University of Illinois Extension Specialists and Educators created the following checklist of common late planting questions.
Corn planting continues in Illinois - should I change maturities? For planting by mid-June, the northern tiers of counties probably need hybrids that are 105 RM or less. On the I-80 corridor it should be 110 RM or less. If planting opportunities extend later into June, even earlier maturities might be in order, but remember that such hybrids aren't developed primarily for use this far south, so be aware of the disease resistance packages of hybrids with maturity shorter than 100 to 105 RM.
What about Soybean? Should I be changing maturities as well? Soybeans with different maturities will flower around the same time (as soon as nights are long enough) when they're planted in mid-June. So there is little need to change to earlier maturing soybean varieties, but for producers north of I-80, varieties no later than MG 2.8 or 2.9 should be used if planting is delayed past mid-June.
Should I change seeding rates in corn and soybean with delayed planting? With corn the answer is no, except that planned rates more than 38,000 or so might be dropped to the mid-30s. With soybean, yes. It is important to consider increasing the seeding rates of soybean as we move later into the month of June. As planting date is delayed seeding rates should increase on a weekly basis such that by the end of June, soybean populations should be similar to those of double crop soybeans (~200,000 plants/ac). If the option exists, narrower rows also provide greater benefit in late planted soybean. Dr. Emerson Nafziger answers many common questions in his recent Bulletin article " Dealing with very late planting"
How can I control big weeds? Whether controlling larger weeds pre-plant, or controlling weeds on prevent planted acres, tillage is often the best option. Our goal is to kill the troublesome weeds, not to make them mad! Some weeds are difficult to control even with tillage as they get larger, an example being Marestail. 2,4-D applications are often ineffective against the established Marestail. Chemical options include glyphosate (we do have glyphosate resistant Marestail in Illinois) combined with metribuzin, or saflufenacil (products like Sharpen). Dr. Aaron Hager answers many weed control questions in detail in his article "Weed Management on Prevented Planting Acres."
Does wet weather mean more disease? It's all about the disease triangle! Disease occurs when you have the correct host, plant pathogen, and environment together. The longer those three factors are together, the more disease will occur. With very late planting, the likelihood of SCN and SDS may be decreased, Pythium and Phytopthora may still be an issue with wet soils at planting, regardless of the date. Don't ignore seed treatments! Dr. Nathan Kleczewski addressed these diseases and more in "What impact will late planting have on crop diseases"
Is there any good news?? Maybe with early season insect pests! Corn rootworm is nearing 50% hatch in central Illinois (June 3). The larvae are hatching into very unfavorable conditions. If they do not locate corn roots within several days of emergence or are in oxygen depleted soils due to saturation, they will perish. As planting is delayed, corn rootworm concerns diminish. However, farmers should scout for later season insects that may concentrate on isolated early or later planted fields, including Armyworms, Bean leaf beetles, Japanese beetles, or Stink bugs.
What to do with bare acres? Cover crops! Choosing the prevent plant option? Consider planting cover crops on those acres. Benefits include weed suppression, nutrient recycling and erosion control. If choosing a grass cover crop, growth regulator herbicides can be used to control later emerging broadleaf weeds (ie. Waterhemp). Economical grass cover crop options include Oats, Wheat and Cereal rye.
How do I make the decision on whether to plant or not? For more information, look at the University of Illinois farmdoc teams articles "Prevented Planting Decision for Corn in the Midwest" and "Prevented Planting, 2019 Market Facilitation Program Payments, Disaster Assistance, and Price Dynamics," for a quick rundown of these options, with examples.