Orchard People

[00:00:00] Introduction and Disclaimer
The following program does not necessarily represent the views and opinions of Reality Radio 101, its advertisers and sponsors, or its listening audience. Listener discretion is advised.
[00:00:18] Welcome to the Urban Forestry Radio Show
Welcome to the Urban Forestry Radio Show here on Reality Radio 101. In this radio show and podcast, we learn about fruit trees, permaculture, aboriculture, and so much more. So if you love trees and especially fruit trees, or if you're interested in living a more sustainable life, then this is the place for you.
I'm your host, Susan Poizner of the fruit tree care training website, orchardpeople. com. Thanks for tuning in.
Welcome to the Urban Forestry Radio Show with your host, Susan Poizner. To contact Susan live right now, send her an email. InStudio101@gmail.com
and now right to your host of the Urban Forestry Radio Show, Susan Poizner. Hey everybody.
[00:01:24] Aphid Invasion in Toronto's Community Orchard
Last spring, I gotta tell you, there was actually an invasion in the Ben Nobleman Park in Toronto, Canada. It happened in our community orchard there and I gotta tell you, it was very scary. So this is what happened.
Now usually here in Ontario we have really frosty winters. But last year, in 2017, the winter was really mild. Still, our trees stayed dormant during the winter, and then as spring approached, they came back to life and dazzled us with their blossoms. That year, our cherry trees looked particularly lush and healthy with lots of new growth, and tender young branches emerged from the buds in preparation for a fruitful season to come.
I felt it was going to be a really wonderful harvest that year. But then, one day, I went to the orchard, and suddenly those tender young shoots did not look very good. The leaves at the end of the branches became curled and twisted, and I looked closer and saw that inside the curled leaves, armies of little black pear shaped insects were feasting on the fresh foliage.
This was an aphid invasion, and it was not a good thing. Now, our cherry trees are almost 18 feet tall, so spraying the leaves with insecticidal soap just wasn't an option. The tree was too big, and the insecticidal soap, you need to, with that stuff, you need to use repeated applications. So spraying would be way too much work, and I didn't know what to do.
The following week, I visited again, and I looked closer at the embattled young leaves. And I got really confused. In addition to the armies of aphids, there were now plump little red and black creatures on the leaves as well. I also saw longer bugs that looked like little mini alligators with their prickly black and orange bodies.
I didn't know if these creatures were friends or foe. I was tempted to panic and cut off all the new insect infested growth, to bag it up in plastic bags and throw it away. And thank heavens I did not do that. Little did I realize at the time that the insects that looked like mini alligators were lady beetle larvae.
And the plump, blobby looking bugs were also lady beetles that were in the pupa stage. The good news was that they had flocked to our cherry trees to feast on the aphids. So when I realized that these little heroes were an active anti aphid SWAT team, I left the tree alone and I let the lady beetles in various stages of development do the work for me.
Once the lady beetles finished feasting, the trees recovered beautifully and we had a good harvest that year. So now, aphids are a problem not only for those of us who grow fruit trees. They also feed on other plants and trees. So in this episode of the Urban Forestry Radio Show, we'll talk about who likes eating aphids, and how and when to attract them to our gardens.
[00:04:31] Meet the Guest: Dr. Stephen Marshall
Now, my guest today is entomologist Dr. Stephen Marshall of the University of Guelph. And he's the author of an amazing full color tome, Insects, Their Natural History and Diversity. So we're going to chat about aphids and the hungry, predacious insects that love to eat them. Now, Stephen isn't an expert in fruit trees.
Instead, he has incredible knowledge about all sorts of insects. He specializes in flies and beetles as well. if you have any questions about insects during the show, now's the time to ask them. Or you can send us a comment or just email to say hi.
Now, let's dig into our topic. Stephen Marshall, thank you for coming on the show today. A pleasure.
[00:05:17] Understanding Aphids: Reproduction and Defense Mechanisms
Okay, so I want to talk about the bad guys first. Can we start off by talking about aphids? What kind of insect are they? And why are they so unpopular with people like me? Oh, aphids are really amazing little insects, unlike a lot of other insect pests that are protected from predation by all sorts of armature.
big mandibles, spines, et cetera. Aphids are apparently defenseless and vulnerable. And the way they, win out, their, wars with various natural enemies, despite that apparent vulnerability, is by incredibly rapid reproduction. And they, They do that with such, such a tremendous success that, one author suggested that, they could, a single aphid could theoretically give rise to over 600 billion progeny in a single season.
