The weather forecast for the rest of April suggests below average temperatures will be likely, which may result in corn planting on soils colder than optimum, which requires careful consideration (see recent ICM News article). Also, fertilizer prices continue to be higher than normal. Therefore, starter fertilization can be useful to complement primary preplant fertilization for corn.
Integrated Crop Management News
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Bean leaf beetle adults (Photo 1) are susceptible to cold weather, and most will die if exposed to air temperatures below 14°F. However, they avoid harsh temperatures by burrowing under plant debris and loose soil. Each spring, adult beetles emerge from their overwintering habitat and migrate to available hosts, such as alfalfa, tick trefoil, and various clovers. As the season progresses, bean leaf beetles move to preferred hosts, like soybean. While initial adult activity can begin before soybean emergence, peak abundance often coincides with early-vegetative soybean.
In addition to checking alfalfa stands for winter injury, it is time to start thinking about scouting for alfalfa weevil. Even with recent cool temperatures, overwintering alfalfa weevil adults have become active, made their way to alfalfa fields, and have likely begun laying eggs in stems. Alfalfa weevil is a cool-season pest and is able to survive less than ideal temperatures by moving under residue or near the crown.
Seedcorn maggot larvae feed on germinating seeds or seedlings of corn and soybean (Photo 1). Feeding can delay development or kill the plant, and plant injury is especially prevalent during cool, wet springs when plants grow slowly. So far, this spring has been cooler and wetter than the past few years and this trend is expected to continue during the next couple of weeks.
As forage stands start to green up this spring, take time to evaluate the stands for any winter injury. It will be especially important to check stands that had significant armyworm damage last fall.
As you evaluate forage stands, Tables 1 and 2 below can be used to help determine what type of action may be warranted in a field. Note that while older stands typically have fewer plants per square foot, they produce more stems per plant. As a general rule of thumb, plan for 100% of normal season yield if there are 55 stems per square foot, regardless of the stand age.
After working with or around pesticides, it is important to properly clean your work clothes. Even if you wear personal protective equipment (PPE) over your own clothes, pesticide residues can be carried on your clothing. Before entering your home, remove your shoes and change out of your work clothes. Keep your work clothes separate from other laundry. Tossing your work clothes into the family laundry basket can transfer pesticide residue to other clothes and accidently to other family members. Many pesticide labels provide limited instructions for cleaning work clothes.
While many farmers already applied nitrogen (N) for corn last fall, others are getting ready for spring preplant applications. Although the fertilizer supply has improved compared with last fall, the prices of N fertilizers have not changed much and are much higher than normal. And, while cash corn grain prices have increased in recent weeks, they are expected to decline later in the summer and the fall. Therefore, this situation warrants a careful review of N fertilization plans.
Chlorpyrifos (e.g., Lorsban and Warhawk) is an organophosphate (Group 1B) insecticide that has been used for many important field crop pests in the United States. In the past 15 years, chlorpyrifos, like many organophosphates, has come under scrutiny due to acute toxicity concerns to humans, especially children. In an effort to protect all ages of humans and the environment, EPA began the process of phasing out many uses of organophosphates. On August 18, 2021, the EPA announced their decision to revoke tolerances for chlorpyrifos.
Corn foliar fungicide trials done at six locations in Iowa in 2021: 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.
Almost all soybean varieties resistant to the soybean cyst nematode (SCN) have been developed from a breeding line named PI 88788. The amount of SCN control varies among the varieties because they have different numbers of copies of the single SCN resistance gene. The Iowa State University SCN-resistant Variety Trial Program evaluates hundreds of commercially available resistant varieties for yield and SCN control each year. In a recently published journal paper, ISU agricultural economists estimated that information from the ISU SCN variety trial provided as much as $205 million of economic value to farmers from 2011 to 2016. This finding underscores the value of selecting and growing SCN-resistant soybean varieties that offer high yields and effective control of SCN.