Regional Crop Update: July 20 - July 28, 2020

July 29, 2020 8:20 AM
Blog Post

While the drought concerns and drought impacts on row crops and forage crops seems to be the big issue especially in western Iowa, other common issues or questions reported by ISU Extension field agronomists this past week included corn rootworm activity, earworm feeding, Japanese beetles causing defoliation in soybeans and silk clipping in corn, low levels of soybean aphids, potato leafhopper damage, gray leaf spot pressure increasing (especially eastern Iowa), low levels of frogeye leaf spot, fungicide application decisions, and continued reports of dicamba injury. Read on for more specifics for what’s happening in different regions across the state.

Northwest Iowa

Joel DeJong (Region 1): “Last week gave this region some scattered showers, but unfortunately most that really needed it got nearly nothing. More fields look stressed in the afternoons, some look stressed all day. There are some badly hurt fields in the region, particularly where compaction from spring work created issues. Corn on corn fields show more stress too, including some pollination reduction due to silk clipping. Fields near the Minnesota border look really good to me. Not many diseases can be found – some gray leaf spot in corn and a little frogeye in beans. Aphid numbers remain low, but lots of painted lady butterflies were committing suicide in my vehicle grill in Woodbury County last week while I was there. It is time to watch for spider mites, but so far, little reported.”

Paul Kassel (Region 2): “Crop conditions have headed two different directions across my area. Areas in Dickinson, northern Clay, Emmet, Kossuth and Winnebago Counties are seeing very good rainfall and growing conditions. However, areas in Clay, Palo Alto, Sac and Buena Vista Counties are currently very dry and are listed as abnormally dry to being in moderate drought on the U.S. Drought Monitor. I would expect that the area of moderate drought will expand when the new drought monitor map is released this Thursday, July 30. Fungicide applications on corn and soybean acres have been mostly completed. Soybean aphid numbers have been low so far. Gall midge activity has also been low with relatively few new discoveries.”

Corn from Winnebago County at the R3 or milk stage. Photo courtesy of Paul Kassel.

 North Central Iowa

Angie Rieck-Hinz (Region 3): “Dry conditions persist in Calhoun and Webster County with D2 (severe drought conditions) and D1 (moderate drought conditions) impacting most of Humboldt, and D0 (abnormally dry) impacting most of Wright, Hamilton and Hardin Counties. Unfortunately, most areas missed rain this past weekend, and I anticipate seeing the U.S. Drought Monitor expand in size and severity, moving eastward and slightly north across the counties I cover. Most corn is R2 to R3, but I did find some corn (102-day maturity) that was starting to dent on July 27. This indicates to me that plant is suffering from lack of water and grain fill will be compromised. Overall, pollination seems to be good. Disease pressure continues to be low, and the fields I have been monitoring for rootworms have low adult rootworm beetle numbers so far. Soybeans are R4, with most pushing R5 (beginning seed) I continue to find thistle caterpillars, although at low numbers.  Frogeye leaf spot is becoming evident in some fields.”

Central Iowa

Meaghan Anderson (Region 7): “Most of Central Iowa received some rain in the last week, though most areas received less than an inch. While my eastern counties have been mostly in a sweet spot this summer getting enough rain (sometimes a little too much), we will need continued rainfall to finish out the crop. Some parts of Marshall County are now <25% of normal rainfall for the last 30 days and most of the rest of my area is <50% of normal. Corn is anywhere from R1 to nearing R4; in some cases, these stages are all happening in the same field. The western part of my area has some corn fields that are really beginning to burn up from the heat and lack of moisture; we’ve scheduled drought meetings for Boone and Dallas County next week, as well as a drought webinar series starting July 30. Corn rootworm beetles are emerging and I’m getting phone calls about concerning levels in both central and eastern Iowa. Corn earworms are beginning to make an appearance in fields. If you find them, check whether your corn hybrid should provide suppression and give your local field agronomist a call if it seems like it’s not working! Soybeans are mostly R3-R4 and look really good. Most fields now have closed rows, but I have seen a few fields with waterhemp sneaking through on end rows or in areas that looked to have been wetter this year. Now is a good time to evaluate why the waterhemp survived and make notes for next year. Most phone calls are about fungicide decisions in corn and soybean, potato leafhoppers in alfalfa, and dicamba injury to soybean.”

