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Field crop health matters throughout the entire growing season. The types of diseases on crops depend on the point in the growing season and the environmental conditions. Many later-season diseases result from soilborne pathogens over which in-season fungicide applications have no control. Most commercial varieties will have ratings for the performance of their selections against various diseases, including those caused by soilborne pathogens.

Harvest season is right around the corner and according to the latest U.S. Drought Monitor, the majority of the state is in a severe drought or worse. These abnormally dry conditions could enhance the potential for combine and field fires this fall. Low relative humidity levels and high winds will further increase the risk of fires. Fires cause millions of dollars in property damage, including loss of machinery, crops, and time.

While it is no secret soybean disease has been more prevalent in soybean fields in southwest Iowa this month. However, not all the problems in soybeans can be attributed to disease incidence. I have received and observed an unusual pest this month, Dectes stem borer! Look at your soybeans carefully to determine the cause of premature death.

The rains earlier in August across much of the state and more moderate temperatures have been replaced by hotter and drier conditions. While some fields across the state look pretty good, others are showing more signs of stress here this week.

I received several questions about blister beetles in alfalfa hay over the weekend. I thought it might be helpful to review what they look like and provide a few management tactics to minimize the negative effects for animals.

While some much welcomed rain fell across most of the state over the last week, parts of NE Iowa missed out on the rain and other parts saw 6+ inches of rainfall. From the field, aphids (in corn and soybeans), spider mites, soybean gall midge, concerns about tar spot, and downy mildew in soybeans were some of the issues or topics of questions Iowa State University and Outreach Field Agronomists received last week.

Soybean aphids, two-spotted spider mites, fungicide decisions despite little disease pressure, and the hot and dry conditions were some of the more common issues or questions Iowa State University Extension and Outreach Field Agronomists have seen or heard about in fields across the state over the last week. Read on for more specifics about what’s happening around the state.

Northwest Iowa

We have now reached the critical period for maximizing yield for both corn and soybeans. I will focus on soybeans for this blog and how soil moisture affects moisture stress in beans and soybean yield. With recent rains across a sizable portion of Iowa in mid-July, soil moisture profiles changed dramatically in areas with precipitation, while other areas are in deficit situations. Mother Nature is now in charge with hot temperatures and low moisture.   

Limited rainfall, the hot weather this week, corn rootworm, weed escapes, insect defoliators, and questions on foliar fungicides have been the more common issues or questions Iowa State University Extension and Outreach Field Agronomists have seen or heard about over the last week. Read on for more specifics about what’s happening around the state.

Northwest Iowa

Over the last week much needed rain was received, but it also unfortunately brought along wind and hail to some parts of the state. Other hot topics coming in from fields across the state this past week included corn rootworm, soybean gall midge, phytophthora in soybeans, tar spot, gray leaf spot, and weed control issues. Read on for more specifics about what Iowa State University Extension and Outreach Field Agronomists have seeing or had questions about around the state in the last week.

Check out the upcoming field days being offered around the state this August. These field days will feature a variety of topics ranging from strip-till and conservation to forage production and corn rootworm management.  

August 1, 2023 | Corn Rootworm Field Day (Northern Research and Demonstration Farm south farm located at 1040 James Ave, Kanawha, IA)

Blister beetles are an occasional late-summer problem in Iowa alfalfa fields. The beetles feed on alfalfa and soybean foliage, but leaf loss is not of economic importance. The bigger concern with blister beetles is their toxicity to livestock when accidentally consumed in feed. The beetles produce cantharidin, an irritant that causes painful blistering when the insects are handled.

Corn rootworm, soybean gall midge, tar spot, drought stress, and weed control issues are some of the common issues or questions Iowa State University Extension and Outreach Field Agronomists have seen or heard about the past couple of weeks. Read on for more specifics about what’s happening around the state. 

North Central Iowa

The smoke from the 2023 Canada wildfires was noticeable in Iowa, especially on June 28 and 29, and concerns about impacts on crop productivity were voiced. The smoke from the California wildfires (August 2021) was evident in Iowa too, however, this did not have a negative effect on crop production. On the contrary, 2021 was a record-yielding year for Iowa.

Although some parts of Iowa have been catching up with moisture deficits, many areas continue to be in severe drought. Drought stress combined with high temperatures is good news for field crop pests like grasshoppers and spider mites. We’ve been getting reports of high grasshopper numbers around the state this year. If your area is hot and dry, consider scouting fields now and throughout August.

While some much needed and welcomed rain fell across most of the state this past week, some areas received minimal to no rain. The dry conditions, herbicide injury, potato leafhoppers, nutrient deficiencies (mainly potassium), weed control failures, and tar spot are some of the highlights on the issues or questions ISU Extension and Outreach Field Agronomists heard about or received this past week. Read on for more specifics about what’s happening around the state.

Well, I’ll be darned! Yesterday I tweeted the only disease being seen in Iowa corn was common smut on leaves. Thanks to an overzealous crop scout from a seed company, we can confirm that tar spot was observed in central Iowa (Poweshiek, Tama, Marshall, Jasper, Story and Polk counties) yesterday. Last year, this same scout also found tar spot for the first time in Iowa on 30 June. (Does this mean Iowa has the best scouts, I wonder?).

Dry conditions causing crop stress, herbicide carryover and drift, nutrient deficiencies induced by the dry conditions, armyworms in forages, and a frost event in NE Iowa were some of the common or big issues or questions ISU Extension and Outreach Field Agronomists heard about or received this past week. Read on for more specifics about what’s happening around the state.

North Central Iowa

On June 14, Iowa State University extension entomologists put out a Pest Alert to scout for true armyworm because of statewide reports of this pest feeding on crops. In addition, there have been multiple reports, primarily coming out of northeast Iowa, regarding true armyworm feeding in hay and pastures. Now is the time to scout to determine if a treatment is warranted. 

Plant Injury

We’re well into the growing season in Iowa. We are in full swing in the Plant & Insect Diagnostic Clinic (PIDC) as growers, certified crop consultants, and field agronomists start to notice problems in their fields. While there is information on our PIDC webpage (https://hortnews.extension.iastate.edu/pidc) about the services that we provide, with some sample snafus this spring, I figured it was time to write a brief blog article to remind you here, too.