Integrated Crop Management News

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Crop Injury Associated with Growth Regulator Herbicides

July 3, 2018
picloram

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

June 29, 2018
physoderma brown spot on corn

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

June 22, 2018
rainfaill map april 1 to june 22

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.

Japanese Beetle Adults Emerge in Southern Iowa

June 14, 2018
degree day map for Japanese beetle

Japanese beetle is an invasive insect that feeds on corn and soybean plus many other plants. This pest has been in Iowa since 1994 but its distribution in field crops is considered sporadic around the state. Statewide populations in field crops have been variable since 2014 and it is unclear if pressure will be significant this year. Several reports around Iowa indicated high numbers of grubs within fields, but it is not clear if they were Japanese beetle or another closely-related species. Adult emergence well before corn silking is noteworthy.


SCN Females Seen on Roots as Early as Ever in 2018

June 12, 2018
Adult soybean cyst nematode(SCN) females on soybean roots collected on June 5, 2018, from a field in southeast Boone County that was planted on May 10, 2018. There are more than a dozen SCN females on the roots shown in the image.

The soybean cyst nematode (SCN) is a major pathogen of soybean in Iowa and throughout the Midwest. Damage often goes unrecognized until lower-than-expected yields are harvested because above-ground symptoms may not be obvious, especially when adequate or excess rainfall occurs during the season. A key way to check fields for this pest is to dig soybean roots and look for the small, round, white adult SCN females. It typically takes 5 to 6 weeks or more after planting for the first SCN females of the growing season to develop and appear on roots.


Navigating Through a Soil Health Assessment

June 7, 2018
no-till and cover crop

Building soil health is important to sustain soil resiliency and productivity. Many conservation practices can maintain and enhance physical, chemical and biological soil properties that contribute to overall soil biological functions as fundamental drivers that support plant growth and productivity. However, these properties are complex and interrelated as each function is influenced by a central building block, soil organic matter (SOM). Soil health is one of the co-benefits of improving SOM through soil carbon sequestration or storage.

Stalk Borers Moving in Central and Southern Iowa

June 6, 2018
Degree day map of stalk borer

Tracking degree days is a useful tool to estimate when common stalk borer larvae begin moving into cornfields from their overwintering hosts. Foliar insecticide applications, if needed, are only effective when larvae are migrating and exposed. Start scouting corn for larvae when 1,300-1,400 degree days (base 41°F) have accumulated. Counties south of I-80 in Iowa reached this important benchmark this week (Figure 1), and therefore scouting for migrating larvae should begin now to make timely treatment decisions. Stalk borer larvae in northern counties will migrate later in June.

Corn Rootworm Egg Hatch Peaked Around Iowa

May 29, 2018
Degree day map of corn rootworm

Corn rootworm egg hatch in Iowa typically occurs from late May to the middle of June, with an average peak hatching date of June 6 in central Iowa. In 2018, the average hatching date will be ahead of the average, despite having cool April temperatures. Development is driven by soil temperature and measured by growing degree days. Research suggests about 50 percent of egg hatch occurs between 684-767 accumulated degree days (base 52°F, soil). Most areas in Iowa have reached peak corn rootworm egg hatch (Fig. 1). Larvae will start feeding on corn roots if available. 

Frogeye Leaf Spot Resistance in Soybean

May 23, 2018
Symptoms of frogeye leaf spot on soybean leaf

Isolates of Cercospora sojina showing reduced sensitivity to quinone outside inhibitor (QoI, strobilurin) fungicides were recently recovered from soybean in Iowa. This pathogen causes frogeye leaf spot, an important foliar soybean disease that can be managed with fungicides. With the confirmation of fungicide-resistant isolates, it becomes especially important to understand when to spray and what products to use for long-term control of this disease. 

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