Iowa crop update Aug. 9 to Aug. 21

August 22, 2016 3:37 PM
Blog Post

Iowa State University Extension and Outreach field agronomists report crop conditions in your area of the state:

Joel DeJong: In the northwest corner of Iowa, we received some rain more than a week ago, which was very beneficial since counties along the Big Sioux River had been missing many of the rainfall events shared widely throughout the state during the last couple of months. However, Lyon County, in the NW corner, still missed much of that rainfall. Most of the area I cover does look quite good at this point.

There aren’t a lot of disease issues out there, but we have had a few counties really see a big increase in soybean aphids, while others still have very low numbers. Treatment is pretty much done at this point, since beans are staged at R5.5 to R6. Corn aphids in a couple of counties have really grown in population, too. Not many diseases are present. Silage harvest has not started, but I expect it to begin soon.

Paul Kassel: Corn is in the late dough to early dent stage. Some corn is in the mid-dent stage - where the milk line is half way down the kernel. Corn aphids have come to life and are raising lots of questions. However, I looked at a field today and it appears as though the corn aphid numbers are declining rapidly. 

Soybeans are in the late R5 to early R6 stage. Insecticide application for soybean aphid is wrapping up. Some fields were treated for the first time last week and some fields that were treated in late July/early August were re-treated. 

Waterhemp problems have reappeared. Some fields that looked good earlier now have lots of waterhemp growing above the canopy.  For the most part however, farmers and retailers have done a good job of managing this weed this year.  

Brian Lang: Corn is early dent and soybeans are around R5-R5.5. I’ve seen some gray leaf spot and sudden death syndrome (SDS) in the fields over the past two weeks. Iowa State University (ISU) has an ongoing study assessing SDS, and is looking for sites with significant SDS in five to eight soybean fields within a 6-mile radius. If you know of region that might fit this requirement, please contact me. ISU plant pathologists would then like to collect plant samples from these fields for their study.

Mark Johnson: There was very little sudden death syndrome (SDS) showing in our area prior to the 4+ inches of rain we received Aug. 10-11. Last week, it showed up in many places, especially the areas that were dryer prior to those rains. Much of our area received 2+ inches of rain overnight on Friday night, Aug. 19.

Soybean aphids have not been high in our area, and now much of the soybean crop is at late R5, so spraying should be done for all but the latest fields. Scouting should continue for late-planted fields. Most corn is well in the dent stage with milk lines moving down. Very little in the way of disease or insects in my area. There have been some cases of Physoderma brown spot in Marshall and Jasper counties.

Aaron Saeugling: Most corn is in the R5 stage with silage chopping beginning this week in southwest Iowa. Isolated pockets of gray leaf spot can be found in fields in this area. At this point, the corn crop looks good. With adequate moisture all season, yields look to be good where water was not a concern early in the season. Bottom fields are suffering from excessive moisture and that could limit yield this fall. 

We have seen an increase in the amount of soybean diseases; most likely sudden death syndrome (SDS) and brown spot. Due to excessive moisture this summer, soybean growth is greater than normal. Currently, tall soybeans are causing lodging issues.

Pastures are responding to the cooler weather with good growth. Hay and alfalfa have been challenging to get baled in a timely manner, so quality could be reduced depending on moisture content at baling. 

South Central, Southeast, East Central
Rebecca Vittetoe: Over the past two weeks, this part of the state has received some more rainfall, ranging from a little over 1 inch to isolated areas getting more than 3 inches. Corn in my area is at R5, with the milking line starting to progress down the kernel. Soybeans are R5-R6.

In corn, you can find some spotty corn aphids as well as random plants with corn borer damage. In soybeans, the talk seems to be around sudden death syndrome (SDS) which is becoming more prevalent in fields. Remember to split the stem and double check to make sure what you are seeing is indeed SDS and not Brown Stem Rot.  
(Click on images for larger view)

Corn aphid in southern Iowa corn field    Corn aphid in southern Iowa corn field
Corn aphids, photos by Rebecca Vittetoe

Virgil Schmitt: Most areas received 2- 4 inches of rain during the last two weeks, with some areas receiving over 6 inches. Corn is early R5 to about 1/4 milk line. Gray leaf spot continues to expand. Soybeans are mostly R6. SDS continues to be the topic of conversation. I am aware of one farmer who had very high bean leaf beetle populations and treated.

Find your local ISU Extension and Outreach field agronomist here!

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Iowa crop update for Aug. 2 to Aug. 8