To spray or not to spray?

Earlier this afternoon I was interviewed by the local television station news program on the occasion of today being Canada’s National Day of the Honey Bee.

As I noted in my previous post, our city is currently being inundated with forest tent caterpillars. They are everywhere, and it’s hard to take a walk in one of our city’s wonderful green spaces without literally bumping into them at every turn as they rappel out of the trees above. Yesterday evening I spent a bit of time in my yard and then spent most of the rest of the evening removing strands of caterpillar silk that had festooned me.

What does this have to do with Honey Bee Day? Well, as the planned news story is bound to point out, the temptation for caterpillar-plagued homeowners is going to be to spray the heck out of the little leaf-munching critters with whatever pesticide they can get their hands on. That urge, I would argue, is a mistake for a number of reasons:

  • At this point in the tent caterpillar infestation, they have done almost as much damage as they can do. I have been observing that they are growing quite well (unfortunately for us!) and are going to be entering their pupal (cocoon) stage shortly. In other words, spraying now won’t do much to reduce any remaining damage that they may still do. The damage is mainly done.
  • In any case, in the face of such a massive infestation, spraying a can of pesticide at a few of the caterpillars is analogous to facing up against the JTF2 with a BB gun. You may inflict some minor damage for a moment, but you’re going to be overrun anyhow.
  • For smaller trees and shrubs (many of which these caterpillars only eat reluctantly at best anyhow), physical removal is as effective as spraying, and definitely much better for the environment.
  • And, spraying WILL impact other arthropods that are beneficial, including enemies of the forest tent caterpillar… and pollinators such as honeybees and various native pollinators (bumblebees and others).

That final point, I believe, is going to be one of the messages of the news item later today. Specifically, don’t lose sight of the forest for the trees.

Or, in other words, don’t lose sight of…

  • the honeybees
  • the native pollinators
  • the spiders that eat garden pests
  • the parasitoid flies that dine on tent caterpillars
  • the ladybugs that eat your aphids
  • the seed-dispersing ants
  • the dragonflies that eat mosquitoes
  • that beautiful swallowtail butterfly that brightens your day
  • …you fill in the blank…

…for the caterpillars.

I realize that even after reading this, some folks are still going to want to buy a can or two of pesticide and use it in their yards. If that is you, then:

  • be sure to carefully follow the directions on the label because they are there for a reason.
  • remember that these are powerful chemicals and that more is not necessarily better.
  • do your best to limit your application to the area in which you deem that it’s needed.
  • protect yourself, your kids, and your pets during and after spraying.

I’ll close with a personal story. The other day I was in a garden store buying a few bedding plants and some soil for our gardens and containers. Near the checkout there was a display of pesticide that is labeled for use against forest tent caterpillar. A customer and a store employee were talking about how best to use the stuff. Being a nosy entomologist I joined the conversation and made my case. Following more discussion between the three of us the customer finally said, “well, I know that this won’t really help with the problem in my yard, but I’m just so grossed out by them that I want to do something.”

I’m not sure if she ended up buying the product or not. But I suspect that a lot of spraying goes on for that very reason – i.e. a general dislike of insects – particularly in vast quantities – combined with a desire to do something… anything.

So, one last plea – please carefully consider your need use a pesticide in this situation. This plague will be over for the year soon enough. If we are lucky, natural enemies and disease will knock the population down this year and we won’t be seeing these creatures in any substantial quantities for quite a few years to come. In the meantime pesticides will not alleviate the problem, but they might end up hurting some friends that you may not even know that you have.

If you would like more information on pollinator conservation, please see this page hosted by the Xerces Society.


(And a small side note: I’ve been seeing a few “friendly flies” around lately. So hopefully their population levels will pick up and they’ll help to wipe out this infestation. Fingers crossed! Keep in mind that these creatures are called “friendly” for a reason. Specifically, they like to land on various surfaces, including people. But they are harmless to everything except for forest tent caterpillar cocoons. If they are going to be a factor in knocking down the tent caterpillar infestation, there are going to be a lot of them around very soon. Here is a picture of one so that you know what to look for. Click on the photograph to enlarge. Notice the stripes on the thorax, the pattern on the abdomen, and the nice, big reddish/burgundy eyes.)