What? Oh my goodness. We'd be very quickly neck deep in, in aphids if they didn't have some pretty cool ways of, getting around the issue of being eaten by everything out there. And the way they do that is by, by incredible, incredibly rapid reproduction. So they, get. The bypass, Eggs, for one thing.
They only typically lay eggs for one generation out of multiple generations in a year. Otherwise, they just give birth to live nymphs. And you can actually watch an aphid. Look at a group of aphids. You'll see they're all going to be females. That's the other thing that they, another thing that they do that speeds up the reproduction.
So that whole cluster of aphids, which is made up of females, look closely. You'll see that some of them are going to be popping live nymphs out, that will immediately start feeding as soon as they come out of their mother's body. no females. No eggs. rather no males, all females not bothering with eggs.
You'll note that most of them are wingless, so wings are expensive. They're metabolically expensive, so unless they really need wings, aphids don't bother to develop wings during the season. They'll typically have a couple of generations with wings to move from host to host, but usually they don't bother if they just go wingless to wingless with all females, no eggs.
Of course. They do use the wings as another strategy to, to, enhance this rapid development strategy when conditions on a primary host become unfavorable, gets too crowded, or the foliage gets too old. They'll, Give birth to, nymphs that will develop wings and then they'll fly to either, other hosts of the same plant or to completely different hosts.
And a lot of the most common orchard aphids will attack your fruit trees, early in the season. But then as the foliage gets a bit older, they'll leave the fruit trees entirely. And develop on, herbaceous plants on, on, on particular weeds. And then they'll typically come back to a woody plant, in some cases the, fruit tree, depending on the species of aphid, to spend the winter.
So they're just marvelously adapted for, spectacular, reproductive, success. I'm sorry, I'm just floored by the fact that there's no males. How is that possible? that's parthenogenesis. A lot of insects use parthenogenesis, rapid population increase, but aphids do it. with just a spectacular success, as any orchardist will know from, going out and, looking at a, branch one day and seeing nothing, and then coming out the next day and seeing thousands of little, as you aptly describe them, soft bodied, pear shaped, sucking insects, with their little thin beaks stuck into the foliage or the twigs, sucking up all that sugar rich, phloem.
Amazing insects.
[00:09:18] Aphid Colors and Their Significance
okay, we were talking about what they look like, and now something that confuses people is you can see them in different colours. Can you talk a little bit about that? Sure, that's actually a handy thing for those of us who want to know the biologies and the life cycles of particular aphids, because coloured.
So one of the most common aphids, on apple, for example, is the green apple aphid, and it's guess green. And another one is called the rosy apple aphid. And it's not really rosy, it's, but it's not green either. It's a dull purplish color, rosy steers you away from green anyways.
And there are other aphids that are spotted and there are even some that feed on, toxic plants. So for example, if you go out and look at milkweed, you'll see, It's a bright orange aphid on milkweed and that is probably a signal to potential predators that they're loading up on poisons from the toxic plant.
So it's a bright warning color. It's great. Yeah, aphids are often color coded for us. I'm glad you like them. I'm glad you like them because I don't and a lot of the listeners don't.
[00:10:34] Aphid Feeding Habits and Honeydew
Let's talk about the, sucking, the idea of sucking mouthparts. And I know a lot of when you're studying entomology, it's very important how these mouthparts work.
so what are they sucking, these aphids? The second most parts that you find on aphids are more or less the same structure that you find on all bugs. And that doesn't mean all six legged arthropods. That means all bugs. Because when an entomologist uses the term bugs, they're referring only to one particular group.
group of insects, one particular order of insects, called the Hemiptera. And that includes, stink bugs, assassin bugs, damsel bugs, leafhoppers, cicadas, aphids, whiteflies, and a variety of other things. in which the most parts are elongated out into kind of like a two barreled syringe. And in most cases, that syringe like set of most parts is slid into the host.
And in the case of aphids, the host is always a plant. and, one of those chambers is used to suck up the contents of the host. There are other bugs that feed. on aphids, so they're sucking up the contents of the aphids. There's even bugs, of course, that feed on people using the same basic mechanism.
some of us have encountered bed bugs, so this is the same. most birds. So in the case of aphids, they're, tapping the, sugar rich but nitrogen poor phloem sap. So the sweet phloem sap. And they're sucking up tremendous quantities of it, because they have to suck up tremendous quantities.
to get enough nitrogen, and this in itself creates one of the aphid problems that I'm sure all of your listeners are familiar with and that is that they poop out all sorts of, sugar rich waste products. They have to pump all this stuff through their system in order to get, enough protein. And that sugar rich Poop, is, known to most people as honeydew, and honeydew is really interesting from a pile of perspectives.
