Determine The Reason For Late Emergence
We’ve all gotten rain and now we’re facing a week of cooler temperatures. These are good conditions for corn to be delayed in emergence and good reasons to scout recently planted fields.
Chilling injury and ponding
Chilling injury can occur when seeds take on cold water and/or seedlings are subjected to prolonged cold temperatures. Symptoms may include seeds that have swelled slightly but never germinate and corkscrewed, or otherwise deformed roots and especially shoots (the coleoptile). As you scout planted fields for emergence progress, be on the lookout for this type of injury. If widespread enough across the field, replanting may be necessary.
If seeds are underwater for too long, they could die due to lack of oxygen, a key component in germination. Just how long seeds and seedlings can remain viable under saturated conditions depends on temperature, but generally only a day or two can be damaging or deadly.
Growing degree days
With cooler temperatures, seeds may not have emerged because they lack growing degree days (GDD). Our general rule of thumb is it takes 110-125 growing degree days for corn to emerge, depending on the hybrid.
GDD are calculated by taking the maximum daily temperature plus the minimum daily temperature divided by two. After reaching that number, subtract 50. For the formula to work correctly, any temperatures above 86 degrees F must be entered at 86 and any temperatures below 50 degrees F must be entered as 50.
For example: if the maximum daily temperature is 60 degrees F and the minimum daily temperatures is 50 degrees F, there would 5 GDD for that given day. [(60 + 50) divided by 2] – 50 = 5.
Stay patient with the cool weather and slow accumulation of growing degree days. Pay attention to GGD for corn emergence instead of number of days. Corn planted into no-till fields, cover crops, fields with abundant crop residue, chickweed or bean stubble will require more GDD to emerge than corn planted into a clean field.
Regardless of the reason for delayed emergence in your fields, it’s important to remember that the longer a seed is in the ground without emerging, the more susceptible it is to injury, disease and pests.
It’s time to scout for alfalfa weevil infestations. Check out this Purdue University Extension map to determine alfalfa weevil development in your area. If you discover alfalfa feeding, consider treating or cutting early.
Check out this Penn State Extension website to evaluate the risk of Fusarium head blight (head scab) in wheat in your area. Wheat in our southern territories is likely to reach full flower this week, if not already. Using a fungicide during early flowering, Feekes stage 10.5.1, is most effective.
Give us a call if you need help this planting season,
Terry, Dan, Rod and Denny