We all know about the bugs, fungi and other small pests that can wreak havoc on grapevines, but winemakers in many regions face bigger problems. They range in stature from pocket-size rodents to predators weighing well over 500 pounds. Regardless of size or intent, they all pose a real threat to vineyards (and a winery's bottom line), and as habitats shrink and local climates shift, some of these visitors are becoming a more frequent problem.
Voles, relatives of mice, don't fit the typical vineyard pest profile, as they don't target grapes or shoots. They do, however, possess that one insatiable trait of all rodents: they love to gnaw. That can leave a grapegrower staring sadly at a vine left hanging in its trellis, completely detached from its rootstock.
Thankfully, Harry Peterson-Nedry of Chehalem Vineyards in Oregon's Willamette Valley says voles haven't been a big issue there since 2007. "Voles and similar burrowing rodents are occasional pests. Fortunately, normal freezes in winter seem to keep populations in control," he said. The best way to combat them? "In abnormal years, organic-friendly salts deposited in their burrows do the trick." Warmer years could cause problems down the road, however.
Deer, whose populations have exploded in some areas, represent a larger problem. But vintners have learned which fences can keep them out. "Deer were a problem in the early years with startup vineyards not able to afford deer fencing," said Peterson-Nedry. "Now with better capitalization—and deer fencing being a primary step in vineyard planning—deer have become less of a problem."
But deer become a bigger problem during stressful weather conditions, when they go looking for food. "Deer are only a pest in extreme conditions like 2011 when they attacked young vines with catastrophic results," said Bobby Cox of Pheasant Ridge winery in Texas' High Plains appellation.
Elk are another matter. "Deer fencing helps some, but if elk herds want to get into a fenced vineyard, they just walk through it," said Peterson-Nedry. He adds that their impact has been lessened due to a change in their habitat. "Elk are still around, but have been pushed into areas bordering the Willamette Valley."
John Skinner of Painted Rock in British Columbia may hold the record for the largest pest: black bear. He faced a worrying "infestation" six years ago. "In September of 2010, we noticed bear scat and evidence that they we eating our grapes overnight. As time went on, more bears arrived, having no problem climbing our deer fence.
"Losing fruit at night is one thing, but the bears started showing up during the day when our staff were busy at work among the vines," said Skinner. The arrival of a competing group of bears had forced the incumbent group to an earlier time slot. "We had to solve the problem with a higher, electrified fence, as well as an electric mat at the front gate."
Skinner expressed some admiration for his furry, uninvited harvest workers. "It was amazing how they would [move from] block to block as the varieties ripened sequentially. They started with our Chardonnay, then switched over as the Merlot was coming online. We were very fortunate that the bears got their fill before our Cabernet Sauvignon and Petit Verdot ripened. We lost 11 tons of fruit in three weeks."
Growers in Italy's Chianti Classico report that they are losing more than $10 million in wine grapes each year to a shorter pest—wild boars. The population of cinghiale has exploded in the past 30 years, and some vintners are blaming local hunters for leaving food out to attract the creatures. Boars are intelligent and both eat grapes and damage vines, sometimes uprooting them. New laws are supposed to bring the population under control, and vintners are erecting two fences—high ones to keep out leaping deer and low, stronger mesh ones to foil the boars.
The most unique—and quite possibly the most intelligent—vineyard pest roams the vines of South Africa's Cape Town region: the Cape chacma baboon. The large, social creatures have been known to break into rural homes looking for food. And vineyards are an easy target.
Prof. Justin O'Riain, director of the Conservation Conflict Research Institute at the University of Cape Town, has been studying the monkeys for over a decade. "Baboons are attracted to vineyards because they provide food for most of the year," he said. The animals eat the young tendrils and leaf buds in spring and come back for the grapes in fall.
The only device that has successfully kept baboon troops at bay is a modified electric fence. "Baboons will run through a standard multi-strand electric fence and accept the shock to get at the vineyard," said O'Riain. "A successful baboon-proof fence needs to include a mesh that forces the baboons to climb and grasp the electric wires."
But the city of Cape Town may have a less-intrusive solution in the form of a virtual fence. "When a troop enters the protected zone, speakers emit the sound of a predator, such as a lion. The baboons immediately sense danger and do not enter the zone," explained Johan van der Merwe, of Cape Town's Mayoral Committee for Energy, Environmental and Spatial Planning. "The virtual fence then becomes a virtual boundary zone in the mind of the troop and ultimately results in the animals staying out altogether."
It takes work to stay one step ahead of innovative animals. So if you're visiting a winery that has a tall, electrified fence, keep your eyes open.