Signs of stress could be seen in corn and soybean fields, especially in the drier areas of the state with the warmer temperatures last week. Most of the corn either has pollinated or is pollinating and soybeans are in the R2 to R3 growth stages. Corn rootworm beetles, Japanese beetles, drought stress, weed escapes, growth regulator injury in soybeans, and questions on fungicides applications were questions or issues received/observed by ISU Extension field agronomists this past week. Read on for more specifics on what’s happening in different areas of the state.
Joel DeJong (Region 1): “Corn seems to be pollinating well, but not complete yet. Some long-term corn/corn rotation fields have had some silk clipping pressure, so be certain to scout fields to monitor pollination progress. Very low numbers of soybean aphids reported so far, but this usually seems to be the week when I start to get more reports, particularly near the Minnesota border. So, bean field scouting is a good idea, too. North of Sioux City we rarely get a report of Japanese beetles, but a few have been an issue further south. Very limited reports leaf diseases, but fungicide applications appear to be common. Rainfall was limited this past week, but these cooler temperatures are helping us buy some time in the dry NW corner – less rolling occurring the last couple of days.”
Gentry Sorenson (Region 2): “Rainfall ranged from a trace to a half of an inch across the nine counties that I cover. The counties of Buena Vista, Clay, Palo Alto, and Pocahontas are listed as D2 (Severe Drought) per the Drought Monitor. With the warmer temperatures and low rainfall over the past few weeks, some fields are showing stress in areas that have lacked precipitation. Pastures are showing little regrowth, with some pastures dormant from the lack of rainfall. Oat harvest progressed rapidly last week with many fields harvested and the straw baled. Second cutting of alfalfa was put up in many areas last week. The corn growth stage is VT to R1 and soybeans at the R2 to the R3 growth stage. Calls last week were about herbicide injury in soybean fields, questions about nitrogen in corn, and questions about fungicide applications to corn and soybeans.”
North Central Iowa
Angie Rieck-Hinz (Region 3): “Generally speaking, things are looking good in NC Iowa. There are areas that are classified as DO, or abnormally dry and this is reflected by dry soil in the upper 4-6 inches and crop stress showing on hot and windy days. For this past week we had 0.3 to 1.9 inches across the area, with northern counties seeing the higher rainfall amounts. After digging roots in several locations this past week, I would say the Highway 3 corridor umbrella is up as that area has drier soils than other places. Corn is R1 to R2. I have not noticed any pollination issues yet, but I did find some silk-clipping in two fields highly infested with western corn rootworm beetles. Disease pressure continues to be very low in corn. Soybeans are R2-R3. I have found frogeye leaf spot. And true to form, I have found some minor patches of phytophthora after some heavy ponding rains in northern Iowa.”
Terry Basol (Region 4): “Corn and soybeans are looking pretty good for the area. Corn fields for the area range anywhere from VT to R1. Corn leaves on average are still looking clean with low pressure of foliar diseases but continue to scout. Tar spot has been found in at least one field in Floyd and Chickasaw counties. Now is also a good time to survey and assess corn fields for corn rootworm feeding, as we are starting to see adult corn rootworm beetles. For more information on scouting, sampling, and using the ISU 0 -3 Node-Injury Score, click here. Soybeans in the area range from R2 to R3. Foliar disease pressure remains low in soybeans as well. Oats in the area have started turning and harvest has begun on the earliest seeded fields this past week, with the remaining fields to be harvested within the next couple of weeks if the weather remains warm and dry. As far as precipitation, according to the Iowa Mesonet, the NE Iowa Research and Demonstration Farm here at Nashua has received 0.72” of rain for the period of July 10 – 25.”
Josh Michel (Region 5): “Over the past week, most of NE Iowa has received anywhere from 0.25 to 0.50 inch of rainfall. Areas in Allamakee and Winneshiek counties however, received up to 3.5 inches of rainfall from a line of severe thunderstorms that came through early Sunday morning. Most of the corn has reached pollination. With fields in the early reproductive stages, I’ve received many questions about scouting and managing for tar spot. Thankfully, the weather for the past week has not been favorable for tar spot development, and producers are reminded to scout fields before making fungicide applications. I’ve also started seeing Japanese beetles in several corn fields but haven’t seen or heard of any reports of silk clipping. Soybeans can be staged from R2 to R3, as pods are beginning to develop in many fields. Japanese beetles have also started feeding in many soybean fields; however defoliation levels have been below threshold limits. I continue to receive calls and emails pertaining off-target herbicide injury, as well as weed management strategies regarding late-season waterhemp emergence. Oat harvest has started in several areas of the region with initial reports of average test weights and yields. Most 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.”
