Penn State research has helped shape apple industry

Jeff Mulhollem
August 17, 2016

UNIVERSITY PARK, Pa. — One glance at a commercial orchard today and you realize these aren't your grandfather's apple trees. Long gone are the 40-foot-high, widely spaced, gnarled and spindly trees of the past. They have been replaced by squat, tightly planted trees loaded with low-hanging fruit.

Key to the transformation has been research conducted at Penn State and other land-grant universities, and Penn State horticulture professor Rob Crassweller has been at the forefront of the effort to boost apple production for more than 30 years. In his role as a faculty member with Penn State Extension, he has presented those findings to growers.

The University's College of Agricultural Sciences has been conducting research on apple tree rootstock at the Russell E. Larson Agricultural Research Center at Rock Springs since the early 1970s, when horticulturists from a number of universities in the Northeast banded together to form a project called NC-140. That federally funded initiative continues today and Penn State will host its annual meeting in November.

"It is a group of us involved in pomology representing 20-some states, three Canadian provinces, and even a cooperator in Mexico," Crassweller said. "We have been cooperatively evaluating rootstock since the mid-'70s because rootstock controls tree size, and we must have size control since we don't want trees to be 40 feet tall. We want them to be no more than 14 feet high — so we can pick all of the fruit from the ground."

In recent years, Crassweller has also been working with the Midwest Apple Improvement Association, helping it evaluate and develop new cultivars. New apple varieties created by breeders have revolutionized the apple industry, he noted. For example, the Honeycrisp variety — which he had a hand in evaluating — has set the apple market on its ear.

apples on tree

Thanks to research that developed new training systems conducted at Penn State, growers are able to plant apple trees one year and actually get some fruit from them the next, and certainly in the third year they will have a good crop. The emergence of the Honeycrisp variety (shown here) has changed the apple market.

IMAGE: Courtesy University of Minnesota Extension

"Although Red Delicious is still the most commonly grown variety, Honeycrisp is catching up, mostly because a 40-pound box of Delicious apples will bring $20-$24 and the same size box of Honeycrisp apples will bring $50 to $60," he said. "People really do like Honeycrisp apples, but I think the price will go down some as supply catches up with demand."

Crassweller's research has helped growers keep up with changing demands in the apple market because it is not easy for them to change the varieties they produce. It takes time to develop new orchards. "Usually, an apple orchard will be there for 20 to 25 years, so growers are reluctant to change varieties, but because of the new training systems we have developed, growers are able to plant apple trees one year and actually get some fruit off them the next, and certainly in the third year they will have a good crop," he said.

"That is totally different from when I started, when we were looking at five to six years before we would get any fruit. These advances allow growers to be more nimble in the marketplace."

The biggest change seen by Crassweller is how closely apple trees can be planted in modern orchards. In the early 1970s, trees were planted 10 to 18 feet apart. Today they are typically planted 3 to 5 feet apart.

"It used to be that about 242 trees were planted to the acre and now new plantings are up in the neighborhood of 800 or even 1,000 trees per acre. We are doing that primarily because growers need to get their returns very quickly."

One of the biggest challenges apple growers face is producing fruit that is not marred by apple scab, a disease that disfigures and distorts fruit, making it unsuitable for sale. Researchers for years have been attempting to develop varieties that are resistant to apple scab.

Crassweller's orchard at Rock Springs has the largest collection of scab-resistant apple varieties in the eastern United States, except for the USDA Plant Repository in Geneva, New York. There are about 50 different trees producing scab-resistant apples at Rock Springs among the 140 trees in his research orchard.

Assisted by Don Smith, a research and teaching-support assistant who has been working with him since 1995, Crassweller maintains the extensive collection of disease-resistant cultivars because apple scab remains a huge concern for apple growers. "Most commercial varieties are not resistant apples — Red Delicious, Golden Delicious, Gala, Fuji — they all get apple scab, although Honeycrisp has some resistance."

The work done by Crassweller is especially important to Pennsylvania because the state is ranked the fourth highest apple-producing state (Washington produces 47 percent of all apples grown in the country, followed by New York and Michigan.) Pennsylvania has a processing industry that produces juice, apple slices, pie filling and whole candy apples. Most of the apple tree research Crassweller has conducted over the years has been done with the Keystone State in mind.

"My paycheck is blue and white and the taxpayers of the state pay my salary, so I always try to help Pennsylvania growers first," he said. "But in the larger scheme of things, the industry in our region really stretches from Pennsylvania south into western Maryland, West Virginia and northern Virginia. So, all of our findings are relevant to growing apples in a five-state region."

(Also participating in the NC-140 Research Project rootstock and training system trials at Penn State are Rich Marini, professor of horticulture, and Jim Schupp, professor of pomology.)

  • Extension apple tree researcher

    Penn State Horticulture Professor Rob Crassweller has been at the forefront of the effort to boost apple production for more than 30 years.

    IMAGE: By Mike Houtz

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Last Updated August 19, 2016