From my perspective as a, fly specialist, I see it as fly fuel. A lot of flies will feed on the honeydew as, as well as nectar and other sugar sources, but honeydew is very important. A lot of the natural enemies of, aphids also feed on the honeydew and build up their population numbers in part due to that resource.
But on the negative side of the ledger, lots of, sooty molds and other unwanted things also develop on, on, honeydew. So I'm sure everybody's familiar with that, that nasty black, guck you get underneath a pile of aphids and that's, that damages your, plants. some insects are, really dependent on the honeydew in odd ways that link their life cycles into aphid life cycles.
[00:13:34] The Role of Ants in Protecting Aphids
if you look closely at a bunch of aphids, among the dozens of other insects you'll see associated with them, you'll often see ants, and the ants are, essentially milking their honeydew. Their aphid cows to take the honeydew and in exchange, they're providing protection to the aphids.
They're protecting the aphids from the many, other predators that depend on aphids as food. How can an ant protect a, an aphid? are ants so strong that Oh, sure. Really? Sure, if you watch an ant hanging around a bunch of aphids, gluttonously consuming the, the, sugar sweet Droplets coming out of the, the aphid's, tail ends and you watch, for example, a lady beetle come marching in to take a snack of, of an aphid, the ant will, rush the, lady beetle and chase it off.
Oh my goodness, they're pretty smart. Yeah, and, there's been, lots of good, solid research showing that if you exclude the ants, the mortality in the aphid cluster goes, way up. So they're effective.
[00:14:41] Factors Influencing Aphid Populations
Now why is it that some years, like last year in particular, was so bad here in Toronto and in Ontario?
some years are worse than others when it comes to aphids. Why? Wow, I'm not sure I can answer that question. most insects have, cycles, and they're relative abundance. And in many cases, that's due to the, the buildup of natural enemies, of parasites, parasitoids, and, predators.
So when, the numbers of a particular species get high, their natural enemies track that abundance and also become more abundant, leading to a population crash in the host, which will lead to lower numbers the next year, which will lead to lower numbers of natural enemies and so on causing a different A perpetual cycle.
So that's one possibility. Another possibility is that it was a climatic thing. A cold winter could lead to a cold wet spring is in some cases more disadvantageous to the natural enemies and to the aphids. So aphids might get an advantage and build up a greater population or vice versa. It depends on the species and the weather conditions.
in other words, I don't know. You've got some ideas, but here's my other question. And I was surprised to see, looking through your book, and there was mention, I think, of weeds. Now, what role does do weeds play in all of this?
[00:16:19] The Impact of Weeds and Other Plants on Aphid Numbers
that's an interesting question. And it's actually a somewhat controversial one.
Because there are several widely cited papers showing that If you have a variety of weeds close to your fruit trees, the numbers of aphids will, according to the papers, either decline or increase. So it's not that simple. In many cases, the numbers of aphids decrease because the weeds provide, a refuge for the diversity of predators and parasitoids.
So the weeds are providing, alternate food sources when the aphids haven't built up their populations. Yet, they're providing a nectar source, a pollen source, a refuge, and that diversity of predators and parasitoids can then move into the fruit trees and drive the aphid numbers way down. There's been quite a number of really interesting studies of that.
It's not just weeds. People have looked at different kinds of flowering plants and, for example, shown that I just recently read a paper that showed alyssum planted in, in orchards, led to aphid, aphid suppression, because the flower flies that like to feed on alyssum flowers, are the major, predators of, aphids.
as the flower fly numbers went up, the aphid numbers went down. Wow. But, as a cautionary note, in perusing the literature about that. That nice simple story. I also found a number of papers that showed the reverse effect. where people, for example, studied the, numbers of aphids in apple trees close to, flowering peach trees.
And they found, for some reason, that, Those flowers, didn't increase the natural enemies in the apple trees, but they in fact led to larger numbers of aphids in the apple trees. So I don't know. As I told you before we started talking, this isn't really my area of research.
I'm casually familiar with the literature, and I haven't sat down and weighed the debate very carefully, but I know with interest that there are two sides to the story. Interesting.
