Integrated Crop Management News

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Measuring Conservation and Nutrient Reduction in Iowa Agriculture

July 9, 2020
Agricultural land use over time in Iowa.

An ongoing public concern is the loss of nutrients from agricultural land in the corn belt. In Iowa, nitrogen and phosphorus losses from farm fields are driven by a variety of factors. Since the mid-twentieth century, statewide corn and soybean acres have increased as extended rotations, hay, and pasture declined. Compared to perennial crops and small grain rotations, corn-soybean and continuous corn rotations are leaky systems.

Soybean Gall Midge Larvae Active in Iowa

July 2, 2020
Soybean gall midge distribution from 2018 and 2019 map

Soybean gall midge was confirmed as an economic pest of soybean in 2018. Worldwide, it is only known to occur in five states in the Midwestern US (Figure 1). Research began in 2019 to monitor the emergence of adults and incidence of larval feeding, as well as management options for the pest. This year, soybean gall midge adults were first collected on June 12 and larvae were detected in soybean on June 23.

Planted Non-Bt Corn? Plan to Scout for European Corn Borer

June 12, 2020

Farmers have enjoyed the benefits of Bt corn since its introduction in 1996, particularly “in the bag” transgenic protection from insect pests and the yield loss they inflict. European corn borer (ECB), Ostrinia nubilalis, was particularly challenging and the target of the first Bt hybrids. The adoption of Bt corn in the U.S. prompted a widespread suppression of ECB. Even so, ECB still shows up in conventional cornfields in Iowa and can be a devastating pest.

Watch for Japanese Beetle Emergence

June 11, 2020
growing degree map of iowa

Several Iowa State University Extension and Outreach Field Agronomists have reported fields with high numbers of grubs this spring. There are a number of grub species in Iowa, including Japanese beetle. With warm temperatures accelerating insect development, expect adult Japanese beetles to begin emergence in southern Iowa counties this weekend (Figure 1). The emergence is about 7-10 days ahead of the last few years. Literature shows Japanese beetle adults need about 1,030 growing degree days (base 50°F) to complete development and will continue emergence until around 2,150 degree days.

Corn Rootworm Egg Hatch Getting a Late Start in Iowa

June 9, 2020

Corn rootworm egg hatch in Iowa occurs from late May to the middle of June, with an average peak hatching date of June 6 in central Iowa. In 2020, the expected hatching date will be behind the average due to cool spring temperatures. Development is driven by soil temperature and measured by growing degree days. Research suggests about 50% of egg hatch occurs between 684-767 accumulated degree days (base 52°F, soil). Most areas in Iowa will reach peak corn rootworm egg hatch in 5-7 days (Figure 1).

Aphids Observed in Alfalfa Fields

June 5, 2020

Alfalfa weevils aren’t the only insect pest being found in alfalfa fields this spring. Reports of aphids, particularly cowpea aphids and pea aphids, have been made around the state. This article will discuss identifying the common aphid species found in Iowa as well as scouting and management recommendations for aphids in alfalfa.

Checking Corn Fields for Damaging Levels of Nematodes

June 5, 2020

Most Iowa corn fields have several different species of plant-parasitic nematodes present at low numbers. It’s only when numbers occur at damaging levels that symptoms appear and damage occurs. The potential for plant-parasitic nematodes that feed on corn to cause yield reductions warrants attention. This article discusses when and how to sample for plant-parasitic nematodes that can damage corn.

Scouting for SCN – Time to Get Digging

June 2, 2020

One of the easiest and cheapest ways to check a field for SCN is to dig roots and look for females of the nematode. This can be done now through mid August. The SCN females will be small, white, round objects on the roots and are much smaller and lighter in color than nitrogen-fixing nodules that occur on healthy soybean roots. Digging roots and looking for SCN females also is a way to check whether resistant varieties are performing effectively.

Start Scouting for Stalk Borers in Southern Iowa

June 2, 2020

In 2019, numerous field edges were infested with common stalk borer. Tracking degree days is a useful tool to estimate when common stalk borer larvae begin moving into cornfields from their overwintering hosts. Foliar insecticide applications, if needed, 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. Much of Iowa has reached this important benchmark (Figure 1), and therefore scouting for migrating larvae should begin now to make timely treatment decisions.