What’s with all these caterpillars?

Prince George, British Columbia, where I live, is in the midst of a forest tent caterpillar outbreak. The number of these little caterpillars has been increasing each year for the past three or so years. And that means that people are noticing them and asking questions. This morning I received a phone call from an affiliated pair of local radio stations and gave them an interview. That has not been my first inquiry on the topic and so, because Twitter is not the best long-term repository for such answers, I’m hoping that this blog post will answer many of the questions that folks might have. I’ll update this post as I receive new questions. So fire away.

What are some of the basic facts about this insect? The forest tent caterpillar is a native species with a range that extends across much of Canada and the USA. They generally present wherever its host trees reside, and they numerous hosts depending upon the geographical locale. Here in western Canada they often feed on aspens and other poplars. They also eat the leaves on some other leafy-tree (angiosperm) species, although there are also some that they avoid. But they do not attack conifers.

Despite their name, forest tent caterpillars do not construct tents. They get their name because they are related to other species – notably eastern tent caterpillars – that do. Forest tent caterpillars do spin silk and often leave large patches of silk in areas where they congregate. Although they do not have tents, they do aggregate in groups and they also move around in little parades following each other from branch to branch and from tree to tree. In some major outbreaks the number of aggregating and parading caterpillars can be so high as to make roadways slippery and dangerous to drive on.

What is the life cycle like? How long will these caterpillars be around? Forest tent caterpillars spend the winter in the egg stage. They hatch out around the same time as bud burst, which means that they have leaves to eat as soon as they leave their eggs. The new caterpillars are quite small, but grow rapidly as they defoliate trees. They move in groups from one tree to the next when food is depleted. The caterpillar stage lasts for a few weeks – usually from about mid-May until the end of June or early-July depending on the local climate. At that point, once they have grown to a good size, they pupate in little cocoons in sheltered locations. The pupal stage lasts a few weeks and then adult moths emerge in July and early-August. The adult moths only live a few days, during which time they mate and the female lays a band of a few hundred eggs around the branch of a host tree. Then the next generation is ready to take on the winter and to emerge the following spring. If you see a lot of adult moths one year (as we did last year here in Prince George), there is a good chance that you’ll have more caterpillars the next year. So keep an eye on the number of adult moths in your area this summer.

Why are there so many of them this year? Forest tent caterpillar populations are cyclical. On occasion – perhaps every ten years or so in any particular location – there can be a population explosion for a few years. The explosions are always self-limiting, as are most biological phenomena. A variety of factors are likely involved in ending an outbreak: disease, predators and parasitoids, starvation, or even untimely inclement weather. Sometimes one of these is all that’s needed to knock the populations down to sub-outbreak levels; often several of these factors work in concert to have that effect.

Are they going to kill my trees? Probably not. Most healthy trees can survive a few years of defoliation. In fact, many trees put out a second set of leaves after losing their first set. Add to that the fact that even in a large infestation, caterpillar populations in any given area may focus on one stand of trees one year, and another the next. So not every tree is necessarily going to be fully defoliated in every year. Defoliation takes away the tree’s food source, because trees, like other plants, make their food by catching sunlight and carbon dioxide with their leaves. So forest tent caterpillars reduce yearly growth in trees. In fact, researchers can study tree rings, which are indicators of growth, to track past outbreaks of defoliators.

A few trees will undoubtedly die if they are already stressed or if an infestation continues on for a number of years before the caterpillar population collapses. But if you see any large tree in an area that harbors forest tent caterpillars, you can bet that it’s already survived a number of previous outbreaks.

What can I do about it? Not much. Once populations get to this level, pesticide spraying is mainly futile, particularly in small areas such as a few trees in your backyard. At most you will spend money and time on a treatment that really won’t have much of an effect. Killing a few caterpillars may make it seem like you’re doing something, but there are plenty more where they came from. At worst, you will kill beneficial organisms (including some that would otherwise be happily killing forest tent caterpillars); you will have deleterious effects on your local ecosystem; and you could be exposing your family and pets to pesticides.

