation, succumb to other stresses such as disease or predation, fail to mate, give birth to fewer young, and give birth less often. In a nutshell, there should be fewer hosts, come spring. And fewer hosts eventually lead to fewer ticks.”

But there’s some bad news, too. Lampman writes, “During the time of high tick numbers and fewer small mammal hosts, each of us, and our companion animals, are at greater risk of coming into contact with questing (waiting on plants for a host) ticks. So, as soon as the temperatures rise into the mid-30s (and we know you will be out enjoying the veritable heat wave), ticks will be questing, and we need to steer clear of ticks and the diseases they carry – the IPM way.”

For more information, click here.

Photo of Deer Tick provided.

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Richard Gast

Richard Gast is a retired Extension Program Educator and has been contracted by Cornell Cooperative Extension Franklin County to continue his informative and thought provoking articles.




13 Responses

  1. Justin Farrell says:

    Interesting article, thanks for sharing.
    I always wondered how much ‘environmental management’ has played a part in the increase of tick populations in areas that historically have never had any tick issues. For example…growing up & living adjacent to the Pine Bush Preserve near Albany, NY ticks were never a problem until the they started “managing” the area, when they started the controled burning efforts throughout the area, and burning up all of the overgrowth & so called invasive species, in the attempt to restore it as a “Savannah” type landscape in order to help save the endangered Savannah Butterflies. Meanwhile the ticks have significantly & increasingly infested the area ever since they started burning up & “managing” this area. Bottom line is the ticks in this area were never a problem until they started burning everything in the area back to sand.

    • I can attest to this. I grew up in the Pine Bush as well. As kids in the 80s, my friends and I would spend hours in the woods and never need to worry about ticks. Then they began the controlled burnings and by the early 2000s the tick population exploded.

      I also feel articles on tick population problems need to inform people that treating clothes with Permethrin not only repels ticks but also kills on the spot them if they make contact with your clothes.

      • Stephen Daniels says:

        Not quite “on the spot”, but from my observations having worn permethrin-treated clothing for three years now, it takes about 30-45 minutes for ticks to die after first contact with the clothing.

      • Brian says:

        It’s not just the Pine Bush area. I grew up 45 miles from the Pine Bush in rural Schoharie County during the 70’s and 80’s and ticks were not prevalent. An encounter with a tick was extremely uncommon unless you went camping. The farm dog picked up a couple of them over the years and I remember those events being so uncommon that we all immediately wanted to see the tick. We haven’t had any controlled burnings in our area in recent memory, yet the tick problem here has been fierce here too. I’m afraid that correlation doesn’t necessarily mean causation.

  2. Steven Daniel says:

    Correlation is not causation- that’s a core principle in any scientific investigation that tries to tease apart factors that may contribute to a particular result. Fact is that ticks have spread and increased exponentially through much of the northeast since the early 1980’s. This has occurred in the managed Pine Bush, and the generally unmanaged areas throughout the region.

    Good article. Insect (and arachnid) populations can fluctuate greatly year to year – weather can certainly play a part. But it is rarely so simple as a single factor, as an extremely cold winter. Other factors play a part as well, such as populations fluctuations of their hosts, such as deer and mice.

    Deer ticks have been known from the upper Midwest (Wisconsin) since the mid -60’s, and started to increase dramatically since the 80’s, as they have in the northeast. The winters there often have extremely cold, below zero, weather that the ticks have survived just fine. Do warmer winters facilitate population increases – they may. The point is that it is a complex situation with lots of moving parts.

    • Brian says:

      One of those moving parts is deer population. Not only has the population of deer ticks gone up, but so has the population of deer. New York at around 450,00 white tailed deer in the late 70’s to early 80’s but by the end of the eighties, the number was heading toward double that at 800,000. Compare that to the year 2016 when the deer population was estimated at over 1,350,000. Oh “deer”!

  3. Paul says:

    One the tick gets on that deer and gets under that blanket of fur they probably don’t even notice the cold! I am curious how the extreme temps might effect (maybe negatively) the spread of the Emerald Ash Beetle populations.

  4. James Marco says:

    Good article, Thanks!

  5. Charlie S says:

    Ticks…..parasites. Nasty little critters and to think how much damage they can do! I have friends, and know of people, who caught Lyme from tick bites and it is not a pretty picture. They’ve been a problem going way back. I found a bit in the Poughkeepsie Journal July 26,1803 from a sheep farmer who was living in London at the time but used to live in the states. He states, “Formerly I lived among you and kept sheep; but could not keep them clean of ticks, enemies of the comfort and health of sheep, and also destroyers of wool and its growth……” His name was Rev. Dr.Peters and as was very common back in them days he was selling an ointment that relieved the animal of ticks. Nonetheless this little bit makes it clear that ticks were a problem over 200 years ago also. I suspect they’re more of a problem nowadays as all things seem to be increasing exponentially, and I suspect their increase in numbers is due to the release of hormones into the food chain.

    where a farmer talks about the damage to sheep and wool from ticks.

  6. Lindsay Groves says:

    Since theyre so tiny, cant they get through cracks between garments?
    Can you shampoo them out of hair with direct hot water and lots of shampoo & rubbing?
    How long from when they hop on to when they attach?

    • geogymn says:

      I hardly ever venture into the woods these days without donning a pair of gaiters. The easiest intrusion is between footwear and pant cuff methinks. I keep ankle gaiters in the truck all summer long just in case I need a quick escape from the madness of money making.

  7. Boreas says:

    Lindsay,

    “Since theyre so tiny, cant they get through cracks between garments?” Absolutely! That is why you see many of us walking around looking like geeks with our socks pulled over our pantlegs. They typically climb uphill until they can go no further – both the ticks and the geeks…

    “Can you shampoo them out of hair with direct hot water and lots of shampoo & rubbing?” Perhaps – if they have not yet attached. But once attached, they will go nowhere unless removed.

    “How long from when they hop on to when they attach?” Varies – usually not long. The amount of time it takes them to find a nice spot to feed. However there is typically a delay of several hours between when they attach and when they begin to feed. Some say disease transmission does not occur until they begin to feed. Others disagree.

    • Stephen Daniels says:

      Note ticks can’t “hop” onto anything, they cling through direct contact to the passing potential host.

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