Plants 'call' for pest predators to come to their aid

14 years ago

The leaves of some plants protect from webworm caterpillars and other pests because as they are chewed, they release a chemical combination of acids and alcohols that attracts pest-eating yellow jackets.

Summary: The yellow jacket hunting for a meal needs a chemical signal. A plant injured by a chewing insect such as a webworm will give off a chemical that would draw in yellow jackets.

"The heat that the webworm produces in its chewing isn't sufficient to identify it, as that's only produced at a low level and mixes with the general heat coming up from the leaves anyway. And similarly for any bubbles of gas from the surface wax of the leaf: a leaf is always releasing microbubbles of wax on its own, so the webworm's contribution is not going to mark it outÂHow could the bush make a signal, using only plant-available materials, that could float and pass on a coherent message to the circling wasp?ÂIt's in two steps. If a plant leaf is damaged, one of the acids that's released changes from its usual heavy form into a lighter kind which evaporates more easilyÂ What the wasp will respond to is a mixture of that smell with something else. In the leaf of our lawn-edge bush, there's another chemical mixed inÂ But suppose it could be made in a way that it would transform into a lighter, evaporating form only when it was crushed by something like the fastidious webworm caterpillar? When the pressure of a biting insect is applied to the second chemical, alcohols much like our ordinary drinking alcohols split loose. Alchohols easily evaporate to carry an odor outward." (Bodanis 1992:58)

Comments (8)

jean001
14 years ago
Okay. thanks
Kimmsr
14 years ago
Kind of what I have been telling people here for years, and have had far too many skeptics try to tell me that I know not what I speak of.
Dan _Staley (5b Sunset 2B AHS 7)
14 years ago
far too many skeptics try to tell me that I know not what I speak of.

Then they have a poor education. Way back when I had a forestry class that pointed this out.

Dan
ronalawn82
14 years ago
anney, the subject of communications in worlds other than ours must be a fascination of the highest order. I recall my skepticism when introduced to phernomones (not a spelling error) more than half a century ago. Then recently a magazine item - plants send out a 911 call- caught my attention and held it and I reflect that I am supposed to become more skeptical with age. The future is really not what it used to be.
Dan _Staley (5b Sunset 2B AHS 7)
14 years ago
'phernomones' is indeed a spelling error. And pheromones are not what is going on here.

Dan
ronalawn82
14 years ago
dan staley, google it. Indeed, phernomones and/or phermones are not what is going on here. Communication is; in worlds and by means that are much different from ours. I was remembering some companions of my youth. We were so brash and dismissive. I am glad to have lived long enough to mend my ways and experience the joys of open-mindeness.
anney
Original Author
14 years ago
ronalawn

I do know what you mean, but the key to it is the differing sensory capacities and their uses by various earthly life forms. A realization that other life may be able to sense and make use of what we cannot tends to keep me humble!

I read on one research site that ancient trilobites had eye-structures that could literally see into infinity, whatever infinity is. Of course they probably didn't have a capacity to philosophize about it and we'll certainly never know what they saw or if it had some survival value, but nonetheless, it's fascinating!

And I think it's male squash bugs that conduct their mating calls on plants by vibrating the leaves or stems of the plants they're on to attract females and perhaps other squash bugs to let them know it's good feeding ground.
Dan _Staley (5b Sunset 2B AHS 7)
14 years ago
ron, one finds many spelling errors on The Google. One finds no such spelling errors in dictionaries or Google Scholar.

Dan