Regional Crop Update July 16 to July 24, 2018

July 24, 2018 3:27 PM
Blog Post

Gray leaf spot, spotting of soybean aphids, and off-target herbicide movement seem to be common and big issues that Iowa State University Extension and Outreach field agronomists saw across the state this past week. Read on for more information about your region’s crop progress and field conditions.

Northwest Iowa   
Joel DeJong (Region 1): “During the last week the NW corner of the state received very little rainfall. But, that is ok considering we are still a long ways above average for the last month. Rivers have returned to within their banks. In areas that have not been too wet, the crops look really good, and wetter areas are showing improved growth now, too. I have not observed many disease lesions anywhere, although I can see and hear airplanes flying. Corn rootworms beetles have emerged, so it is a good time to evaluate root systems for injury. Soybean aphids are just starting to appear in the region, although numbers seem to remain low at this point. Reports from our neighbors to the north have been on an uptrend for a while, so scouting should be on-going now.”

Paul Kassel (Region 2): “Crop development has progressed very well recently, but corn development varies a great deal. Corn fields that were planted in early May on pattern tiled fields are in the blister stage/early milk stage (R2 to R3). Corn fields that were planted in late May on fields that were less well drained are just beginning the pollination process. Many of these later planted fields have severely stunted areas as a result of waterlogged conditions in late June. The soybean crop is developing at a similar rate. The early planted soybean crop is approaching the R4 (full pod). Farmers are considering fungicide application on some of the better looking fields – which is a difficult decision with the current commodity prices. Soybean aphids have been at very low levels; however, farmers are concerned that the soybean aphid populations will develop with the onset of the predicted cooler weather." 


Soybean aphids appeared in this Buena Vista County field this week. Take time to scout for aphids in your fields. Photo by Paul Kassel.

North Central Iowa
Angie Rieck-Hinz (Region 3): “Herbicide efficacy from the group 14 products and dicamba have not been all that good. Waterhemp was large due to adverse conditions delaying spraying of post-applied products. The tops of many waterhemp are dead, but if you look lower on the plant, the plant is still alive and shooting new growth. I have been chasing dicamba off-target complaint calls. I have yet to find any soybeans aphids. In terms of corn, gray leaf spot is present, but the pressure has been relatively low in this area. Rainfall ranged from 0 inches at Rockwell City to just over 2.0 inches at Northwood.” 

Southwest and West Central Iowa
Aaron Saeugling (Region 10): “Conditions are good in SW Iowa right now. Corn is in the R2 (blister) to R3 (milk) stage. Some fungicide applications still being made. Soybeans are in the R2 (full bloom) to R3 (begin pod) with a few in the R4 (full pod) stage. Some areas have received rain in the last few weeks while other areas would welcome an inch or two of rain. Potato leafhoppers have been an issue in some alfalfa fields.” 

Central, East Central Iowa, Southeast, and South Central:
Meaghan Anderson (Region 7): “Crops are continuing to move relatively quickly through reproductive stages in Central and East Central Iowa with corn mostly in the R3 growth stage and soybeans in the R3-R4 growth stage. The cooler temperatures and rainfall for much of East Central Iowa early last week were welcome breaks from the heat and dry conditions. Much of Central (and East Central) Iowa could use a good rain, but the forecast does not look promising for the next week. Problems in the last week have continued to include dicamba or other plant growth regulator injury to soybeans, increasing abundance of gray leaf spot in some corn fields, and concern regarding Japanese beetles defoliating soybeans and eating into corn ears on field edges. Our rootworm entomologist on campus has visited several fields with suspected Bt trait failures across the state and will visit one in central Iowa next week. Now is a good time to check fields for presence of northern or western corn rootworm beetles and dig roots to check for feeding. More information on identifying rootworm beetles, rating root injury, and management options here.”


Rootworm feeding found on some corn roots from a field with a suspected Bt trait failure in Central Iowa. Photo by Meaghan Anderson. 


Adult western corn rootworm found in a corn field in Central Iowa. Western corn rootworms are yellow with a dark head. The females have three black lines on the forewings that do not extend to the wing tip while the forewings of the males often look like a black smudge. Photo by Meaghan Anderson. 

Rebecca Vittetoe (Region 8): “Overall crops are looking really good. Corn ranges from late R2 (blister) to R3 (milk). Gray leaf spot seems to be the biggest issue in corn this year. A lot of fungicide applications seemed to be made last week with some wrapping up this week. Soybeans range from R3 (begin pod) to R4 (full pod). The biggest issues in soybeans seem to be off-target herbicide movement and late season weed escapes. There were some isolated areas that unfortunately received wind and hail damage from the storms that occurred last Thursday.”


Gray leaf spot has moved into the upper canopy in some corn fields in Southeast Iowa. Photo by Rebecca Vittetoe.

Virgil Schmitt (Region 9): “In the area I cover, there was between 0.5 and 2 plus inches of rain, with the most rain being close to HWY 20 and close to the Missouri border. Corn is mostly R3 (milk) and is generally looking good with the exception of gray leaf spot. Soybeans are mostly R3 (begin pod) and generally looking good except for some Septoria brown spot making its way into the mid-canopy in some fields. Call last week were mostly about Japanese beetles, gray leaf spot, and dicamba off-target movement.”


Rainfall totals across the state of Iowa for the past 7 days as of July 23, 2018. Source: http://www.weather.gov

Josh Michel (Region 11): “While some counties in Southeast Iowa received some much needed precipitation last week, unfortunately many areas across my region didn’t receive any last week. Pastures and hayfields continue to show signs of stress from the persistent dry conditions. Most of my area is either moderate (D1) or severe (D2) drought and small area is considered in an extreme drought (D3) according to the most U.S. Drought Monitor (released July 19, 2018). Most corn fields are R2 (blister) and R3 (milk). Corn fields in the region are looking ok, except for those in the driest part of the region. Those fields are showing signs of stress. Soybean fields are at R3 (begin pod) to R4 (full pod), and generally are looking good. In the dry areas, spider mites could become an issue. Calls last week consisted of drought stressed corn, gray leaf spot, alfalfa and soybean defoliation, and group 4 herbicide damage in soybeans.”

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


Map showing the regions and counties field agronomists cover.

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Rebecca Vittetoe Field Agronomist in SC Iowa

Rebecca Vittetoe is an extension field agronomist in southeast/south 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, so...