[00:18:42] Listener Emails and Questions: How effective are purchased lady beetles, what attracts aphids
We've got some emails, so let's go through them and see what we've got. So we've got an email from Chris, but I don't know where Chris is emailing from.
So here it is. Hi, my squash was so inundated with aphids that the fruit was deformed. I tried neem oil and ladybugs. The neem oil looked like it did nothing and my 8 dollars worth of ladybugs hit the road after a couple of days. Pulled the squash to protect my tomatoes.
that's interesting. I think a lot of people have had this kind of experience. We'll talk about ladybugs in a minute, but do you have any comments on that about How ladybugs might deform the fruit? it's a complicated one. First of all, your listener was absolutely correct about the lady beetles taking off.
I've actually played around with that myself in past years, I've gone to suppliers that were selling bagged, convergent lady beetles for biological control in home gardens. And just for fun, I've released them in my home garden and then tracked, I've identified the lady beetles I've caught in the coming days.
And as predicted by others, those bags of lady beetles disperse immediately and it makes sense. The convergent lady beetles, it's a common native species called Hippodamia convergent. The ones you buy here are from California. And they're harvested by, heavy machinery, basically, that's used to scoop them up in aggregations that they form.
During the, the dormancy and so that during the dry season, they'll come up from the valleys in California and the form aggregations up in the mountains, and they'll normally sit there in active aggregations until, the rains come again, and then they'll fly back down into the valleys, but they're susceptible to, being harvested in huge numbers, such huge numbers and so efficiently that they can be sold to.
by the thousand for a few dollars in, in various garden centers. I don't see them much anymore. 10 or 10 or 15 years ago, they were sold everywhere. But they're fun. They're probably more or less harmless, but they're not gonna do any good in your garden because when you dump outta that bag, their sort of natural instincts will be, oh, I've just come out of dormancy and I'm in an aggregation of millions.
Of other lady beetles, I better just disperse out to look for some space and some food, and indeed that's what they do. And your 8 dollars is wasted. They may cause harm by introducing parasitoids and, diseases which we wouldn't have had in our native lady beetle populations. But that's probably not as serious a problem as the exotic lady beetles that we're releasing, or that we now have in, throughout North America, things from Asia and Europe.
They're very much a double edged sword. We'll talk about that. We'll talk about that in a minute. We're going to go into lots more detail on Lady Beatles. I'm just going to go through two more quick emails. Bob writes, Hi Susan, I cannot believe you're doing a show on this topic.
Amazing! I was wondering where I could get information on this topic. Thank you! Perry writes, How can I get rid of cane borer aphids on raspberries? Oh, no, Perry doesn't write that. Rita writes that.
And I don't know where people are from. Okay, Rita, we're going to talk about some more information about predators that might feast on those. Cane borer aphids. So we'll talk about that in a minute. And was there another email here? And Duane, what is the main thing that attracts aphids to gardens?
So what do you think, how do they know one garden is better than others, these aphids? Boy, that's a, tough question. I think that, if, the host is near the overwintering host and there's foliage at the right, right stage, they're likely to show up on that foliage. there are some kinds of aphids which are, particularly attracted to damage or to unpruned trees.
for example, probably the most commonly encountered, apple aphid in Ontario, at least the ones that I get brought into me for identification, the most often are the woolly apple aphids. And, they're attracted to damaged trees, so they'll, form clusters on the wood, near where it's been damaged, a broken twig or something like that.
that might be in part an answer to your question there. I wonder, do they, smell out the good stuff, or do they see it, or? Oh boy, that's a tough question and it's, I'm not sure what they're responding to, whether they're responding to something volatile. They have a fairly long antenna and, they probably are picking up on something.
Something volatile. Interesting. Okay, and we'll talk about, let's both remember to talk about the raspberry canes in the next part of the show. because I'm sure with raspberry canes, will it be the same as with other aphids, whether it's on fruit trees? Again, the predator insects will be helpful. Is that true with raspberries?
Yeah, absolutely. There's a number of different aphids that attack raspberry and blackberry. And, the, suite of predators will be more or less the same as you'd get on your roses, your peach trees, your apple trees, whatever. in, in There are specialized parasitoids, so the wasps that develop inside the aphids are often quite different in the different aphids associated with different host plants.
But the predators, which tend to be more general, such as the flower flies, which are the most important predators, the lady beetles, which are probably the most conspicuous predators, they're very similar from host to host. Okay, interesting.
