UM expert: Fruit growers battle climate change
COLLEGE PARK, Md. — Over the last several decades, apple and blueberry farming has expanded far beyond the traditional fruit belts into regions such as Delmarva.
Growers in these areas now have to consider a new challenge, a University of Maryland fruit specialist said last month: climate change.
“We’ve seen a lot more warmer, wetter and windier weather,” Chris Walsh, a horticultural professor, said during the Extension’s virtual Bay Area Fruit Meeting on Feb. 10.
Walsh detailed the Extension’s research into apple orchard and blueberry farming. The university is continuously searching for ideal cultivars that thrive in the region’s unique weather and soil conditions.
“Where do we get the right germplasm to maintain orchard sustainability in the next decade or two?” he said.
Apple orchards face a number of challenges, particularly honeycrisp apples, which have become popular. Due to the region’s increasingly warmer, wetter weather, honeycrisps are prone to rot and cracks from swelling during rainy periods. In addition to fire blight, they are also bedeviled by unknown diseases, he said.
“Losses of trees in orchards has been a big problem for us in the last decade, and it’s something that most people don’t want to talk about,” Walsh said.
In response, the Extension launched two studies in Keedysville in 2010 and Queenstown in 2011. Wind turned out to be a major culprit.
“While we didn’t lose many trees to fire blight, we had a number of storms in 2011, 2013 and 2014 which lead to trees snapping off, in a number of different ways,” Walsh said.
Brookfield Gala and Cripps Pink cultivars were grown with varied rootstocks resistant to fire blight to identify the most resilient. The studies, which continued to 2017 and 2019 respectively, showed a 50-percent Cripps Pink tree loss with some rootstocks. While there was a 50-percent loss with a Geneva 41 rootstock and nearly as many with Geneva 935, almost 100 percent of trees with Geneva 202 rootstocks survived in both cultivars.
“If you’ve got open land around you, you really need to think about putting wind breaks in at the same time you’re putting the planting in,” he said. “So what we have is a tradeoff. We get fire blight tolerance on the rootstock, but then we are looking at a potential problem with wind damage.”
The Extension completed another study with Fuji trees in Queenstown between 2011 and 2019. Disease has been a major problem for Fuji apples on the Eastern Shore. Walsh said he was particularly excited about rootstock CG 5257, slated for release this year, which had a 100-percent survival rate with relatively high efficiency during testing.
“It was the toughest one to get out of the ground,” he said. “As we make the trees smaller and hang more and more fruit on them, they have no reserves to essentially grow roots, and if you take the trellis away, some of them almost fall off on their own. I’m not sure that we want ultra-efficient trees that just become more prone to root damage.”
Blueberry growers are also struggling to adapt to weather and soil challenges, particularly in the Delmarva region’s upland soil, which is very different than more typical blueberry environs such as Maine, New Jersey, Florida and Washington. Blueberries typically grow in spodosol, a coarse, acidic soil high in organic matter.
“I kind of view blueberry (pick-your-own) operations in many cases as the right plant in the wrong soil,” Walsh said. “Some varieties do well, but they really struggle to get going. Other ones struggle so hard that after two or three or four years, it’s a very frustrating thing when you think you’re going to get into production and the plants just haven’t done particularly well.”
An Extension trial in Upper Marlboro in 2018 examined Blueray — a northern highbush berry — and New Hanover, a southern highbush berry. The Blueray had limited sodium uptake.
“If you are doing something to fertilize and ameliorate your upland soils, be very careful with how much salt is going into the planting,” Walsh said. “Are you introducing sodium into the planting? I think that’s a big potential problem, and it may be an unseen problem.”