Regional Crop Update: Aug. 12 - Aug. 27, 2024

Soybean aphids, fall armyworms (mainly in southern Iowa), tar spot, and sudden death syndrome have been more of the hot topics or issues and concerns ISU Extension and Outreach field agronomists have been either hearing or seeing. Read on for more specifics about what is happening in fields around the state.

Northwest Iowa

Gentry Sorenson (Region 2): “We received a shower in the evening of Monday, August 26, but before that only trace amounts of rainfall were received across my region. Corn growth stage is R5, and soybeans are entering R5 growth stage. Replants and fields that were affected by rainfall earlier this spring are at varying growth stages. Corn diseases I am seeing are common rust and some northern leaf blight, but in low levels. Corn fields that suffered from wet conditions at planting look rough across my area. Soybeans diseases include white mold and SDS. Soybean aphids have also been found in fields in my region. Fields with levels above economic thresholds have been treated for soybean aphid. A recent article titled “Is it too late to Spray Soybean Aphids” is a helpful resource, for challenges with soybean aphid. Field calls and phone calls have mainly centered around soybean aphids, alfalfa, and nutrient deficiencies.”

Northeast Iowa

Josh Michel (Region 5): “Over the past two weeks farmers in NE Iowa have able to take advantage of the dry weather to stay caught up on alfalfa harvest. While some scattered showers came through the area, precipitation amounts generally ranged from .50 inches, up to 1.25 inches of rainfall. The rainfall has been welcomed as crops are beginning to reach the final stages before maturity. The majority of corn fields are reaching R5 (dent stage), prompting silage harvest to begin within the next 7 to 10 days for many operations. Southern rust and tar spot findings are beginning to increase, but shouldn’t be a concern due to how far along most fields are at this point. In general, most corn fields continue to look very good. Soybeans are generally around R5 to R6, and also look good at this point. I’ve received several field calls relating to soybeans aphids, and isolated pockets of SDS beginning to show up. There’s also some concern about fall armyworms advancing from the south before fields reach physiological maturity. Temperatures and precipitation will be critical for the next few weeks as our crops will work through the grain fill period and reach maturity.”

Central Iowa

Meaghan Anderson (Region 7): “Most of central Iowa received some rainfall in the last two weeks, including some isolated high rainfall totals in Madison County. Corn fields are mainly in the mid-R5 (dent) stage, with some fields on either side of that. The biggest things I’m noticing in corn are rootworm beetles seeking food, nitrogen deficiency and senescing corn, and leaf disease picking up in some fields. As we near the end of R5 and physiological maturity, it’s a great time to walk corn fields and check the ear leaves and upper canopy to see how far leaf disease advanced prior to maturity, push tests to check stalk integrity, and yield checks. Most soybeans are in the R5 growth stage as well, but some are nearing or are at R6 (full seed) and will soon start yellowing as they reach maturity. Soybean fields seem to have a little bit of everything in them, but aphids and waterhemp are the two most prevalent things I’m talking about with farmers in soybean fields. Soybean gall midge is more obvious in some fields where plants are wilting or breaking off at ground level, but it has overall been a quieter year for soybean gall midge in central Iowa.”

Southwest Iowa

Aaron Saeugling (Region 10): “Southwest Iowa has been very spotty for rainfall in August. Portions along Hwy 92 that missed a few rains and are showing advanced crop development, and the thin soils are showing their hand. Corn is in the R4 to R5 stage in most fields.  Recently, I have had calls on western bean cutworm damage as well as fall armyworm. Late disease has showed up in a few fields but overall minimal severity. Corn silage harvest has begun here this week, and we should get a good feel for crop yields. Soybeans are the fastest mover with hot and dry conditions. Soybeans are all over the board on growth and development. Earlier planted fields with earlier maturities should expect early harvest conditions. Dry areas are at R6 growth stage. Late planted fields or replant fields will need a rain and a LONG September to get where we would like them. Late season disease and lower canopy diseases are present but not a big concern in most areas of SW Iowa. Soybeans are always a guessing game on yield, but we have yield potential in areas that received good rains. Seeing lots of pods, but pod fill is challenging with severe heat and lack of moisture.”

East Central and Southeast Iowa

Rebecca Vittetoe (Region 8): “Before this last weekend and this week here, we’ve had more moderate to even cooler temperatures for August. Rainfall totals the last two weeks in my region have been between 0.5 to 1.5 inches. Some areas in Johnson County received the most rain, with totals just shy of 3 inches. With the recent warmer temperatures, we could use some rain. Corn is mainly in the R4 (dough) to R5 (dent) growth stages, and soybeans are mainly in the R5 (begin seed fill) to R6 (full seed) stages. I have started to see a few of the earlier maturity soybean fields starting to change color. On the forage side of things, there was a lot of hay put up in the last week. Some of that was due to fall armyworm pressure, especially south of Hwy 92. Late season tar spot, sudden death syndrome, and fall armyworms have been the main topics or issues I’ve looked at or have received question on. Additionally, now is a great time to do yield estimates in corn as well as to start monitoring fields for any stalk rot or standability issues with either the push test or pinch test.”  

Virgil Schmitt (Region 9): “Rainfall during the last two weeks in the counties I cover was from 0.5 inch to over 2.5inches, with the heavier amounts generally between Wapello and Davenport and lesser amounts with distance from those cities. Most corn is early to mid R5 and looks good. Low levels of gray leaf spot, tar spot, and southern rust can be found in most fields, but the levels are low enough that yields should not be negatively impacted. Most soybeans are at R5 to R6 and also look good. Some fields have leaves that are starting to scenese Minor Septoria brown spot in some fields and minor leaf feeding from Japanese beetles can be found in most fields, but levels are not a concern from a yield perspective. Some soybean fields in Scott and Clinton Counties are showing sudden death syndrome (SDS). A majority of hay fields were harvested this past week, with no rain, making the quality generally good. Fall armyworms are feeding in some fields along and south of Highway 34. Contacts last two weeks mostly involved diseases and fungicides for both corn and soybean.”

Check out the map below to find your local ISU Extension field agronomist and find their contact information here!