Tipping back on corn ears due to the dry conditions. Photo courtesy of Meaghan Anderson.

An earworm found feeding on an ear in a Central Iowa field. Photo courtesy of Meaghan Anderson.

 Southwest Iowa

Aaron Saeugling (Region 10): “Sporadic rain showers have cover portions of SW Iowa in the past week. Some areas received a nice general rain while isolate areas have missed any measurable precipitation. For the most part corn looks very good where rain has not been limiting, and most corn is R2 to R3. While I would rate the disease pressure in corn to be low to moderate, fungicide applications are occurring. Soybeans range from R2 to R4, and I’m seeing sporadic insect feeding in soybean fields. Recently, I have been seeing heavy painted lady butterfly (aka adult thistle caterpillars) activity. Alfalfa is very slow to dormant in dry areas. Pasture conditions have been poor due to the hot and dry weather. With measurable precipitation I expect some crop conditions to improve over the next week.” 

East Central, Southeast, and South-Central Iowa

Rebecca Vittetoe (Region 8): “This past week rainfall totals for parts of EC Iowa ranged from trace amounts to about an inch with some local areas getting a little more. Corn is mainly R1 to R3 and soybeans are mainly R3 to R4. In general, corn and soybeans are looking pretty good. I’m continuing to see more gray leaf spot pressure in corn, and I happened to find some southern rust in Washington County this past week. Japanese beetles, corn rootworms, potato leafhoppers, grasshoppers, and low levels of soybean aphids have been insects I’ve seen or gotten questions about this past week. Most questions this past week encompassed fungicide application decisions, insect pest concerns, and even a few dicamba related calls in soybeans yet.”

Southern rust found in a corn field in Washington County. Southern rust pustules are almost exclusively found on the upper leaf surface, are smaller and look more orange compared to common rust. Photo courtesy of Rebecca Vittetoe.

Virgil Schmitt (Region 9): “Rainfall last week was generally light, with the heaviest being less than 1.0 inch. In general, temperatures last week in the counties I cover and statewide were near normal. Most corn fields are at VT/R1 to R2. Soybean are mostly R3 to R4. Overall the corn and soybeans look good except from the storm damaged fields. Gray leaf spot pressure is increasing in corn fields. Katydids are starting to “sing.” Corn rootworm trait failure (continuous corn), Japanese beetles, dealing with storm damage to crops, and dicamba drift were common topics of discussion last week. I also had two unrelated calls from people who believed there conifers had been killed by dicamba drift. Upon questioning, both admitted to using “just a little” Tordon on brush amid the trees.”


Josh Michel (Region 11): “Light rainfall provided some minor relief as most of the region received 0.25 to 0.50 inch this past week. With the drier conditions corn, alfalfa, and pastures are continuing to show signs of stress. Corn mainly ranges from R1 to R3, with gray leaf spot being the dominant concern. There’s also been several field calls regarding Japanese beetle and corn rootworm feeding. Soybeans are currently R2 to R4, and generally look pretty good. The majority of soybean related field calls are centered around herbicide injury, defoliation estimates, and weed escapes. Hay fields and pastures continue to see poor growth from above average temperatures and limited rainfall. Many alfalfa fields are also seeing severe insect damage from potato leaf hoppers and grasshoppers.”

Alfalfa field in Davis County with severe potato leaf hopper feeding as evident by the yellowing of the leaves (aka hopper burn). Photo courtesy of Josh Michel.

Check out the map below to find your local ISU Extension field agronomist and find their contact information here!


Rebecca Vittetoe Field Agronomist in EC Iowa

Rebecca Vittetoe is an extension field agronomist in east central Iowa. Educational programs are available for farmers, agribusiness, pesticide applicators, and certified crop advisors.

Areas of expertise include agronomy, field crop production and management of corn, soybeans, and...