We did receive some precipitation in the area over the weekend (June 17 & 18). If dry conditions persist, grasshoppers and spider mites are known pests to be aware of. Soybeans are in the V4 to V5 stage for the area, and post emerge herbicide applications are very close to being finished up. Many areas have reached peak corn rootworm egg hatch, including NE Iowa (see map below). We expect to see corn rootworm adults emerge 7-10 days after reaching the peak egg hatch. Research suggests about 50% of egg hatch occurs between 684-767 accumulated GDDs (since January 1 base 52☏, soil). Soil texture, snow cover or residue, and depth of egg placement will all effect the ADD (accumulated degree days), which regulates corn rootworm egg hatch and development. This is also a good time to start scouting for corn rootworm larvae, especially in fields with continuous corn. Leaf rolling can be observed in fields with lighter soils due to dry topsoil conditions. All field operations are pretty much wrapped up for now. Terry Basol (Region 4): “Drier conditions continue for NE Iowa. Left: Potassium (K) deficiency in soybeans, found on lower leaves in young plants Center: Iron Deficiency Chlorosis characterized by chlorotic (yellow) leaves with green veins Right: HPPD, Group 27 carryover in soybeans, characterized by white leaf tips. Left: Potassium (K) deficiency in young corn characterized by yellowing of leaf margins on the oldest leaves Right: Sulfur (S) deficiency in young corn, characterized by interveinal striping. Dry conditions can also slow soybean growth causing the plants to more slowly metabolize herbicides and consequently showing injury symptoms. I have seen very little insect or disease pressure in crops this year, but grasshopper pressure is increasing on field margins.” Most of my recent field calls, phone calls and texted messages are regarding herbicide carryover to soybeans, off-target movement of herbicides to soybeans, and iron deficiency chlorosis (IDC). I should note that herbicide carryover can be exacerbated by high pH soils causing those soybeans to look even more chlorotic and have more injury. Soybeans are V3 to R1. For the most part soybeans are really short (so far) this year, mostly due to dry conditions. However, if you are not applying manure or any sulfur source, make plans now for a sulfur application for corn for next year.
This does not necessarily mean you are deficient in sulfur, it means soils are dry and mineralization of sulfur from organic matter in soils is very slow this year.
If it continues to be dry in your location, you might expect to see these symptoms for a while longer. Hopefully, if you got some rain this past weekend, that issue will resolve itself. I am still receiving texted photos and phone calls about sulfur deficiency showing up in corn.
Read on for more specifics about what’s happening around the state.Īngie Rieck-Hinz (Region 3): “Corn across NC Iowa varies in stage, but most is V7-V9. Dry conditions causing crop stress, herbicide carryover and drift, nutrient deficiencies induced by the dry conditions, armyworms in forages, and a frost event in NE Iowa were some of the common or big issues or questions ISU Extension and Outreach Field Agronomists heard about or received this past week.
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