Yellow bud bacteria does most of its damage in January and February, according to a news release from the university. That is particularly troublesome for the Vidalia onions because they are planted in late fall and grow during the winter. Sweet onions in warmer and drier regions would be less susceptible, Gitaitis said in release.
The bacterium lives on the leaf surface and survives on nutrients it leeches out. There can be remission, depending on weather, according to Gitaitis’ research.
Gitaitis reported the best method of control is copper bactericide.
“But it may be particularly difficult to control this bacterium in that manner as the timing of the spray is super critical,” Gitaitis said. “The spray has to be applied in advance. Once established on the leaf surface, this bacterium can colonize the hollow center of onion leaves and escape the bactericidal copper residue on the leaf’s exterior from that point forward.”