[00:24:56] Lady Beetles: The Natural Aphid Predators
all right, let's take a moment now, that we're all freaked out about aphids.
We're freaked out that they only give birth to girls, that they have so many children. So Stephen, when we think about aphid eaters, we think about lady beetles, right? Some of us call them ladybugs. So we can recognize them, they're sweet little spotted red beetles that flutter around our gardens and children love them.
So what kind of insect are they and why do they have such a taste for aphids? Yeah, everybody seems to pick lady beetles first because they're so attractive and cute and everybody knows about them. And there are a lot of them out there. There's a figure often quoted from Robert Vandenbosch, one of the great fathers of biological control.
He was a California entomologist who came up With the number of convergent lady beetles, that's just one species of lady beetle, feeding on aphids in California every year. He said that every year in California, 7. 5 million convergent lady beetles consume 3. 75 trillion aphids.
Those numbers are so huge, they're meaningless to me. But the take home message is that there's a lot of lady beetles out there. And, if you, watch a bunch of aphids, as you pointed out at the start of your program, you're very likely to see the alligator like larvae, long legs, nasty looking jaws, and typically some colors and spikes on, the, the body.
You'll see them marching through a bunch of aphids, eating them, Just, one after another. They really chomp through a lot of aphids. So they're conspicuous and they are common.
[00:26:38] Diverse Diets of Lady Beetles
And most of them. eat aphids. We have about 450 North American lady beetle species, of which a lot were deliberately introduced in North America from other places.
That's something we might get back to later. It's, a practice I'm not entirely enthused about, but of that, of those, native species here, most, Some feed on aphids, but some feed on scale insects. There are some that, that are specialized predators of mites. And there are even some that feed on, on mildews and molds.
And there's actually a few lady beetles that eat plants. not, fruit trees. But there are some lady beetles that attack, beans and, related plants. Not so many here in North America, but there are quite a few. phytophagous lady beetles elsewhere. So it's, although it's a diverse family, the great majority are conspicuous brightly coloured aphid munchers.
So we like them for that reason. And they're so cute. And also I, think I read in your book they do also eat mealybugs. Is that true? Yeah, some do.
[00:27:46] Lady Beetles as Biological Pest Control
It's, unusual for the same species of, lady beetle to Move from aphids to mealybugs, but there are some Mealybug specialists which have a great reputation for knocking those pests right down Some are actually sold by garden centers and used quite effectively in greenhouses and other Enclosed limited environments.
There's an Australian lady beetle, the usual name for it among entomologists is the crypt, Cryptolaemus montrouzieri. it's a kind of a dull little, blackish blue lady beetle that has larva that looked just like mealybugs. They're all covered with the white mealy stuff, but like a wolf and sheep's clothing, they march through the mealybug masses, chomping down on them and killing great numbers.
So they're a very, effective, almost like a biological pesticide. Wow, that's incredible. So all of these bugs you talk about, so many of them you can find in fruit trees.
[00:28:48] Understanding Insect Mouthparts
Now, I wanted to talk about, again, the mouth parts. Often when I find, when people talk about insects, they talk about what the mouth parts are used for.
So the aphids suck. They suck the sweet, yummy, life out of your trees and plants. But, these guys, these lady Bugs, or lady beetles, they chew, am I right? They chomp, that's right. They chomp. As a matter of fact, the name beetle is from the old English bitula for biter. And it refers to the fact that they have, chewing mandibles.
Chewing mandibles are basic to most insects. It's just that in the, lineage leading to the true bugs, the mandibles have become extended out to, to form the parts of, these, syringe like sucking mouthparts. And I should point out that they don't just suck, they also spit.
Remember when I described those mouthparts to you, I said there's two channels. One for slurping stuff out, there's also one for spitting. And that's actually a critical point. when you consider what, these things do to their hosts, plants or animals. for example, if you look now at, the, aphids on, the spring foliage on various fruit trees, that where the aphids are feeding, they're often, deformed and curled.
They actually, fold into a little house for the aphids, in which the cluster of aphids are hidden. And that deformation is caused by a toxic saliva that they spit into their host plant. they don't just suck, although they do suck, obviously, in various, contexts, but they also spit.
Whereas, as you pointed out, lady beetles have very different kinds of mouthparts. Simple, chewing, big massive, chunky mandibles. Now if we move to some of the other common aphid predators, they have different kinds for most parts.
