Early reports of Goss’s wilt are showing up in Nebraska, which is your signal for intense early monitoring if you farm in the Corn Belt. Early wet weather and continued storms plus high humidity incubate the bacteria and spread it.
After several seasons of diffusion across the entire Midwest, all it will take to intensify the disease spread are the right conditions for bacterial growth.
June 30, 2017 — Scouting early and often can help detect early signs of the infection. You can find several extension web pages showing you what symptoms to watch for. One of the more detailed PDF reports comes from University of Nebraska plant pathologists, at this link: http://extensionpublications.unl.edu/assets/pdf/g1675.pdf
Udate July 7: Iowa crop consultant Bob Streit says that he has encountered several fields of corn testing positive for Goss’s wilt: “We found our first lesions about 3 weeks ago and it can be found on most plants that have reached the V9-V10 growth stage.”
He adds, “Many of our customers are having tissue testing done and realizing they need micros. WakeUP is going on with the micronutrients.”
Even before leaf or stalk symptoms emerge, you can read the “beginnings of stress” in your corn by digging some roots, splitting the stalks vertically and checking for brown staining and plugging of xylem tubes, especially in the root crown and stalk nodes. When the pith starts browning, it indicates disease organisms and their decaying residues are getting filtered out and deposited in the xylem. That weakens the plant’s ability to bring up nutrients and moisture, impairing its immune system. Early plugging symptoms are showing up on the stalk on the left (nearby photo) and more advanced plugging is occurring on the stalk on the right side. Since Goss’s wilt is sometimes introduced through infected seed, it can emerge under “incubator” conditions even though you don’t hear much about the disease in your neighborhood.
AgDia testing strips for clavibacter, the Goss’s wilt bacteria, are $50 for a pack of five strips ($140 for 25 strips), including the reagent baggies and instructions. You trim out a sample of the suspected corn tissue, chop it into small pieces and crush the pieces in the bag so juices mingle with the reagent in the bag. Insert the strip and watch for the indicators. When two pink lines form across the strip as shown on the nearby photo, it signals a positive reaction to for the Clavibacter michiganensis bacteria.
A few years ago, there wasn’t much you could do when seeing a Goss’s wilt invasion. Now there is at least one deterrent, an enzyme and miner-containing product called Bio-Empruv. One of our main WakeUP distributors, Central Iowa Agronomics, can provide Bio-Empruv for you. We tested it for two seasons on our own research farm. It was effective for improving yield, even when applied later than recommended. We didn’t spray until after tasseling. And as usual with foliar-applied products, WakeUP Summer enhanced effectiveness. The earlier you apply it, the more you’ll benefit from disease resistance and recovery.
Even before leaf or stalk symptoms emerge,Plugging of xylem shows up as brown stains in root crown and sieve tubes at nodes
Consultant Bob Streit’s current crop watch column on the Central Iowa Agronomics website observes:
“In past seasons about this time, extension pathologists have often announced that they have found the disease caused by Clavibacter bacteria. This happened around June 15 in Nebraska this season. I began seeing the caramel-colored lesions on corn plants around June 20 in fields that had received enough rain to allow the bacteria to form their brown slime.
“This indicates that plugging of the vascular tissue is beginning. In areas with lots of late planted corn acres this season, there’s potential for major yield losses from plants that will have their fill period cut short next fall. Growers had best be aware of this finding. Any rookies scouting for this symptomology might want to order their immunoassay strip kits from Ag Diagnostics out of Elkhart, IN soon, as in last week.
“At this point the lesions are small, but they are like a small fire in the attic. We hope to explore further the use of thermal imaging cameras to detect the disease appearing or moving into corn fields. This has been the case with an aerial pilot in NW Iowa who has such equipment. He has shown that he can detect the disease moving in, and then disappearing after the Bio-Empruv is applied. A three to five degree temperature rise from the disease is detected via the thermo-graphic equipment. Be sure to scout your fields, looking for leaves sloughing off near ground level from the brown, slimy mottling.”