Crop Update July 10 - July 18

The spotty rain and dry weather saga continues in many parts of the state. The U.S. Drought Monitor has just over 47% of the state as abnormally dry and 16% of the state in a moderate drought.

Source: U.S. Drought Monitor 

According to the USDA Crop Progress & Condition report that came out on Monday, July 17, Iowa's corn conditions are 1% very poor, 5% poor, 23% fair, 58% good, and 13% excellent. For soybeans, conditions are 2% very poor, 8% poor, 27% fair, 54% good, and 9% excellent. Iowa State University Extension and Outreach field agronomists share what's happening in their respected parts of the state. Read on for more information about your region's crop progress and field conditions. 

Northwest Iowa

Paul Kassel (Region 2): “The dry weather has persisted over much of the area. The corn crop is looking fairly good and but a recent trip to Sac and Buena Vista county showed lots of corn fields with silvery colored leaves and leaves that were rolled up in the summer heat. Rainfall is predicted for much of the area early this week. Some fairly serious yield damage may occur to the corn crop if we miss that rain. Parts of Winnebago and Hancock did receive some rainfall on July 4 and July 10.  However, a lot of crop damage from hail and wind accompanied that rainfall in the Klemme and Garner area. There has been concern over dicamba drift that has originated from dicamba tolerant soybean fields.  So far, this damage to non-dicamba tolerant soybean varieties has not been real severe.”  

Giant ragweed in Hancock county 1 day after Engenia application. Photo by: Paul Kassel.

Giant ragweed in Hancock county 9 days after Engenia application. Photo by: Paul Kassel.

Giant ragweed in Hancock county 16 days after Engenia application. Photo by: Paul Kassel.

North Central Iowa

Angie Rieck-Hinz (Region 3):  “The story of the day is continued spotty rainfall. The western part of my counties is dry and the northern part continues to receive good moisture and crops look good there. Corn is V18 to R2. Again, disease pressure in corn is little to none. Most of my time has been spent in soybean fields, but I did manage to dig corn roots last week and did not find any rootworm feeding. Soybeans are R2 to R3. There have been a few scattered reports of aphids- at low levels, but I have not found any. Most of my phone calls have been concerning off-target movement of dicamba.” 

Northeast Iowa

Terry Basol (Region 4): “Corn that was planted the earliest here in NE Iowa has now tasseled and is beginning R1 or silking. Later planted corn is close and on the verge of tasseling. In regards to foliar diseases, there has been very low disease pressure observed so far. Some common rust can be found, but continues to be at very low thresholds. Soybeans continue to progress and almost all can be found in the R2 or full flowering stage. Septoria Brown Spot has been observed in NE Iowa soybean fields in the lower canopy. Continue to monitor, as research has shown a fungicide application is more beneficial if the disease moves up into the middle of the canopy. We were able to get some precipitation last week here at the NE IA Research and Demonstration Farm. According to the Iowa Mesonet, we received 2.1 inches of rain from July 9^th through July 15^th.”

Southeast and East Central:

Rebecca Vittetoe (Region 8):  “According to the U.S. Drought Monitor, all of my counties are either considered abnormally dry or in a moderate drought. What rainfall we have had, has been pretty spotty. Most corn is VT to R1, but there are some fields still on the verge of tasseling. Soybeans are in that R2 to R3 stage. Corn is showing moisture stress by rolling leaves and you can also see firing in the lower canopy in certain areas. Pastures are also looking pretty sad with the lack of moisture. The Iowa Beef Center has a web page that lists several drought-related resources, found here. For those wanting to stretch your pastures, check out this Beef Center article: "Stretch Pastures During Drought Conditions."  For alfalfa producers, the article, "Effect of Drought on Alfalfa and Managing for Next Growing Season"  from the University of Wisconsin does a nice job of discussing the impacts of drought on alfalfa.  Insect or insect-like pests to keep an eye out for include Japanese beetles, spider mites, grasshoppers, and corn rootworm beetles. The dry weather has definitely kept diseases at bay as I’ve yet to really see any foliar diseases in corn or soybeans.  The most common call I've had this past week has been on dicamba injury in soybeans.”

Corn plants starting to fire in certain areas of SE/SC Iowa due the the moisture stress and high temperatures. Photo by: Rebecca Vittetoe. 

Meaghan Anderson (Region 9): “East central Iowa received a well-needed 1"+ of rain in the last week. Most of the area is on the drought monitor as either abnormally dry or in a moderate drought. With hot temperatures remaining through the week, this might be a tough time for corn pollination. Most corn in east central Iowa is tasseling (VT) or silking (R1). You can check how corn pollination is going in your fields by doing a quick and easy test to see how many ovules have been fertilized. 

Checking on the corn pollination process. Photo by: Meaghan Anderson. 

I've seen very little for corn disease, aside from some common rust and holcus spot. Western corn rootworm beetles are emerging in many fields. Monitoring emerging beetle populations is one way to determine if action is necessary the following year to manage this pest. Soybeans are mostly in the R2 or full bloom stage. Continue monitoring for defoliators as threshold levels for insecticide treatments are 20% defoliation during reproductive stages. Calls continue coming in regarding Japanese beetles and dicamba injury. Also, be keeping your eyes out for Palmer amaranth. It was discovered in a 2017 seeded conservation planting. Please continue scouting crop fields and 2016 and 2017-seeded conservation plantings for this weed.”

Be keeping your eyes open for Palmer amranth. Learn key traits to help identify iPalmer amaranth the ISU publication CROP 3105: Palmer amaranth identification. Photo by: Meaghan Anderson. 

Virgil Schmitt (Region 10): “During the last week, areas north of I-80 generally received less than a half inch of rain while areas south of I-80 received between 0.5 and 2 inches of rain, with some heavier amount in Lee County. In general, the counties that needed rain the most received it. Second cutting of hay is winding down. Corn is mostly R1 to R2 and soybeans are mostly R2. Both crops look healthy. During the last week, Japanese beetles have been the major issue, with dicamba concerns being second. Japanese beetle feeding appears to be winding down.”

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Map showing rainfall totals for Iowa over the last week. Source: http://www.weather.gov.  

Find your local ISU Extension and Outreach field agronomist here!