Transcript of the Episode and Show Notes
UNH cooperative extension presents Over-Informed on Fruit IPM
Hello there podcast listeners. Have you or any of your loved ones earned a PhD recently? For most, it’s a pretty traumatic process, taking a bright young person and convincing them that, although they thought they were pretty smart…nope, no, not at all, you really, really don’t know anything… also, especially for scientists, you should probably get over thinking that you’re a pretty smart person real fast because the crushing maw of the unknown is about to hit you. Nothing epitomizes this feeling more than a PhD student’s qualifying exams. Every university department is a little difference but every phd has had to prove that they are a worthy candidate for the degree through a grueling process of written and oral examinations. These exams can take days or weeks and are administered by a committee of 2-4 professors, although technically anyone is welcome to take part in the questioning, and anything can be asked. Anything. As you can imagine, as with most traumatic experiences, every phd will have a moment that sticks with them, one they talk about long after the exam. A friend of mine told me about a question she got hung up on: what’s the best way to learn about something new. She spent lots of time talking about how she goes about conducting a literature review, what the best journals were for the topic, the best books, online resources, and on and on, but her inquisitor was still unhappy. Finally, she gave up and the answer the committee member was looking for was “ask an expert”.
Well that certainly stuck with me and this certainly will be a theme through this series of podcasts – it’s a lot faster to ask someone who has been up to their eyeballs in the topic…perhaps because they have spent the past 3-5 years studying an insect for their phd, or the past 20 years studying a system because that commodity is part of their job description, or because that insect has thrust itself upon you as an invasive or an outbreak pest.
I’m to new to New Hampshire…well I’m originally from New Hampshire, grew up here, but its been about 20 years since I struck out to find my fortune…so I’m new to New Hampshire as an entomologist. I’ve heard a couple people mention winter moth and I panicked a bit because I didn’t know what it was, anything about the biology or the pest status of the insect, where it was, or what to do about it if an apple grower or a blueberry grower had a problem with it. So I asked an expert:
Intro: Heather Faubert, University of Rhode Island:
Anna: But wait, before we over-inform you on winter moth, let’s start with the basics. With a common name as simple as “winter moth” it’s important to emphasize that this is the invasive geometrid moth from Europe we’re talking about here, first introduced to North America in Nova Scotia in the 1930, winter moth spread to various parts of the US and was first reported in New England states in the 90s. This species is unusually cold tolerant and lays it eggs on its tree hosts until November or December. These eggs overwinter and hatch very early in the spring. Damage is done when these larvae feed on new buds of apple trees, pear trees, and blueberry bushes. These are the buds that lead to fruits so, losing these buds to winter moth will lead to yield loss in these fruiting crops. Fruit growers who are worried about winter moth should scout during tight cluster however, winter moth could be considered a “sporadic pest,” or one that is only serious in outbreak years, so most of you will not be impacted by winter moth. But speaking of outbreak years, Back to Heather…
Heather: Well my life became really taken over by moths in 2005. I started doing a lot of work with winter moth, with Joe Elkington. Monitoring and helping growers figure out when they should be doing applications. We started seeing winter moth in Rhode Island in 2004, it had come through Cape Cod in the 1990s from Nova Scotia. It’s been in Nova Scotia since the 1930s. The female doesn’t fly so the spread is pretty slow. When the population gets really huge, I was recommending that growers spray right at egg hatch. Egg hatch is right around MacIntosh green tip, which is really early in the season. Green tip is when the apple flower buds just start cracking open and there’s just a little bit of green tissue showing. Around here its right in the beginning of April.
What happens is the overwintering eggs will hatch and the larvae will just wriggle into the buds. They don’t chew their way in, they wriggle their way in. I was having people put on pesticides right then to try and stop them from getting into the flower buds. The population was so high, you couldn’t let a few in and spray later.
Anna: Are you trying to use something that smothers the eggs or something that gets the larvae before they get into buds?
Heather: The problem is there probably aren’t that many overwintering eggs in the orchard. It depends what happened the year before but, in a commercial orchard that’s managed, there may not be a huge number. But our orchards are typically pretty small and surrounded by woods. The caterpillars that hatch can balloon into the orchard. So even if you smother the eggs in your orchard or your blueberry patch, you’re not stopping the ones from ballooning in.
Anna: I’m just going to jump in here and define ballooning – for all you Charlotte’s Web fans out there, you’ll remember all of Charlotte’s babies floating away in the wind after, spoiler alert, after Charlotte dies. Which I guess fits in with this episode’s theme of traumatic memories sticking with you. Well that stuck with me. Anyway, many species of immature spiders and some young caterpillars, are known to release a silk thread or dragline. These small threads allow very small bugs to catch enough wind resistance to carry them through the air. Usually pretty short distances but it depends on where the wind takes them. Back to Heather:
Heather: So in Rhode Island now, its about 14 years later, natural enemies have built up and the number of winter moths isn’t as large as it used to be. Plus we’ve released a biocontrol agent that’s contributing to winter moth control. This tachinid fly – a fly that only attacks winter moth – that’s been released at 44 locations in New England. Mostly in Massachusetts but up through Maine and down in Connecticut. And the fly has been recovered in at least 33 locations.