As pointed out by another entomologist on Twitter, there are some cases where larger scale use of Btk, which is not toxic to most creatures other than tent caterpillars, is advisable:

But those are usually special, large-scale situations, often involving aerial applications.

In most cases you can take a non-pesticide approach in your yard. You may want to do this if you have young trees in your yard that may not be as resilient as older, larger trees. You can remove caterpillars by hand or with your garden nozzle. And you can use sticky bands on the trunk so that nomadic parades of caterpillars can’t get to the leaves by climbing up the tree (although they may descend from above on little silk lines). Besides that, though, it’s best to just let nature take its course. The population will collapse soon enough, and in the meantime it is an interesting biological phenomenon to observe.

Have you done any research on forest tent caterpillars? Yes. About a decade ago I was involved in work on tree responses to having their leaves fed on by this insect. In one study we surveyed all of the genes that were turned on and off in leaves while the tree was being fed on. In another study, we found that while the caterpillar was feeding on some leaves, undamaged leaves in other parts of the tree began to release chemical signals into the air. We think that those signals are used to attract in enemies of the caterpillars. In other words, it seems that the tree is calling for help when it detects that it is being fed upon. There is still more work to do on that, however.  For instance, we are not sure which of the chemicals that the attacked tree is releasing – if any – serve to attract enemies of the caterpillar.

Can you make these things into wine? Yes.

Where can I find more information? Along with some of the links above, you can look here, here, and here.


A few of the many reasons that I love baseball:

1. Baseball is a sport in which you don’t run out of time, you run out of opportunities. Baseball doesn’t rely on massive bodily collisions or continual action. Baseball is all about suspense.

2. My dad used to take my mom, my sisters, and me to Calgary Cannons games when I was a kid. He would buy us each a hotdog, soda, and then ice cream cones for dessert. Dinner at the ballpark.

3. Winter is, alas, not my favorite season. Spring training, and then opening day, are the perfect markers of the end of snow and the beginning of sun.

4. There is nothing in the world like a lazy summer late-afternoon at the ballpark. And the crack of a bat.

5. Memories of my dad listening to baseball games on the radio in the evening. He is a San Francisco Giants fan and, if the weather was just right, he could pick up their broadcasts all they way up in Calgary. Of course, these days you can just listen on the internet (and I often do).

6. Speaking of that, baseball is the one sport that seems like it was completely made for radio. You can close your eyes while listening to a baseball broadcast and the entire game comes alive in your head. Try doing that with football, hockey, or basketball. This is particularly the case when listening to great play-by-play guys.

7. Baseball is the first professional sport that I remember watching live; watching Fernando Valenzuela pitch against the Montreal Expos at Dodger Stadium. And, being one excited little league kid, of course I brought my glove to the game.

8. Baseball has its own anthem, and everybody knows it by heart.

9. Baseball has many incredible stories.


AND, going into extra innings…


10. Baseball has deeply held traditions.

11. Baseball begets poetry.

12. Baseball has Yogi Berra.

Open data

by Dezene Huber and Paul Fields, reblogged from the ESC-SEC Blog.

Have you ever read a paper and, after digesting it for a bit, thought: “I wish I could play with the data”?

Perhaps you thought that another statistical test was more appropriate for the data and would provide a different interpretation than the one given by the authors. Maybe you had completed a similar experiment and you wanted to conduct a deeper comparison of the results than would be possible by simply assessing a set of bar graphs or a table of statistical values. Maybe you were working on a meta-analysis and the entire data set would have been extremely useful in your work. Perhaps you thought that you had detected a flaw in the study, and you would have liked to test the data to see if your hunch was correct.

Whatever your reason for wishing to access to the data, and this list probably just skims the surface of the sea of possibilities, you often only have one option for getting your hands on the spread sheets or other data outputs from the study – contacting the corresponding author.

Sometimes that works. Often times it does not.

