Plants Can Call 911- So Says Science

How? Call in the enemy of their enemy. Think you know how? Well a somewhat recent study from 2011 lays out the 911.


Cicada with fungus.

I learn so much from Cornell Cooperative Extension, and I rarely share it here, mostly because I think it might bore your socks off. The University has remarkable studies in every department from, ecology, evolutionary biology, entomology, botany, and horticulture. I recently read this study rather than contacted the researcher, which I have done on occasion.

You have all heard of beneficial insects. My guess is you might think of them flying around on the prowl actively searching for their prey. There is a slight problem with this scenario in that the insects they are looking for are quite small. So how do they find them so readily?


Hollowed out, yet still alive.

One study caught my eye done by Professor Andre Kessler, professor of ecology and evolutionary biology. He and Ian Baldwin of Max-Planck Institute for Chemical Ecology did a study and subsequently released a paper called, The enemy of my enemy is my friend. You can download the 2011 abstract in pdf form for further reading. Pressem_Kessler2001_en

The paper noted four ways to benefit when plants emit infochemicals.

  1. They signal to herbivores the plants defenses have been activated.
  2. The released volatiles let other herbivores know that the plant is under attack and to avoid further competition, they should decide to feed elsewhere.
  3. They let the predators know that their prey awaits.
  4.  Because the plant attracted predators, it signals the hungry herbivores “that it is a well-guarded fortress.”

Now this does not occur with every plant because some are toxic to herbivores in their own right, and have little need to attract predators. But…


Drone Fly with Fungus

The study found that some plants are not passive when under attack by munching herbivores and will give off a distress signal.


So interesting is that the plants will release volatile organic compounds like a dinner bell to parasitoids and predators. They essentially put out word to the insect world, “here is an insect worth eating” or worse, one to feed and incubate their young. This in turn attracts predators to act as the plant’s bodyguard and savior.


An example you might be familiar with is the case of the cabbage plant and the Cabbage Moth. Those little caterpillars do quite a number on the cabbage plant.


Cabbage White Butterfly

But, the cabbage plant has defenses and emits the specific VOC that will attract a species of parasitic wasp, Cotesia glomerata that will be happy to swoop in and attack the moth or butterfly eggs and any caterpillars that have hatched from them. We have the Cabbage White butterfly here, and it too is attacked by Trichogramma brassicae and Cotesia glomerata.


Drone fly with fungus feeding.

The caterpillar incubates the wasp brood as it develops, with the larvae feeding on the caterpillar from the inside out. Damage is done to the plant but the caterpillar will be dead as a result of this act of nature. If you are curious as to how this process unfolds….

The really amazing part of this drama is the parent wasp might never have found the prey had the plant not sent out the invitation.

“These herbivores are small and don’t smell a lot. They’re difficult to find,” said Poelman, of Wagenigen University in the Netherlands. “We had an idea that these wasps might use something that was already detectable.”


It is the odor of the VOC that acts as the olfactory cry for help. Kessler was not part of the Dutch study, but noted the signal can be interpreted by any available predator that is able to read it, which means it could also be attracting uninvited insects to the dinner table.

The plant loses control once the signal is sent, because “plant-insect interactions are played out in an ecological arena that is larger than the plant itself and incorporates many community-level components,” says Kessler.


Pretty amazing how plants actively react to threat. Did you know they also give off the distress signal after a lawn mowing? Now how cool is that. Pretty confusing to the parasitoids though.

What is new to the thinking here is that what was commonly once thought a twosome pairing of partners now is an active threesome. Think about the complexity of this. It is not just the hunted and the hunter. The plants and insects evolve right along making this complex world pretty darn amazing.

I had no images of caterpillars getting eating from the inside out, but do have a Drone Fly and Cicada suffering a similar malady. Both insects were alive despite such horrific damage. The Cicada was almost completely hollowed out, possibly from the fungus Massospora cicadina, even into the head. Nature is cruel in many respects. This is another example of a threesome in play. The mating pair, genetics, and good old-fashioned passing off the fungus to the offspring.

