Hail and wind damage, corn rootworm, Japanese beetles weed escapes, insect, and questions on foliar fungicides have been the more common issues or questions Iowa State University Extension and Outreach field agronomists have seen or heard about over the last week. Read on for more specifics about what’s happening around the state.
Northwest Iowa
Leah Ten Napel (Region 1): “Crop conditions across NW Iowa continue to be variable. A majority of soybean fields are R2 to R3, and earlier planted corn fields are VT to R1. The effects of ponding or flooding can still be seen across the counties and replanted corn acres I have seen are significantly behind in development. This will most likely lead to a prolonged harvest season. Most growers dealing with flooded acres have replanted to cover crops or soybeans depending on crop insurance and initial crop. Rainfall over the past week has been less than 0.5 inch across my region. High temperatures and low rainfall can make for stressful pollination for corn fields in the VT-R1 stage. Cooler temps going forward will help lessen the stress on these corn fields but may welcome more disease pressure! Reported insect and disease pressure is low. One disease I have seen popping up is Goss’s wilt, but a fungicide application will not control this corn disease. Keep scouting fields for fungal diseases before making the decision to apply fungicide this season!”
North Central Iowa
Angie Rieck-Hinz (Region 3): “For the past week we had highly scattered showers. The storm that came through late afternoon of July 15 dumped anywhere from 0.5 to just over 4 inches of rain in a very short amount of time. There was some hail and wind damage. Corn is late vegetative to R2. I have yet to find anything but common rust for corn disease pressure. Rootworm beetles are present. Soybeans are R2 to R3. The most common diseases I have been finding in soybeans are bacterial blight and frogeye leaf spot. The majority of calls this past week have been in regards to the hail damage from July 6 and fungicide applications, but not fungicide use as a result of hail. Continue to scout for crop diseases and Japanese beetle silk clipping.”
Northeast Iowa
Josh Michel (Region 5): “Farmers were able to take advantage of a dry stretch between storm systems last week to finish alfalfa harvest and start scouting for crop pests and diseases. While most of the region received around an inch of precipitation from widespread thunderstorms, some isolated areas received up to 1.5 inches. Any remaining second crop of alfalfa has been put up, with some dairy operations already working on their third crop harvest. Potato leafhopperscontinue to be found in most fields. Many corn fields are beginning to tassel, and I’d expect to see some early brown silks by the end of the week. Tar Spot disease pressure remains low, but producers should still scout for other diseases such as gray leaf spot before making a fungicide application. While some wet spots continue to be seen in fields, generally most of the corn looks good throughout the region. Soybeans are generally around R2, with some early fields approaching R3. Japanese beetles continue to be the main defoliators found throughout most fields. All but the last of the oats have turned, and harvest started last week in a few areas. Most of my field calls last week centered around forage and small grain management, disease pressure and scouting, weed escapes and control, and a few calls regarding possible herbicide injury.”
Central Iowa
Meaghan Anderson (Region 7): “Most of central Iowa received less rainfall in the last week, though parts of Marshall and Tama counties received higher amounts. Most corn is in early reproductive stages, as far along as R2 (blister) in some fields. Tar spot and other diseases are becoming easier to find, but still very low incidence. Common rust remains the most common foliar disease pathogen I've found in fields. Corn rootworm dominates most of my conversations, with problems apparent in many continuous corn fields (western CRW) and an ever-growing number of rotated fields (likely northern CRW). Soybean is mostly R1 (beginning bloom) to R3 (beginning pod) and has filled in the rows in many fields but not all fields with 30 inch rows or replant. Other insect activity seems to be relatively low, but Japanese beetles are the most common insect I've found in soybean. Mysterious herbicide issues and waterhemp survival from POST herbicide applications, fungicide application decisions, and corn rootworm were common topics of conversation last week."
Southwest Iowa
Aaron Saeugling (Region 10): “Weather has become more seasonal with warmer and drier conditions across most of SW Iowa. Crops have rapidly entered the reproductive phase, most corn is R1 to R3, depending on planting date and maturity. Soybean is in the R1 to R3 also with early planted beans further along. No pressing issues with corn or soybean. Isolated reports of insect hot spots and disease incidence but all currently low levels. The most common corn disease at this point is common rust. The next two weeks will be critical to disease development for several corn and soybean diseases, so scouting will be important. Crop water usage is now in high gear, so we can now use some of the excess soil moisture we have accumulated this season."
East Central, Southeast, and South-Central Iowa
Rebecca Vittetoe (Region 8): “Rainfall totals for the week before Monday evening’s storm ranged from 0.4 to 2.5+ inches across EC Iowa. Corn ranges from late vegetative to R2 and soybean fields are mainly R1 to R3. We are seeing more of the unevenness that we saw earlier in the season again showing up again in how corn fields are tasseling. In general, disease pressure is low, but I can find some tar spot, common rust, the start of gray leaf spot, and also bacterial leaf streak. So far it has all be in the lower part of the canopy, except for bacterial leaf streak, and all at low levels. In soybean fields I am mainly seeing bacterial diseases. On the insect side, Japanese beetles and corn rootworm have been the two main pests I’ve had questions about this last week. It wouldn’t surprise me if Monday evening’s storms alert us to more fields with corn rootworm issues. Other questions or issues from the last week included concerns about waterhemp surviving post applications, herbicide injury (drift and tank contamination), and foliar fungicide decisions.”
Virgil Schmitt (Region 9): “Rainfall during the last week in the counties I cover was from less than 0.2 to over 2 inches, with the smallest amounts in Henry County and northeast Jackson County and the largest amounts in Cedar County. Most corn is about R1 and looks good. I have seen a few fields with brown silks. Most soybeans are at R2 and look good. I have not seen any fields at R3, but I suspect there are some. Oats continues to mature look good. Hay making is a challenge with the frequency of rainfall. All crops appear to have few disease or insect issues except potato leafhoppers are above threshold in many alfalfa fields.Contacts last week mostly involved herbicide drift, fungicides for both corn and soybean, Japanese beetles on both corn and soybean, potassium deficiency in corn, yellow soybeans in low areas of fields, and potassium deficiency in corn. I was also in a soybean field with substantial phytophthora root rot last week.”
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Rebecca Vittetoe Field Agronomist in EC Iowa
Rebecca Vittetoe is an extension field agronomist in east-central/southeast Iowa serving Iowa, Jefferson, Johnson, Keokuk, Poweshiek, and Washington counties. Vitteoe works with farmers, landowners, and ag retailers to answer agronmy-related questions. Her areas of expertise include general ...