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. Read on for more specifics about what’s been noted in fields across the state.
Leah Ten Napel (Region 1)
Cherokee, Ida, Lyon, Monona, O'Brien, Osceola, Plymouth, Sioux, Woodbury counties
“Crops across northwest Iowa look generally good, although rainfall has been variable across the region. During the Aug. 3 – 9 reporting period, many areas received around 0.75 to 1.50 inches of rain, with some locations receiving considerably less and others picking up heavier amounts from localized thunderstorms. The recent rainfall was beneficial, but the variability means moisture conditions can look very different from one field to the next. Corn is progressing rapidly through the dough stage and into dent. At this point in the season, adequate soil moisture remains important for maintaining grain fill and maximizing kernel weight. Fields that have received timely rainfall should have good conditions for continued grain fill, while areas that missed recent storms will need to be monitored for increasing moisture stress and premature plant senescence. Soybeans are also moving through an important reproductive period, with most fields setting pods. Adequate moisture during pod development and seed fill will be important for protecting yield potential. Continue scouting for soybean diseases, particularly in fields with dense canopies and frequent moisture, is warranted. Insects should also be monitored as crop development continues. Diseases may still develop or spread with additional moisture, but there would likely not be a ROI with an additional fungicide application at this point in crop development. Overall, crop conditions across northwest Iowa remain fairly positive, but rainfall variability continues to be something to watch. The next couple of weeks will be important for corn grain fill and soybean pod and seed development. Where soils are beginning to dry, additional timely rainfall would be beneficial as the crops work to finish out the growing season.”
Gentry Sorenson (Region 2)
Buena Vista, Clay, Dickinson, Emmet, Hancock, Kossuth, Palo Alto, Pocahontas, Winnebago counties
“The area has been dry, and rain was welcomed across the area even if rainfall totals were spotty. While some areas of my region received over 1 inch of rainfall for the week, other areas only received a trace amount. Concern has been over the dry conditions. Tip back is present in fields because of the dry conditions. Lighter soils have struggled with the heat and lack of moisture and are visible in scouting trips. Much of the area that I serve is rated as D1 or D0 drought on the U.S. Drought Monitor. On average the corn is at the dough stage. Insect pressure has been light. Calls have been related to weed control and fertilization questions.”
Josh Michel (Region 5)
Allamakee, Buchanan, Clayton, Delaware, Dubuque, Fayette, Jones, Linn, Winneshiek counties
“Farmers were able to take advantage of a mostly dry week, before severe weather came through the region on Friday. While most of the region received anywhere from 0.5 to 1 inch of rainfall, some isolated areas in Buchanan and Linn counties received up to 1.5 inches of precipitation. Unfortunately, the severe weather last Friday resulted in some crop damage across multiple counties. High winds and large diameter hail caused severe damage specifically in parts of Buchanan, Delaware, Jones and Linn counties. Crop damage assessments are being conducted, and information will be disseminated later this week. In general, most of the corn is around R3 to R4, while soybeans are around R3 to R5. Disease management continues to be a concern while crops are going through reproductive stages. That said, disease pressure remains moderately low across most of the region. Some dairy operations have started harvesting a fourth crop of alfalfa. The majority of recent field calls have centered around scouting for insect pests and crop diseases.”
Meaghan Anderson (Region 7)
Boone, Dallas, Jasper, Madison, Marshall, Polk, Story, Tama, Warren counties
“All of central Iowa received rainfall in the last week, though totals vary from less than a half inch (parts of Marshall and Tama counties) to more than three inches (parts of Boone County and far northwest part of Dallas County). More rainfall to come this week that will likely benefit crop and disease development in fields. Corn is in the R4 to R5 growth stages and fields I’ve looked at remain remarkably clean. Curvularia is more common to see but still very low severity and sporadic. Disease pressure overall remains very low, though other non-pathogen-related spots are showing up in the upper canopy, primarily in areas on leaves where dust and pollen has settled. Insect pressure remains low, but northern corn rootworm beetles have been flying in and out of corn field edges in the past week. In addition to some of the pollination issues noted several weeks ago, tip back is prevalent in some fields, especially those that were in early grain fill during hot conditions and had less soil moisture available to them. Soybeans are in the R4 to R5 growth stage as well and seem to be VERY tall. I’ve received several calls about lodging from the recent rainfall and winds. Disease pressure is low in soybean, though I’ve seen a couple diseases in the canopy that are not treatable with fungicide – downy mildew, bacterial pustule. Weeds are starting to peek over the crop canopy in some fields. Most calls in the last week have been about identifying diseases, weed management, insect ID, and soybean lodging.”
Rebecca Vittetoe (Region 8)
Iowa, Jefferson, Keokuk, Poweshiek, Washington, Johnson counties
“The past week was a wet one with rainfall totals ranging from 0.5 inch to closer to 2.5 inches in part of Jefferson and Keokuk counites. Unfortunately, with the storm last Friday night, there was also some strong winds and hail that resulted in crop damage. Most corn is now in the R4 stage with some of the earlier planted fields reaching R5. Soybeans are R4 to R5. With some of the recent rain events and stronger winds, there are some soybean fields that have lodged. Disease pressure remains low in both corn and soybeans. I have had a few more reports of southern rust and reports gray leaf spot being more prevalent in the lower part of the corn canopy. In the last week, I’ve noticed more rootworm beetles flying around, particularly northern corn rootworms. I’ve also seen and have had reports of corn aphids in fields. Questions this past week have been on disease pressure, late season weed management, concerns about “poor pollination” or incomplete kernel set on ears, and rootworm beetles.”
Virgil Schmitt (Region 9)
Cedar, Clinton, Des Moines, Henry, Jackson, Lee, Louisa, Muscatine, Scott counties
“During the last week, most of Lee County received 2.5 inches to over 3 inches of rain while the other the counties I cover have generally received from 0.1 to 0.75 inch of rain. Most corn fields are in the R4 or early R5 growth stages and generally look good. Little disease or insect pressure is present. Most soybeans are at R5 and also look good. Again, little disease or insect pressure is present in soybean fields. Forages also are doing well. Calls last week were mostly corn diseases and fungicide application decisions and late season weed management.”
Logan McCrea (Region 11)
Appanoose, Davis, Lucas, Mahaska, Marion, Monroe, Van Buren, Wapello, Wayne counties
“South-central Iowa continues to push through the growing season and received some more rainfall ranging from 1.5 inches to 5+ inches in portions of Wayne, Appanoose, and Van Buren counties. Corn ranges from R4 to R5 and diseases are becoming easier to find within fields, though still not at alarming levels and far too late for it to majorly impact yields. Soybeans are mainly R4 to R5 and generally look good. The state fair flush of weeds has begun to emerge from the canopies and are noticeable when driving through the countryside. I have not noticed any sudden death syndrome (SDS) symptomology within soybean fields yet but would not be surprised if they begin to appear soon. Pastures have enjoyed the recent rains and got their feet back under themselves after looking rough for the drier second half of July. Hay continues to get put up when breaks between the rainfalls allow.”
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- Field Agronomist in EC/SE Iowa