By Clint Thompson
Strawberry plantings had not even begun this fall when alarm bells were ringing about the potential impact of Neopestalotiopsis disease in this year’s crop.
While the disease has a history in Southeast strawberry fields dating back to 2018, the concern this year stemmed from its presence in plug plants at nursery sources in Canada. It prompted Phil Brannen, University of Georgia (UGA) Cooperative Extension fruit disease specialist, to issue an alert on the UGA Extension Strawberry Blog.
“As far as we are aware, this is the first year that there has appeared to be a direct and immediate link to Prince Edward Island, and that is a major concern for the industry as we move forward,” Brannen wrote. “With that said, we have to do the best we can with the hand we have been dealt.”
Disease Background
Neopestalotiopsis has been a danger to strawberry plants every year since it was first discovered during the 2018–19 season on five farms. The disease’s initial discovery was attributed to one nursery source in North Carolina. More than 20 farms experienced the disease during the 2019–20 season after it was attributed to two nursery sources early in the season in North Carolina and Canada.
The disease’s confirmed presence in plants before they even left nurseries this year has left some producers in a no-win situation. Plant and risk the disease spreading. Don’t plant and don’t generate any strawberry revenue.
“It’ll be one of those deals where growers are going to have to make a decision because it’s a high risk. I can’t really tell them whether to plant or not plant. For some of them, I know they’re going to decide not to plant,” Brannen said in September. “If it’s a smaller operation and this is not their main livelihood, they can do without it for a year. If they’ve got like an acre or two you-pick and they just supplement their income with that, they may decide to hold off and wait another year.
“For other people, this is pretty much what they do. A lot of it is agritourism, but in the spring timeframe, a lot of these people depend on that for a major part of their income in some way. They’re going to have to find plants if they can. In that case, they may have to take plants that are coming through from the plug plant producers where they know they came from Prince Edward Island and could have this disease.”
Jeff Cook, UGA cooperative Extension agriculture and natural resources agent for Peach and Taylor counties, estimated that half of the plants utilized in Georgia and the Carolinas originate from Prince Edward Island. It’s the same place that had major nurseries informing customers that they are canceling orders or telling plug plant producers and growers to take plants at their own risk.
“I really appreciate the nurseries for being up front and transparent. I don’t think we used to see that in the past. They’re really being hurt but are still communicating. I think that’s really important that the communication is there,” said Natalia Peres, professor of plant pathology at the University of Florida Institute of Food and Agricultural Sciences Gulf Coast Research and Education Center. “They’re finding right now it’s impacting those growers that use plug plants, which we don’t use that much in Florida. We mostly use bare roots. It’s unfortunate because it shows it is spreading more to other geographic areas, especially other geographic nursery areas. It’s very concerning.”
X Factor
While alarm bells have been sounded over the disease’s potential impact in this year’s crop, experts agree the X factor will be weather conditions this winter before harvesting begins.
Neopestalotiopsis can lead to severe leaf spotting and blighting under favorable weather conditions, specifically during extended periods of wetness. That makes next spring’s weather a huge factor in whether the disease’s potential becomes a reality.
“The key word is potential. A lot will depend on their source of transplants of course, but really the weather and what we experience going into the spring,” said Ed Sikora, professor and Extension plant pathologist in the department of entomology and plant pathology at Auburn University.
“The information that came out of Canada and elsewhere that growers are basically starting behind the eight ball with potentially or likely infected transplants or tips definitely raises the level of risk, of course. However, if we go hot and dry again in the springtime, pre-harvest or during the harvest season, the disease might not be as bad as it could be.”
There is projected to be a La Niña weather pattern during the winter, which is expected to bring warm and dry conditions to the Southeast. That would benefit growers attempting to stave off the disease’s impact.
“Neopestalotiopsis is not easy to control when you start with infected plants. But if growers decide to take the risk, there are a few things we know already. For one thing, the weather conditions are going to dictate how much of a loss they’re going to have,” Peres said. “They’re going to have some loss by taking infected plants, but it’s hard to predict how much. If the weather is dry and not conducive, they might still be able to get a good crop. But if the fruit fields get some rains and there are conducive conditions, they might get hurt.”
Fungicide options are limited and not totally effective.
“We do know about some sprays that might minimize the loss. They’re not perfect. But Switch, Thyram and some DMI (demethylation-inhibiting) fungicides like Rhyme have been shown to give some suppression of the disease. I say suppression because it’s not really control,” Peres said.