May 2, 2013

High-density system can increase pear yields

Terence Robinson, a professor of horticulture at Cornell University, has studied apples for decades, but lately he’s been “somewhat enthused” about the potential of pears, especially in the eastern United States.

Robinson discussed high-density pears during the annual winter conference of the International Fruit Tree Association, recently held in Boston. He’s been studying pears since he first planted a trial block in Geneva, N.Y., in 2003.

Most apple growers in the eastern United States don’t share Robinson’s enthusiasm for pears, and with good reason. The crop faces a number of challenges. Pears, traditionally, are very slow to come into production – hence the saying, “You plant pears for your heirs,” Robinson said.

The quality of pears grown in the east can be variable, too, often with very little fruit set. Pears have a relatively low mature yield compared to apples. Fire blight and pear psylla are consistent problems, he said.

The biggest problem for pears, however, might be a lack of interest in the marketplace. Many consumers don’t know how to eat pears, or ripen them. Prices remain relatively modest, even low, he said.

So, with all those obstacles, why would any grower want to plant pears?

Well, there are buyers out there who have shown interest in high-quality, good-tasting pears. And as for the challenges, many of them can be solved by treating the pear more like an apple – using high-density plantings, resistant varieties and more intensive management, Robinson said.

Promising alternatives

Established markets still accept traditional pear varieties, but prices are low and demand is in decline. Traditional varieties grown in the United States include Bartlett, Bosc, D’Anjou and Comice. Bartlett and Bosc are grown in New York state, while out west it’s primarily Bartlett and D’Anjou, he said.

Robinson is enthused about several new fire blight-resistant varieties, which he said could be the foundation of a new pear marketing industry in the east. He likes Harrow Crisp, Harrow Sweet and Sundown. There aren’t many Sundown acres in the United States yet, but the variety is “going great guns” in Canada, he said.

Magness is a USDA variety. It’s a wonderful pear, but has some trouble with fruit set. That could possibly be solved with better rootstock. Other promising varieties include Potomac, Blake’s Pride, Sunrise, Shenandoah and Gem, which was released last year, Robinson said.

All of those alternative varieties have promise, but to really go the non-traditional route you have to build a market. Savvy farm marketers, who mostly sell to local consumers, can develop demand for such promising pears, but it will be a bigger challenge for wholesalers, he said.

Most high-density pear orchards in the world are grown on quince rootstock. Quince is loved because it can produce large fruit, bigger than any Pyrus rootstock. Quince is a bit of a risk for U.S. growers, however. It’s not resistant to pear decline, and it’s more susceptible to cold damage than Pyrus. Climate change could make that less of a risk, but worries about tree loss will still be in the back of every grower’s mind, Robinson said.

Quince also requires intensive management to grow well, including irrigation and fertigation, he said.

There are several good rootstock options for U.S. pear growers, but many aren’t yet readily available at nurseries. For the moment, Robinson suggested growers use OHxF 87 or Pyro 2-33. If you can’t get those, OHxF 97 is a good alternative.

In Robinson’s opinion, tall spindle is the best growing system for high-density pears. At about 1,200 trees per acre, tall spindle’s planting density is high, but not excessively so – whereas super spindle requires more than 2,000 trees per acre.

Robinson likes a four-wire trellis with 12-foot posts holding up the trees. In his ideal system, you don’t head the leader at planting. That can be a problem when the trees from the nursery are 8 feet tall, however. He prefers trees that are 5 or 6 feet tall.

Tie the branches down to induce flowering, he said.

“Traditional pear experts say this is crazy, but I don’t believe them anymore.”

Limb renewal pruning is a must. You have to take out big branches every year to keep the trees small. Begin branch renewal in year four or five, by taking out any branch that exceeds three-quarters of an inch in diameter. You want a structure with no branches; just a stem, he said.

He gave other recommendations: Use root pruning to control vigor. Use Maxcel as a chemical thinner. NAA sprays in summer can be useful, too.

“Limb renewal pruning, root pruning, ringing and growth regulators will allow us to manage these close spacings for 20 or more years,” Robinson said.

All in all, you can increase pear yields by a “massive amount” by planting at higher densities. Yields can reach up to 70 tons per hectare, he said.

The bad news: planting density negatively affects fruit size. As you pack the trees in closer, you tend to get smaller fruit, Robinson said.

– Matt Milkovich