Crop Update July 17 - July 25

We’ve got the terrible too’s in weather extremes across Iowa. Parts of northeast Iowa received too much rain and experienced flash flooding while many other parts of Iowa are in desperate need of rain and have seen too little rain. Iowa University Extension and Outreach field agronomists share crop reports on what they are seeing in their respected areas of the state.   

A flooded field on July 21, 2017 a few miles West of Fredericksburg as a result of the flash flooding that occurred in NE Iowa. For the most part, streams are now back in their banks and it is hard to see any remnants of the flooding or standing water in fields. Photo by: Terry Basol. 

A corn field near Ottumwa on July 24, 2017 that was really showing signs of the drought with leaf rolling and leaf firing. Photo by: Rebecca Vittetoe. 

Northwest Iowa

Joel DeJong (Region 1): “Rainfall here remains spotty, as it does in much of the state. Areas that have received rain recently typically got more last week, but the driest areas again received very little. About half the area I cover are in the Moderate Drought category, and the fields are exhibiting the stress that lack of rainfall provides. We have areas at less than 25% of normal rainfall for the last 60 days – meaning under two inches. Corn pollination continues, so we are watching that closely and will monitor kernel abortion over the next two weeks. Some areas look to be pollinating well, others are struggling, and ear tips still seem to be retaining silks (not pollinating). Soybeans are starting to grow pods, and in the areas where it is drier the canopy on 30” rows isn’t closing. A few spider mite calls have been received, mostly in corn. Aphids can be found a little easier than a week ago, but still not common or in high numbers. Dicamba movement calls are continuing.”

Stippling on a corn leaf caused by spider mites, which can be found on the under side of the leaf. Photo by: Rebecca Vittetoe. 

Paul Kassel (Region 2): "The dry weather continues this week. There are lots of cornfields on good soil that have their leaves rolled up and have a silvery appearance. We will see what the US Drought Monitor says this Thursday – but I expect much of Buena Vista, Clay, Palo Alto and Pocahontas counties to be under a ‘moderate drought’ designation. Much of Sac county has been under a ‘moderate drought’ designation since July 20. Off-target movement of dicamba continues to be a popular question. It appears that the soybean crop has was affected by off-target movement of dicamba are not recovering very fast. It is likely that the dry weather is reducing the ability of the soybean plants to recover from this injury. Fungicide application has begun also on corn and soybean crops." 

Cupped leaves from an uppermost node after a June 26, 2017 dicamba application in an adjacent field. Photo by: Paul Kassel. 

Northeast Iowa

Terry Basol (Region 4): “Most of the corn crop in NE Iowa has pretty much tasseled and is in the silking or R1 stage. For the early planted fields, some corn is beginning or in the very early R2 or “blister” stage. An interesting note; when the corn plant has completed the R2 stage, the ear will be at its maximum length. Foliar diseases continue to remain at low levels. Soybeans are primarily in full bloom or the R2 stage. Some soybeans have begun the R3 stage, in which pod formation begins, and you can find a pod at 3/16 of an inch in length at one of the 4 uppermost nodes of the soybean plant. Foliar diseases continue to stay at relatively low levels for soybeans as well. In regards to soybean aphid, populations are currently at low levels. NE Iowa received heavy rains and flash flooding with some areas getting as much as 7-10 inches July 21-22 (see image below from the National Weather Service). According to the Iowa Mesonet, we received about 5.5 inches of rain from July 16 through July 23 at the NE IA research and demonstration farm near Nashua.”

Radar estimated precipitation from 5 AM July 21 through 5 AM July 22, 2017. Source: http://www.weather.gov/arx/jul2117

Southwest and West Central:

Aaron Saeugling (Region 11): “Most corn is in the R2 with a few fields in the R3 stage. Corn has begun to fire in the bottom leaves. Isolated spots with little to no moisture in the past several weeks are turning grey and rolling in afternoons.  Some small pockets of common rust and Grey Leaf Spot have appeared last week. Moisture is need to slow kernel abortion in fields with moisture stress. Most soybeans are R2 to R3.  Hot temps and low moisture has caused them to be short. Spraying of fungicide continues and a few fields have been sprayed for Japanese beetles. Waterhemp is escaping in some fields due to dry conditions. Drift/ Vapor drift issues continue to occur. Early-sprayed fields with physical drift are recovering. Pastures are brown and going dormant in most cases. Supplemental feed maybe need in the next few weeks. Third crop alfalfa is and has been mowed in many cases. Quality is good however tonnage is short."

Southeast and South Central: 

Rebecca Vittetoe (Region 8): "The crops and pasture are looking pretty tough in this part of the state due to the drought conditions. Some areas haven’t seen much measurable rainfall since May. According to the U.S. Drought Monitor, I would say 80% of the area I cover is in a moderate drought, with the rest being in abnormally dry. Most of the corn pollination has wrapped up. In general it appears that corn pollinated, but not necessarily the whole ear. I’ve observed a lot of ear tips were the silks were still attached, meaning they didn’t pollinate. Now the question becomes how many of those kernels will we see abort and how much tipping back will we see? Additionally with the corn, I've also noticed fields firing with some fields having firing higher up in the canopy already, especially in compacted areas, areas with corn rootworm feeding, or areas that might have other issues affecting root growth. Soybeans are starting to pod. In general, soybeans are shorter this year, and it’s not uncommon to see fields that haven’t canopied yet. Seeing and hearing more reports about spider mites in soybeans as well as in a few corn fields. Most pastures are pretty dry and crispy. With not much feed left, many producers are feeding bales already. The Iowa Beef Center has a web page that lists several drought-related resources, found here for cattle producers looking for some additional information and resources. Additionally, I’ve had a few calls asking about taking corn silage already.”  

Variety of ear sizes seen in a corn field from near Leighton, IA on July 23. Note the silks still hanging on to the tips of the ears.Tipping back can also be seen on the larger ear as well. Photo by Rebecca Vittetoe. 

Virgil Schmitt (Region 10): " Rain continues to be spotty. Corn is mostly R1 to R3 and soybeans are R2 to R3. Generally health is good. Issues last week include Japanese beetles, Group 4 injury, and weed escapes (waterhemp, marestail, Palmer amaranth)."

Map showing rainfall totals for Iowa over the last week. Source: http://www.weather.gov.  

Find your local ISU Extension and Outreach field agronomist here!