To Ann, Roberto, and others on SANET:
This thread touches on something that has bothered me for years, as an
entomologist hanging out with organic farmers. The organic philosophy says
that if you get the soil and growing conditions right, the plants will not
be attractive to one group of herbivores -- i.e. insects. However, at the
same time the philosophy says the plants will be more attractive to another
group of herbivores -- humans (maybe), cows, mice (and presumably other
vertebrates).
I have heard Larry Phelan speak (he came to the Farmer/Scientist conference
I organized), and he acknowledged how hard it is to pin down exactly what is
going on in his experiments with European corn borer oviposition preference.
(They laid more eggs on plants grown in soil from conventional farms than in
soil from farms that had been organic for many years, even when the plants
were grown in pots in the greenhouse.) He has been working away at it for
quite a while now. And this is just one insect species on one plant species
(of the hundreds of species that the European corn borer attacks).
I gotta say that I am deeply suspicious of sweeping generalizations,
especially when they are made about insects, because I have some idea of how
diverse insects are -- in how they feed, in what volatiles attract them, in
their level of specialization or generalization in feeding. Frequently the
exact same chemical, morphological, or genetic change that makes a plant
resistant to one insect pest makes it more susceptible to another. In
recent years we have been learning more about the symbionts inside the
insect digestive system -- and there's another whole level of diversity
there, which means that the basics of insect digestion aren't even uniform.
I am prepared to believe that you can make plants resistant to European corn
borer by improving the soil. I am even prepared to believe that the same
treatment may make the corn plants resistant to some other pests as well.
But not that the same treatment will make all plants resistant to all pests.
Maybe there is a perfect soil balance that results in perfect plant health,
so that the plant is resistant to all pests and delectable to humans and
livestock. But maybe, on the other hand, we live in a world of compromises
and trade-offs.
Kimberly Stoner
CT Agricultural Experiment Station
P.O. Box 1106
123 Huntington Street
New Haven, CT 06504
203-974-8480
Kimberly.Stoner@po.state.ct.us
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