Meaghan Anderson (Region 7): “Hot and dry weather persists through central Iowa, with only the northernmost part of my area receiving much of a measurable rainfall in the last week (maybe 0.5-1.5”). The crops are showing some stress when you look at fields from the road and when you step inside corn fields, with some lower leaves firing on corn plants in drier areas. The cooler temperatures the last couple days have been nice but rainfall would be much appreciated. Corn is mostly in the silking (R1) to blister (R2) stage and we’ll soon be able to see how well pollination went when the kernels start to change color at R3. Disease pressure is low in corn, but we can find very occasional gray leaf spot, tar spot, and Physoderma brown spot. Soybean is in the R2-R3 growth stage and many fields are closing the rows; I’ve seen very low disease pressure in soybean fields as well but Japanese beetles are prevalent (but all below threshold levels). Weed escapes are prevalent in soybean, as many fields were sprayed when the weeds were just too big and weather conditions did not favor good kill. Questions in the past week have been on weed identification, fungicide applications and production selection, and Japanese beetle feeding/silk clipping in corn and soybean.”
East Central, Southeast, and South-Central Iowa:
Rebecca Vittetoe (Region 8): “You could definitely see the hot and dry weather take it’s toll on the crops this past week, especially in the southern half of my area. Unfortunately, parts of EC Iowa missed out getting much for rain this past week with some areas just barely getting the sidewalks wet to parts of Benton, Linn, and Jones counties getting 0.5 - 1 inch or more of rain. Most of EC Iowa is considered abnormally dry and parts of Washington and Keokuk counties are now in a moderate drought. With the dry conditions, I have had some isolated reports of spider mites showing up, so keep your eyes open. The hot and dry conditions have helped to keep disease pressure low in both corn and soybeans. I can see some gray leaf spot, a little tar spot, and common rust in corn fields. I haven’t really noted any soybean diseases yet. Corn is mainly in the R1 to R2 growth stages, and soybeans in the R2 to R3 growth stages. Questions this past week mainly involved fungicide applications and fungicide product selection for corn and soybeans, potato leafhoppers in alfalfa, Japanese beetles, and weed escapes.”
Virgil Schmitt (Region 9): “Rainfall last week in the counties I cover was an inch or less, with areas south of I-80 generally receiving 0.2 inch or less. In general, temperatures during the last week in the counties I cover were two to five degrees above normal. Most corn is R1-R2 and looks good to excellent except for areas showing drought stress. There are low levels of gray leaf spot in some fields and tar spot can be found here and there, but I have seen no fields that justify a fungicide application. Most soybeans are at R2-R3 and also look good to excellent except for areas showing drought stress. Again, disease levels are very low. Japanese beetles continue to be found in all the counties I cover. Potato leafhoppers continue to be present in alfalfa and there are winged grasshopper adults in grassy areas. Phone calls and emails last week mostly involved suspected dicamba drift, waterhemp management, fungicide application, and fungicide product selection.”
Clarabell Probasco (Region 11): “The past week in SC Iowa carried a lot of hot and dry weather with it. The northern row of counties in the territory have been designated as "abnormally dry" with part of Wapello and most of Jefferson County being designated as a "D1 drought" on the U.S. Drought Monitor map. Many corn fields have been tasseling and going through the pollination and appear to be pollinating well. Soybean fields are seen in the R2 and R3 stages across the area. Fungicide applications are continuing to be made in both corn and soybean fields. Japanese beetles are still making their presence known across the area, very heavily in trees. Second cutting of hay is in full swing across the region as well. Field calls have been centered around insect identification as well as herbicide injury.”
Check out the map below to find your local ISU Extension field agronomist and find their contact information here!