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.

To terminate or not to terminate?

Current cool temperatures increase the risk of failures in terminating cover crops. While cereal rye continues to grow during these conditions, activity of herbicides is reduced. Translocation of glyphosate to growing points is reduced under cool temperatures, slowing activity and increasing the potential for control failures. It is generally recommended to avoid applications when nighttime temperatures fall below 40 F, and we prefer temperatures at application to be at least in the mid-50s with clear skies.

Check FieldWatch® Before Pesticide Applications

Prepare for a safe pesticide application season by checking the FieldWatch® registry before making pesticide applications. The FieldWatch® registry provides easy-to-use, accurate, and secure online tools to enhance communications and awareness between crop producers, beekeepers, and pesticide applicators.FieldWatch® features a voluntary mapping tool through Google Maps™ that shows pesticide applicators the locations of registered sensitive crops and beehives so they can make informed decisions regarding pesticide applications.

Alfalfa Weevils Active throughout Southern Iowa

Adult alfalfa weevils become active and start laying eggs as soon as temperatures exceed 48°F. Like other insects, the development of alfalfa weevil depends on temperature, and we can use accumulation of growing degree days (GDD) to predict activity. Alfalfa weevil egg hatching begins when 200-300 GDD (base 48°F) have accumulated since January 1.

Seedcorn Maggots Get an Early Start

Seedcorn maggot is a seed and seedling pest of corn and soybean. The larvae, or maggots, feed on germinating corn and soybean seeds or seedlings (Photo 1). Feeding can delay development or kill the plant. Plant injury is especially prevalent during cool and wet springs when plants are growing slowly. Infestations tend to be field-wide instead of in patches like for many other pests. To confirm seedcorn maggot injury, check field areas with stand loss and look for maggots, pupae and damaged seeds (hollowed out seeds or poorly developing seedlings).

Preemergence Herbicides, Dry Soils and Rain

‘Preemergence herbicides need rain to be effective’

The potential for continued dry weather across the state raises concerns about the impact of dry soils on preemergence herbicides. Preemergence herbicides kill weeds by being absorbed into the seed as the seed imbibes water. To be effective, the herbicide must be located within the soil profile at the depth where weed seeds germinate (primarily the upper inch of soil). In addition, there must be sufficient water to keep the herbicide dissolved in soil water. Both factors can be adversely affected by limited rain early in the season.

Best Management Practice for Spatial Layout of Field Trials

If you are planning on conducting field trials this growing season, how you set up the field trial can determine the accuracy of your yield data at harvest. To reap the full benefits of gathering yield data to improve crop management and influence input decisions, it should be part of your management plan year-round.

2020 Summary of Foliar Fungicide Applications on Corn in Iowa

This article summarizes 2020 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.

2020 Summary of Herbicide Evaluations for Marestail (Horseweed) Control in Soybean

Marestail infestation in a soybean field at the ISU Research and Demonstration Farm near Ames, IA in 2020.

Marestail is one of the most widespread and troublesome weeds in Iowa croplands. It can grow to a height of 1.5 to 6 feet, produce up to 200,000 seeds, and can reduce soybean yields up to 80% if not controlled (Figure 1). Marestail seeds are light and disperse across landscapes with winds. Seeds have little dormancy and can germinate soon after seed shed. In general, 75% of seedlings germinate in fall, remain in rosette-stage until spring, begin stem elongation in April, and start flowering in July. About 25% of seeds germinate in the spring.

ISU SCN-resistant Soybean Variety Trial Program results for 2020

Iowa State University has evaluated the nematode control and yield performance of soybean varieties that are resistant to the soybean cyst nematode (SCN) in hundreds of experiments conducted over nearly three decades. The results of the 2020 experiments are now available and are highlighted in this article.

Summary of 2020 Insecticide Evaluations for Soybean Pests

Each year, the ISU Soybean Research Laboratory conducts insecticide efficacy evaluations for soybean aphid, and two emerging pests, Japanese beetle and soybean gall midge, were added in 2019. Details about pest biology, research plot design, sampling methods, and additional results can be found here.

Soybean aphid

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