Skip to Content

Crop Disease Update and Corn Planting Reminders

(Dr. Bob Kemerait)

Caution is the Better Part of Valor

After several weeks of unseasonably warm and often dry weather, the rains and cold weather are back for the rest of the week. From a disease management standpoint growers should be careful about getting in too big a hurry to plant. The kind of weather we have had has corn growers having to fight the urge to put seed in the ground; I know some already have. The cold in wet that is in the forecast will certainly be PERFECT for onset of seedling diseases and other problems. 

Despite the weather over the next few days, the La Nina winter (warm and direr) has certainly set the stage for increased problems with nematodes in our corn, cotton, peanuts, and soybeans, at least on the Coastal Plain. Growers need to anticipate this and recognize that variety selection, crop rotation, and use of nematicides at the beginning of the season are their only tools for what can make for a very long cropping season.

With cost of fertilizer and diesel and everything else, growers may hesitate to put a nematicide under their field corn. This could be a tactical error. Our field corn is attacked by root-knot, sting, and stubby-root nematodes in Georgia and we do not have resistant varieties to manage them with. Growers CAN use Counter 20G (5-6 lb/A and DO NOT use ALS herbicides with Counter [see more information below]), Propulse (8 fl oz/A) and Velum (3.0 fl oz/A). DO not mix a starter fertilizer with Velum or Propulse. Growers can also use Telone II (3 gal/A) if they wanted to. From my research, protecting corn against nematodes with these nematicides increases yields from not treating by 10 to 60 bu/A, depending on type of nematode and choice of nematicide.

(Dr. Eric Prostko)

Counter (terbufos) and Herbicide Reminders

1) Why is it a bad idea to apply certain herbicides, particularly ALS herbicides and some HPPD herbicides, following an in-furrow (INFR) application of Counter in field corn?

Both the insecticide and the herbicide are metabolized (i.e. broken down into non-lethal compounds) by the mixed function oxidase enzyme (MFO) system.  Simply put then, the use of both products overloads the field corn plant’s ability to metabolize the chemicals.  

2) What does corn injury from this negative interaction look like?

3) How much can corn yields be reduced?

4) Where can I get more info about herbicides that can or cannot be used following an INFR application of Counter?

a) Check out the the following information from AMVAC:

https://www.amvac.com/sites/default/files/_media/product/document/2022_Counter_Tech_Sheet.pdf

b) You should also be able find this information in 2022 Georgia Pest Control Handbook:

https://extension.uga.edu/content/dam/extension/programs-and-services/integrated-pest-management/documents/handbooks/2022-comm-chapters/Corn.pdf