Crop Update August 15 - 23 (NW, NE, and SE IA)

Iowa State University Extension and Outreach field agronomists report crop conditions in NW, NE, and SE Iowa. 

Northwest Iowa

Joel DeJong (Region 1): “The rainfall amounts in NW Iowa during the past two weeks have been quite generous, for the most part. Some in the area, with about 10 inches of rain during that time, might think it has been nearly excessive. However, it has taken so long to total those amounts for the summer that I believe no one is going to do much complaining. Soybeans are starting to fill pods, so this rain is greatly appreciated for that crop. Corn is reaching the early dent stage, and this moisture is increasing kernel weights in most fields. There is no doubt that some locations will have greatly reduced yields, but others will still perform quite well this fall. Aphid numbers have reached thresholds in some fields, but in less fields than in many other years. Plus, the grass in greening up again – making everyone feel a little better. Finally, I believe that the dicamba drift calls are tailing off."

Rainfall totals across the state of Iowa for the last 14 days as of August 21. Source: www.weather.gov.

Paul Kassel (Region 2): “A large part of my area has received some decent rainfall amounts in the past few days. Many of the weather stations in my area reported three to five inch rain totals for the August 15 to August 21 time frame. Corn is mostly in the late dough stage (R4) to early dent (R5) stage. Corn in some of the really dry areas has progressed a little faster and is in the ¼ to ½ milk line stage. The recent rainfall may really benefit the soybean crop. Much of the soybean crop is in the late R5/late pod stage to the early R6/full bean stage. Soybean aphid populations have increased lately. There are some fields that are currently scheduled for insecticide application. Farmers are encouraged to check for soybean aphid activity through the late R5/late pod stage to the early R6/full bean stage.”

Ears of corn from 99 day hybrid on the right and 111 day hybrid on the left from Pocahontas County. Photo by Paul Kassel.

Northeast Iowa

Terry Basol (Region 4): “Crops in general for NE Iowa remain to look good. Corn is primarily in the R4 or dough stage yet with early-planted fields beginning the R5 or dent stage. According to NASS (National Agricultural Statistics Service), as of August 20, 15% of the corn has dented in NE Iowa, which is up 6% from last week. On average, it takes a little over 30 days for the corn to go through the R5 stage, depending on growing degree-days. There have been some reports of Goss’s Wilt in the North – Northeast part of Iowa. For more information on identifying Goss’s Wilt, please click on the following links: Tips for Diagnosing Goss's Wilt and Leaf Blight & Goss's Wilt and Leaf Blight. Soybeans are primarily in the early stage of R5 or beginning seed fill (seed is 1/8” long in the pod at one of the four uppermost nodes on the main stem). Foliar diseases have continued to remain at very low levels throughout NE Iowa. Soybean aphid populations also remain low for the area, but continued scouting and monitoring still needs to be conducted until the soybeans reach the R5.5 stage. Precipitation was welcome this past week, as we received about 1.2 inches of rain from August 14 through August 21 at the NE IA research and demonstration farm near Nashua, according to the Iowa Mesonet.”

Southeast and South Central: 

Rebecca Vittetoe (Region 8): “Like other parts of the state, some much needed rain finally did fall over the past week. It was spotty with some areas having rainfall totals of less than an inch and other areas with 4 inches or more. We’ll take what we can get though. The rain will help with grain fill in the corn and pod fill in the beans. It will also benefit the pastures and alfalfa fields. Corn is mostly R5 or dent and the milk line is starting to progress down the kernel. I'm seeing in some areas 1/4 to 1/2 milk lines on kernels. Soybeans are primarily in that R5 stage, which is beginning seed fill. Some soybean fields are showing quite a bit of yellowing, especially on the poorer soils. Yields are going to be variable not only from field to field but even across the field this year. The major pest issue now is the weed escapes in soybean fields as well as corn fields. I encourage you to double check that those waterhemp are really waterhemp and not Palmer amaranth." 

Corn ears all taken from the same field in Wapello County. Ear size was quite variable. Photo by Rebecca Vittetoe. 

Starting to see more soybean fields with yellow areas appearing in them. Photo by: Rebecca Vittetoe. 

Meaghan Anderson (Region 9): “Much needed rains hit east central Iowa in the last week, providing some hope for grain fill in corn and seed production and pod fill in soybeans. Crops are continuing to look extremely varied across my area - from the garden spot of Buchanan County to the much drier Keokuk County. Stressed areas are showing up frequently in soybeans and are worth investigating to see if you can determine why the particular area is suffering more than others. I suspect SDS may also begin to show up in some fields now that my area has received rainfall. Now is a good time to begin checking corn for yield estimates and keeping an eye out for anything that might lead to grain quality issues this fall like insect-damaged kernels, ear rot development, or poorly-filled kernels. Calls continue regarding potential for yield loss in dicamba-injured soybeans and what to do about waterhemp escapes in soybeans. The first question requires a wait-and-see approach, while the second has a simple (but annoying) answer. The best revenge on weed escapes in soybeans this time of year is hand removal. While you're out, make sure none of those waterhemp are Palmer amaranth!”

Virgil Schmitt (Region 10): “Rainfall during the last week ranged from zero to a little over an inch, with zeroes and over an inch being observed in both my northern and southern counties. In general, lack of rainfall along and south of Highway 92 causes crops to continue to struggle. Corn is generally in R5 and about ¼ - 1/3 milk line. Common rust is common (pun intended). Soybeans are generally in late R5. Soybean death syndrome is showing up north of the Highway 92 corridor and cercospora leaf blight is common. Beside the weather, Japanese beetles, waterhemp, Palmer amaranth, and dealing with hail damaged crops were the main issues last week."