Integrated Crop Management News

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Scout for Black Cutworm in Corn Early this Year

Black cutworm (BCW) is a migratory pest that arrives in Iowa with spring storms each year. Black cutworm moths lay eggs in and near crop fields, and larvae can feed on leaves or cut corn seedlings. Larvae must attain a certain size (4^th instar) to be large enough to cut corn plants, and cutting can occur until plants reach the V5 stage. Black cutworm is sporadic and unpredictable, making it essential to scout to determine whether BCW larvae are present in a field and if management is required.

Soybean Aphid Egg Hatch is Complete

Iowa’s most significant soybean insect pest, the soybean aphid, alternates between two hosts to complete its development. The primary host of soybean aphid 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 happens when the host resumes spring growth. If eggs hatch too soon, aphids can suffer mortality from starvation because they feed on phloem from actively growing tissue.

Variable Overwintering Success for Bean Leaf Beetles this Year

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.

Alfalfa Weevil Larvae Active in Southern Iowa

Accumulated growing degree days graphic.

In addition to checking alfalfa stands for winter injury, it is time to start thinking about scouting for alfalfa weevil. Despite recent warm temperatures, alfalfa weevil development is slightly behind last year. However, it is likely adults have emerged from their overwintering sites to lay eggs in alfalfa stems in southern Iowa.

Establishing a New Stand of Alfalfa

Spring has arrived and many fields are full of activity. April is a great time to seed alfalfa whenever the soil is fit. Shallow-seeded forages will germinate and grow very quickly with adequate soil moisture and just a few warm days. The key to getting a great alfalfa stand is proper soil preparation and timing of the seeding.

Seedcorn Maggot Activity Beginning 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. Even with variable weather so far this spring, seedcorn maggot development is on track with previous years. Forecasted temperatures suggest that seedcorn maggot will likely develop quickly in the next few weeks.

Scouting for Winter Injury in Alfalfa Fields

While row crops are generally the focus of attention this time of year, spring is a great time to scout for winter injury in alfalfa fields and assess stand health. This is especially true if stands did not have adequate snow cover or were covered by sheets of ice during the winter. Several other factors may contribute to alfalfa winter injury, including soil moisture, 4-inch soil temperatures, and other stresses like soil fertility, stubble height, as well as the age of the stand.

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.

Washing Work Clothes After Working with Pesticides

Internal view of a washing machine, by nexusseven/stock.adobe.com

Pesticide residues can be carried on your clothing even if you wear personal protective equipment (PPE) over your own work clothes. Therefore, it is important to properly clean your clothes after working with and around pesticides. Many pesticide labels provide limited instructions for cleaning work clothes. In situations where no instructions are provided, follow these guidelines for washing contaminated clothing.

Newly Updated Phosphorus and Potassium Guidelines

Guidelines for soil-test phosphorus (P) and potassium (K) interpretations and application rates were last updated in 2013. Since then, significant field research was conducted to assure that nutrient management guidelines are kept current. The new response data, increased crop yield levels in Iowa, and better awareness of usually large spatial soil-test variability in production fields indicated a need for adjusting the boundaries of soil-test interpretation categories and suggested nutrient application rates.

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