[00:30:40] Aphid Predators: Lacewings and Flower Flies
So lacewings are also very common. Predators of aphids. Lacewings are those delicate, green winged insects that you'll, the adults aren't often seen during the day, you're more likely to see them at night, where their golden eyes reflect the light from your porch light, sometimes called golden eyes.
But if you find a larva, they look like a lady beetle larva, but instead of having chunky mandibles that they're grabbing, prey with, they have, What looked like sickles, two long, curved, hollow mandibles, and they impale their prey with these long, thin, sickle like mandibles, lift them up, and suck their contents out.
that marks the, the, lacewing group. It's another order of insects in Europtera. And yet, another group of aphid predators, and indeed by far the most important one from the grower's perspective, is the, flower flies. The flower flies are, nectar and pollen feeders as adults.
They're not, taking aphids as adults, but they're important pollinators. But the larva, which you'll find if you look really closely in clusters of aphids, I describe them as looking like green land leeches, because most of them are greenish in color, and they look like leeches.
If you look at their head end, it's tapered, and it ends in a pair of hooks. And they jab things with those two hooks, raise the front end of their body, and then suck out the contents of their prey. They're very sloppy eaters. They suck half the contents out of the prey and then throw it away and then kill another one.
It's easiest to watch that at night when they're most active. But you can find them almost invariably in any cluster of aphids. And they're the most important of aphid predators.
[00:32:23] Managing Aphid Infestations in Orchards
I've got an interesting question from Anthony. And, I wonder this myself. He says here, and Anthony's from Baltimore.
In Susan's example to start the show, she noticed a horde of aphid predators that came to feed on the aphids. But what if aphid predators don't show up in our orchards? What do we do to rid the orchard of aphids? I'm not going to directly answer that, any
kind of pesticide use. And secondly, they may not be showing up in good enough numbers. It's, analogous to the problem you have with pollinators. If you have an enormous industrial orchard covering square miles, with no natural habitat to in sight, that's, there aren't gonna be enough pollinators.
And by the same token, there's, it's gonna take a long time to, to get, any aphids, aphid colonies, suppressed with, the few natural enemies available. but they're always there. I just. I really believe me. And unless there's some mitigating factor like pesticide use, it's very unusual to find a cluster of aphids without some predators working their way through the prey.
So I find this interesting because in our orchard park, it's on a busy, street here in Toronto. And yet, like I said, literally we had armies of these. Beautiful creatures coming to eat the aphids. Now, in our park, we have a beautiful pollinator garden. It's large. It's got flowers that, that are blossoming it every time.
I just wonder if having an incredible diversity of plants and nurturing your space in a, sort of polyculture way, you're more likely to have, these aphid eaters. And I know because I visit other, areas in Toronto, I visited home. backyards with terribly smitten trees and nobody came to rescue them, like nobody came to the rescue.
So I wonder if having, just creating a beautiful and diverse, area for these to attract these beneficials would really help. I think so. As I mentioned,
it's still hot. That shows that in the
middle of an orchard or a weedy strip along the edge can actually lead to higher aphid populations or higher aphids, higher populations of some aphids and not others. So the answer's never really that simple, but I am inclined personally, to like the idea that, diversity begets balance and might.
I don't have a great problem with aphids in my garden because I'm an entomologist and I like to have a diverse property. So I have lots and lots of parasitoids and lots of predators.
[00:35:48] Community Solutions for Aphid Control
Okay, I'm going to read a few, and this is also relating to Anthony's question, a few comments from Facebook that I got with some solutions that people suggest.
These are all people who are passionate about growing fruit trees. Jana in Pittsburgh wrote, I had trouble with my shaded currants. Solution was more sun, so she somehow either moved the currants or cut the shading branches off. Maybe it just made a better environment, for the beneficials. We've got Andy from California wrote, first and foremost, ant exclusion.
Tanglefoot resin spread on stretching grafting tape, band around the trunk. So he puts this band of tape around the trunk. He puts Tanglefoot on it and it stops ants from crawling up and farming those aphids. That's interesting. Yeah, he's absolutely right. And that is a. I pointed out earlier there's been, there's, technical literature showing that in some cases that, ant exclusion, drives the, parasitism and predation rate way, way up because otherwise the, parasitic wasps coming in to lay their eggs would be chased off by the ants.
