Welcome!
July
12, 2010
CORN
Japanese
Beetles
Japanese
beetles can be easily found in some corn fields in Clinton, Jackson, Muscatine, and Scott
Counties. Generally, they do not cause
economic injury to corn unless they are keeping silks clipped to within one-half inch of
the end of the ear prior to pollination being complete; generally it takes three or more
beetles per ear to accomplish this level of feeding. Once
pollination is complete, the silks can be eaten entirely away without causing yield loss.
For
more information on Japanese beetles and their management, see https://www.extension.iastate.edu/CropNews/2009/0630hodgson.htm
and https://www.extension.iastate.edu/CropNews/2009/0727hodgson.htm.
SOYBEAN
Whats
eating my soybeans?
Bean
leaf beetle numbers continue to be low, but Japanese beetles, green cloverworms, and/or
larvae identified by Tom Hillyer, Hillyer AgriService, as
celery leaftiers are causing noticeable feeding in some fields. For soybeans in or past beginning bloom, the
threshold for treatment is 20% loss of total leaf area.
In general, soybean defoliation looks worse than it is. The following graphic may help you in determining
the level of defoliation.
For
more information on Japanese beetles and their management, see https://www.extension.iastate.edu/CropNews/2009/0630hodgson.htm
and https://www.extension.iastate.edu/CropNews/2009/0727hodgson.htm.
For
more information on green cloverworms and their management, see https://www.extension.iastate.edu/CropNews/2010/0712hodgson.htm.
Celery
leaftiers are not known to be a problem in soybean, so information related to soybean is
scarce. The mature larva is slender and pale
green with a narrow, darker green band along the back and with a broader, whitish band
along each side, and it tapers toward each end. The underside of the caterpillar is
yellowish and faintly mottled with brownish yellow. The full grown larva is two-thirds to
three-fourths of an inch long. The larvae
usually damage the underside of the leaves by skelonizing them. The plants have a silvery
appearance when heavily infested. Later, the damaged areas become pitted. A slight, silken
web is spun in a leaf, or between two adjacent leaves and the leaf is folded or woven
together to form a shelter area in which the larvae feed; thus, the name leaftier. They seem to be concentrating in the lower part of
the soybean canopy.
Soybean
Aphids
Brian
Lang, my counterpart to the north, reports, Initial aphid migration from Buckthorn
to soybeans in May-early June was at a low level. The wet June kept aphids at low
levels. Summer migration of aphids usually begins around mid-July to spread to other
fields. With these low initial aphid populations, it is uncertain as to how rapid or
how high a population of aphids can develop. Thats why we continue to
scout. On July 11 at this trial I found my first winged aphids (only 4 so far) since
the migration of aphids from Buckthorn. So this marks the beginning of the summer
migration. However it is starting from very low initial populations, so no one can
predict yet if aphids will be much of a problem.
populations (are) still
matching up with low populations from other even years. The rapid
increase in populations in 2008 appeared to come from a summer migration of winged aphids
from Minnesota. Without that, we would likely not have had much trouble from aphids
in this region in 2008.
FOR
YOUR CALENDAR
Northeast
Iowa Research and Demonstration Farm, Nashua
Demonstration
Garden Field Day on August 7,, 2010 at 4:00 p.m.
Fall
Field Day on August 26, 2010, 1:30 p.m.
Details
are and will be posted at https://www.extension.iastate.edu/Pages/eccrops/meetnerf.html.
Muscatine
Island Research and Demonstration Farm, Fruitland
Demonstration
Garden Field Day on August 9,, 2010 at 6:30 p.m.
Details
are posted at https://www.extension.iastate.edu/Pages/eccrops/meetmusc.html.
Southeast
Iowa Research and Demonstration Farm, Crawfordsville
Fall
Field Day on September 15, 2010
Tentatively
there will be a manure application field day in the morning followed by a more
traditional field day in the afternoon. More
details will be posted at https://www.extension.iastate.edu/Pages/eccrops/meetserc.html.
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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