Integrated Crop Management News

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Soybean Aphid Egg Hatch Nearly Complete

Iowa’s most significant soybean insect pest, the soybean aphid, has host-alternating biology. Its primary host is buckthorn, an invasive shrub often found in hedgerows and roadside ditches, and its secondary host is soybean. For most of the year, soybean aphids exist as cold-hardy eggs on buckthorn branches near leaf buds. For many aphids that overwinter as an egg, hatching often happens when the host resumes spring growth. This makes biological sense because the aphids feed on phloem from actively growing tissue. If egg hatch happens too soon, they can suffer mortality from starvation.

When is it too Late to Seed Forages?

With the cool and wet spring in 2022, there haven’t been many opportunities to seed forages. Looking at the calendar date, is it getting too late to plant forages? The short answer is that there is still some time to seed forages this spring. While the typical planting window is late February (frost seeding) through late April, planting forages in May can still be successful. For areas south of I-80, agronomists suggest seeding by the middle of May, whereas north of I-80 could get by seeding even a little later in May.

Estimating First Crop Alfalfa Harvest using PEAQ

Alfalfa growth and development is affected by many factors, including temperature, soil moisture, stand age and even cultivar. Alfalfa growth has been slow this spring due to cooler than normal weather. This is a reminder that using the calendar date to determine when to harvest the first crop of alfalfa may not be the best method. In order to accurately predict the optimal time for the first cutting, the University of Wisconsin developed the Predictive Equations for Alfalfa Quality (PEAQ) method.

Cold Spring and High Fertilizer Prices may Make Starter Fertilizer More Important

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.

Another Tough Winter for Bean Leaf Beetle

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.

Scout for Alfalfa Weevil in Southern Iowa

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 Maggots Emerging in Southern Iowa

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.

Check Alfalfa Stands for Winter Injury

Healthy white tissue in the crown and taproot of an alfalfa plant with lots of new, symmetrical shoots.

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.

Washing Pesticide Work Clothing

graphic showing different washing instructions

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.

Considerations for Spring Preplant Nitrogen Application for Corn with High Fertilizer Prices

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.

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