Timing of monarch butterfly larval feeding in the Corn Belt
ours1 at web.net
Sat Sep 11 17:12:35 EDT 1999
Hello. My name is Vijay Cuddeford, and I consult to World Wildlife Fund
Canada. We've been following the monarch/Bt corn issue, and want to create
a "risk map" for monarchs in the Corn Belt States and Ontario.
To create such a map, we need information on when larval feeding occurs in
various parts of the Corn Belt. To be more accurate, I'm looking for larval
feeding times in Ontario plus Illinois, Indiana, Iowa, Kansas, Minnesota,
Missouri, Nebraska, Ohio, South Dakota, and Wisconsin. (These are the top
ten corn-growing states.)
If there are monarch watchers out there who can pass along such information,
I'd be very appreciative. I have talked to people such as Chip Taylor and
Lincoln Brower about this, by the way.
I've been led to believe that in the Midwest, larval feeding can occur any
time from April or May to October or so. But I assume that there are much
greater numbers somewhere in the middle of that time frame. Also, I don't
know how discreet or overlapping generations are in any one place.
Corn pollen dispersal occurs from about the end of June to the first week of
August in the Corn Belt, with the majority of pollen drop occurring for two
weeks or so in the middle of July. If larval feeding occurs during this
time, then there is risk. Of course, we have to rule out preferential
avoidance of pollen, look at the abundance of milkweed in or near
cornfields, how far pollen is dispersed, look at the dose-response
relationship, etc. etc. But I'm trying to nail down this one factor right
now, the larval feeding time.
Again, I'm grateful for any information (or contacts) you can pass along.
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