Western Integrated Pest Management Center

 

by Steve Elliott

Western IPM Center

 

It sounds like an ad for a 1950s drive-in horror movie: Zombie plants emerge from New Jersey bogs! Can experts stop their catastrophic cross-county crawl before it’s too late?   

But this is not “The Day of the Triffids” meets “Creature from the Black Lagoon.” 

Instead, it’s the latest Western Integrated Pest Management Center-funded research, a bi-coastal project looking to keep West Coast cranberry farms safe from false blossom disease, an insect-spread pathogen that’s plaguing East Coast cranberry producers.

False blossom disease is spread by only one known insect vector, the blunt-nosed leafhopper. The pathogen doesn’t kill cranberry vines. Instead, infected plants continue to flower year after year but never again bear fruit.

“It’s a zombie plant,” said Cesar Rodriguez-Saona, an entomology extension specialist at Rutgers, the state university of New Jersey. “It’ll keep growing and using resources, but it won’t produce fruit. It just serves as a reservoir of disease and its only purpose is to keep transmitting the disease to other healthy plants.”

The good news for cranberry growers in Washington and Oregon is that neither the disease nor that particular leafhopper are known to be on the West Coast. And Laura Kraft, a cranberry extension specialist at Washington State University, wants to keep it that way.

Kraft is leading a Western IPM Center outreach and implementation project that hopes to leverage the experiences of East Coast growers to educate and prepare their West Coast colleagues. The idea came at a North American Cranberry Research and Extension Workers Conference last year.

“We had a tour of a facility in New Jersey where they sell cranberry vines and we kept asking questions about the disease and the blunt-nosed leafhopper and what they were doing about it,” she said. “They said, ‘Well, we’re not that worried because everyone’s got it.’ That set off alarm bells for me because we don’t have it. There’s something worth protecting on the West Coast.”

An Old Disease Resurgent

False blossom disease isn’t new. A century ago it almost destroyed the cranberry industry in the Northeast, until varieties that were resistant to leafhopper feeding were introduced and widely planted. Broad-spectrum insecticides introduced after World War II kept leafhopper numbers in check for the next several decades.

Then two things happened that unleashed false blossom again in the early 2000s: growers moved away from broad-spectrum insecticides that kill everything to more selective products that target the fruitworms and fireworms that actually feed on cranberries and cause economic damage, and at the same time growers widely planted new varieties that produce high yields and high-quality fruit but appear to be more susceptible to leafhopper damage and false blossom disease.

That brought about a resurgence in the use of broad-spectrum insecticides, more sprays, and tough questions for growers like Mike Haines of Pine Islands Cranberry Company, whose family has farmed cranberries since 1890.

“We scout our bogs in the pre-bloom stage with sweep nets, then we decide if we should treat or not based on the number of insects per sweep,” he said. “But what’s the threshold for treatment? With fireworms, there’s a number where it economically makes sense to treat. But leafhoppers, they’re not affecting us directly. They’re not consuming fruit. They’re not having an immediate impact this season, but it’s having a huge impact later when the plants are rendered unproductive forever.”

And there really aren’t cultural control options yet (although researchers are looking for them). Unlike citrus trees or blueberry bushes that can be removed and replanted if they’re disease-infected, cranberry plants form a dense intertwined mat across the bottom of a bog and it’s impossible to tell where one plant ends and the next begins. The only cultural control currently is to wait until the bog gets so badly riddled with false blossom that’s it’s no longer economically productive, then burn it all and replant the entire bog.

But how long do you wait?

“That’s crossed my mind,” Haines said. “We have a bog with a lot of false blossom and it still produces but yields less than that variety can produce. So you ask, ‘How much more can we be producing?’ But on the other hand, even if we’re still getting good production out of it, are we causing more problems by leaving that reservoir of infected material out there to spread the false blossom further?”

Capitalizing on Close Connections

To keep producers in Washington and Oregon from having to grapple with these questions, Kraft is hoping that experiences of New Jersey growers like Haines will help spur new vigilance among West Coast growers.

“At the research meeting, when growers learned I was from Washington they’d ask about growers out here by name,” Kraft said. “Cranberry growers travel around and meet other growers and I realized there’s this really strong connection between them.”

To tap into connection, Kraft and her Rutgers cooperator Rodriguez-Saona are producing two videos featuring East Coast growers speaking directly to their West Coast counterparts.

“One video will educate growers about the biology of the insect and how growers monitor for it and manage it, and about the disease itself and how to identify it,” Rodriguez-Saona said. “The second video will be about grower experiences with the insect and the disease because in New Jersey, most of them have the problem.”

It’s the grower-to-grower message Kraft hopes will resonate.

“There’s really a lot of trust between growers and a lot of knowledge that’s shared,” she said. “I think there’s potential for these growers in New Jersey to make this problem seem very tactile in a way that as a researcher I can’t.”

And Kraft hopes that will help West Coast growers become more proactive.

“I think there’s a lot of pessimism right now,” she said. “It’s like, ‘Even if we don’t have it, it’s coming.’ And I don’t think that’s inevitable. I’d really like growers to know that not only don’t we have it, but we have the tools to keep it that way. And even if we just delay it, if we get 10 more years of production without the extra insecticide and the extra herbicide and everything that goes with it, that’s huge.”

Kraft is promoting integrated pest management principles – avoiding the disease by purchasing only tested and disease-free plants and increasing monitoring for both the disease (which is easy to spot in a field) and the blunt-nosed leafhopper. 

And beyond avoidance, there may be opportunity. West Coast cranberry vines are disease-free, and that’s worth something to growers in all the cranberry-producing regions in North America. There may be a market.

“Right now, the industry sources all its vines from the East Coast,” Kraft said. “After a focus group with growers in Oregon, some growers went to their extension specialist and said, ‘Hey, we might be interested in propagating.’ Seeing propagation begin on the West Coast would be great.”

And seeing false blossom disease and the blunt-nosed leafhopper stay in New Jersey would be even better.

“It’s a big daunting task, but as an invasive species biologist, it’s so important to find these moments where prevention is possible,” Kraft said. “The best way to manage invasive species is absolutely at the prevention stage.”