With hot weather and few rain chances in the forecast, concern turns toward soil moisture reserves and the ever-important pollination timing in corn. ISU Extension field agronomists observed corn rootworm beetles, Japanese beetle feeding, grasshoppers, numerous diseases, and more off-target herbicide movement this week. As crops are now reaching reproductive stages, now is a good time to refresh your memory on corn and soybean reproductive staging. Read on for more specifics on what’s happening in different areas of the state.
Joel DeJong (Region 1): “Most of the region I serve is in one of the drought categories, and the weather forecast for the next 10 days concerns me a lot. We will see how well our hybrids handle the heat stress during and after pollination. On Monday afternoon, there was a lot of leaf rolling in many fields, particularly in the D-3 (extreme drought) area noted in the most recent Drought Monitor. We are presently similar to the amount of water available to the crop that we had at this time last year, but this forecast is much warmer, which means daily demand will be higher than we observed last year. Of course, areas that received more precipitation so far do look a lot better. Corn flattened by the Derecho of a few weeks ago have goose-necked back up, but likely will not tolerate stress quite as well. Not much greensnap was reported, fortunately. Tasseling has begun, and some reports of silk feeding by emerged western corn rootworm beetles in continuous cornfields have been reported. Don’t forget to scout! Grasshoppers on field borders seem to be causing more problems, also. Beans are blooming, and a lot of fields exhibit abnormal growth on the top part of the canopy here in NW Iowa – some of my “travel counting” would say about half the fields in many areas exhibit this injury.”
Gentry Sorenson (Region 2): “Rainfall was light across the area that I serve with only a trace of rainfall seen at several sites. Corn is at the late vegetative to R1 growth stage with tassels appearing in many fields across the area and in some fields silks are present. Corn that was damaged by the derecho has formed a gooseneck at the base of the stalk along with brace roots to right itself. Some fields are displaying greensnap damage that I have visited; I would encourage farmers to scout their fields to understand if you have greensnap damage. I am seeing grasshoppers in some field edges. Soybeans are at R1 to R2 growth stage. Concerns and questions this week were about soybeans that were damaged from off target movement and corn rootworm beetles.”
North Central Iowa
Angie Rieck-Hinz (Region 3): “Rainfall across the eight counties I cover ranged from 0.14 inches at Hampton to 0.65 inches at Eldora, which is 0.50 to 1 inch behind normal for that same week. With this week’s extreme temperatures and few chances for rain, our crops need to rely on soil moisture reserves. The Iowa Crop Progress report shows 27% of NC Iowa is short on topsoil moisture, so I anticipate seeing signs of crop stress this week, especially in those areas that were dry last year. From April 1 to July 18, Fort Dodge is at a negative 3.2 inches of rain compared to the long-term average. Corn is late vegetative stages to R1. The majority of soybean fields are at R2 or full bloom. I spent all day Monday, July 18, in Worth, Cerro Gordo and Mitchell counties and did not find any corn leaf diseases or corn rootworm beetles. I also have not found any soybean aphids yet. The majority of my phone calls are still herbicide related issues. “
Josh Michel (Region 5): “Over the past week, most of Northeast Iowa has received anywhere from 0.5 to 1 inch of rainfall. Some isolated areas in Allamakee, Clayton, and Winneshiek Counties however, received up to 3.5 inches of rainfall from a line of severe thunderstorms. Most of the corn in Northeast Iowa continues to grow rapidly and tassels can be seen in some of the early planted fields. With fields approaching reproductive stages, I’ve received many questions about scouting and managing for Tar Spot. Thankfully, the weather for the next couple weeks does not look conductive for Tar Spot development, and producers are reminded to scout fields before making fungicide applications. Soybeans can be staged from R1 to R3, as I was able to find several fields last week that had pods starting to develop. Fungicide applications have started taking place on soybeans in many areas, and I continue to receive many calls and emails pertaining off-target herbicide injury. The last remaining fields of second crop alfalfa were finally put up and generally regrowth is looking good so far. Nearly all of the oat fields I drove past last week have turned and I’d expect harvest to possibly start within the next week or so in some of the early planted fields. The majority of my field calls over the past week have consisted of alfalfa pests and scouting, Japanese beetles, small grains and forage management, herbicide injury in soybeans, and managing for Tar Spot.”
Aaron Saeugling (Region 10): “Pivotal weeks ahead for most of Southwest Iowa. A warm June and early July have allowed growing degree days make up for the cool damp spring this year. The counties of Pottawattamie, Cass, Adair, Montgomery, Adams, and Union in Southwest Iowa are in the D0 (abnormally dry) drought classification. Corn has been rolling in portions of Adams and Union County for a few weeks. Late planted soybeans are also suffering more form the lack of rain at this point than temperatures. South of Highway 34 corn is all tasseled and most soybeans have closed the row. North of highway 34 and East of highway 59 crops are a bout a week behind.
Insect pressure has ramped up this past week with reports of Japanese beetles, and gall midge. Fungicide applications have begun and will continue for a few weeks. Light disease pressure observed at this point in the growing season is observed. Group 4 herbicide symptoms have been observed across the region similar to previous years.”
Meaghan Anderson (Region7): “With the hot weather, we’d all appreciate a little drink of rain in most of central Iowa; most of my counties have gone over a week since we’ve had any substantial measurable rainfall. Crops are really moving along, with some soybeans beginning to shade rows and numerous corn fields now reaching the silking (R1) growth stage. In corn, rootworm beetles are beginning to emerge in larger numbers and we will start trapping for them next week in this area. While we can find disease in the corn canopy, including tar spot in some fields, remember the weather conditions that are conducive to spread – typically high relative humidity or extended periods of leaf wetness – which we may not see for some time given the forecast. Soybeans are mostly in the R2 (full bloom) growth stage. Most phone calls in the last week have been about herbicide injury in soybean (misapplication, off-target movement of plant growth regulators), Japanese beetle feeding in soybean, and tar spot in corn. While the majority of my counties are not currently on the drought map, we may start to see some effects of lack of rainfall and heat in the next week.”
East Central, Southeast, and South Central Iowa
Rebecca Vittetoe (Region 8): “Over the last week corn has gone from seeing a few tassels sticking out to whole fields are now at VT/R1 and are pollinating. I am seeing more corn rootworm adults emerging. With pollination, keep an eye on any silk clipping from either corn rootworms or Japanese beetles. From a disease perspective, I can find a little gray leaf spot and tar spot lower in the corn canopy at low levels and some common rust starting to come in, again at low levels. On the soybean side, most fields are at R2. Most of my soybean related questions have been on growth regulator injury in soybeans. I’ve also had some questions on defoliation in soybeans from Japanese beetles. With the hot forecast this week and corn pollinating, most areas would welcome some rain.”
Clarabell Knapp (Region 11): “As we move into the heat of summer, South Central Iowa has experienced smaller amounts of rainfall compared to the rainfall amounts that have occurred throughout the planting and early growing season. Over the past week, much of the area received a few tenths of rain out of a handful of systems that passed through. Corn fields can be seen in the late vegetative stages up to tasseling. The vast majority of soybean fields are in the R1 to R2 stages. Many of the questions I have received have been over Japanese beetles and fungicide applications in both corn and soybean fields.”