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The Plant Health Initiative was founded by the North Central Soybean Research Program (NCSRP) with soybean check-off dollars to coordinate soybean production research on a regional level. The North Central region includes Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin. Our goal is to better understand and manage soybean pests and diseases and make the latest information readily available to soybean producers.

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USDA PIPE soybean aphid maps show soybean aphid detections from sentinel plots in each state. Use these maps for general information about aphid populations in your area, but decisions on the optimal timing to protect yield must by made on a field-by-field basis.

Soybean Aphid Populations Building in North Central States; Researchers Confirm 250 Action Threshold

August 12, 2008

According to state extension reports on the USDA PIPE web site, aphid populations are quite variable, but are building to threshold levels in some fields in Minnesota, South Dakota, North Dakota, Nebraska, Iowa, Illinois, Wisconsin, and Michigan. Temperatures most favorable for rapid aphid population growth and development are between 75° and 80° F. The risk of yield loss due to aphid feeding is greatest when aphid populations peak at beginning flower — because of the impact on pod set.

Extension entomologists in the region continue to recommend scouting and the use of 250 aphids per plant as an action threshold if aphid populations are actively increasing. This threshold has been continually reevaluated and continues to work well in late vegetative (right at first bloom) to R4 soybeans. Extension entomologists at Iowa State University also reevaluated the threshold based on current higher crop values and confirmed the recommendation in a recent Integrated Crop Management article. Remember that the 250 aphids/plant is designed to allow a 7-day lead time to treat before aphids reach the actual injury point. Thus, the safety factor to prevent yield loss is already built into the threshold. Spraying at or beyond R6 has not been documented to increase yield, especially if the crop has grown well through the vegetative stages.

So-called "insurance" insecticide treatments for soybean aphids, such as spraying insecticide together with an herbicide, or spraying at below-threshold levels, is not considered a good management strategy. This was recently summarized by Ken Ostlie, Extension entomologist at the University of Minnesota, and his colleagues in a recent Minnesota Crop eNews article. They cite several reasons why this strategy rarely works:

• Cost. There is no data to suggest that very low aphid populations hurt yield. Early applications are more likely to be re-colonized and require re-treatment.
• Resistance. The more often soybean aphids are exposed to insecticide, the more quickly insecticide resistant populations will develop.
• Increasing populations of soybean aphid and spider mites by removal of beneficial species. Newly-arrived aphids reproduce extremely quickly when predators are removed.
• Poor insect and/or weed control. Ideal nozzle, water volume, and pressure selection for insecticide and glyphosate applications are not the same.

For more information on current soybean aphid research, read the 2008 NCSRP Aphid Research Update (online in pdf format), or order a print copy by calling NCSRP at 1-800-383-1423.
Read more about soybean aphids»

Now is a Good Time to Check Soybean Roots for Soybean Cyst Nematode

July 29, 2008

The adult females of SCN can be seen on roots without magnification, Photo credit: Greg Tylka, Iowa State University.

Most growers know that the soybean cyst nematode (SCN) is one of the most important yield-robbers of soybeans. Yet many farmers don't know if their fields are infested with SCN —- you often can't tell SCN is there from looking at the field. According to Iowa State University Plant Pathologist Greg Tylka, “We’ve done research funded by the soybean checkoff that have shown you can have 40 percent yield loss occurring and the plants will not look sick above ground. The plants won’t look stunted or yellow, but you will surely find these little, white females on the roots".

July and August is a good time to look for SCN females. Dig plants with a shovel, and simply shake the soil away from big roots to see if any females are present. Adult SCN females will be white or light yellow, and lemon-shaped. They will be a lot smaller than the nitrogen-fixing nodules, about the size of the period at the end of a printed sentence. You can see them without magnification, but a hand lens may be helpful. The other way to scout is to take soil samples and you can do that any time of year. 

There are many management options for SCN, but the best way to manage is to keep the numbers low, instead of driving high numbers down. To do that, SCN must be discovered early by scouting even before the top of the plant looks sick. Another important management strategy is a good crop rotation system.
Read more about midseason SCN sampling»
Read more about SCN»

Giant ragweed Photo credit: Chris Boerboom, University of Wisconsin

Good Weed Management Requires Informing Yourself About Glyphosate Resistance

June 13, 2008

Glyphosate-resistant biotypes of giant ragweed and common waterhemp have recently been confirmed in Minnesota. Confirmed glyphosate-resistant giant ragweed has been reported in Arkansas, Kansas, Indiana, Ohio and Tennessee. Nine different species of weeds have developed resistance to glyphosate in the United States.

The Glyphosate Stewardship Working Group, a coalition of university weed scientists, has formed in response to this issue. They maintain the Glyphosate, Weeds and Crops website, a comprehensive site containing the latest news and information about glyphosate resistance in weeds and the consequences of development. The group has written a series of weed-specific biology and management publications that can be ordered or downloaded from the site.

Field Crop Fungicides For The North Central United States

May 15, 2008

With the threat of soybean rust, more foliar fungicides than ever before are available on the market for use on soybeans. Plant pathologists Daren S. Mueller, at Iowa State University, and Carl Bradley, at the University of Illinois, have written a comprehensive brochure published by the North Central IPM Center and CSREES (Cooperative State Research, Education and Extension Service) to help producers understand what fungicides are and how they affect plant pathogens.

The 29-page, full-color publication includes sections on fungicide use, why fungicides fail (diagnosis, sprayer calibration, environmental considerations), safety, and fungicide use restrictions. There is an extensive section on fungicide classes, fungicide resistance, and the FRAC code. The FRAC code represents the mode of action of individual fungicides and is important to consider when choosing and mixing fungicides. The code was developed by the FRAC (Fungicide Resistance Action Committee), a group of professionals who work to prolong the effectiveness of fungicides likely to encounter resistance problems and to limit crop losses should resistance appear.

Order your free print copy of Field Crop Fungicides For The North Central United States
by calling the NCSRP at 1-800-383-1423 or view online in pdf format.

Information on these pages is from the cooperative effort of researchers throughout the North Central states. Information from this site can be copied and distributed for educational use. Please credit the source with our name and URL: NCSRP Plant Health Initiative at www.planthealth.info. Please do not use copyrighted photos without permission.