WSU sweet cherry research integral to blossoming industry

Legend has it that the adolescent George Washington demonstrated his honesty when he confessed to chopping down his father’s lone cherry tree. Today, one of his myriad namesakes, Washington State University, is rectifying the Founding Father’s youthful indiscretion. WSU is demonstrating its commitment to state and regional agriculture through research and marketing innovations in support of the burgeoning sweet cherry industry — an industry for which Washington is the nation’s top-producing state.

Fondness for the fruit exhibited by Washington’s dad hasn’t diminished over the centuries. In fact, acreage and production rates of fresh cherries in the U.S. and the Pacific Northwest are on the rise. U.S. cherry production was about 276,550 tons in 2004, a 52 percent increase from 2002, according to the National Agricultural Statistic Service.

A record crop in 2005 saw 12 million 20-pound boxes harvested in Washington, Oregon, Idaho and Utah, according to the Northwest Cherry Growers in Yakima. Part of this was due to increased acreage, which, for example, has grown from about 25,000 acres in Washington in 2000 to 30,000 acres in 2006.

With growth comes the need for labor, which already is in short supply, according to the Washington Growers League. Because of their small size and scattered distribution in trees, cherries are known as the most labor-intensive fruit crop. But a sufficient pool of future agricultural labor is doubtful, due to potential changes in immigration reform and other issues.

Enter researcher Matt Whiting, WSU horticulturist at the Irrigated Agriculture Research and Extension Center in Prosser. Supported by a $40,000 grant from WSU’s IMPACT (International Marketing Program for Agricultural Commodities & Trade) Center, he has worked with the Washington State Tree Fruit Research Commission for three years to test a novel mechanical harvester that could decrease the need for manual labor in the sweet cherry industry. Preliminary testing has shown potential for the mechanical harvester to reduce harvest costs by 80-90 percent.

Whiting’s results were encouraging; 90 percent of the cherries were removed from the trees and, of those, 88 percent were collected and packaged. These levels are expected to increase if trees are trained to be more accessible to the mechanical harvester — what Whiting calls “matching biology with technology.”

But there may be a glitch. The harvester results in cherries with no stems. And that raises at least two questions: 1) does the shelf life of stemless cherries meet or exceed that of cherries with stems; and 2) will the public buy stemless cherries?

Hung up on stems?
Results so far show that 39 percent of consumers prefer the stemless cherries. That figure is from a study of 200 consumers in Calgary, Alberta, funded by the IMPACT grant and conducted by IMPACT fellow Jill McCluskey, associate professor in the School of Economic Sciences. The average price these customers were willing to pay for stemless cherries was $3.47 per pound.

In order to mechanically harvest cherries, a plant bioregulator must be sprayed on before harvest to loosen the stem-fruit junction. But 57 percent of the Calgary consumers surveyed said they are worried about the long-term effects of pesticides in agricultural production. The plant bioregulator involved — ethylene — is not a pesticide but a naturally occurring gaseous plant hormone. But it still could affect consumer decisions to buy stemless cherries, McCluskey said.

However, that could depend on how the information is presented. She noted that pears also are treated with a ripening agent, and they have not experienced a negative consumer reaction.

McCluskey plans to collect and interpret more data to more accurately examine consumer response.

Meanwhile, new Ph.D. student Erick Smith is working with Whiting to evaluate the shelf life and postharvest characteristics of stemless cherries.

While others at WSU have done research pertinent to the shelf life of cherries — for example, Eugene Kupferman in Wenatchee, Michael Willett and Gary Apel in Yakima, and B. W. Poovaiah in Pullman — there have been no similar investigations for cherries without stems. Whiting’s team will collaborate with John Fellman, professor and scientist in Horticulture and Landscape Architecture.

Improving varieties
Stems and shelf life are two factors that influence consumer interest in sweet cherries. Others include cherry variety and growing season.

While Bing cherries were the dominant variety 10 years ago, today’s growers are planting cherries that have been selected for being either late bearing or early bearing in comparison to Bings, Whiting said. He directs a sweet cherry variety breeding program initiated two years ago with funding from the Washington Tree Fruit Research Commission that evaluates, among other characteristics, harvest timing for more than 70 varieties and experimental selections.

Adding new varieties and planting at higher elevations has led to an 11-week harvest, and longer consumer season, compared to the traditional four-week harvest, said Roger Pepperl of Washington’s Stemilt Growers, the largest sweet cherry packing/shipping organization in the world.

Rootstocks also are changing, Whiting said. Many new orchards planted in Washington use new varieties grown on rootstocks that induce fruiting within three years from planting, compared to five years on the old rootstocks. The new rootstocks also reduce tree size, which means more trees (and fruit) per acre and, most important, easier and less-expensive harvesting.

WSU’s support of the cherry industry doesn’t end at production and harvest. Pricing and marketing research also is a valuable contribution. The total market value of fresh cherries in Washington was $236 million in 2004.

Thomas Marsh and Thomas Wahl have developed a straightforward model to predict the wholesale price of fresh sweet cherries. The model is what economists know as an inverse demand system.

“With help from IMPACT funding, we also identified key factors important to cherry pricing,” Marsh said. They found that the amount of cherries produced in each state, as well as the amount supplied to domestic and international markets, explained most of the variation in the annual fresh cherry price for Washington, Oregon, Utah and California.

The full paper discussing price influences, as well as the formula developed to estimate cherry prices, can be obtained by contacting Marsh at

In their study, the amount of cherries produced in each state had a smaller effect on price compared to the quantities supplied to foreign markets. In other words, if U.S. farmers produced more, prices domestically would not necessarily go down much. But the role of international markets can markedly affect cherry prices, the study found.And the international influence is expected to increase. Iran and Turkey are the top world producers of sweet cherries, but they are not significant competition to the No. 3 United States — yet, according to Whiting. Because of their short shelf life and the challenges of growing and packing, sweet cherries mostly are consumed domestically. But as growing, handling and shipping technologies improve, Whiting predicts these countries and China will become strong competitors, especially because they are closer to key export markets in the Far East.