Integrated Crop Management News

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Survey of Herbicide-Resistant Waterhemp in Iowa Corn and Soybean Fields

Waterhemp infestation in a soybean field in Iowa. September 2019.

The escalating spread of herbicide-resistant weed populations has become a production challenge in the corn-soybean based cropping system of the Midwest. With the evolution of weed resistance to major herbicide groups used in corn and soybean, we have a limited number of herbicide options left, which is even more disconcerting as no new herbicide site of action has been discovered in the past three decades. A new site of action coming to the marketplace in the next 5-8 years would also be a rare event.

Key Tips to Prepare for a Variable Crop Harvest

Harvest is quickly approaching and most are anticipating a highly variable corn and soybean crop. Below are some reminders for regular maintenance, adjustments, and final checks to make sure your combine is ready to hit the fields soon.

Grain Drying Considerations this Fall

With delayed planting across the state in 2019, it is important to monitor crop development to determine unique grain drying needs this fall.

Plan Ahead for Potential Harvest and Storage Challenges this Fall

With delayed planting across the state, it is important to plan ahead for potential harvest challenges. Scout your fields for crop development to determine whether you might have potential problems with immature, frost-damaged grain, and wet grain.

Potential challenges:

Frost-damaged soybean will have a slower dry-down in the field and may produce green/yellow soybean with above-normal shrink from drying. The green color may subside within two weeks of maturity if allowed to dry in the field or after several weeks of aeration.

Plan Ahead to Minimize Soil Compaction During Harvest

Ruts made when harvesting soybean under saturated soil conditions

While there is significant uncertainty about this year’s harvest weather, the struggles with previous year soil compaction may still be lurking in corn and soybean fields across Iowa. This article will highlight challenges with wet conditions at harvest and opportunities to minimize the long-term consequences of harvesting fields with wet soils.

Nutrient Removal When Harvesting Corn Stover

Increasing demand to use corn plant biomass for producing energy and various products has spurred interest in harvesting corn stover and specific plant components in addition to grain. Harvesting more biomass means increased carbon (C) and other nutrient removal from fields. What is the nutrient removal when different corn plant components are harvested?

Can Weed Seed Production be Reduced with Late-season Herbicide Applications?

Problems caused by unfavorable conditions this season have resulted in greater than normal weed escapes. These weeds may reduce crop yields and definitely will contribute to future weed problems via new seed. While it is too late to protect crop yields, a common question is whether herbicides can be used to reduce the quantity of viable weed seed produced by weeds. While there is no simple answer due to the many different scenarios across the state, in most situations late-season applications are not warranted.

Upper Soybean Leaves Began Showing Potassium Deficiency Symptoms Since Early August in Some Iowa Fields

Since early August, soybean in several fields began showing typical potassium (K) deficiency symptoms on leaves located in the middle to upper canopy. This is not surprising in fields or portions of fields with soil-test values in the very low or low K soil-test interpretation categories that did not receive adequate preplant K fertilization. Potassium deficiency symptoms are well-known and very common in older leaves during early growth stages.

Scout Now for Palmer Amaranth

Palmer amaranth leaf with petiole longer than leaf blade

Now is a great time to scout for Palmer amaranth (Amaranthus palmeri) in Iowa crop fields. As of late 2018, this species had been identified in over half of Iowa’s 99 counties. While new identifications have waned since the widespread introductions in 2016, Palmer amaranth is a species to watch out for in virtually any Iowa crop field.

Assessing Corn Rootworm Activity Using Sticky Traps

Western and northern corn rootworm are major corn pests in Iowa and surrounding states (Photos 1 and 2). Farmers have seen several management changes, including the release of four Bt-rootworm traits to suppress corn rootworm larvae since 2003. Although both species are persistent pests, western corn rootworm is particularly adaptable. The Gassmann Lab at Iowa State University (ISU) has confirmed western corn rootworm resistance to all Bt rootworm traits in Iowa.

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