Blog

Input costs like fertilizer and limestone continue to be worrisome for farmers. Maximizing the plant availability of soil nutrients is crucial to optimizing crop production and nutrient supply to crops. One way in which to do this is by managing soil pH – actually it is one of the more important management practices. Soil pH is often overlooked when considering nutrient inputs.

The following content is summarized from the What in the Weather Podcast by Dan Fillius, Justin Glisan, and Madelynn Wuestenberg. 

You can find more information about weather impacts on specialty crops and home horticulture on Dan Fillius' website and information from today's podcast on the latest newsletter. 

Regional Update: 

As the growing season starts to wind down, sudden death syndrome, western bean cutworm, Goss’s wilt, southern rust, tar spot, weed escapes, and the start of corn silage harvest are some of the topics or issues ISU Extension and Outreach field agronomists are seeing or hearing about in fields across the state. Read on for more specifics. 

It was only a matter of time before this article needed to be written. Yesterday, we scouted a field in Des Moines County in southeast Iowa. The short story: red crown rot (RCR) was identified in a swath stretching across part of the field. In talking with the farmer, he noted that the same area had shown up on the yield monitor map two years ago, but he assumed it was sudden death syndrome (SDS).

Agronomists across the state are opening corn ears for yield and disease assessments and are surprised by western bean cutworm larvae feeding inside. Western bean cutworm is one of several caterpillars found in corn ears this time of year, but people are seeing them more frequently in recent years. Western bean cutworm was historically a common pest that caused economic injury to corn in Iowa in the early 2000s, but sightings have been rare since 2009.

The following content is summarized from the What in the Weather Podcast by Dan Fillius, Justin Glisan, and Madelynn Wuestenberg. 

You can find more information about weather impacts on specialty crops and home horticulture on Dan Fillius' website and information from today's podcast on the latest newsletter. 

Determining how much nitrogen fertilizer (N) to apply is a constant challenge facing farmers. The amount of N needed to maintain yield and healthy soils is highly dependent on weather and agronomic management, and therefore differs across years and fields (Table 1). 

The buzz around Palmer amaranth may have quieted it down compared to several years ago, but it is still important to keep your eyes out for this weed. Two new Palmer amaranth sites were confirmed in Johnson and Washington counties just this summer. If a new infestation is found, it is still possible to prevent the establishment and spread of Palmer amaranth in a field. Early identification, coupled with a focus on preventing seed drop and spread is critical.

Red crown rot (RCR) of soybean has NOT yet been found in Iowa, but it has cropped up in several neighboring states. RCR is fairly widespread across Illinois and has been identified in Missouri, Wisconsin, and Minnesota (Fig 1). It is likely only a matter of time before RCR is identified in Iowa. 

To help producers, crop advisers and agricultural lenders make informed nutrient management decisions amid high fertilizer costs, Iowa State University Extension and Outreach is offering three Fertilizer and Finance workshops across Iowa this August. 

Overall disease pressure for the 2026 growing season has been relatively low, especially compared to the southern rust outbreak we experienced last growing season. Gray leaf spot, northern corn leaf blight, bacterial leaf streak, Curvularia leaf spot, southern rust, tar spot, Goss’s wilt and Physoderma brown spot have all been observed in corn fields across Iowa this growing season. However, no one disease has become particularly severe and threatened yields so far. 

The corn crop is advancing in growth stages, and farmers, agronomists, and crop scouts are all keeping a close eye on fields to monitor for the development of foliar disease. While some diseases are present in fields, pressure is significantly lower than in 2025. Many images have come in of other corn issues – some disease, some not. Questions about what is and isn’t Curvularia leaf spot, a new disease to Iowa, are by far the most common.

The following content is summarized from the What in the Weather Podcast by Dan Fillius, Justin Glisan, and Madelynn Wuestenberg. 

You can find more information about weather impacts on specialty crops and home horticulture on Dan Fillius' website and information from today's podcast on the latest newsletter. 

Risk of ear rot and mycotoxins in hail damaged crops

Since the crop started grain fill, there have been several reports of hail damage to crops. Apart from shredding leaves, hail can bruise ears leaving them at risk for infection by ear mold fungi and consequently mycotoxin contamination.

Past research on the effect of hail damage on ear rot and mycotoxin contamination

Most of Iowa received some amount of rainfall this last week with totals ranging from a trace to over 4.5 inches in parts of southwest Iowa. Unfortunately, with that rain, there were also some strong winds, hail, and tornados. In addition to some crop damage from the storms, concerns about the drier conditions in northwest Iowa, late season weed flushes, corn aphids, rootworm beetles, and crop diseases were other topics of conversation this past week for ISU Extension field agronomists.

The 2026 growing season has presented a wide range of challenges across Iowa. Some areas have received excessive rainfall, while others have struggled with limited precipitation. As the corn crop advances toward maturity, it is important to assess how those environmental conditions may have influenced corn development and yield potential. Most corn fields in Iowa are now in the mid to later reproductive stages of development.

July really pushed corn and soybean development along. Corn fields across the state are mostly in the late R3 to R5 growth stages, and soybeans are mostly in the R4 to R5 growth stages as well. Even though it may feel like we are heading into the downhill stretch for these crops, continue to scout fields. Below, ISU Extension and Outreach field agronomists share what they have been finding and hearing about in fields around the state this past week.

A modern 110-day corn hybrid in central Iowa produces about 19 leaves but can only maintain 12-14 leaves on the plant. The first leaves begin senescing around the V5 stage, and by silking (R1) approximately 6-8 bottom leaves have already senesced (Figure 1). From R1 to R5, leaf senescence progresses slowly, with about 2-3 additional leaves senescing. Most leaves are rapidly senescing near physiological maturity (R6) or black layer.

The “cooler” temperatures were welcomed last week. Rainfall was spotty across the state, and unfortunately, the western part of the state, which has been drier, missed out on most of the rain. Corn pollination has wrapped up or is wrapping up, and soybeans are starting to fill pods. Overall, disease and insect pressure remain low across the state. Read on for more specifics on what ISU Extension field agronomists are hearing and seeing in fields around the state.