Integrated Crop Management News
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June 9, 2025Corn 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. Development is driven by soil temperature and measured by growing degree days (GDDs).
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May 26, 2025Authors
The regional rootworm trapping network enters its sixth year in Iowa. We will be monitoring corn rootworm adults throughout Iowa to get a sense of how populations vary across the state, both in numbers and in species composition (ratio of westerns to northerns). Since this is a huge undertaking, we are asking for volunteers to monitor sticky traps this summer.
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May 19, 2025Authors
An open house will recognize a new research and extension facility as well as the 95th anniversary of Iowa State University’s Northern Research and Demonstration Farm.
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May 6, 2025Authors
Black cutworm (BCW) is a migratory pest that arrives in Iowa each spring. We monitor moth activity around the state with our Iowa Moth Trapping Network, and there has been quite a bit of BCW moth activity this spring. The female BCW moths lay eggs in and near crop fields. The eggs hatch and the larvae can feed on corn leaves or even cut corn seedlings. Larvae must attain a certain size (4th instar) to be large enough to cut corn plants, and cutting can occur until plants reach the V5 stage. We predict when BCW will big enough to cut corn plants based on growing degree day data and the occurrence of significant flights.
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May 6, 2025Authors
Alfalfa growth and development is influenced by factors including temperature, soil moisture, stand age, and variety. With a mild winter leading into spring this year, many areas are seeing earlier green-up and more rapid growth. As such, relying solely on the calendar to determine the timing of the first alfalfa cutting may not be the most accurate approach. To stay ahead of forage quality, producers should base harvest on plant development, not just the calendar date. To better estimate the optimal harvest window, the University of Wisconsin developed the Predictive Equations for Alfalfa Quality (PEAQ) method, which uses the height and maturity stage of the tallest alfalfa stem to estimate relative feed value.
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April 30, 2025Authors
Bean leaf beetles overwinter as adults (Figure 1), which are susceptible to cold weather, and most will die if exposed to air temperatures below 14°F. They avoid harsh temperatures by burrowing under plant debris and loose soil. In early spring, the adult beetles migrate to available hosts, such as alfalfa, tick trefoil, and various clovers. They are strongly attracted to soybean. Adults move locally in the landscape to soybean fields with emerging seedlings. While initial adult activity can begin before soybean emerge, peak abundance often coincides when the early-planted soybean fields start to emerge, leaving those fields prone to defoliation.
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April 10, 2025Authors
As temperatures warm up, the questions are already rolling in from inquisitive folks wondering how insects fared the winter in Iowa. Some insects have adapted to survive freezing temperatures. A prior article delves deep into the topic of “How do insects survive the winter?” and is worth reading for more information on general strategies.
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April 7, 2025Authors
2024 marked the fifth year of a coordinated effort to monitor corn rootworm adults across Iowa and the fourth year of combining this effort with the Regional Corn Rootworm Monitoring Network. The Hodgson Lab receives funding from the Agricultural Biotechnology Stewardship Technical Committee to distribute traps to farmers across corn-growing regions in the U.S. and Canada. The 2024 Regional Corn Rootworm Monitoring Network Summary is now available and this article summarizes the Iowa results.
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April 1, 2025Authors
With above average temperatures this year, alfalfa weevil development is well ahead of schedule compared to recent years. Adults have already emerged from their overwintering sites to lay eggs in alfalfa stems throughout the southern half of Iowa.
Adult alfalfa weevils become active and start laying eggs when temperatures exceed 48°F. Alfalfa weevil egg hatching begins when 200-300 growing degree days (GDD; base 48°F) have accumulated since January 1. Based on accumulated GDD, alfalfa weevils are active throughout southern Iowa and are likely active in other areas as well (Figure 1). You can track GDD for alfalfa weevil by visiting the Pest Maps and Forecasting page and comparing benchmark GDD to the map. Additionally, if you choose the nearest weather station on the right side of the page, you can see forecasted GDD for your area for the next two weeks.
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March 31, 2025Authors
Seedcorn maggot larvae feed on germinating seeds or seedlings of corn and soybean (Photo 1). Feeding can slow development or kill the plant, and plant injury is more prevalent during cool, wet springs when plants grow slowly. With planting right around the corner, we recommend that farmers track growing degree days, plant during the fly-free period, and avoid planting into cool, wet soils, especially in fields at high risk for injury. High-risk fields include those with a history of seedcorn maggot injury, recently tilled fields, and fields where organic matter was recently incorporated (e.g., manure or cover crops).
