Dry conditions causing crop stress, herbicide carryover and drift, nutrient deficiencies induced by the dry conditions, armyworms in forages, and a frost event in NE Iowa were some of the common or big issues or questions ISU Extension and Outreach Field Agronomists heard about or received this past week. Read on for more specifics about what’s happening around the state.
North Central Iowa
Angie Rieck-Hinz (Region 3): “Corn across NC Iowa varies in stage, but most is V7-V9. I am still receiving texted photos and phone calls about sulfur deficiency showing up in corn. Hopefully, if you got some rain this past weekend, that issue will resolve itself. If it continues to be dry in your location, you might expect to see these symptoms for a while longer. This does not necessarily mean you are deficient in sulfur, it means soils are dry and mineralization of sulfur from organic matter in soils is very slow this year. However, if you are not applying manure or any sulfur source, make plans now for a sulfur application for corn for next year. Soybeans are V3 to R1. For the most part soybeans are really short (so far) this year, mostly due to dry conditions. Most of my recent field calls, phone calls and texted messages are regarding herbicide carryover to soybeans, off-target movement of herbicides to soybeans, and iron deficiency chlorosis (IDC). I should note that herbicide carryover can be exacerbated by high pH soils causing those soybeans to look even more chlorotic and have more injury. Dry conditions can also slow soybean growth causing the plants to more slowly metabolize herbicides and consequently showing injury symptoms. I have seen very little insect or disease pressure in crops this year, but grasshopper pressure is increasing on field margins.”
Terry Basol (Region 4): “Drier conditions continue for NE Iowa. Corn ranges from V5 up to the V7 stage. All field operations are pretty much wrapped up for now. Leaf rolling can be observed in fields with lighter soils due to dry topsoil conditions. This is also a good time to start scouting for corn rootworm larvae, especially in fields with continuous corn. Soil texture, snow cover or residue, and depth of egg placement will all effect the ADD (accumulated degree days), which regulates corn rootworm egg hatch and development. Research suggests about 50% of egg hatch occurs between 684-767 accumulated GDDs (since January 1; base 52°F, soil). We expect to see corn rootworm adults emerge 7-10 days after reaching the peak egg hatch. Many areas have reached peak corn rootworm egg hatch, including NE Iowa (see map below). Soybeans are in the V4 to V5 stage for the area, and post emerge herbicide applications are very close to being finished up. Continue to scout for insect activity. If dry conditions persist, grasshoppers and spider mites are known pests to be aware of. We did receive some precipitation in the area over the weekend (June 17 & 18). The southern part of my territory (south of Waterloo/Cedar Falls) received about 0.5 inch and rainfall totals incrementally decreased northward to the Minnesota border. For this past week, according to the Iowa Mesonet, the NE IA Research and Demonstration Farm here at Nashua received 0.11” and 0.8” of rain on June 17 and 18, respectively.”
Josh Michel (Region 5): “Isolated light rain showers delivered small amounts of precipitation throughout NE Iowa over the past week. Generally, most of the area received less than 0.10 inch, although a few isolated areas were able to receive up to 0.20 inch. Because of the below average precipitation, crops are continuing to show signs of heat stress, especially on lighter soils. The current U.S. Drought Monitor shows most of NE Iowa is in D1 (moderate drought). Additionally, parts of NE Iowa experienced a very late frost event on June 12. Initial reports and crop assessments suggest that damage was only superficial and most of the affected crops will be ok. Most corn fields are currently around V4 to V7. Post herbicide and side dressing applications are finishing up in most areas. Soybeans are generally around V2 to V3, with many post herbicide applications finishing up. Due to reduced growth from limited soil moisture, there’s some growing concern about soybeans planted on 30-inch rows not reaching canopy closure. Oats are around 75% headed out and looking good so far. Alfalfa continues to slowly bounce back from first cutting, but regrowth has been very concerning and insect pest pressure, mainly armyworms and potato leafhoppers, continues to be a scouting priority. Pastures across most of the region are showing signs of moisture stress and recently were the focus of many armyworm field calls. Other field calls for the week centered around herbicide applications and injuries, weed identification and management, as well as crop assessments related to the drought.”
Photo courtesy of Hallie Sanderg, Linn County Extension Director.
