—by Matt Milkovich
Researchers shared both good and bad news about the spotted lanternfly during the Great Lakes Fruit, Vegetable and Farm Market EXPO in December.
The bad news: The invasive pest continues to spread across the United States, posing a threat to vineyards wherever it goes.
The good news: After a few alarm-filled years of uncertainty about their vineyards’ future, growers in Southeast Pennsylvania, SLF’s “ground zero,” are implementing management strategies that can control the invasive pest. Several growers have even resumed planting new vineyards, said Cain Hickey, Penn State University associate teaching professor of viticulture.
“SLF remains a problematic pest for vineyard owners, but the fact that new vineyard blocks are being planted is encouraging and suggestive of previous success in managing the pest,” he said.
But adapting management methods learned in Southeast Pennsylvania — where most grapes are destined for wine and harvested by hand — to other regions might not be a straightforward process. The other two speakers on the SLF panel, Michigan State University entomology professor Rufus Isaacs and Cornell University extension associate Jennifer Phillips Russo, both represent regions that predominantly produce processing grapes in mechanized vineyards.
Predictive models show that Southwest Michigan, the state’s largest vineyard region, would be an attractive environment for spotted lanternfly. No SLF have been found there yet, but a few have been found in nonvineyard areas in Southeast Michigan, Isaacs said.
The Michigan grape industry hasn’t been idle, however. After studying the lessons learned in Pennsylvania, Michigan growers now have multiple insecticides registered for use against SLF, including a special local-needs label that will allow for postharvest applications, he said.
“While a new pest is never welcome, our concern about (SLF) has gone down because we have tools and strategies to adopt out of the gate,” Isaacs said.
Spotted lanternfly hasn’t been found in the Lake Erie grape region, either, but growers there are wary of its arrival. Thirty-two thousand acres of vineyards stretch along the southern shore of Lake Erie — from Western New York southwest through Pennsylvania and into Ohio. Four out of every five acres are Concord grapes, most of them processed into juices, jams and jellies.
The pest can hitchhike on vehicles and railcars, and Lake Erie vineyards are transected by many railroad tracks connecting them to regions where SLF has already established itself. There are also some abandoned vineyards and woodlots that could serve as SLF reservoirs, said Phillips Russo, leader of the Lake Erie Regional Grape Program, a Cornell and Penn State partnership.
There are many unanswered questions about how to manage SLF in mechanized vineyards. Will the machines scare off or attract the pest? Will SLF end up in harvested grapes? How many additional insecticide sprays will be needed, and how many can growers afford? Processing grapes have slimmer profit margins than wine grapes, and the increased costs associated with SLF mitigation could easily exceed those margins, Phillips Russo said.
Processor concerns about potential SLF taint, cross-contamination and quarantine zones also must be considered. One or two SLF adults found in a 22-ton load of processing grapes could be enough to reject the entire load. In wine grape regions such as Southeast Pennsylvania, bugs can be removed by hand at multiple points in the process. But in mechanized regions such as Lake Erie, no human hands touch the crop from harvest through delivery to the processor, she said.
So, how can they keep the bugs out of the bins?
To start finding answers to these questions, the Cornell and Penn State researchers found a Southeast Pennsylvania grape grower with a mechanical harvester who was willing to leave a few of his rows unsprayed so the researchers could check his machine for the presence of spotted lanternfly after harvest.
“We were hopeful we weren’t going to find bugs in the mechanical harvester, and they would all fly away and life would be rosy,” she said.
Unfortunately, that wasn’t the case. About 60 percent of the bugs on the vines ended up in the harvested fruit, an unacceptable amount for processors. Phillips Russo’s team wants to gather another year or two of data to be sure, but she doesn’t expect the results will be much different. More research is needed to find cost-effective SLF mitigation options for mechanized grape regions, she said.
The EXPO speakers said one of the most effective things growers can do before SLF arrives is to eradicate any nearby tree of heaven, a favored host of the invasive pest. There’s also the option of preserving one tree of heaven as a trap tree. If or when spotted lanternfly infests the trap tree, inject it with insecticide to kill them all. •
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