Integrated Crop Management News

Links to these articles are strongly encouraged. Articles may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If articles are used in any other manner, permission from the author is required.

Instances of Frogeye Leaf Spot Resistance to QoIs Abundant in Iowa

January 27, 2020
frogeye resistance map of counties in Iowa

Iowa State University researchers, with funding from soybean checkoff through the United Soybean Board and Iowa Soybean Association, have confirmed that over 70 isolates of the pathogen Cercospora sojina (cause of frogeye leafspot in soybeans in Iowa) are resistant to quinone outside inhibitor (QoI) fungicides.

Summary of Foliar Fungicide Applications on Gray Leaf Spot and Yield of Corn in Iowa in 2019

January 27, 2020

This article summarizes our 2019 corn foliar fungicide trials that were done at six locations in Iowa: ISU Northwest Research and Demonstration Farm (NWRF), Sutherland; Northeast Research and Demonstration Farm (NERF), Nashua; Northern Research and Demonstration Farm (NRF), Kanawha; Southwest Research and Demonstration Farm (SWRF), Lewis; Southeast Research and Demonstration Farm (SERF), Crawfordsville; and the Ag Engineering and Agronomy Farm (AEA) near Boone.

Summary of 2019 Insecticide Evaluations for Soybean Pests

January 13, 2020
Soybean aphid colony

The 2019 growing season was challenging for farmers in many parts of the state, especially because cold and wet soil conditions in April significantly delayed planting. Thistle caterpillar was the most abundant insect statewide, though multiple species of caterpillars, Japanese beetle, soybean aphid, and soybean gall midge were observed in soybean.

Income in SCN-infested Fields Can Be $200 Per Acre Less With PI 88788 Than With Peking Resistance

January 9, 2020

The soybean cyst nematode (SCN) has been managed for decades with resistant soybean varieties. Almost all soybean varieties have SCN resistance from a breeding line named PI 88788, and SCN populations have developed high levels of reproduction on the PI 88788 resistance. The results of a field experiment in southeast Iowa in 2019 foreshadow alarming yield loss due to SCN in the future if farmers continue to have only PI 88788 SCN resistance available in soybean varieties.

Choosing a Corn Hybrid or Soybean Variety

November 25, 2019

Choosing corn hybrids and soybean varieties is one of the most important crop management decisions to be made. It is a hard decision to make because it is typically made months before the growing season begins. This article will explore where to find yield trial information, how to interpret yield trials, and what to consider in selecting cultivars.

Considerations for Continuous Corn

November 18, 2019
corn after corn in field

Continuous corn is a "three strikes and you’re out" situation. And the first strike is automatic – high residue volume. This is how a farmer recently described it to me.

Making continuous corn work means knowing what you are up against. First, realize that the yield drag for continuous corn can range from 0% to 30% but is typically between 5% and 15%. Yield drag has been associated with cooler and wetter soils, nitrogen (N) immobilization, increased disease risk, and allelopathy – all of which are influenced by corn residue volume.

SCN-resistant Soybean Varieties for 2020

November 12, 2019

Resistant varieties continue to be a key tool for managing the soybean cyst nematode (SCN).  With financial support from the soybean checkoff through the Iowa Soybean Association, Iowa State University annually compiles a list of SCN-resistant soybean varieties that are available for use in Iowa. 

The updated list of maturity group 0, I, II and III varieties is now available for free online in the Iowa State University Extension Store.

Corn Residue Breakdown as Affected by Tillage and N Application

November 5, 2019
Rate of CO2-C released as an indicator of residue breakdown/decomposition from control (bare soil) and Bt and non-Bt corn residue mixed into the soil or un-mixed with soil (left on soil surface).

Crop residue serves an important role in physically protecting soil from erosion during rain events or high winds, as well as enhancing the soil biological activity by providing sources of organic carbon and nitrogen for its energy needs. In order to understand how residue decomposes, we need to understand how the degradation processes are influenced by environmental and soil conditions; namely, air and soil temperatures, soil moisture availability, soil pH, oxygen, and type of microbial community.

Managing SCN for 2020 Should Begin Now

November 5, 2019
sampling map

A critically important fall activity that can pay large dividends for next year’s soybean crop is sampling fields for the soybean cyst nematode (SCN). Also, some farmers might consider sampling fields in which soybeans were grown in 2019 if disappointing yields occurred for no apparent reason. This article discusses how to collect a meaningful SCN soil sample, where to send the sample to get it processed, and how to interpret SCN soil sample results from Iowa State University.

Fall Fertilizer Nitrogen Application

October 30, 2019

Fall nitrogen (N) fertilizer application continues to be popular for several reasons, including lower cost, time for application, equipment availability, often better soil conditions, and competing springtime field activities.

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