Meaghan Anderson (Region 7): “Central Iowa was again the recipient of much-needed rainfall, with most of us getting more than 0.5 inch and some getting over 2 inches of rain on Saturday. Corn is really starting to take off, with many fields beyond the V10 growth stage now, green, and closing rows. I’ve noticed a number of waterhemp that will limp through the POST herbicide application and likely remain to produce seed under the corn canopy this summer. Rescue options are limited (but it’s not impossible) at this stage of growth. In some fields, nutrient deficiency symptoms are persisting, often related to compacted root systems or dry conditions. Corn under more substantial crop residue is very noticeable in many fields this year, with those plants often shorter and yellow compared to corn in less residue. Soybeans are in the V3 to V4 growth stage and I’m sure some are already beginning to put on flowers ahead of the summer solstice. I’m hearing a lot about the prevalence of soybean cyst nematode this year, so it’s a good idea to check your fields for this issue, especially if you’re noticing yellowing. Large yellow areas are also the result of iron deficiency chlorosis (IDC) that is apparent across central Iowa yet again this spring. Phone calls in the last week were mainly about herbicide mixes for waterhemp control, armyworm, and uneven corn.”
Aaron Saeugling (Region 10): “Southwest Iowa crop conditions are a mixed bag from excellent to abnormally dry. Corn is in the V8 to V12 stage and where precipitation has been over the past two weeks, the corn looks very good. Unfortunately, the western portions of Cass and a large portion of Montgomery and Pottawattamie counties continue to be short on moisture. Soybeans are slow and short in stature due to limited moisture; however, with recent rains in some locations, I expect them to begin shading the rows in the coming weeks. Time will tell how long the crop can last in areas with low subsoil moisture. Pastures are burning up and reports of wells going dry are starting to come in. Still not much activity on insect pressure in crop fields or pastures at this point except for a few grasshopper questions. River levels are extremely low, indicating lower than normal subsoil moisture.”
East Central, Southeast, and South-Central Iowa
Rebecca Vittetoe (Region 8): “Areas across East Central Iowa received some much needed rain over the weekend, but rainfall was again spotty. While some areas received over 1.5 inches of rain, others only received a tenth or less. Corn is mainly in the V8 to V12 stage, and soybeans in the V4 to V5 stage. I have started seeing more soybeans flowering here and there in fields, and I expect to see fields at R1 this week. Crops were showing more signs of stress over the last week with the drier conditions, especially in thinner soils or in more compacted areas. I also received my first report of spider mites. Just like the corn and soybeans, you can see the dry conditions really taking their toll on pastures and forages. Issues and questions received over the last week have included nutrient deficiencies (potassium in corn and soybeans and sulfur deficiency in corn), armyworms in pasture and hayfields, and herbicide injury (carryover and drift).”
Virgil Schmitt (Region 9): “Rainfall in the last week in the counties I cover has been generally less than 0.5 inch. Rainfall continues to be very hit-and-miss. Shallow-rooted grasses, such a bluegrass, continue to go dormant in many places. In areas where first cutting was taken early due to alfalfa weevils, mowers began cutting second cutting last week. It appears this will be a below average harvest in terms of quantity, but quality should be good. Armyworms in pastures and grass in areas along and north of Highway 30 was the hot topic last week. Some alfalfa fields have high populations of potato leafhoppers. Most corn is V8 to V9 and looks good to excellent except in areas of coarse soils, clay soils, and compacted areas. Questions about UAN left on the surface with applications after the May 8 rainfall event are coming in. People are wondering how much was lost and if dribbling on more UAN is warranted. Most soybeans are V3 to V4 and looks good to excellent except for areas of coarse soils, clay soils, compacted areas, and areas where crusting issues have lowered populations. Phone calls, emails, and field visits last week mostly involved sulfur and potassium deficiency symptoms in corn, compaction issues in corn, supplemental nitrogen for fields where UAN was left on the surface, and armyworms in pastures and grass hay.”
Clarabell Probasco (Region 11): “Over the past week many counties in south central Iowa have been added into the D2 drought zone while the remainders still sit in the D1 drought zone. Crop fields are showing the stress from lack of moisture across the region. Corn fields are around the V11 stage, and soybeans are around the V6 stage. Soybeans are staying short and branching out heavily and some fields are beginning to flower. First cutting hay crops are still being put up. The quality of hay is good for most fields, but tonnage harvested is down from average yields in years past. Majority of field calls have been in regards to the lack of moisture and crop stress.”
Check out the map below to find your local ISU Extension field agronomist and find their contact information here.