The drier parts of the state finally received some much-needed rainfall, and unfortunately parts of southern Iowa that are pretty well saturated also received some more rain this past week. Herbicide injury in soybeans, yellow soybeans, corn rootworms, and foliar fungicide decisions were common questions or problems observed or received by ISU Extension Field Agronomists. Read on for more specifics on what’s going on in different areas of the state.
Joel DeJong (Region 1): “It was a very good week – significant rainfall finally occurred over much of the area. Rainfall was still somewhat spotty, but most measured at least an inch, with some reports up to 6 inches. The risk of running out of water still exists in much of the area, but at least we have “spoon fed” the crops for several more days. Tassels are emerging, as are silks, which should give us a good chance to pollinate successfully. We still have a long way to go. Rootworm damage on continuous corn acres became more visible with the storms that moved through the area, and adult beetle emergence has begun. While pollinating, be sure to walk your cornfields to insure that silks aren’t clipped and pollination completes successfully. On the soybean side, gall midges can be found on field edges in many locations, but no aphid reports yet. Cupping of several trifoliates is common on about 40% of the soybean acres, creating lots of discussion and concern. I have been in organic, conventional, Liberty tolerant, Round-up Ready and Enlist fields with this problem over the past three weeks.”
Gentry Sorenson (Region 2): “Much needed rainfall fell across the area last week in the form of some nice showers throughout the week. It was nice timing for many of these showers going into pollination for corn this week. The area has favorable weather forecasted for corn pollination with moderate temperatures and a chance of rainfall again this week. Corn started to tassel in many fields the past few days, and fungicide applications have also started this week in corn. I encourage growers to visit the ICM article “Can a fungicide benefit drought-stressed corn?”. This article will help with making decisions on fungicide applications to corn this year. Soybeans are at the R1 to R2 growth stage. Off-target movement of herbicides into soybean fields have been most of the incoming phone calls and field visits this past week.”
Terry Basol (Region 4): “Corn has started to tassel (VT) in the area, and the soybeans range from R1 to R2. The R2 growth stage is defined as an open flower at one of the two uppermost nodes of the main stem. Crop conditions in NE Iowa vary depending on rainfall amounts and soil types within fields. The northern part of the territory looks good, as it has had some nice rain events in the past couple of weeks, with up to 4 inches in isolated areas, whereas the Southern area has only received 0.25 – 1.0 inch according to the National Weather Service. For the NE Iowa Research and Demonstration Farm, the Iowa Mesonet reports of 1.18 inches from June 28 to July 11. The last couple of weeks have been busy with looking at soybean fields injured with growth regulator herbicides. Insect activity has picked up some, partly due to the drier weather conditions. I have noticed increased grasshopper activity as I’ve been walking through the grass looking at fields. Currently they are still small nymphs (see picture), and usually start feeding in the borders of fields, so continued scouting and monitoring is recommended. Also, keep a watchful eye out for two-spotted spider mites in soybeans as we continue drought conditions, I looked at my first soybean field this week that was infested. Spider mites cause damage on the soybean leaves called stippling. They use piercing-sucking mouthparts to feed on the sap on the underside of leaves, which produces tiny white or yellow spots, giving leaves a stippled or mottled appearance (see pictures). For more information on identifications and management decisions, check out this article here. Second cutting hay went well and primarily finished up last week, as the low humidity helped growers get it cut and harvested within 3 to 4 days.”
Josh Michel (Region 5): “Most of NE Iowa received some rainfall throughout last week and over the weekend. Up to 1 inch fell in parts of Allamakee, Clayton and Winneshiek counties, while areas along Highway 20 only received around 0.5 inch. Corn is generally around V11 to V12, and I would expect to see some tassels by the end of the week. Soybeans are generally around R1 to R2. Alfalfa second crop harvest is mostly completed. Oats are mostly headed out, with around 50-60% turning color. I’d expect any oats that are planned to be combined to start within the next couple weeks. Recent rains have helped provide some relief to pastures. Field calls and questions continue to center around pesticide drift complaints, as well as managing forages and small grains.”
Aaron Saeugling (Region 10): “More rainfall fell in the past week with some areas receiving over 3 inches. This was welcome for the corn and soybean crop with corn pollination now in full swing this week. Isolated wind and hail damage were reported, which cause some crop damage. Soybeans have made great progress with the additional rainfall and warm temperatures; most POST herbicide applications have been applied. Drift calls continue to come in concerning dicamba movement. Some insect activity is being reported across SW Iowa. The focus the next few weeks will turn to fungicide applications in corn and soybeans. Farmers should be on the lookout for northern corn leaf blight in corn because we have had ideal conditions for this disease to develop. These conditions include moist corn leaves (greater than 6 plus hours) and temperatures have cooled off to the ideal temperatures of 64- 81 degrees for disease development. More information on Northern corn leaf blight can be found here on the Crop Protection Network website.”
East Central, Southeast, and South Central Iowa
Rebecca Vittetoe (Region 8): “Tassels were just starting to poke out early last week in some cornfields, and by the end of the week it was not uncommon to see cornfields at VT/R1. Soybeans are mainly in the R2 stage, and the most common issues in soybeans this past week has been growth regulator herbicide injury and also why some soybean fields look yellow. Insects noted in fields this past week included grasshoppers, Japanese beetles, and corn rootworm beetles. If you have continuous cornfields, now is a great time to dig corn roots and evaluate for any rootworm feeding. I haven’t observed much for disease pressure yet, but with the recent environmental conditions continue to scout fields for diseases. Rainfall this past week was heavier in my southern counties with most areas getting 1.5 to 2 plus inches, whereas in my more northern counties, rainfall totals seemed to range from a couple tenths to about an inch. There was some hail and wind damage reported from the storm system that moved through last Friday.”
Virgil Schmitt (Region 9): “Rainfall during the week of July 5 to July 11 in the counties I cover was generally 1.5 to 3 inches south of Highway 92 and generally 0.75 to 1.5 inches north of Highway 92. There was some hail in Henry and Lee counties. In general, temperatures during the week of July 5 to July 11 in the counties I cover were near normal. Corn is generally V16 +/- a leaf collar to VT/R1 and soybeans are generally at R2. There are few insect or disease problems at this time. Many oats fields are turning color. Calls and farm visits last week mostly involved herbicide drift.”
Clarabell Knapp (Region 11): “The region experienced rainfall, tallying anywhere from 1 to 3 inches, over the course of a few days. Early planted corn fields are beginning to tassel, and fields that have hybrid splits are very interesting to look at as they are tasseling at different times. Most of the soybean fields in the area have reached R2. Field calls have been looking at soybean fields that are more yellow in color than normal due to the saturated soils. Wheat and oat crops are in the process of being harvested and yields have been average to slightly above average. Hay crops are continuing to be harvested in between rains and regrowth is coming well. Japanese beetles are being seen in many fields. It will be important to continue watching for insect and disease pressure."
Check out the map below to find your local ISU Extension field agronomist and find their contact information here!