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Several labs in the Midwest have been monitoring the distribution of soybean gall midge in Iowa since 2018. Last year, we sampled many counties in western Iowa but only confirmed three new counties. This year, we focused on the counties just east of the distribution in 2021 and were able to confirm eight new counties in Iowa that had soybean gall midge: Humboldt, Kossuth, Palo Alto, Pocahontas, Polk, Ringgold, Warren, and Webster (Figure 1).

While the story of the "haves" and "have nots" continues across the state, some areas in NW did finally get some much-needed rain early this week. And unfortunately, the Zearing area in Central Iowa also had some hail damage. Some of the observations or questions coming in from the field this last week have been on or have included: spider mites, new counties in Iowa found to have soybean gall midge, soybean aphids, tar spot, SDS, and potato leafhoppers.

You are invited to attend the upcoming field days that will be hosted at the outlying Iowa State University Research and Demonstration Farms this fall. These field days will feature the latest information on crop production and crop management practices. Below is a list of the upcoming field days that will take place in August and September and what topics will be featured at each field day.

Twospotted spider mites have been noted in fields across much of Iowa already this summer, as much of Iowa is in abnormal or extreme drought (D0-D3, US Drought Monitor). Scouting for spider mites in field crops is encouraged with prolonged drought. Twospotted spider mites can increase whenever temperatures are greater than 85°F, humidity is less than 90 percent, and moisture levels are low.

It’s the story of the haves and have nots when it comes to rainfall across the state. Unfortunately the areas that could really use the rain, seem to miss the rains. Consequently, some parts of the state are looking pretty tough with the drought conditions.

Parts of the state are classified as being abnormally dry to being in an extreme drought based on the most recent U.S. Drought Monitor map. With the hot temperatures returning this week and little to no rainfall in the forecast, there are concerns about what this might mean for corn and soybean crops and other issues we could start to see in fields as a result.   

Impact on Crops

The past week brought again spotty rainfall across the state. With the dry conditions and warmer temperatures forecasted there are concerns about what this may mean for the crops. Spider mites, corn rootworms, grasshoppers, aphids, and weed escapes were other observations or concerns coming from the fields this last week. Read on for more specifics about what’s happening in fields across the state.  

Northwest Iowa

This is the time of the year when late-season pigweeds (waterhemp and Palmer amaranth) poke through the soybean canopy and produce seeds. These late-season pigweeds either emerged after herbicide applications, or survived inappropriately timed or less-than-effective postemergence herbicides. Given waterhemp and Palmer amaranth’s propensity to evolve resistance to herbicides, it is also possible that the survivors are resistant to the postemergence herbicide that was used.

While crop development is behind this year due to the late planting, warm weather in the forecast will result in faster development than we prefer during reproductive growth stages of our crops. Appropriate identification of reproductive growth stages can be important for numerous reasons like timing fungicide and insecticide applications and understanding important crop development factors like water use, dry matter accumulation, and the effect of stress on the crop at various stages.

Signs of stress could be seen in corn and soybean fields, especially in the drier areas of the state with the warmer temperatures last week. Most of the corn either has pollinated or is pollinating and soybeans are in the R2 to R3 growth stages. Corn rootworm beetles, Japanese beetles, drought stress, weed escapes, growth regulator injury in soybeans, and questions on fungicides applications were questions or issues received/observed by ISU Extension field agronomists this past week.

Western and northern corn rootworms are serious pests of corn throughout the Corn Belt (Photo 1). We recommend that farmers scout every cornfield every year, regardless of the management tactic(s) used, to evaluate management decisions and prepare for next year. It is a good idea to scout for larvae early in the season, assess root injury when larval feeding wraps up, and monitor adults later in the season.

With hot weather and few rain chances in the forecast, concern turns toward soil moisture reserves and the ever-important pollination timing in corn. ISU Extension field agronomists observed corn rootworm beetles, Japanese beetle feeding, grasshoppers, numerous diseases, and more off-target herbicide movement this week. As crops are now reaching reproductive stages, now is a good time to refresh your memory on corn and soybean reproductive staging.

As mentioned in my previous ICM Blog article this year, June 20 was the cut-off date for over-the-top applications of dicamba products (Xtendimax, Engenia, and Tavium) in dicamba-tolerant soybean in Iowa. This was an amendment to the federal cut-off date of June 30.

Did an earlier cut-off date mitigate the problem in 2022?

The most effective way to make treatments decisions for pests with chewing mouthparts (e.g., Japanese beetle, bean leaf beetle, caterpillars, and grasshoppers) is to estimate defoliation. I’m a “lumper” and don’t try too hard to distinguish feeding by species. Replicated data over multiple growing regions consistently shows economic thresholds for soybean are 30% in the vegetative stages and 20% in the reproductive stages. This threshold applies to the entire field.

Iowa Soil Health Workshop Planned for August 4th

Topics will include fertility tests, cover crops, and evaluating soil health with a microscope

While there was some much-needed rain across the state last week, the rain also brought some wind with it as well that resulted in lodged or leaning corn as well as some greensnap in fields. In addition to the wind damage, herbicide injury in soybeans, tar spot concerns, and Japanese beetles were the common observations or topics of questions received by ISU Extension field agronomists. Read on for more specifics on what’s happening in different areas of the state.

Western and northern corn rootworm are serious pests of corn throughout the Corn Belt. We recommend that farmers scout every cornfield every year, regardless of the management tactic(s) used, to evaluate management decisions and prepare for next year. It is a good idea to scout for larvae early in the season, assess root injury when larval feeding wraps up, and monitor adults later in the season.

In the evening hours of July 5, 2022, a derecho moved through South Dakota into northwest Iowa.  Gusts in South Dakota were as high as 99 mph with winds that lasted up to 20 minutes.  The path of the storm’s length was about 600 miles.  A map is available to help understand the wind speed, path, and damage to property from this event.  In addition to the derecho, a tornado was also confirmed in Emmet County on the same evening by video footage of the tornado and damage tha

Herbicide injury in soybean, Japanese beetles, potato leafhoppers in alfalfa, tar spot being found in Marshall and Jones counties (and some additional counties since) at low levels, and some hail damage in NE Iowa were some of the issues observed by ISU Extension field agronomists this last week. Read on to see what’s happening, particularly in the the eastern part of the state.

Northeast Iowa