Integrated Crop Management News

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Corn Rootworm egg Hatch Behind Schedule this Year

June 21, 2022
Accumulated soil degree days in Iowa.

Corn rootworm egg hatch in Iowa typically occurs from late May to the middle of June, with an average peak hatching date of June 6 in central Iowa. Even with recent warm temperatures, hatching is a bit delayed this year due to cool spring temperatures. Development is driven by soil temperature and measured by growing degree days (GDDs). Research suggests about 50% of egg hatch occurs between 684-767 accumulated GDDs (since January 1; base 52°F, soil).

Japanese Beetle Adult Emergence Begins in Southern Iowa

June 21, 2022
Growing degree days map.

The cool spring has delayed development of many important crop pests across Iowa. However, with recent warm temperatures, Japanese beetle adult emergence has been on track with previous years. Japanese beetle adults begin emergence when approximately 1,030 growing degree days (GDD; base 50°F) have accumulated since January 1 and will continue emerging until 2,150 GDD have accumulated. Japanese beetle adults likely began emerging in the southern portion of the state last week, and emergence will likely occur within the next two weeks in northern Iowa (Figure 1).

Soybean Gall Midge Adult Emergence Begins

June 17, 2022
Soybean gall midge adults.

This week, the first soybean gall midge adults (Photo 1) were collected in Iowa near Wall Lake in Sac County (Monday) and near Sutherland in O’Brien County (Thursday). This is similar to when soybean gall midge emergence was first detected in Iowa in 2021. The first Midwest report of soybean gall midge emergence in 2022 was on June 7 near Davey, Nebraska. You can keep up with soybean gall midge emergence at soybeangallmidge.org/.

Go on the Offensive Against Soybean Cyst Nematode

June 16, 2022
Digging soybean roots in late June to check for SCN.

The best way to manage the soybean cyst nematode (SCN) is to grow SCN-resistant soybean varieties in rotation with the nonhost crop corn. Almost all soybean varieties planted by farmers in Iowa in 2022 contain SCN resistance genes from the breeding line PI 88788. Unfortunately, PI 88788 resistance has lost much or most of its effectiveness.

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.

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