Predators would be chased off by the ant. Oh, cool. That's great. And that explains it. Yeah. We've got another one from Japheth. I don't know. I'm probably mispronouncing his name. I'm so sorry. Anyways, he says soap first, pyrethrum second, tobacco juice third. On my leafy vegetables, I stick with soap and he's talking about insecticidal soap.
Or, I yank them out, he says, in the case of, in the case of mustard. My daughter's honeysuckle gets terrible aphids that I can't lick. I do not worry much about the trees unless they're killing the tips of new grafts. now just one thing I want to note, even insecticidal soap can harm some best beneficial insects, am I right?
so if you're spraying your aphid, your aphidy leaf on your cherry tree, and there happens to be some beautiful, lady beetles on there in some stage or another, would you hurt the lady beetles? I, would expect so. If you look closely at those clusters of aphids, the two most common predators that I see in, aphids on a wide variety of hosts, little tiny orange aphid midges.
They're really fantastic. And these, little green larvae, soft bodied larvae that I described as looking like land leeches, and they're the flower flies. The technical literature suggests the flower flies are the most important predators. And in some circumstances, these little wee orange aphid midges are, also extremely effective, and they're both very soft bodied insects and would, quite likely succumb to, exposure to insecticidal soap.
But I'm, saying quite likely because I don't actually have any personal experience with that. But those little orange aphid midges are something that I should mention. If you're sharp eyed, you should look for them and watch them for a bit. Because they really do a job on an amazing number of larvae.
But they're very small. And the adults look like the tiniest mosquito you could imagine. go to your tiniest mosquito, divide it in half and make it more delicate. That's what the adults look like. But the larvae are, very conspicuous because of their orange color, despite their minute size.
And they're voracious predators of aphids. Wow, great. That's good to know. oh, we got another email here from Bonnie. I don't know where Bonnie's from. I forgot to tell people to tell us where they're writing from. But anyways, Bonnie says, Wow, what a creepy topic, but very interesting. Know your bugs is what I say.
And thank you, Bonnie, because honestly, I'm discovering how fascinating the world of insects is. I've just, it's amazing. I used to think insects were an inconvenience and now I'm realizing they're fascinating. They can be on our side and most insects are good ones. we've got another email here from Ron.
Hi Susan, very interesting show as usual. Where can I get more information on Dr. Marshall? He is fantastic. Wow, that's lovely. Stephen, do you have a website or anything if people want more information? The easiest way to find it is to Google University of Guelph Insect Collection and just follow the link.
Oh, perfect. Okay, University of Guelph Insect Collection. Thank you, Ron, for that question.
[00:40:12] The Role of Flower Flies in Aphid Control
Now let's get back to the topic of insects that can help get that aphid eating job done. Stephen, can you tell me a little bit about flower flies? Where will we find them? What do they look like? And how can they help us with our battles against the aphids?
flower flies are ubiquitous features of, any sunny day, really. you'll find them on, foliage, flower splatters of honeydew under those, notorious clusters of aphids. The flower flies that most people are familiar with are the bright black and yellow things. Some of them look a little bit like bees and wasps.
Some of them look a lot like bees and wasps. As a matter of fact, I've seen a number of magazine articles and books with covers labeled, here's a bee on a flower, and in fact, the photo on the cover is of a, flower fly. Wow. They're so Close in, in appearance to, to bees and wasps. But the ones that are most important in aphid control are, not really all that bee like, they're typically banded in black and yellow.
So they're fairly bright, they're fast flying flies. A lot of them are, able to hover over the foliage of the flowers. And they're very, sometimes they're called hover flies for that reason. the adults are probably most likely to be seen on flowers, though they're major pollinators.
The larva are much less conspicuous and the larvae that are, of interest in, today's conversation belong to just a couple of, the, subfamilies of syrphids. And most of them are in a subfamily called the Syrphidae. And the syrphids are the, The typical little black and yellow ones.
They're the ones with the larvae that I described as green land leeches. Maybe that's a silly way to describe them, but that's the way they look to me. They're, soft bodied, eyeless, legless, they're maggots, let's call them what they are. Although that's a negative name, isn't it?
Predacious maggots that come crawling along through the masses of aphids. They'll, their heads are pointed, and they end in two little hooks. They sink those hooks into the aphids, they lift them up, and consume, or partially consume them. There's also some very specialized, flower flies.
