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Showing posts from 2012

Watch For Potential Corn Ear Rots and Mycotoxins After Dry and Hot Weather in Parts of Minnesota

By Dean Malvick, Extension plant pathologist
Development of corn ear and kernel rots and associated mycotoxins in grain may have been favored by the dry and hot weather in some areas of Minnesota this summer. Although few problems with ear rots or mycotoxins seem to have been reported so far, only about 12% of corn was harvested in Minnesota as of September 16 and there is much grain to be harvested where potential problems may have occurred. Several different types of ear rots occur in Minnesota, but Aspergillus ear rot and Fusarium ear rot are of greatest concern because they produce mycotoxins and are favored by hot and dry conditions.

Performance problems surface again with Bt corn rootworm traits

By Ken Ostlie and Bruce Potter, University of Minnesota Extension

Bt-RW problem field with lodged corn
Calls over the last two weeks indicate Bt-RW trait performance problems may be expanding in scope. Field observations suggest corn rootworm populations have increased markedly in corn after corn fields since 2011; recent calls indicate a major expansion of the geography of performance problems into SC and WC Minnesota. Unfortunately the drought has masked the primary tip-off to severe corn rootworm injury—lodging. With injury largely completed and corn rootworm emergence peaking, now is the time to check fields for signs or symptoms of performance problems with your Bt-RW traits. Getting a handle on Bt trait performance is critical before making seed purchases for 2013. You may need to change your corn rootworm management strategy/strategies.

Tall Off Types in Wheat.

Jochum Wiersma, Small Grains Specialist

Photo 1. Variable wheat height. A fair number of spring wheat fields appear to be quite variable in plant height this season. Obviously varying degrees of drought stress can create height differences that are, in some instances rather striking (Photo 1). Differences in height, however, are more interspersed and without clear delineations and/or transitions as is the case in photo 1, it is probably not drought stress per se but one of three things:

a variety blenda variety that is segregating for plant heighta variety that suffers from a genetics anomaly that results in a chromosome being lost across generations.

Freeze injury in small grains

Jochum Wiersma, Small grains specialist
The last two mornings thermometers have dipped below 32°F in many places across Northwest Minnesota. Unlike the freezing temperatures we endured in April, these lows may have actually caused some damage as most fields are now at or past the jointing stage. Kansas State University has published an excellent bulletin about freeze injury in wheat that describes in detail what the damage looks like and what the yield impact can be. Simply follow this link: Spring Freeze Injury to Kansas Wheat

Understand that any freeze injury is probably localized to sheltered and low lying areas. You should also now that damage to the growing point may not be evident immediately. Leaf tissue that is damaged should show symptoms after a day or two.

Volunteer Corn - An Issue in Corn and Soybean

By Liz Stahl and Jeff Coulter
Growers are finding high populations of volunteer corn in their fields this spring. Factors likely contributing to this include lodging in many fields last fall due to poor stalk quality and drought conditions, and higher harvest losses due to low grain moisture at harvest. Other factors that can lead to high populations of volunteer corn the following year include storm damage and ear droppage. The question arises: When are populations of volunteer corn high enough to warrant control?


Figure 1. Volunteer corn in corn

Update on Aster Leafhoppers in Wheat

by Ian MacRae, Jan Knodel, Bruce Potter, Jochum Wiersma
High populations of Aster Leafhopper (also called 6-spotted Leafhopper) have been reported in small grains over the past couple of weeks. Starting in the south but now spreading to northern MN and ND. Aster Leafhoppers are greyish leafhoppers; the adults have clear wings and 6 spots between the compound eyes (Figure 1). Other than their coloration, the adults and nymphs both very much resemble potato leafhopper. The leafhopper uses it's piercing sucking mouthparts to feed on the plant's sap. The damage caused by Aster Leafhopper feeding is more localized than that produced by potato leafhopper. Feeding may produce localized necrosis or stippling (Figure 2), however, damage is much less than that caused by the Potato Leafhopper.