That was Joe Elkington out of UMass, wonderful forest entomologists, has worked on gypsy moth and lots of other insects in his career. So in Nova Scotia, they had released three different parasitoids against winter moth in the 1950s. The one that was the most specific and seemed to be doing the most good was this tachinid fly. It’s pretty unique, I don’t know of any other biocontrol agent that works this way, the fly lays its eggs on leaves where there’s high populations of winter moths. The caterpillar consumes the leaves and accidentally eats the eggs. Then the egg hatches and develops inside the caterpillar. Come pupation time, you’ll get a fly emerging rather than a winter moth.
Anna: What a fascinating system! I’m so glad I got a chance to ask Heather about this.
While I was at it, I was curious about gypsy moth. Now you might be familiar with gypsy moth – it’s a forest pest of historical importance. It’s one of the most damaging forest pests in the world as the larvae are voracious eaters and they have a pretty wide host-range, eating pretty much any tree they come across. Gypsy moth was introduced to the states in 1869 in Medford, MA. For you Doug Pfeiffer fans out there, that’s just down the street from where he grew up. But the introduction was accidental, by an entomologist who was hoping to interbreed gypsy moth with silk moths to create a silk industry in North America. Silk moths are pretty finicky eaters so it may have been a great idea to breed them with an insect with such a wide host range…until they got out. He did his best to inform the proper authorities but his warnings fell on deaf ears.
Like winter moth, gypsy moth is slow to spread on its own but it wreaks havoc on forests when it does. Efforts to slow the spread of gypsy moth are ongoing in mid-Atlantic and southern states – but gypsy moth has been here in New England ever since the 1860s and every once in a while, sporadically, it becomes a serious pest of tree fruit. I asked Heather about what we know about the cause of gypsy moth outbreaks:
Heather: Alright, we are just getting out of huge numbers in 2015, 16, and 17. In 2016 and 17, pretty much the whole state was defoliated. In those years, I was seeing a whole lot of caterpillars, first in blueberries and apples. When they’re little, early in the season, Bt does a really good job at controlling gypsy moths. But the problem was, the population was so large that they were in the woods and just marched back into apples and blueberries later in the year. At this point, caterpillars are 5th instar, they’re bigger, much harder to control. Probably a Delegate insecticide would have been the best thing but growers were having a hard time, making lots of sprays to save their trees. I do know one apple grower who went away for his son’s wedding, was gone for a week at a bad time. He came home to a defoliated orchard that is finally now recovering but they can do a lot of damage. That being said, we hadn’t had an outbreak since the 1980s, so we went quite a long time without outbreak conditions.
Anna: So what do you think caused that outbreak?
Heather: So we had really dry springs, May and June, when the gypsy moths are out there. We had really dry springs in 2014, 15, and 16. In dry conditions, the entomopathogenic fungus that usually keeps gypsy moth in check, it can’t be transmitted from caterpillar to caterpillar like it does in a normal year. To have three really dry years in a row lead to really high numbers of caterpillars. I did a lot of PR stuff in 2015 and 16, around winter moth and gypsy moth, trying to explain to people – I see gypsy moth every year. Just nowhere near the crazy defoliation we saw those years. I think the biggest populations we had ever seen and we’re attributing that to the dry conditions we saw starting in 2014.
Anna: Now there are other players in this system, a virus and some parasitoids, but gypsy moth makes a good example of a sporadic pest that is almost never a problem until it’s a serious problem. Unfortunately, these outbreak years are hard to predict and, even more unfortunately, it sounds like they may be associated with extreme weather conditions.
Well that’s it for this episode. My apologies for being such a bummer. But my appreciation goes out to Heather Faubert from University of Rhode Island, who saved my but with some good winter moth information when I needed it! And special thanks to Brentwood’s favorite son, Jason Lightbown, who wrote and performed our theme music.
End credits: 'Over-informed on IPM' is a production of University of New Hampshire Cooperative Extension, an equal opportunity educator and employer. All music is used by permission or by Creative Commons licensing. Views and opinions expressed on this podcast are not necessarily those of the University, its trustees or its volunteers. Inclusion or exclusion of commercial enterprises in this podcast does not equate endorsement. The University of New Hampshire, New Hampshire counties and the U.S. Department of Agriculture cooperate to provide Extension programming in the Granite State. Learn more at Extension.unh.edu.
