Integrated Crop Management News

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Soybean Potassium Deficiency Symptoms During Early and Late Growing Stages

August 21, 2018
Soybean potassium deficiency symptoms at early vegetative growth stages.

Since early August, farmers and consultants have been reporting what they believed were potassium (K) deficiency symptoms in soybean leaves located in the middle or upper canopy. This is not surprising in fields or portions of fields with soil-test values in the very low or low K interpretation categories. Moreover, K deficiency symptoms could develop at these growth stages with drought conditions, even in fields with adequate soil-test K levels. Sometimes symptoms occur in late summer with rainfall events after a dry period.

When is it Too Late to Spray for Soybean Aphid?

August 8, 2018
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.

SCN Development in 2018

August 6, 2018
Map the initial soybean cyst nematode (SCN) egg population densities (top) and an aerial image (bottom) taken in September of the sampled area in an SCN-infested field at the Iowa State University Northern Research and Demonstration Farm just south of Kanawha, Iowa.

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.