Iowa crop update for Aug. 2 to Aug. 8

August 8, 2016 5:17 PM
Blog Post

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

Paul Kassel:
There was not much rainfall this past week, and it has been about three weeks since we have had any major rainfall in most of my area. Corn is in the late milk stage to early dough stage. I saw my first field of corn that was in the early dent stage today.  

The soybean crop is in the R4 to early R5 stage. Soybean aphid numbers have been mostly on the low side to date, but since aphid numbers are on the increase some soybean acres have been treated with an insecticide. I did some see some sudden death syndrome (SDS) in some soybean fields, but at a low level.

North Central
Angie Rieck-Hinz: For the week of Aug. 1-7 we had from 0.2 to 2.13 inches across my nine counties. Parts of southern Hardin, Hamilton and Webster counties are drier than other areas. Corn is R4 (dough) to R5 (dent). Disease pressure continues to be less than years past with common rust and gray leaf spot being the most prevalent. I have seen what I am sure is Physoderma brown spot in one field.

Soybeans are R4 (full pod) to R5 (beginning seed). Sudden death syndrome (SDS) is showing up in more and more fields. There have also been some scattered reports of white mold. There are fields that have reached threshold for soybean aphids and have been treated; but once again, these are scattered. Producers should continue to monitor aphid activity until R5.5.

Brian Lang: My traditional scouting site near Decorah just tipped the scale on reaching threshold via Speed scouting (as of Aug. 1). The recommendation on the speed scouting card is to recheck the field in another three days to verify, and if so, then treat. Many fields in the region have less aphids than for my Decorah field site, but there are usually also a few 'hot spots' somewhere. Maybe this season my Decorah site is one of those 'hot spots.' Scout regularly to be timely with any treatments. Speed scouting is the easiest/best/quickest way to scout for this pest.  You can download a Speed Scouting card here: Speed Scouting for Soybean Aphid

When speed scouting, pull the entire plant out of the ground to more easily count aphids on the whole plant. Aphid distribution spreads throughout the plant, so do not just rely on what you see at the very top.

Mark Johnson: Soybean is in R4 to early R5, and corn is in R4 to early R5 in most cases; some late-planted is in R3. In soybean, I have not seen much SDS and no white mold. In corn, I’m also not seeing anything of concern. We did have a storm go through Jasper and Marshall counties Thursday evening. With the exception of some down corn south of Newton, there is no major crop damage that I am aware of.

South Central, Southeast, East Central
Rebecca Vittetoe: This part of the state caught some rain last week. Rainfall totals ranged from 0.5 inches up to 4+ inches of rain. A lot of the corn is now at R5 (dent), and soybeans are either at R4 (full pod) or R5 (begin seed).

Sudden Death Syndrome (SDS) is showing up in soybean fields. An uncommon disease I’ve seen in a soybean field this year is Anthracnose. In corn, gray leaf spot seems to be the disease of the year. Walking some corn fields I have spotted an occasional ear with Diplodia ear rot.

Meaghan Anderson: Corn in my area is mostly R4-R5, but a few fields are likely still in the R3 stage.  It looks beautiful, but I’ve heard some reports of pollination issues and poor kernel set in certain fields. Soybeans are in the R4-R5 stage, as well. They look really nice, but sudden death syndrome (SDS) continues to show up in this part of the state. The recent discovery of Palmer amaranth in two CRP fields in Iowa has everyone on high alert. Please scout newly-seeded CRP fields for Palmer amaranth and give your local Iowa State Extension and Outreach Field Agronomist a call if you find something suspicious.

Photo by Meaghan Anderson

Virgil Schmitt: In the last week, we had anywhere from 0.5 inches to over 2 inches of rain in southeast Iowa, and a heavier amount in the south, which is the area that needed it most. There was some wind damage to structures and some soybeans lodged.

Corn is R4-R5 and soybeans are R4-R5. In corn, some grey leaf spot is present at generally low levels. There is discussion about the impact of all of these warm nights on yields. In soybean, SDS is showing up more. Some industry people are pushing fungicides for Septoria brown spot in the lower canopy. You can find some bacterial blight, downy mildew, and Cercospora leaf blight in soybean.

Find your local ISU Extension and Outreach field agronomist here!

Related articles:
Iowa crop update July 26 to Aug. 1