  • The corresponding author may no longer be affiliated with the listed contact information. Tracking her down might not be easy, particularly if she has moved on from academic or government research.
  • The corresponding author may no longer be alive, the fate of us all.
  • You may be able to track down the author, but the data may no longer be available. Perhaps the student or postdoc that produced it is now out of contact with the PI. But even if efforts have been made to retain lab notebooks and similar items, is the data easily sharable?
  • And, even if it is potentially sharable (for instance, in an Excel file), are the PI’s records organized enough to find it?*
  • The author may be unwilling to share the data for one reason or another.

Molly (2011) covers many of the above points and also goes into much greater depth on the topic of open data than we are able to do here.

In many fields of study, the issues that we mention above are the rule rather than the exception. Some readers may note that a few fields have had policies to avoid issues like this for some time. For instance, genomics researchers have long used repositories such as NCBI to deposit data at the time of a study being published. And taxonomists have deposited labeled voucher specimens in curated collections for longer than any of us have been alive. Even in those cases, however, there are usually data outputs from studies associated with the deposited material that never again see the light of day. So even those exceptions that prove the rule are part of the rule of a lack of access to data.

But, what if things were different? What might a coherent open data policy look like? The Amsterdam Manifesto, which is still a work in progress, may be a good start. Its points are simple, but potentially paradigm-shifting. It states that:

  1. Data should be considered citable products of research.
  2. Such data should be held in persistent public repositories.
  3. If a publication is based on data not included in the text, those data should be cited in the publication.
  4. A data citation in a publication should resemble a bibliographic citation.
  5. A data citation should include a unique persistent identifier (a DataCite DOI recommended, unless other persistent identifiers are in use within the community).
  6. The identifier should resolve to provide either direct access to the data or information on accessibility.
  7. If data citation supports versioning of the data set, it should provide a method to access all the versions.
  8. Data citation should support attribution of credit to all contributors.

This line of reasoning is no longer just left to back-of-napkin scrawls. Open access to long term, citable data is slowly becoming the norm rather than the exception. Several journals have begun require, or at least strongly suggest, deposition of all data associated with a study at the time of submission. These include PeerJ and various PLoS journals. It is more than likely that other journals will do the same, now that this ball is rolling.

The benefits of open data are numerous (Molloy, 2011). They include the fact that full disclosure of data allows for verification of your results by others. Openness also allows others to use your data in ways that you may not have anticipated. It ensures that the data reside alongside the papers that stemmed from them. It reduces the likelihood that your data may be lost due to various common circumstances. Above all it takes the most common of scientific outputs – the peer reviewed paper – and adds lasting value for ongoing use by others. We believe that these benefits outweigh the two main costs:  the time taken to organize the data and the effort involved in posting in an online data repository.

If this interests you, and we hope that it does, the next question on your mind is probably “where can I deposit the data for my next paper?” There are a number of options available that allow citable

(DOI) archiving of all sorts of data types (text, spreadsheets, photographs, videos, even that poster or presentation file from your last conference presentation). These include figshare, Dryad, various institutional repositories, and others. You can search for specific repositories at OpenDOAR using a number of criteria. When choosing a data repository, it is important that you ensure that it is backed up by a system such as CLOCKSS.

Along with the ongoing expansion of open access publishing options, open data archiving is beginning to come into its own. Perhaps you can think of novel ways to prepare and share the data from your next manuscript, talk, or poster presentation for use by a wide and diverse audience.


* To illustrate this point, one of us (DH) still has access to the data for the papers that stemmed from his Ph.D. thesis research. Or at least he thinks that he does. They currently reside on the hard drive of the Bondi blue iMac that he used to write his thesis, and that is now stored in a crawlspace under the stairs at his house. Maybe it still works and maybe the data could be retrieved. But it would entail a fair bit of work to do that (not to mention trying to remember the file structure more than a decade later). And digital media have a shelf life, so data retrieval may be out of the question at this point anyhow.

Happy π Day!


(Note: If someone is thinking of baking me a π, here’s the preferred recipe.)