Integrated Crop Management News

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Start Scouting for Stalk Borers in Southern Iowa

June 10, 2022

Stalk borer is an occasional pest of corn, but it can be persistent in some fields, especially those fields near fence rows, terraces, and waterways that serve as overwintering sites. Tracking degree days is a useful way to estimate when common stalk borer larvae begin moving into cornfields from their overwintering hosts. Foliar insecticide applications are only effective when larvae are migrating and exposed to the insecticide. Start scouting corn for larvae when 1,300-1,400 degree days (base 41°F) have accumulated.

Using the Late Spring Soil Nitrate Test in 2022

June 7, 2022
Nitrogen management chart.

This year, corn planting was delayed due to an unseasonably cold spring, and at this time corn growth stage ranges mostly from the V2 to V6 across the state. Many producers had doubts concerning preplant nitrogen (N) application due to high N fertilizer prices, and now some are wondering about possible in-season diagnostic tools to assess a potential need for supplemental in-season N application.

Scout for True Armyworms this Spring

June 7, 2022
True armyworm feeding on soybean leaves.

True armyworm is a migratory pest from the southern U.S. Each spring, volunteers help us monitor for true armyworm moths during April and May and weekly updates are posted on the ICM Blog. Although a trapping threshold does not exist to indicate whether a certain area might be at high risk for true armyworm feeding, we can use information from the trapping network to guide scouting efforts.

Equisetum: From the Ditch to the Field

May 20, 2022
Scouringrush invading no-till soybean field.

Scouringrush (Equisetum arvense) and field horsetail (Equisetum hymale) are two species of the Equisetum genus found in Iowa. There are 15 Equisetum species worldwide. They are primitive perennials that produce spores rather than seeds and spread primarily by rhizomes (underground stems). These two weeds are commonly found in roadside ditches, preferring poorly drained soils. More information about scouringrush, its lifecycle and its history can be found here.

Aphids Showing up in Alfalfa

May 18, 2022
Common aphids in Iowa alfalfa.

Aphids are common insects to see in field crops, especially in alfalfa. In Iowa, there are at least four aphid species that colonize this crop. A quick scouting bout in central Iowa yesterday (May 17) revealed at least two species feeding within the same field. Learning to distinguish aphids in alfalfa takes a little practice, but is worth knowing for making sound treatment decisions.

Begin Scouting for Black Cutworm in Corn

May 13, 2022
Estimated black cutworm dates for each Iowa crop district.

Black cutworm (BCW) is a migratory pest that arrives in Iowa with spring storms each year. It is sporadic and unpredictable, making it essential to scout to determine whether BCW larvae are present in a field and management is required. Because BCW is sporadic, it is usually not economical to use preventative insecticide applications; however, rescue treatments can be very effective if scouting reveals larvae are present.

Soybean Aphid Egg Hatch Nearly Complete

May 11, 2022
Growing degree days map.

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?

May 6, 2022
Young forages growing in field.

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

May 6, 2022
alfalfa measurement against ruler

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.