If you are scouting for that notorious corn disease Goss's wilt, focus your attention on fields that are planted to susceptible hybrids, have a history of the disease, have surface corn residue, and have been recently injured by severe weather. That's the recommendation of Alison Robertson, Iowa State University Extension plant pathologist.
This past weekend, Dr. Tamra Jackson-Ziems at University of Nebraska-Lincoln reported that Goss's wilt had been spotted in multiple cornfields in three counties in south central and eastern Nebraska. She suspects that infection may have occurred as a result of plant wounding due to severe storms earlier in the growing season. The infected corn plants were at the V6 growth stage and had characteristic lesions of Goss's wilt. A few plants were systemically infected.
In Iowa, Goss's wilt was found on a few plants in a field Calhoun County on Monday, June 11 (see photo). The field had been planted to a very susceptible hybrid in 2011, had severe Goss's wilt and crop residue was present on the field surface, says Robertson. She says strong winds that have occurred in the area likely caused damage to the leaves and enabled infection.
If you are scouting corn fields for presence of Goss's wilt, here's what to look for
The Goss's wilt bacterium, Clavibacter michiganensis subsp nebraskensis or CMN, survives well in infested surface residue. "Infection is usually associated with severe weather events that injure the corn leaves and thereby enable entry of the bacterium into leaf tissues," says Robertson. "In the greenhouse, we typically see symptoms on corn seedlings 10 to 21 days after inoculation with CMN."