Upcoming… Bugs We Love and Plants They Hate. Why not bug the bugs before they bug YOU!


About Garden Walk Garden Talk

I love to photograph, paint, draw, design, garden, travel the world, and pass on a few tips and ideas that I learned through experience as a Master Gardener and architect. I am highly trained in my field and enjoy my work each and every day. I garden in Niagara Falls, NY in zone 6-B. Find me at:
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53 Responses to Plants Can Call 911- So Says Science

  1. Wonderful bug and flower photos. I never knew that flowers gave out the alarm when being attacked. How did they ever figure that out?

    • It is amazing, no? They measured the chemical composition of the VOC’s released to identify the compound.What they found was a specific insect was targeted, but others that were receptive to the same olfactory cue responded as well. Some were good for the plants and others had no effect on the targeted predator. The article explains it so much better than I can though. Way too long since my bio and organic chem days.

  2. This stuff is really fascinating. It must mean that by studying plants we can come up with much more effective and subtle means of pest management.

    • No doubt. Pest management for me is whatever nature provides. I may assist in removing Japanese beetles and slugs by hand, but that is about all. I have seen the predatory wasps, but never photographed them. They are really small and fast too.

  3. Fascinating to think about Donna…plants sending out alarms…

    • It is a pretty amazing study. The scientists had to be very observant to think the plants were acting an a way with such intent. We don’t think of plants having intent, after all they have little physiology to support the idea.

  4. sharon says:

    how clever are plants….what an amazing world thanks

  5. terryshirkie says:

    dear donna…i never found this boring at all…to me it is very very interesting..
    my high school days are far behind me and i forget a ;lot but i remember one time in biology, we were leaning about r.n.a in plants and studying different kinds of plants and their “nervous system”.
    one time the teacher was telling us of a plant and i forget in which country it lived,, but somehow tests were made on the plant with some kind of meter device attached to the plant…..the plant was calm, just straight lines when it was first tested.
    well then a person passing by suddenly started to pull the plants apart, stomp on them and really lay a beating on them[this was just an experiment]…the person finally left ….shortly after when that same person came back and passed the plants, the meter rating went wild and not smooth…it seemed very much that the plant recognized the danger…i wish i could explain this better donna..
    the teacher also told us about some plants when they feel danger approaching pop their heads right into the ground!
    donna, i have never liked to pick flowers..i enjoy them so much, but i just can’t bring myself to pick them!! death comes soon enought to them..let then live while they can……yeh i think i am an odd ball, eh?
    these photos are just gorgeous…i have got a little more respect for some of these insects too donna….this was such an enjoyable post……… terry

    • Those were interesting experiments, but they seem to have been discredited. You can read more in this Wikipedia entry, which may not be complete, but does seem to contain some solid information.

      Also read more about plant perception in this short (and easy to read!) piece from Scientific American. Plants have many ways to perceive and react to the world around them.

      Great post, Donna!

      • Connie, your reply was only to the comment on the comment above as being discredited, right? I am aware of the findings on ‘plant feelings’, but it was nice of you to post the links. I read the study in Science on the story I posted. I am an AAAS member and cannot post the full report. I need to read more of the associated work on this project, but I understand it is under review due to pending corroboration with additional study ongoing. Kessler did not work on the original study and was one to note that a specific predator is also part or a larger group in the work he did on this subject. It is factual the production of the VOC’s. What is under further study is the response and effect of the players I believe.

        • Yes, I tried to put my comment in the right spot. I was referring to Terry’s comment. I think she is referring to studies by Cleve Backster in the 1960s which have been since discredited. Your post on the current work was very interesting. Thanks for reading the journals and translating them for us laypeople!

    • Thank you for such interest in the story. Connie, below, did add the follow up to your comment. Plants are sentient much differently than us, but have the same desire to live.

