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    Iowa Field Reports: Crops Shutting Down Early from Drought Stress

    Drought stricken corn.

    As the growing season winds down, ISU Extension field agronomists share what they are seeing out in fields or are getting questions on. Some of the common observations include the drought stress resulting in crops shutting down early, tar spot becoming more prevalent in fields, sudden death syndrome in soybeans, and plenty of waterhemp escapes. Read on for more specifics across the state.

    North Central Iowa

    Angie Rieck-Hinz (Region 3): “Nearly all of my counties caught some much-needed rain over the weekend, from 0.68 inches at Mason City to 0.92 inches at Fort Dodge. And while that rain came too late for most of the corn, it may have helped some later maturing soybeans. Corn is mostly at R5.75 and some is at black layer from early senescence due to lack of moisture. Corn grain harvest has begun south of Fort Dodge and corn silage harvest has been in full swing for the past 10 days. I don’t have any yield reports as of today.

    “I have been scouting corn fields for late season diseases and have found northern corn leaf blight, gray leaf spot, common rust and tar spot. The worst I have seen tar spot is shown in the photo below. This photo is taken of one leaf below the ear leaf.  While I can find tar spot lesions on the ear leaf and above, the incidence and severity has been low, and this observation holds for both fields with a fungicide and fields without a fungicide applied. Soybeans are R6 (full pod) to R7 (beginning maturity). There is some sudden death syndrome (SDS) present in soybeans this year.

    Tar spot on corn near Bolan, (Worth County) Iowa.  Photo courtesy Angie Rieck-Hinz.

    Northeast Iowa

    Terry Basol (Region 4): “Corn and soybeans for NE Iowa look good going into fall right before harvest. Corn fields for the area are in the R5 (dent) stage and range anywhere from ¼ to ½ milk line, respectively. On average, we’re still looking at needing about 15-20 days to get to R6 (physiological maturity). The cooler temperatures have helped lower plant stress, which helps with kernel dry matter accumulation, directly helping test weight.

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    “We have seen tar spot incidence develop later this season due to conducive environmental conditions. Research shows that a fungicide applied at VT – R2 is still the best timing, and it is too late if applied during thr R4 and R5 stages. Soybeans are primarily in the R6 stage (full seed pods contain green seeds that fill the pod to capacity at one of the four uppermost nodes on the main stem.). Most of the fields in the area are starting to turn.

    “In general, foliar disease pressure for soybeans has been low, but we have seen some isolated areas of sudden death syndrome and brown stem rot. As far as precipitation, we received some welcome precipitation over the weekend. According to the Iowa Mesonet, the NE Iowa Research and Demonstration Farm at Nashua has received 0.9 inch of rain since September 1.

    Josh Michel (Region 5): “Over this past weekend, most of NE Iowa received anywhere from 0.25 to 0.50 inch of rain. Before this weekend’s rain, farmers have been able to take advantage of several days of dry weather. Most of the corn in NE Iowa is currently at R5 (dent), ¼ to ½ milk line. Silage harvest has been ongoing in many areas as weather and field conditions have allowed. Soybeans are mostly at R6-R7.

    “I continue to see and hear about reports of SDS showing up in a few areas. Alfalfa forth crop harvest is taking place in many areas. Potato leafhoppers and grasshoppers continue to be the main pests being scouting for. Pastures are in good to excellent condition with consistent rains and cooling temperatures. Most of my field calls over the past week have consisted of silage harvest timing, forage management, alfalfa pests and scouting, as well as weed management in pastures.”

    Central Iowa

    Meaghan Anderson (Region 7): “Central Iowa received some welcome rainfall in late August and early September to help finish out this crop and we hope it translates to larger soybean seeds and corn grain. Parts of central Iowa, particularly eastern Warren County, SE Polk County, and southern Jasper County received recent rain but remain dry. Corn is mostly between ½ milk line (R5.5) and physiological maturity (R6).

    “Tar spot and waterhemp are both easy to find in fields now. Grasshoppers are prevalent on some field edges. I’m concerned about stalk integrity as we approach harvest in many fields; with the significant nitrogen deficiency symptoms and late tar spot coming into some fields, stalk rot assessments will be important to help determine harvest order.

    “Soybeans are changing quickly across my area but some of the replanted areas are still bright green. The most apparent thing in central Iowa soybean fields is waterhemp above the canopy. Field calls have been on pasture weed management, tar spot, poor corn pollination, and fertility.”

    East Central, Southeast, and South-Central Iowa:

    Rebecca Vittetoe (Region 8): “Over the weekend we received some welcomed rained in EC Iowa. Rainfall totals ranging from 0.5 inch to 1.5 inches. Most of the drier areas in my region that had been showing up on the US Drought Monitor as being in a severe or moderate drought received almost an inch of rain or more. Corn ranges from about ½ milk line (R5.5) to physiological maturity (R6).

    “Some fields in the drier parts of my area did shut down early. Tar spot is becoming more prevalent in fields across EC Iowa. Also, as we head into harvest, do keep an eye out on stalk quality this fall. A lot of soybean fields turning as well. I’ve been seeing some sudden death syndrome and frogeye leaf spot in soybean fields.

    “It’s also not hard to spot waterhemp that escaped this growing season in soybean fields and even some corn fields. Calls have mainly been on pasture weed management or preparing for pasture renovations next year, tar spot, cover crops, and  weed ID.”

    Virgil Schmitt (Region 9): “Rainfall in the last 30 days in the counties I cover was about 1.0 inch south of Highway 92 to over 6.0 inches near Highway 30. Areas roughly south of Highway 92 are listed as DO (abnormally dry) to D2 (severe drought) on the September 8, 2022 Drought Monitor. In general, temperatures during the last month in the counties I cover were one to three degrees below normal.

    “Most corn is R6 or within a few days of R6 and looks good to excellent except for areas showing drought stress. There are low levels of gray leaf spot and northern corn leaf blight in some fields and tar spot can be found here and there. Most soybeans are at R6 and also look good to excellent except for areas showing drought stress. Again, disease levels are very low. However, there is considerable white mold in Cedar County.

    “Potato leafhoppers continue to be present in alfalfa and there are winged grasshopper adults in grassy areas. Phone calls, emails, and field visits last week mostly involved weed management and cover crops.”




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