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I am sure many of you are frantically
trying to finish some scouting or spraying and will be trying to relax
on the 4th. This weekend, I'll try to finish a "How yield loss happens"
article in anticipation of an upcoming spraying frenzy. It may be worth
thinking about a couple issues as you evaluate fields next week.
Alfalfa
Potato leafhopper numbers are
relatively low but increasing. Third cutting may be at the highest risk
this year. Some new seeding fields have been treated.
Alfalfa weevil larvae are scarce
in fields near Lamberton but NW, WC, C and extreme SW Minnesota have had
some problem fields.
I would keep an eye on alfalfa
plant bug and alfalfa caterpillar numbers when sweeping over the next
few weeks.
Yellow Beans
Yellow soybeans
are common on alkali rims soils in western Minnesota. Before you blame
all problems on poor IDC or glyphosate tolerance in the variety (yes,
some folks did poorly on variety selection), I would investigate a couple
of other potential causes.
Check root systems for
root rots induced by saturated soils and more importantly soybean cyst
nematode (SCN). SCN resistant varieties have been widely adopted by producers
in this part of the world. However, you can have a nematode problem on
soybeans sold as SCN resistant for two reasons: 1) Low SCN resistance
in the variety and 2) The selection for SCN races (Hg types) that can
feed and reproduce on the source of resistance planted in the field.
Based on the Hg types detected
in limited 2007 SW MN soybean field samples, the later case should be
of great concern to both producers and seed companies. I sense that it
may be getting close to time to panic with respect to SCN management in
SW Minnesota. Acknowledging a problem is always the first step.
Soybean Aphid Scouting Note:
We
have had a period with good weather for soybean aphid populations for
the past couple weeks.
Soybean aphid behavior
is a bit unusual at the Southwest Research and Outreach (SWROC) center
this spring.
Typically, field edges
and more vigorous soybeans are colonized first. However, we are seeing
hot spots confined to eroded knolls with visibly stressed (poor tilth,
low fertility and organic matter, SCN and yellowing). Nearly all nymphs
have wing pads and I suspect the adult females will leave these stressed
soybeans. Several have reported heavily colonized volunteer soybeans.
I suspect, but cannot confirm, that this pattern has to due with a lack
of emerged soybeans when aphids made the move from buckthorn. On the other
hand, beans with iron deficiency symptoms have very few aphids.
Sure, with the high soybean
and fuel prices insurance treatments seem cheap. They are, however, not
without risk and do have the potential to hurt yield (chaos theory fans
take note). Like many producers, the 2008 growing season has me a bit
on edge but I'll do my best to let y'all know when it's time to panic.
Weed Control
Things aren't really so
simple. Glyphosate tolerant soybeans are not tolerant to glyphosate drift
from corn if broadleaf herbicides have been tank mixed. By the way, the
same holds true for tank mixes containing grass herbicides drifting from
soybeans to corn. There are a few more examples out there. It is a good
idea for producers to communicate to their advisors and applicators what
actually got planted where. I'm just saying.
Upcoming Events
I hope to see many of you
at:
Crop
Production Field Day, University of Minnesota Southwest Research and
Outreach Center, Lamberton, July 8, 8:00 a.m. to 1:00 p.m.
Summer Center Day, University
of Minnesota West Central Research and Outreach Center, Morris July 10,
Tours start at 8:00 a.m.
Bruce Potter
IPM Specialist SW Minnesota
University of Minnesota
Extension Service
Department of Entomology
University of Minnesota
Southwest Research and Outreach
Center
23669 130th Street
Lamberton,
MN 56152
Ph:
507.752.5066
Fax: 507.752.5097
E-mail: bpotter@umn.edu
http://swroc.cfans.umn.edu/SWMNPEST/swmnpest.htm
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