  6. catmint says:

    bore the socks off us??? I don’t think you’d know how, Donna, even if you tried! One of the reasons I love reading sci fi, is that it prepares me for the reality that often turns out to be even weirder. Plant – insect communication falls into that category. btw – I took a photo of a black bird and followed your advice to raise the ISO. It worked!

    • Many of the ideas for those stories (especially horror) and movies came from what happens in the insect and plant world. Nature is by far more ‘creative’ in devising organisms to scare the living jeepers out of us. You might read my post Happy Monday From Pandora. It is a look at the movie Avatar. Talk about creativity……

      Thanks for telling me about your trying high ISO. I went looking for the photo, did you mean the magpie at the birdbath? That is an action shot and a good capture.

  7. Love your captures and your new header oh so cute:) Happy Sunday!

    • Thanks, Renee. It is a large illustration drawing (46″ long) I did on illustration board when I was back in advertising and was drawing during my lunch breaks. It was actually used in an award winning ad back then for the irony of oddity, even though I only was drawing it for fun. It is all crazy in that there are no spruce trees in Antarctica, Emperor penguins don’t wear clothes and don’t have a laugh at each others expense. I entitled it Going South. I had to distort it a bit and add some landscape to the right to make it proportionally into a header. I have one of baby penguins too that could be a header.

  8. HolleyGarden says:

    There is so much in nature that we don’t know. We just don’t have the senses to detect this sort of thing. Which is probably good. I suppose it sends out a 911 when we harvest the vegetables, if they do so when we mow the lawn. Almost sends chills down your spine, thinking about hurting their ‘feelings’.

    • So true Holley. That is a reason I am a member of so many organizations. I just love to learn new things about nature and how things work. I can not fathom what a plant experiences when getting harvested. One thing I do know is that they go into faster production, all with the intent to pass along their genetics to the next generation in a growing season, not to feed and nourish us. But some plants produce knowing they will be devoured to pass along genetic traits. Like seeds passing through a bird’s crop and being rolled around with grit. I believe the seeds exposed to the digestive acids often does better at scarification than just laying on the ground waiting for what nature throws its way. Cedars are an example.

  9. Fascinating and thanks for bringing this to my attention. Thanks to you, I have a renewed (actually “newed”) interest in plant biology. BTW, contacting a researcher is a good idea, I did it as a student and always got a great response (if occasionally slow) and I am more than happy to answer questions from non-scientists about my work.

    • I just love all things science and tech related. I was in academia for a short stint (could have been longer, I was asked to prof a class of my design) and chose to do the practical thing and practice architecture rather than teach. I sometimes regret the decision because learning has always been important in my life. So having access to those in research never made me shy about finding out what I want to know. I am a member of AAAS so I can read up on new scientific developments. Even environmentally conscious materials in the architecture field are always under new development for energy savings and public safety.

  10. One who grows Organically I was not bored at all I love the good bugs that slam the bad ones 🙂

  11. Hi Donna, I am fascinated with this stuff. There is so much we don’t know about the plant world, the insect world and their interaction…..amazing. The tomato horn worm and tobacco horn worm are other examples of host insects. Love seeing the wasp cocoons on the back of the horn worms. Nature at work!!
    You said you needed my blog link, sometimes the gravatar link pops up and I don’t realize it. Hope this is better.

  12. terryshirkie says:

    dear donna….i read this post to bernie and he really loved it…donna, a person COULD go to wikipedia but i just find that the way you explain this most interesting topic is so much easier for me to understand…thank you!… terry

    • Thank you much Terry. Wikipedia is a great resource but you always have to double check the entries. Not always are they accurate. Don’t you just love how nature takes care of the pests? It makes for a gory horror story.

  13. Barbie says:

    Now that is amazing stuff! I love the science for nature! Very interesting and if you ever you feel it will bore us to death – IT WON’T! 🙂

  14. Alistair says:

    I like all this kind of stuff, I would like to say it appeals to my scientific brain, more likely its the science fiction stuff that goes on in there. Must remember though, its 999 over here.

