Italian pomologist Dr. Stefano Musacchi strides ahead of field day attendees before his inaugural talk as an endowed chair at Washington State University at the Sunrise Research Orchard in Wenatchee, Washington on August 7, 2013. Musacchi is an expert on the biaxis tree training system and will work on a systems trial with WSU’s new apple variety, WA 38. Photo by TJ MULLINAX

Italian pomologist Dr. Stefano Musacchi strides ahead of field day attendees before his inaugural talk as an endowed chair at Washington State University at the Sunrise Research Orchard in Wenatchee, Washington on August 7, 2013. Musacchi is an expert on the biaxis tree training system and will work on a systems trial with WSU’s new apple variety, WA 38. TJ Mullinax/Good Fruit Grower

When Dr. Stefano Musacchi arrived in Washington State in August, he knew the expectations were high.

Musacchi, a world-renowned pomologist from Italy, was appointed to a new position at Washington State University created with funding from a special grower assessment to enhance tree fruit research.

Musacchi arrived with plenty of ideas about how to help Washington apple and pear growers but no intention to revolutionize the industries.

“My idea is that you don’t have to be a revolutionary person,” he told Good Fruit Grower. “I think the best work that a researcher can do is to try to understand and improve what’s possible to improve in the short term and think ahead, because we like to be stable in life until things force you to do something different. The growers will have problems in the future, and I hope we will be ready to fix problems when they arise.”

Pear growers in Europe have been forced to adopt more labor-efficient growing systems, largely because of high labor costs. In Washington, however, many growers still find they’re able to succeed growing pears on big old trees.

“I wish that the pear growers can make money for a long time with the traditional systems,” Musacchi said, “But at the same time they have to be ready to change or start to look for different solutions that will make more profitable what they’re doing now.”

Musacchi is well-qualified to help both the apple and pear industries. He’s visited Washington State several times since 2010 and has been learning where he can play a role in collaboration with other scientists.

In apples, he sees potential to help growers with one of their most profitable but problematic varieties, Honeycrisp. He’d like to test shade netting in various colors, which has the potential to reduce sunburn as well as protect the trees from hail and improve fruit color. Horticultural solutions need to be variety specific, he stressed.

“I cannot imagine that a high-value crop like Honeycrisp can be managed without a net because if you have one year of hail, you lose such a high amount of money that probably in one year you repay your investment,” he said.

Apple systems

He’s also heading a new trial planted at WSU’s research orchard comparing WSU’s new variety WA 38 on three different training systems: slender spindle and a V system—two systems commonly used in Washington State—along with the biaxis system that Musacchi pioneered while at the University of Bologna. When mature, the biaxis system forms a fruiting wall that produces high-quality fruit and is suited to mechanization.

Originally, the biaxis system involved planting a tree that had been grown in the nursery with two leaders, rather than one. Trees grow vigorously in the Po Valley in Italy, where Musacchi was based, and one of the objectives was to reduce tree vigor by dividing growth between the two leaders. Compared with a spindle, the biaxis tree has twice as many branches, which are half as long. Typically, the biaxis tree has more fruit buds.

However, the technique used to develop biaxis trees—using a double graft with two chip buds at the same height on the rootstock—has been patented by Mazzoni Group Nurseries and trademarked as Bibaum. This has prevented other nurseries from supplying those types of trees.

An alternative is to plant a standard nursery tree in the orchard, and cut it back to leave only two branches that will grow into the leaders. It takes one more year to develop the tree this way.

The biaxis system was conceived for pears as a way to reduce tree vigor in the absence of a dwarfing rootstock, but in Italy, it has been more successful for apples. In both apple and pear trees, branches are renewed periodically by cutting them back, leaving two lateral buds that will grow into new shoots. If a tree has 25 to 30 branches, about three or four can be renewed each year.

Musacchi said the major pear variety grown in Italy, Abbé Fétel, is not the best match for the biaxis system. The variety is acrotonic; that is, it tends to put on vegetative growth at the top of the tree, rather than the lower part. Bottom branches get old and develop poor flower buds, therefore the fruit tends to be small.

However, he thinks the biaxis system could be a great match for Washington’s major pear variety, d’Anjou, which produces ample flower buds on old wood.

“Each variety is a different story, and I am strongly convinced that for d’Anjou the biaxis can be a nice solution combined with the rootstocks that are available now, such as

[Old Home x Farmingdale] 87 or  97,” he said.


Growers in Italy use semivigorous quince rootstocks, which are reputedly not hardy enough to endure Pacific Northwest winters. Musacchi said there can also be problems with scion incompatibility, though the Polish quince selections, S1 and S3, would be worth testing. “If they can survive a winter in Poland, I assume they can survive a winter here,” he said.

In the long term, however, he thinks dwarfing pear rootstocks will be the key to updating the industry. At the University of Bologna, Musacchi ran a pear rootstock breeding program and selected 34 dwarfing genotypes that have the potential to induce early bearing and high productivity without sacrificing fruit size. Thirteen of them are already in in vitro propagation, and he is trying to introduce those genotypes into Washington State.

Musacchi also sees a need to update varieties.

“For sure, the pear industry needs worldwide innovation because I think the perception of the consumer is that pears seem like an old species,” he said. “In Italy, we made a study, and we realized that consumption of pears is very low in young guys under 30, and it’s the first choice for people over 55. I am frustrated about this situation. If you don’t learn to eat pears when you’re young, I am not sure you will eat pears when you’re old.”

New pear varieties would not compete with the old ones, he said, but would be niche varieties that could expand consumption of pears.

Italian releases

In Italy, Musacchi bred new pear varieties and is planning to bring four of his releases into the United States through National Clean Plant Network’s ­quarantine program at Prosser, Washington—a process that will take at least three years.

The varieties are being tested in Italy for fireblight resistance, which would be desirable because antibiotics cannot be used to control the disease in Europe. In his program he also had selections that were resistant to psylla, a major insect pest in pears.

Learn more about Musacchi’s work in Europe.