Yellow bud bacteria has been spreading through the Vidalia onion growing region in recent years, but it is not considered an imminent threat and growers have not lost measurable volumes because of it.
Researchers at the University of Georgia-Tifton, led by plant pathologist Ronald Gitaitis have been tracking the bacteria and reported earlier this month that yellow bud has spread through the entire 20-county area where state-certified Vidalia onions are grown.
However, growers and others in the Vidalia onion industry said they are not losing sleep over the airborne bacteria.
“It’s been around, but I haven’t heard about that report,” said Kevin Hendrix, chairman of the Vidalia Onion Committee and vice president of Hendrix Produce Inc., Metter, Ga.
Bob Stafford, manager of the Vidalia Business Council, said the growers are aware of the disease, but it is not yet a major threat.
“We’re helping with some research and putting together some proposals, but we are letting Cliff Riner over at the Vidalia Onion and Vegetable Research Center sift through the information and advise us on the situation,” Stafford said.
The research center is in the heart of Vidalia onion country in Toombs County and has been working with growers and the industry since 1999. Riner, superintendent of the center, said July 21 he respects the work done by the university, but cautioned that growers have not had any economic loss to the yellow bud bacteria yet.
“Dr. Gitaitis is a world-renowned plant pathologist,” Riner said. “This is very interesting to researchers because it hasn’t been confirmed in other growing regions. We’ve seen it for four or five years now, but it is insignificant in terms of impact on the crop.”
Riner said the disease was “very hard to find” in the 2014 crop. “You might find 10 plants in a 30-acre field,” he said. “We have 12,000 acres of Vidalia onions total and I don’t think if you put together all of the plants we’ve seen with it in the past four or five years that you would even come up with one complete acre.”
Courtesy University of GeorgiaA disease so far unique to the Vidalia onion growing region, yellow bud is a bacteria that turns the onions' foliage yellow, as it has in this University of Georgia research speciemen. Vidalia onion growers say they have not had crop losses related to the disease, but they are monitoring the situation.When the bacteria’s telltale signs of yellowing foliage do appear, Riner said growers alert him and staff from the research center collects samples.
“Even when you do find it you don’t have yield loss,” Riner said. “You might have a little smaller size but it doesn’t change the overall yield or flavor of the Vidalia onions.”
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.”