  15. TufaGirl says:

    Thank you for the scientific explanation. I explain to gardeners all the time that a sick plant is like the wounded animal in the pack and the lions know there is easy prey. “The bugs know.” (They just look at me.) Such great things out of Cornell – wished I lived closer.

  16. Marguerite says:

    Donna, feel free to keep sharing these articles! I wouldn’t even know I was interested in this type of thing until I read it on someone’s blog. Fascinating stuff and it’s great to have someone summarize the information so I don’t have to read the entire paper.

  17. Brian Comeau says:

    I feel twice as bad about running over some of my wife’s flowers with the mower now. Creation is complex… Amazing. Thanks for sharing!

  18. Wow, fascinating studies! I’ve found a lot of helpful info through Cornell, too. Tough images to see, but very interesting.

    • Cornell Cooperative Extension is a great resource. Their site has a wealth of info. The article actually came from the University though, after I saw the title and researchers listed at the Extension site. I went to Science for the full paper.

  19. Indie says:

    Crazy awesome! That is so fascinating. I love entomology and learning about things we never usually notice. Sometimes I feel like a whole other world going on out there… What a great post!

  20. Andrea says:

    Hi Donna, i can’t come here earlie as maybe i have some problem, the lower portion of your site is always moving, very difficult for me to focus. Anyway I managed to read and comment despite it! I read all the comments and maybe I am the only one who already know this before this post, nevertheless i still enjoy it. You have the style of writing which entice the readers. You remind me of Lewis Thomas, author of many books, one is The Lives of a Cell. He was able to write the complicated into very simple terms which laymen can easily understand. If only I can do it that way! Have you encountered the term allellochemics, that is another intriguing topic in plant physiology. By the way, i am so surprised today as there is someone who didn’t know that oxygen comes from green plants!

    • I have no idea what you are talking about with my site Andrea. Maybe you are not accessing my site but a mirror site that was hijacked. I am very sorry you are having so much trouble visiting.

      I knew about VOCs before the post too, but never found the paper until recently. The study was some time ago, but since that time, many researchers are still working on it to find out more. We had to read Thomas’ The Life of a Cell in college. I am surprised you would compare since I do struggle a bit simplifying.

      I have read on alleochemicals. They and other metabolites are released by plant roots and play an important role in rhizosphere signalling, plant defence and responses to the plant’s safety and stress. The plant can exert a negative physiological effect on the another species when the chemicals are released into the immediate environment. Many people here are familiar with Black Walnut toxicity and the chemical called juglone, 5 hydroxy-1, 4-napthoquinone. I have a black walnut on my property line, so I am very familiar with its alleopathy. I may write on it sometime. There are other significant finds on this plant too.

      • Andrea says:

        Thanks Donna, I put the comparison to Lewis Thomas as a compliment because i like his writing style. I know the topic in technical terms but reading it ‘laymanized’ is enjoyable, easy reading. You are a wonderful lady, shifting from so many special talents with ease and passion, but always with excellence! More power to you, as a lot of us learn so much from your posts. Take care.

        BTW, that moving window below is the slider of a new window, which just in my case opens, when i open your page. Maybe we have an incompatibility, i don’t know. But never mind i will just manage. thanks.

  21. AMAZING what goes on out there. Invaders, plant distress signals, savior insects. Truly WILD!

  22. I wouldn’t be surprised if we only knew 5% of the interactions in the natural world. It was all designed to work so well together seemingly without the interference of humans. Are we part of the process or are we destroying the process? Hard to know. On a happier note, I love the penguins.

    • I believe we are part of the process, but one of do before we think it through. Nature is too complex for science to think of all the ramification of action. The more we know, seems to show how little we know. I just read a study on the demise of old growth trees and how they will be a think of the past. I will post on this study in the future. I am still reading supporting papers. It really is depressing. Some is human action directly and some is human action as it affects nature and weather.

  23. b-a-g says:

    Really interesting. My lupins need to learn how to do that.

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