Illinois Crop Update – August 4, 2023

Russ Higgins – Extension Commercial Ag Educator

Grundy County

Soil Conditions: Mildly Dry (soil is drier than normal, plant growth may have slowed)

Scouting corn this week, I’m starting to find some leaf disease, mostly lower in the canopy. To date, I have yet to find tar spot in fields I have visited but am aware it has been confirmed in Indiana counties east of NE Illinois. Predicting what if any yield drag may arise from our dry June should be easier to determine as we progress through the reproductive stages. An interesting comparison of ear size collected from two different fields can be seen below. The larger ear was collected from a heavier soil with greater water holding capacity. The second smaller ear was collected nearby growing in a lighter sandier soil on a knoll in the field.

Figure 1: Leaf Disease. Grundy County, Aug 2, 2023.

Figure 2: Ear size – heavy vs, sandy soils.

Doug Gucker – Extension Local Food Systems and Small Farms Educator

Macon County

Soil Conditions: Moderately Dry (soil is dry, plants may be browning or stressed, water bodies are low)

Early planted corn fields are in “dough” or R4 stage and later planted fields are in “milk” or R3 stage. Most soybean fields are in the “beginning seed” or R5 stage. In my 3-county area, the 9 straight weeks of being listed in the “moderate drought” category by the U.S. Drought Monitor has reduced our incidence of leaf diseases in corn and soybean fields. This week. a little SDS is just beginning to show up in a few soybean fields. The above SDS photo was from an area of a field with deep soil compaction.

Figure 3: Sudden death syndrome in soybeans just beginning to show up in a few fields.

Talon Becker – Extension Commercial Agriculture Educator

Champaign County

Soil Conditions: Moderately Dry (soil is dry, plants may be browning or stressed, water bodies are low)

With little rain over the past week, perhaps a few tenths over the weekend, soil conditions in most of Champaign County are on the dry side.  However, most fields of both corn and soy look relatively healthy with minimal external signs of drought stress.  Measurements from the local Illinois Soil and Water Survey monitoring station show plant-available soil moisture at depths of 8+ inches, and it seems that most crops in the area have been able to reach some of that deeper soil moisture.  That said, signs of drought stress including stunted plants and dying lower canopy leaves can be found in compacted areas of fields as well as the few hilltops we have in the county.  Tip dieback and ear size was variable in the corn fields I surveyed, and most were in the late R3 (milk) growth stage moving into early R4 (dough).  Soybeans were generally around R5 (beginning seed).

Figure 4: Soybean pods at R5 (beginning seed) on right and approaching R6 (full seed) on the left – Champaign County, August 3, 2023