A silly clown

It’s quite funny how hysterical professional gardeners and greenhouse staff get when they see aphids. I get it, aphids are the devil – that is, when you’re a tomato grower or whatever. I cannot count count the number of times I have been warned about all the horrors that are aphids – as if I don’t know what they are – by the (otherwise excellent) gardening staff at our local greenhouse facilities. Sure, there are plenty of other projects that are ongoing in these greenhouses, involving tomato, maize, potato, pea, and barley. Sure, my plants will attract aphids, and potentially many of them. That’s kind of what happens when you grow plants in an open-top and open-side greenhouse (which honestly would not be the way I would have designed it, but fine). I don’t particularly care much about the influx of aphdis myself. Their concern, however, is that my plants are a threat to all of the other projects that are being conducted in parallel with mine. I would – of course – care about this deeply, if I would know it to be true. I wouldn’t want to jeopardize anyone else’s experiments. I’m not that kind of asshole.

But it doesn’t matter what I tell them. Maybe it is my crappy German. Maybe they don’t want to hear me. (Maybe it is the red nose and the orange wig I am wearing when I walk around the place?) I work with Tansy plants. This plant species supports a bunch of aphid species, most of which do not eat anything else, or only a very narrow set of host plants (i.e., mono- or very oligophagous herbivore species). To them, however, an aphid is an aphid. There is no difference, and all are equally horrible, and need to be killed with fire. It is almost like trying to explain to my mother the difference between a lawn and a natural grassland. Green is green, right? Wrong! Sure, an aphid is an aphid, but that doesn’t mean that they’re all the same! Perhaps one of the funniest aspects of it all is that they do not seem to (want to) understand that I am actually interested in the aphids, and more importantly, WHY I would be. They always want to spray everything to death – preferably preventatively. As an entomologist, I obviously have my reservations about that kind of approach. And so, aphids come in, and I’m quite fine with that.

Last week, one of the gardening managers forbid me to get into my greenhouse compartment if I had anywhere else to be, because there were many aphids colonizing my plants, and I would certainly introduce them to other parts of the building. To bring him at ease, I promised to only bring the plants directly outside – when the time would come – but not enter other areas of the facility. I also, once again, told him that the aphids very likely would only be interested in Tansy, not in other plants. He was – of course – not convinced. Anyway, over the past two days I brought the first batch of plants (for one new experiment) outside. He was right. There were many aphids on the plants. However, Tansy is one of these plants that actually does not seem to care all too much about the aphids that are on it. The plants looked just fine. This plant is so bad-ass, that it keeps growing like a beast, even when it is covered in (thousands of) aphids. I have done quite a bit of checking on the plants, to see what was going on here. The fact that there are mainly specialized species on the plant, of course does not exclude the possibility that a few more polyphagous ones come in and colonized. I checked out quite a lot of them, and from what I have seen, it is mostly two species that have come in. They are easy to identify, and their names give away that they like to feed on Tansy (which is scientifically named Tanacetum vulgare).

Uroleucon tanaceti – plenty of these bright red aphids around, although most colonies are rather small, like the one pictured here. They are a bit shy, and hide on the bottom-side of leaves. A shame, as it is a damn fine-looking aphid species, if you ask me. It feeds on Tansy (as the name implies), but can also be found on Chrysanthemum cut flowers (which we don’t grow).
Macrosiphoniella tanacetaria – These bad boys are a bit more prominent than the previous. They tend to feed on the fresh shoots, and are thus very much in your face. They do accept a few other species as their hosts, but predominantly those in the Asteraceae family. (I am the only person growing asteraceous plants in the facility)
M. tanacetaria on a developing shoot. Any disturbance in these aphids leads to a wave-like pattern throughout the entire colony, that seems somehow very well-coördinated. These aphids look quite neat with their black legs and dark antennae, and are also quite chunky and robust, unlike the flimsy and tiny Sitobion avenae I work with in other current projects.

Although I can somewhat understand the sentiment in the gardening team, discussing with them sometimes feels quite challenging, and induces a lot of self-doubt. Although all of them are very helpful, and they generally do what I ask from them, quite often some go off on a tangent, explaining to me how it is that I should be working with plants. Now, I have worked with plants professionally for 22 years, and academically for seven. In this time I have produced hundreds of thousands of plants, and I take pride in never having lost a single experiment due to plant problems. The number of times I have been laughed at by the gardeners, often to my face, about some of the things that I do or study, tell me that they do not take me, or the field of ecology, very seriously. I really sometimes feel like I’m some silly clown to them. It’s quite exhausting to keep explaining that I am actually interested in aphids, thrips, pollinators, heck, even leaf pathogens, coming to my plants. The whole point of this project is to investigate how plants that look the same, but are chemically very different, change their interactions with the (biotic) environment. So yeah, let them come.

… and of course I realize you ideally don’t plant a field experiment in late July. I’m not that stupid. However, it was either the compost heap or a new life in a field experiment for these leftover plants, so the optimist in me just wants to give it a shot.

I guess I am a silly clown. (But I also like to prove people wrong.)

“Freising Field Experiment 1” – I finished planting this one this morning. Yesterday’s plants still looked amazing. I now installed a watering hose, so I can actually give them a drink when they need, although I think they would have been just fine without it. In the empty part in the back, I will be planting out “Freising Field Experiment 2”, which is basically a stock of 120 mother plants, of which I have collected a range of vegetative traits, and also determined the chemotype.
A sad attempt at capturing this hoverfly. There were hundreds! I should plant a few Tansies in my garden too.
A lone (presumably) Lasius niger exploring the plants after less than one day. Great, as a third specialized aphid on Tansy, Metapeurum fuscoviride, needs (these, or other) ants for colonies to thrive.
I guess I’ll sow a grassland mixture on the paths or so. Some coverage wouldn’t hurt.

Published by Robin Heinen

Father of two | Husband | Entomologist and Ecologist | Postdoctoral Researcher @ TUM | Traveler | Coffee Addict

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