July 19, 2004
aphids can be found in many fields in the area, but at very low levels. Brian
Lang reports an average of 0.5 aphids/plant in the research
plots near Decorah. To put this in perspective, here is a
comparison of aphid populations in research plots near Decorah for the last few
years. The 2002 populations never justified treatments.
Average Aphids/Plant at Research Plots Near Decorah
2002 2003 2004
Because of the potential of this insect to populate under the right conditions, no one is saying to ignore aphids this season (not yet), but they will have to come a long way before treatments can be justified.
soybean fields have been sprayed for Japanese beetles in the
Bean Leaf Beetle
The first of the 1st generation Bean Leaf Beetles are showing up now. Information on scouting the first generation to make decisions on treating the second generation can be found at http://www.ipm.iastate.edu/ipm/icm/2001/7-16-2001/scoutblb.html.
The rootworm larvae are about done feeding on the roots. They are pupating and the adult beetles are/will be emerging. There have been many complaints about fields with significant root injury from rootworm feeding. The main reason for these problems is probably because of displacement of soil insecticide from the "protection zone" due to excess rainfall. If you want to rate rootworm control, next week is the best time to do so. Go to the following web site for the methodology of rating rootworm control.
For more information check out the corn rootworm home page:
Western Bean Cutworm (WBC)
This is a relatively new
insect pest in corn for eastern
It is time to scout for this insect now and continue as long as scouting reports (linked to the web site above) show high levels of moth flights. The following link has a photo of an egg mass to help you ID it when scouting.
White Mold in Soybeans
Stress Induced Potassium Deficiency in Corn
There are a number of fields again this year that have areas of stunted corn
where the lower leaves are yellow along the leaf margins. This is a symptom of
K deficiency, so soil test levels should be checked for future years. Over the past 15 years Ive seen numerous
fields that show these symptoms in a haphazard pattern across the field except
that the endrows usually look the best. If
this endrow pattern is evident, it is likely that the
symptoms are not only being caused by a soil fertility problem, but also an
environmental phenomenon where slight differences in the soil structure make a
big difference in root function.
This year I am seeing this endrow pattern even in fields that don't show these K deficiency symptoms. In some fields it is evident that there is more surface compaction where the corn looks good and the soil is more mellow where the corn looks bad. This was also seen in many fields last year, and I assume has something to do with soil-to-root contact. There are other odd patterns showing up in both corn and soybean fields this year related to traffic patterns, wheel tracks, and past tillage patterns.
August 4 & 5, CCA Exam
Preparation Training, Iowa City
I am offering a course designed to help ag professionals pass the CCA exams on August 4 (1:00-5:00) & 5 (9:00-1:00) in the Johnson County Extension Office at
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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