It’s the story of the haves and have nots when it comes to rainfall across the state. Unfortunately the areas that could really use the rain, seem to miss the rains. Consequently, some parts of the state are looking pretty tough with the drought conditions. Besides the drought conditions in parts of the state, other observations coming from the fields this week or topics of questions that ISU Extension field agronomists have recieved include: soybean aphids, spider mites, weed escapes, grasshoppers, and disease management. Read on for more specifics about what’s happening across the state.
Northwest Iowa
Joel DeJong (Region 1): “There are “haves,” and “have nots” in the NW corner of Iowa. Along the Minnesota border a nice rainfall occurred over the weekend. Much of this area looks quite good. However, the area of NW Iowa that needed rain the most received very little in most cases. Temperatures during the previous week certainly put pressure on the crops in the drier areas near the Missouri and Big Sioux Rivers. The western parts of Plymouth, Woodbury, Monona and Sioux counties showed the most stress, but crops improve as you travel east. In those drier areas you can find plenty of kernel abortion on ear tips, firing of lower leaves, and significant yield loss. Reports of silage harvest beginning in at least one field that didn’t pollinate well, and additional questions about early silage harvest were received. Bean stress in those locations is common, too. Spider mite injury was apparent in several Monona County fields, too. It is certainly a mixed range of potential in this region.”
Gentry Sorenson (Region 2): “Precipitation fell across the area with heavy rainfall occurring in some locations on August 6 to August 7. Reports were of up to 4 inches of rainfall in the northern tier of counties and lesser amounts further south in my region. Corn fields I scouted before the rain had low disease pressure to no disease found. The most prevalent disease found on stops was low levels of northern corn leaf blight, other diseases were not found on stops made while scouting. Before the rain, stress was showing in some areas of corn and soybean fields from lack of moisture. In areas shorted on rainfall, drought stress with leaf rolling and a gray appearance could be found on corn. Soybeans in impacted areas of dryness were flipping their leaves during the day. The Iowa drought monitor has five counties in my region under D2 (severe drought). Stress from lack of rainfall was seen in these areas during my crop tour before the rain.”
Northeast Iowa
Terry Basol (Region 4): “Corn and soybeans for NE Iowa continue to look good for this time of the growing season. Corn fields for the area range anywhere from R1 to R2. Foliar disease pressure for the area remains to be low. Depending on hybrid tolerance/resistance, gray leaf spot and northern corn leaf blight have been detected in some of the fields I’ve looked at in the past week, but at very low levels. A few more counties have been confirmed with tar spot. Counties in my area confirmed with tar spot include Mitchell, Floyd, Chickasaw, Butler, and Bremer counties. Soybeans are primarily in R3 and beginning R4. So far foliar disease pressure for soybeans remains to be low as well. Due to some isolated areas receiving higher rainfall amounts in NE Iowa, be on the lookout for Sudden Death Syndrome (in particular if you had wetter soil conditions at planting and a history of SDS in the past). This can be confused with Brown Stem Rot (to learn more on differentiating between the two pathogens, click here). Also, in regard to scouting, continue to scout for soybean aphid and bean leaf beetle feeding. As far as precipitation, we were blessed over the past weekend in the area with a nice weather event, which was welcome as the topsoil was starting to show signs of needing moisture. According to the Iowa Mesonet, the NE Iowa Research and Demonstration Farm here at Nashua has received 3.01” of rain for the period of July 31 through August 8, with 0.72 and 2.06 inches falling on August 7 and 8, respectively.”
Josh Michel (Region 5): “Over the past week, most of NE Iowa received 1 to 3 inches of rainfall, with isolated heavier amounts of 4 inches in parts of Buchanan and Delaware counties. Most of the corn in is currently at R2 to R4. I continue to receive calls about disease and corn rootworm management. Soybeans are mostly at R3 to R4, and I continue to receive calls regarding leaf defoliation and weed management strategies regarding late-season waterhemp emergence. I’ve also heard of some SDS starting to show up in a few areas. The majority of oats have been harvested, and I’d expect most of the remaining oats to be harvested this week pending favorable weather. Third crop alfalfa harvest continues across the region, as farmers scout for grasshoppers and potato leafhoppers. The majority of my field calls over the past week have consisted of alfalfa pests and scouting, soybean defoliation, small grains and forage management, weed management in pastures, and managing for corn and soybean diseases.”
Central Iowa
Meaghan Anderson (Region 7): ““Central Iowa farmers are mostly in the large swath of ‘have nots’ in the state again this week. A small band of storms came through on Sunday and provided some lucky folks with 0.5-2” of rainfall. Areas of corn and soybean showing significant stress have been getting larger and looking tough earlier in the day recently. While spring felt overly wet (and cold) this year, the last 30-60 days have been very dry, with the 30-day percent of normal rainfall mostly running less than 25% of normal in central Iowa. Corn development is moving along quickly, with most of the corn in the R3-R4 stage. Disease pressure remains low in most fields, but insect activity remains a concern. We are hearing of pockets of corn rootworm activity that will be concerning for future years. Soybeans are mostly in the R3-R4 growth stage as well. While Japanese beetle activity is slowing down, I’m hearing more reports of two-spotted spider mite activity that are concerning with the continued hot and dry conditions. Most phone calls in the last week were about soil fertility, disease pressure, weed identification, and pesticide drift.”
Southwest Iowa
Aaron Saeugling (Region 10): “Large portions of SW Iowa have missed timely and measurable rains during July and the first few weeks of August. Corn on the light soils is rolling and changing color daily. Heavy clay sidehills are brown and have essentially died. Most corn in in the blister to milk stage (R2-R3), so without rainfall in the next two weeks we are approximately three weeks ahead of normal and reproductive stages are occurring at faster than normal rates. Pollination appears to be good on most fields, but we are aborting kernels and tipping back. Soybeans are struggling as well with most beans in the R3-R4 growth stage. Later planted beans are short and have not closed the row, allowing a few weed escapes. Pastures are now dormant, and cattle producers are looking for supplements. The Greenfield Iowa Research Farm has less than 1 inch of plant available moisture as of August 8. In 2022 we had approximately 4 inches of plant available moisture at this time. SO, IT’S DRY!”
East Central, Southeast, and South-Central Iowa
Rebecca Vittetoe (Region 8): “Variable describes how things look in EC Iowa. The crops in the northern half of my area, which has been catching more of the rains, look pretty good. Unfortunately, the southern half of my area seems to continue to miss the rains and things are looking more tough. Corn ranges from R2-R4. In my drier areas, ears are starting to tip back and corn fields are firing pretty good in areas. Soybeans are R3-R4. Gray leaf spot, tar spot, and common rust continue to be the main foliar diseases I spot in corn fields. On the soybean side, I’ve noticed a little more bacterial blight and some pockets of SDS showing up. On the insect side of things, I’ve gotten reports of soybean aphids in Linn and Jones counties. I’ve also been able to find corn aphids lower in the corn canopy as well. Other insect activity has included corn rootworms (adults), grasshoppers, and two-spotted spider mites. Big questions this past week have been on weed escapes, spider mites, and nitrate testing in sorghum-sudangrass and corn.”
Check out the map below to find your local ISU Extension field agronomist and find their contact information here!
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 ...