By Ryan McGeeney
U of A System Division of Agriculture 

Researchers with the Cooperative Extension Service are studying an emerging disease impacting strawberries in an increasing number of locations across Arkansas in recent months.

Aaron Cato, extension horticulture integrated pest management specialist for the University of Arkansas System Division of Agriculture, said the disease was initially detected in Arkansas in 2020 but has kept a low profile until this year.

“It’s not completely new to Arkansas,” Cato said “We first saw this neopestalotiopsis several years ago — it killed a bunch of plants at one farm and in some of our trials. It’s not new to specialty crops per se, but this aggressive disease is new to the strawberry landscape in the United States.”

Neopestalotiopsis is a genus of plant pathogens belonging to the family Sporocadaceae. While the fungus is pathogenic in strawberries, it does not pose a health risk to humans.

Cato said growers in Florida were first confronted with the disease in large numbers in 2018. In 2020, the fungus “blew up in the nurseries that produce strawberry plant starters, and seemed to be related to excessive rainfall.

“It’s ‘new’ in the sense that we don’t fully understand it,” he said. “But we’ve been on the lookout for it for the last five years.”

Cato said researchers have not yet clearly identified the various causal strains of the fungus, or which species they belong to.

“This happens sometimes when we get new crop pests,” he said. “This fungus is something we might have seen randomly in the past. You might find it on a plant here and there, but it’s never been aggressive or widespread enough to cause problems for most growers.

“The ‘newness’ of it is that it’s either a shift in strain, or even a new species of this neopestalotiopsis,” Cato said. “We know it’s not just one species — there’s two or more aggressive strains, or some kind of species complex, because we see differences in how plants react, how damage occurs, and so on.”

Cato said that depending on the causal pathogen, strawberries may suffer from “crown rot,” which will cause the plant to collapse and die in plug trays or when they begin to produce fruit if not sooner, or “fruit rot” and “leaf rot,” which tends to attack plant leaves and is more visually identifiable. The crown is where the plant’s leaves and roots originate.

“There’s just a lot to nail down before we can definitively say, ‘yes, this is what you’re dealing with, this is what you can expect and here’s how to deal with it,’” he said. “We’re just not there yet. Growers are really trying to do everything they can with an integrated approach to prevent losses in a high-risk year.”

Managing the fungus

Cato said several fungicides commonly used in Arkansas strawberries are not necessarily effective in controlling the new fungus. Many growers are relying on cultural practices, such as destroying any plant that looks as though it may succumb to the disease and trying to reduce transmission between plants through touching.

“I think growers have just buttoned up their operations, in addition to using fungicides we know are effective from work in Florida and Georgia,” he said. “I’ve been to a lot of farms where they’re doing a good job keeping the pathogen at bay and are now producing bumper crops.”

Cato said researchers expect increased fungal activity in strawberries as temperatures rise in May, especially if rainfall is pervasive.

To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit www.uaex.uada.edu. Follow us on X and Instagram at @AR_Extension. To learn more about Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website: https://aaes.uada.edu/. Follow on X at @ArkAgResearch. To learn more about the Division of Agriculture, visit https://uada.edu/. Follow us on X at @AgInArk.