Frogeye Leaf Spot Making an Appearance Across Iowa Soybeans
Iowa State University Extension and Outreach field agronomists have reported the appearance of frogeye leaf spot in soybeans as much of the crop across Iowa enters the R3-R5 growth stage.
Integrated Crop Management News
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When is it Too Late to Spray for Soybean Aphid?
Soybean aphid is the most important insect pest of soybean in Iowa. Foliar insecticides, mostly pyrethroids and organophosphates, have been the primary management tactic for soybean aphid in Iowa since 2001. Regular scouting and timely treatments will protect yield. Our research and extension program at Iowa State University (ISU) is focused on evaluating insecticide efficacy for soybean aphid on a wide range of products. We are also screening soybean aphid populations for pyrethroid resistance in northern Iowa.
You “Mite” Want to Scout Drought-Stressed Crops
According to the U.S. Drought Monitor, southeastern and south central Iowa are experiencing prolonged heat and moisture stress. In early August, there were twospotted spider mites detected in corn and beans. I recommend scouting corn and soybean fields for mite infestations this month, especially in these areas.
SCN Development in 2018
The activities of the soybean cyst nematode (SCN) are significantly affected by environmental conditions. Greatest SCN reproduction occurs during hot, dry conditions. SCN development likely is accelerated this season, and hastened development could result in greater-than-normal increases in SCN numbers. Every year, as fall approaches, patches of early-maturing plants will begin to appear in soybean fields. Early-maturing patches in soybean fields can be an indirect symptom of SCN damage. Farmers are encouraged to have fields soil sampled to determine SCN population densities prior to growing soybean crops and to take an active, integrated approach to managing the nematode.
Check Your Corn for Aphids
Since 2010, aphids have been colonizing corn later in the summer and are building up to striking levels in Iowa. They can be found at the base of the stalk, around the ear and sometimes above the ear leaf. It seems these aphids have been sighted in corn again this summer (Photo 1).
New Soybean Pest in Iowa: Soybean Gall Midge
In 2016 and 2017, there were isolated reports of soybean injury by soybean gall midge in northwest Iowa. Confirmations were reported in 2011 from Nebraska and in 2015 from South Dakota. In 2018, the distribution in Iowa has spread to twelve Iowa counties (Figure 1). This article hopes to raise awareness about a new soybean pest and confirm any additional infested Iowa counties.
Identifying, Scouting and Management of Bacterial Leaf Streak
Watch a video on testing and sampling for bacterial leaf streak!
Crop Injury Associated with Growth Regulator Herbicides
While off-target dicamba injury to soybean has dominated the news the past year, it is important to recognize that dicamba is not the only Group 4 herbicide (HG4) capable of injuring soybean. These herbicides mimic the activity of indole acetic acid (IAA), a hormone that regulates the activity of numerous genes involved in plant growth. IAA also is referred to as auxin. HG4 products can induce plant responses at lower doses than most other herbicide groups, thus off-target injury has been a problem since their introduction in the 1940’s. This article will discuss some of
Weather Conditions Ripe for Physoderma Brown Spot and Node Rot and Gray Leaf Spot
With most corn in Iowa at the V7-V12 range, it’s important to be aware of potential corn diseases at this particular time. Given the wet growing conditions over the last month, corn in parts of Iowa will be very susceptible to Physoderma brown spot and node rot, caused by the fungus Physoderma maydis, and gray leaf spot, caused by the fungus Cercospora zeae-maydis.
Potential Nitrogen Loss - 2018
High rainfall in some areas the past couple of weeks has produced another wet spring in Iowa. This leads to questions about nitrogen (N) loss and need for supplemental N application to corn. Unfortunately, this question has become almost the norm - I have written approximately 20 articles on the subject since 2007.