> The crime is the loss of crops, but which is the real
> culprit - rotation, insecticides, test plot, evolving
> beetles, migrating beetles - or was it a conspiracy?
I think you are attributing too much organizational skill to the
agrochemical industry. But seriously, the rootworm story is an interesting
look at pest evolution in response to crop management. It points out the
need for a dynamic approach.
Betty said:
> They don't have alternatives? Why in $%^%#@ not?
> Why can't they grow barley, oats, wheat, rape, sugar beets,
> whatever, for a few years? Why can't they diversify - don't
> 1,400 acres of any one crop invite trouble?
Greg said:
> I still believe the biggest overlooked choice in the
> US is hay or pasture. A concientious effort by someone
> to put grass fed animals on an equal footing with feedlot
> animals would do as much for crop rotations as anything.
As Jim Quinton pointed out, the returns from corn-soybean rotation have been
very good, although if commodity prices stay as low as they are for very
long, maybe that will change. Growers will change the rotation if they need
to.
I just read in the University of Illinois Pest Management & Crop Development
bulletin #23 (Kevin Steffey Ed.) that the incidence of western corn rootworm
adults in soybean fields is considerably down this year. Same news from
Purdue (Pest and Crop #28, John Obermeyer). This suggests that pressure
will be low in the eastern corn belt, although local scouting is always
important.
The corn seed industry has been selecting for tolerance to this pest (ie.
resistance to root lodging) for a hundred years. Current corn varieties
stand very well compared to traditional varieties. Now all the big
companies are trying really hard to develop corn (perhaps using some Bt
variant, or a spider toxin) that is truly resistant. I am skeptical because
it is difficult to get much protein expressed in roots. Everyone is working
on use of novel, safe insecticides as seed treatments, although getting
sufficient spreading of the agent in the root zone is difficult. New safer
alternatives to Counter and Furadan have been developed for band application
over the row, and work pretty well.
One promising approach is use of baits to kill adults. Rootworm was
originally a pest of cucurbits, and they are strongly attracted to
cucurbits. Cucurbit extracts can be combined with insecticides to make
baits that kill the pest without actually being sprayed on the crop. I
wonder if cucurbits can be used as trap-crops to pull adults away from
soybeans? Perhaps a small grain could follow cucurbits grown in strips in
soybean/corn rotation.
Dale
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