Integrated Crop Management News

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Asian Copperleaf Makes a Return

May 24, 2024
Asian Copperleaf.

As of this spring, we’ve identified Asian copperleaf (Acalypha australis) in crop fields in six counties, and it's likely in more. As we find more populations, it is easier to monitor their development through the growing season. Field agronomists have been monitoring two of the infestations this spring and have observed many emerged seedlings in Boone and Franklin counties. As farmers scout fields and prepare for postemergence herbicide applications, it is important to keep an eye out for this new Iowa weed.

Blast from the Past: European Corn Borer is Back on the Radar

May 19, 2024
European corn borer moth

European corn borer (ECB) is a pest that most farmers haven’t had to think about since the late 1990s. ECB was the main target of the first Bt corn hybrids introduced to the market in 1996. Since then, Bt hybrids have effectively managed ECB populations and even provided economic benefits to farmers that don’t use Bt through areawide suppression. Before this, ECB was estimated to cost U.S. farmers over a billion dollars annually in yield losses and control costs, earning it the title of “the billion dollar bug.”

Start Scouting for Black Cutworm in Emerged Corn

May 8, 2024
Black cutworm cutting map.

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 (fourth instar) to be large enough to cut corn plants, and cutting can occur until plants reach the V5 stage (five leaf collars present). Black cutworm is 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 Finished

May 2, 2024
Accumulated growing degree days map.

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. Overwintering eggs hatch around the same time buckthorn resumes growth in the spring, which allows them to synchronize their life cycle with availability of their host plant to limit death by starvation.

Warmest Winter Ever Means Low Mortality for Bean Leaf Beetle

April 17, 2024
Adult 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.

Seedcorn Maggots Likely Active throughout Iowa

April 12, 2024
Seedcorn maggot.

Seedcorn maggot larvae feed on germinating seeds or seedlings of corn and soybean (Photo 1). Feeding can slow development or kill the plant, and plant injury is more prevalent during cool, wet springs when plants grow slowly. Even though most of Iowa has been in a drought, recent rain events have likely created pockets of damp soil that are ideal for developing larvae. High risk fields include those with a history of seedcorn maggot injury, recently tilled fields, and fields where organic matter was recently incorporated (e.g., manure or cover crops).

Weeds took Advantage of a Mild Winter

March 12, 2024
Winter annual weeds have resumed growth.

February and early March 2024 will go down in the history books as unusually warm and dry (Figure 1). Many winter annual, biennial and perennial weeds have resumed growth earlier than usual (Figure 2). Managers will need to be especially vigilant to treat these “early” weeds in a timely manner this spring.

What does this Warm Winter Mean for Insects?

March 12, 2024
Estimated total snowfall for Iowa.

Except for a few extremely cold days, Iowa has experienced a mild winter. In fact, February 2024 was the warmest February in Iowa’s weather history, and this winter is one of the warmest ever for the state. In addition to warmer temperatures, the total snowfall for our state has been low (Figure 1) and below average compared to a normal year (Figure 2). Much of the snowfall this winter was during a two-week period in January. As a result, many people are asking how a dry and mild winter might impact overwintering insects.