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    Iowa Field Reports: Pest/Weed Management, Flooding, Replant Considerations

    Replanted corn in wet field. Photo: Purdue University

    Cutworms and armyworms, flooding, replant considerations, and weed management/herbicide application considerations were some of the more common questions ISU Extension Field Agronomists received over this last week. Read on for more specifies about what is happening and being seen across the state.

    Northwest Iowa

    Gentry Sorenson (Region 2): “Rainfall across this area for the week ranged from a trace to about 1 inch per the Iowa Mesonet. Corn is currently at the V2-V3 growth stages, with early planted fields approaching V4. Soybeans range from emergence (VE) to the V1 growth stage.  Post herbicide application on corn started and sprayers were found in many fields making applications before the recent rainfall.

    “Woolly cupgrass, giant ragweed, waterhemp and lambsquarters were observed in fields that I visited last week. Alfalfa harvest got started. Pea aphids were observed in a few alfalfa fields but were below thresholds. Alfalfa height in Winnebago County was 31 inches on June 5th with a RFV of 152.

    “Some recent replanting of soybeans has occurred due to a past hailstorm and some replanting has also occurred due to windblown soil shearing soybeans off below the growing point. Field calls consisted of questions on weed identification and insect identification.”

    Northeast Iowa

    Terry Basol (Region 4): “This past week’s weather provided great conditions for field operations in my area. According to the National Agricultural Statistics Service (NASS) as of June 5, 99% and 98% of the acres have been planted to corn in North Central and Northeast Iowa, respectively. Corn fields for the area range anywhere from VE-V2, with the early planted fields near V3.

    “Soybean acres are estimated to be 99% and 94% planted for North Central and Northeast Iowa, respectively. Precipitation events in the past few weeks have been very helpful in the activation of pre-emergent herbicides and giving a good foundation of weed control for grasses and small seeded broadleaves in both corn and soybean fields.

    “Continue to scout acres and monitor stand counts for emergence and any early issues. Some soybean fields have been struggling to fully emerge due to challenges caused by soil crusting. For soybean replant/thickening decisions, please refer to the recent article titled “Soybean Replant Checklist” here.

    Also, continue to scout corn fields for black cutworm activity. First cutting of hay is well underway, as last week’s weather was favorable for getting it cut and baled in a timely fashion. As far as precipitation, according to the Iowa Mesonet, the NE IA Research and Demonstration Farm here at Nashua has received 2.91 inches of rain for the period of May 23 – June 6.

    “This was primarily the result of two events that occurred on May 24 -25 and June 4-5 that gave us 1.84 and 0.98 inches of rain, respectively. Other field activities that began this past week included postemerge herbicide applications and sidedressing nitrogen.”

    Josh Michel (Region 5): “A few days of dry weather have allowed farmers to finish up field work, conduct post-emergence herbicide applications, and start first crop alfalfa harvest. Over the past week scattered rain showers delivered anywhere from 0.25 to 0.50 inch of precipitation across most of the region, with isolated amounts of up to one inch of precipitation in parts of Fayette County.

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    “Approximately 80%of the corn has emerged and can be staged from VE up to V3 in some early planted fields. Many fields are currently receiving their first post-emergence herbicide applications, and some fields are starting to see side-dressing treatments taking place. I have received a couple calls regarding uneven emergence, especially in no-till fields.

    “Approximately 60%of the soybeans have emerged and can be staged from VE up to V2. Like corn, many soybean fields are starting to receive their first post-emergence herbicide applications. Several fields of oats are starting to head out. Most of the alfalfa first crop harvest has been completed, with reports of good to excellent harvest quality.

    “Pastures continue to look good as well. Recent field calls and questions have consisted mainly of weed management, small grains and forage management, and questions about corn and soybean stand assessments.”

    Central Iowa

    Meaghan Anderson (Region 7): “Central Iowa received a deluge of rainfall in the past couple days, with totals topping 5 inches in some places. Rainfall totals over the last week were mostly in the 1-2 inch range for my counties, but the areas that received heavier rainfall saw significant soil and residue movement, as well as ponding that will stick around for some time yet.

    “We have nice Encyclopedia articles on how long corn and soybean can survive in standing water, as well as resources on corn replant and soybean replant/filling in stands. The single report of true armyworm activity in fields with cover crops quickly turned into a significant hot spot of armyworm activity in Marshall/Hardin/Grundy counties last week.

    “They were still present yesterday and feeding has begun on soybeans. Most corn fields had the cover crop terminated early enough to miss the armyworm pressure. Most phone calls in the last week have been about weed identification and control, herbicide injury, and insect issues.”

    Southwest Iowa:

    Aaron Saeugling (Region 10): “Southwest Iowa is catching up on crop growth, with most all the crop planted in the final days of May. First cutting hay has been cut and most of it baled last week, a few fields remain. Hay yields were better than expected, especially after our cool spring. Pasture conditions have improved dramatically due to May rainfall and warmer weather.

    “Early planted corn and soybean are in the early vegetative stages and look good. Later planted crops are catching up and would welcome more sunshine and temperatures in the 80’s. Most of SW Iowa has missed the heavy rainfall, and over the last week received less than 0.5 inch.”

    East Central, Southeast, and South Central Iowa:

    Rebecca Vittetoe (Region 8): “This past week saw many field activities from wrapping up planting and starting in on sidedressing to post herbicide applications and mowing/putting up the first alfalfa cutting. Most corn is in the V3-V4 growth stage and soybeans VC-V2 growth stage. I’ve had a few reports of black cutworms being found in corn fields, particularly in  Johnson, Marion, and Mahaska counties.

    “Questions and calls over this last week included: herbicide injury, weed management, weed identificationreplant considerations, and insect scouting/management (mainly cutworms, armyworms, and bean leaf beetles).”

    Virgil Schmitt (Region 9): “Rainfall last week in the counties I cover was generally less than 0.5 inch. In general, temperatures during the last week in the counties I cover were one to four degrees above normal. Most corn is V3-V4 and looks good to excellent. Sidedressing is occurring. I have seen minor cutting from black cutworms.

    “Most soybeans are at VC-V1 and also look good to excellent. Alfalfa harvest is about 80% complete. Calls last week mostly involved weed management, weed identification, and black cutworm management.”

    Clarabell Probasco (Region 11): “South Central Iowa is in the stages of wrapping up the planting season and is shifting focus to herbicide applications. First cutting hay crop is also being harvested in many areas across the South Central counties. Slight rain showers were seen throughout the past week but were very isolated and typically only carried up to a few tenths of moisture with them.

    “Corn and soybeans are emerging and developing well. Many corn fields are in the VE-V4 stage, and soybeans are in the VE -V2 stage. Some areas are seeing crusting in fields that experienced heavier rainfall amounts after planting. Field calls have been centered around checking corn and soybean stands as well as weed identification and herbicide applications.

    “We have experienced moderate temperatures and the forecast looks to continue this pattern for the near future with chances of additional rain showers later on.”




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