August 28, 2012
WEED SEEDS WANTED (REALLY!)
As you make your final scouting trips for the season, do you see weed escapes that might be herbicide resistance? If so, would you like to avoid this in the future? Mike Owen and Bob Hartzler, ISU Extension Weeds Specialists, are conducting an intensive study of herbicide resistant weeds and are in need of seed from weeds suspected of being herbicide resistant. Waterhemp is the main focus, but giant ragweed and marestail are also of interest. See http://www.extension.iastate.edu/CropNews/2012/0823owen.htm. For the field history, they would like to know the crop, herbicide resistance gene, fall tillage, spring tillage, cultivation, and herbicide history going back as far as practical, up to 10 years.
We would like to receive at least two samples from each county. If you have such (a) field(s) and would be willing to
1. grab enough seed heads to half fill a shopping bag,
2. record the GPS coordinates of the field(s),
3. gather as much field history as practical, and
4. get that to us,
it will help us all better manage weeds in the future. Contact me for more details. If you would like, Ill be happy to swing by and pick up the sample(s) from you.
Thanks in advance.
Ear Rots and Mycotoxins
In the August 2, 2012 edition, I talked about Aspergillus falvus, Aspergillus Era rot, and Aflatoxin. Reports of fields testing positive for aflatoxin are now coming in, so be sure to inspect and manage fields as they mature, as described.
Fusarium ear rot is also being found on corn in the area, especially in fields that had some insect feeding on the ears by Japanese beetles, rootworm beetles, and western bean cutworm. This disease is also more common with hot, dry weather. It causes a white to pink cottony mold that is often at the tip of the ear or anywhere there is insect damage. This fungus produces the mycotoxin fumonsin. Pictures and more details are contained in this 2009 ICM News article by Alison Robertson.
Another unusual ear abnormality that is being found in some fields is kernel red streak, which causes red streaks on the sides of the kernels. It is caused by a toxin spread by the wheat curl mite, but is mainly cosmetic and does not affect the feed value of the corn. More information can be found at http://pubstorage.sdstate.edu/AgBio_Publications/articles/ec929.09.pdf, page 9 (page 63 on the image).
Harvest will pose combine adjustment challenges in retrieving grain of variable size from plants of variable size. Mark Hanna, ISU Extension Ag Engineer, has some suggestions at http://www.extension.iastate.edu/CropNews/2012/0808hanna.htm.
Harvesting in warm, dry, windy conditions also poses special threats for combine fires. Prevention is key. Mark Hanna addresses this at http://www.extension.iastate.edu/CropNews/2012/0808hanna2.htm.
Black Corn Plants / Black Dust
There are areas in some fields where corn plants are very black. Farmers running combines through those areas report a cloud of black dust and their combines are black afterwards. Most commonly, these are areas of the field that died some time ago. The black dust is spores of saprophytic fungi. Saprophytes are bacteria, insects, fungi, etc., that are part of Mother Natures system of breaking down dead organic materials. So the saprophytic fungi are there breaking down the dead plant material. There are no overt health problems known to be associated with exposure, but people working where dust is flying probably should wear a dust mask. Chuck Schwab, ISU Extension Safety Specialist, suggests a minimum of a NIOSHapproved N-95 respirator.
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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