There's some that, go down on, actually go onto the roots of fruit trees, where you find things like, woolly apple aphids, making gulls. Causing damage to the roots. The larvae of these flower flies will go down and attack those aphids right on the roots. There are, aphids, or, flower flies that are great generals.
They'll feed on, all sorts of, different aphids. There are some that are specialists and will only lay their eggs, for example, in a mass of woolly apple, aphids. And taking as, taken as an aggregate, they're by far the most important, predators of, aphids. And they have the bonus of being the most important pollinators, too.
Wow. A lot of bee people would argue that, not with me. and now you say they're the most important, and yet we were talking about lady beetles and how much they eat. Are you telling me that, flower flies will eat more aphids than lady beetles? Every paper I've ever read that has, stacked up to contribution or the numbers, has ended up with flower flies on top.
They're just a little less conspicuous. Aphids, stand there, and they're bright red and black, and they don't fly away when you, approach, them as adults. And the, larvae are fairly conspicuous, not, hidden away in green like most of the syrphids. So Lady Beetles get a lot of the credit and they deserve a good deal, but they're not as important, in my opinion, as syrphids.
Now, I understand, am I right to understand that the flower flies actually, they like the honeydew, they like the nectar. so why would they eat the aphids too? Why don't they farm them like ants do? That's a good question. I don't know of any fly that actually farms, aphids. I don't think it would be a very adaptive strategy since, adult flies have soft, spongy mouthparts, and they wouldn't be very good in, defending.
most adult flies have soft, spongy mouthparts, the ones associated with aphids. Anyways, there are flies with, spear like mouthparts, robber flies that, that attack other insects. but They're not like ants that can grab invaders with their mandibles and tear them to pieces or chase them off.
But why do they go for the honeydew? a lot of flying insects require honeydew. energy, and the, main sources of that energy, that, those sugars are nectar and honeydew. And, both are very, important to syrphids. Interesting.
[00:45:05] Damsel Bugs and Other Predatory Insects
Now, we are unfortunately coming to the end of the show, but I wanted to just say one word about damsel bugs.
Now, I'm hoping that after this show, the listeners are going to go online, look for pictures because from my experience, Knowing what to look for is going to be key. Whether you, you see a maggot on a leaf, you think, is this a good thing? Is this a bad thing? So if there's anything we can do, it's looking up these beneficials and knowing to recognize them.
So tell me a word or two, a word or two about damsel bugs. Why are they also good guys for us? yeah, I mentioned damsel bugs because, they're, one of many groups of predacious true bugs. So they also have sucking mouth parts, fundamentally the same as, aphids. But they look really different because if you pick up a damsel bug, it's a small brown bug with it with a conspicuous beak, and you look at that conspicuous beak.
It looks like a weapon. It's this big sword slung underneath the head. it looks like it means business, and indeed it does. They can spin that out and impale a wide variety of prey items. The same is true for the assassin bugs, which look a lot like damsel bugs, but a little bit bigger. Although right now the most common assassin bug is green, whereas damsel bugs and some other assassin bugs are brown.
There's actually a significant number of different predation species of bugs that you'll find in orchards. Probably about a dozen different.
So we've talked about just a few of them now.
And for everybody listening to the show, do research the types of insects we talked about today. There's so much to learn, but we're starting in a nice little chunk of aphids and aphid eaters.
[00:46:53] Conclusion and Farewell
I want to thank you so much, Stephen, for coming on the show today. It was so interesting. I feel like we could have other conversations on other different types of insects, and we'd learn so much from you.
My pleasure. Oh, thank you so much. So goodbye, for now. Hopefully we will talk again. Okay. Thanks, Susan. Goodbye. Bye. So that was entomologist Stephen Marshall of the University of Guelph. And that's it for today's episode of the Urban Forestry Radio Show. I really hope you enjoyed the show. Thank you so much for tuning in today. You've been listening to the Urban Forestry Radio Show on Reality Radio 101.
I'm Susan Poizner from the Fruit Tree Care Training website, OrchardPeople. com. And I look forward to digging into a new fruit tree care topic with you next month.
You've been listening to the Urban Forestry Radio Show on Reality Radio 101. To learn more about the show and to download the podcast where I cover lots more great topics, you can visit orchardpeople. com slash podcast. The show is broadcast live on the last Tuesday of every month. And each time I have great new guests talking to me about fruit trees, food forests, and arboriculture.
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Thank you for listening to the Urban Forestry Radio Show with your host Susan Poizner, right here on Reality Radio 101.