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March 4, 2025Authors
As temperatures begin to increase following winter, we are entering a period of warm days and cold nights. These conditions result in our soils going through freeze thaw cycles, which make for a perfect time for frost seeding. Frost seeding involves strategically broadcasting or overseeding legumes into pastures, hayfields, or small grains. It is a potentially cost-effective solution to revitalize a diminishing stand or introduce new legumes. However, success hinges upon assessment of the existing stand, proper timing and soil conditions.
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October 24, 2024Authors
Growing resistant soybean varieties is critical to achieving and maintaining profitable soybean yields in fields infested with the soybean cyst nematode (SCN). Information about SCN-resistant soybean varieties in maturity groups 0-3 available for use in Iowa is compiled annually in ISU Extension publication CROP1649. The newly updated publication lists 920 SCN-resistant soybean varieties from 33 brands offered by 25 companies. This article contains information about the varieties, their genetic sources of resistance, and several other important attributes of the varieties.
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September 11, 2024Authors
As corn and soybean are taken out of fields, some fields may reveal an unexpected mat of Asian copperleaf lurking below the canopy. As of this summer, we’ve identified Asian copperleaf (Acalypha australis) in crop fields in eight counties: Calhoun, Humboldt, Boone, Wright, Franklin, Hardin, Grundy, and Black Hawk. Early identification of this species is key to adopting effective management tactics to reduce its spread to other fields.
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August 26, 2024Authors
Soybean aphid is still the most important insect pest of soybean in Iowa, despite low populations throughout the state in recent years. This summer, we have seen high populations throughout Iowa, with hundreds of aphids per plant, honeydew, and sooty mold development on leaves. We have also heard various reports about performance issues with pyrethroid applications. This has prompted many questions about when to spray soybean aphids and which insecticides to use.
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August 22, 2024Authors
Key Points:
Precision spray technology is available in the ag marketplace to provide selective post-emergence herbicide applications. Iowa State University conducted a field scale demonstration of a commercial precision spray system on five conventionally managed soybean fields totaling 415 acres. Herbicide savings per field was 90.6%, 87.6%, 87.2%, 71.2%, and 43.9% respectively. Herbicide savings were directly influenced by the initial weed pressure in the field. Average product savings across all fields was 76% and had an economic savings of nearly $6,500 ($15.7/ac) from reduced herbicide use. -
August 19, 2024Authors
Corn earworm is a pest that causes direct injury to corn ears. Corn earworms do not survive winters above the 40th parallel but some migrate north to the Corn Belt every year. Economic injury in field corn is uncommon due to the high adoption rate of Bt traits in Iowa (e.g. Cry1Ab, Cry1F, Cry1A.105+Cry2Ab2, Vip3A). However, non-Bt sweet corn and popcorn is at risk every growing season, and the financial impact in these specialty crops is especially important.
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August 2, 2024Authors
Weed communities in three cropping systems suitable for the Midwestern USA were studied from 2017 through 2020 to examine how crop diversification and the intensity of herbicide use affected weed stand density and aboveground mass. A baseline 2-year cropping system with corn and soybean grown in alternate years was diversified with cool-season crops, namely oat and red clover in a 3-year system, and with oat and alfalfa in a 4-year system. Herbicides were not used in the cool-season crops.
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July 30, 2024Authors
Farm fields that have been covered with flood waters may need structural (physical) repair before returning to full production. Flood debris, sand, silt, erosion, and loss of soil structure may all result as residual effects of flooding.
Before You Begin
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July 29, 2024Authors
Grasshopper activity in field crops has picked up recently, and these jumpy insects and their defoliation have caught the attention of crop scouts and agronomists across the state. Grasshoppers tend to thrive under dry conditions, and although most areas have received adequate moisture in 2024, consecutive drought years have likely led to higher than usual populations. This article discusses identification, scouting and management of grasshoppers in corn and soybeans.
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June 28, 2024Authors
Those looking for any bit of good news among all the rain-soaked suffering we have endured this growing season have asked if the overabundance of moisture has drowned SCN. Unfortunately, the answer is no.