The world’s most widely used weed killer is not responsible for perpetuating Sudden Death Syndrome (SDS) in soybeans, research shows. A collaborative effort among soybean researchers in the United States and Canada and found that glyphosate does not increase SDS severity or adversely affect yields in soybean fields. Scientists from five Midwest universities and the Ontario Ministry of Agriculture Food and Rural Affairs, led by Daren Mueller of Iowa State University (ISU) in Ames, participated in the three-year study.
Japanese beetle is becoming a more common field crop pest in Iowa. Literature shows adults need about 1,030 growing degree days (base 50°F) to complete development. Japanese beetles will continue emergence until around 2,150 degree days. Based on accumulating degree day temperatures in 2014, Japanese beetle adults should be active in some areas of southeastern and southwestern Iowa this week (Fig. 1). Expect adults to emerge in central and northern Iowa in about 7-14 days if warm temperatures continue.
Farmers in the Midwest may be concerned about white mold (also called Sclerotinia stem rot) in soybean this year. The disease, caused by the fungus Sclerotinia sclerotiorum, is not common every year, but farmers who have battled the disease in the past will want to assess the risk of white mold development as soybeans approach flowering (growth stage R1 – plants have at least one open flower at any node).
One thing we have learned from outbreaks of sudden death syndrome (SDS) in years past is that this disease likes it wet. Last year we wrote about the risk of SDS increasing with the early season rain. But at the end of the article we threw in one caveat – soybeans were planted very late in the season, which reduced the risk of SDS developing. And after we published the article, the rains essentially stopped. Fast forward to the end of the 2013 season -- we still had some SDS in parts of Iowa in 2013, but it was not as nearly as bad as it could have been.
Soybean samples have been arriving almost daily at the ISU Plant and Insect Diagnostic Clinic this year. Early season problems were primarily damping off diseases and problems with herbicide carryover or sometimes a combination of the two.
Since 2000, soybean aphid has been the primary soybean insect pest in Iowa. Infestations are sporadic and unpredictable, but this insect has the ability to cause significant yield loss during periods of optimal reproduction. Several notable infestations have been reported, particularly in north-central Iowa, this week, and therefore scouting to determine population densities is strongly encouraged. Fields that have a fairly uniform infestation with low densities (e.g., 50% of plants infested with an average of 40 aphids per plant) should be closely monitored in August.
Soybean diseases are starting to show up in Iowa fields this growing season. In an On-Farm Network trial in north central Iowa, brown stem rot (BSR) was recently found. This disease is caused by the fungus Phialophora gregata, and infection can result in yield loss for Iowa farmers.
We will have a fair amount of corn tasseling shortly after the weekend – so fungicide application season is about here.
In talking with farmers and retailers the last week or so, based on all the rainfall and wet soils this is shaping up to be a big year for fungicide applications, so just a few thoughts for guys “on the fence” and trying to decide whether to spray or not.
High school students from across Iowa are invited to compete and showcase their scouting abilities in corn and soybean on August 5 at the Iowa State University Extension Farm. The competition will be a one day event with both indoor and outdoor components. The theme for this years competition is Crop Scouting Innovations. Monetary prizes will be awarded to winners. Click HERE for more information and registration.
This regional field day features key researchers and specialists participating in the North Central Soybean Research Program discussing ongoing research and recommendations for managing soybean aphid. There is no fee to attend but advance registration is requested to assist with facility and catering arrangements. CCA credits may be available. Click HERE for more information.