WashCo Test County WSU Extension
My County > Agriculture > Tree Fruit > Pear Rootstock Research Project

PNW Pear Rootstock Research Project 2002 - 2010

JUSTIFICATION and OVERVIEW:

Most pear orchards in the USA have rootstocks that induce high vegetative vigor.  While many of these orchards are quite old relative to other tree fruit orchards, the well-managed pear orchard continues to produce good yields of high quality fruit.  However, many do not, often because high tree vigor brings multiple production and storage problems.  These include:  increased cost related to pruning, suckering, thinning and harvest labor, difficult insect management leading to additional sprays, fruit quality problems related to low fruit calcium, alternate bearing and crop loss due to post-harvest diseases that could have been greatly reduced with ground-applied fungicides a few days prior to harvest.  Efforts to treat these symptoms of excessive vigor have cost a significant percentage of pear research dollars for decades, but the same problems need careful management and seem to remain at consistent levels through the years. There has recently been very little obvious economic reason to change existing pear orchard systems, or even plant significant acreages of new pears.  However, over the past two decades, it has become apparent to at least some industry leaders, that pear growers may be forced to replace the current 1950’s style pear orchard with either another profitable fruit, or, if they decide to stay in pear production, to grow their next pear orchard with smaller, easier to manage trees.  In order to make the switch to possible semi-intensive or intensive systems, it seems obvious that dwarfing or semi-dwarfing rootstocks will be critical to the entire process, as they were to apple producers.  While there had been efforts to create or test various pear rootstocks in the Pacific Northwest for several decades, and a few rootstocks in the Old Home x Farmingdale series had gained some recognition and use, there was general dissatisfaction with the speed and direction of the pear rootstock development and evaluation effort.  It was proposed that trials be placed in environments that represented the wide variation existing in the Pacific Northwest.  Therefore, pear rootstocks from various sources were tested with D’Anjou, Bartlett and Bosc in trials set up in Cashmere, Tonasket and Hood River. 

In 2002, after several years of preliminary effort, a pear rootstock trial was established in four locations in the Pacific Northwest. Grower cooperators provided sites in Tonasket (Bosc) and Cashmere (D’Anjou), one trial was established on the TFRC property in the mid-Yakima Valley (Bartlett grown as for processing), and one trial was planted in Hood River at the OSU-MCREC in Hood River (D’Anjou). Seven rootstocks were included the first season, and an additional four were planted on these sites in 2005. The trees/rootstocks have been evaluated on the following:
  1. Survival,
  2. Suckering,
  3. Tree size (trunk cross sectional area),
  4. Yield, and
  5. Fruit size.

 
 Planting Pear Trees    

 Virtual Tours of the Various Trial Sites: (Under Constant Construction)


2010 Project Summary

 1.    A number of potential rootstocks, including some that were being sold commercially in Washington and Oregon, were shown to be inferior due to disease or cold injury susceptibility, yield, fruit size, the production of thorny root suckers, or a combination of these attributes.  Early release of this negative data resulted in the cessation of production and sale of a poorly-tested rootstock that in all three of the trials lagged behind the standard OHxF 87 as much as $20,000 per acre in gross receipts by the 8th leaf.  No one will ever know how many acres of thorny roots-suckered, smaller-fruited, low production rootstocks would’ve been planted in the absence of this trial.  Each 50 acres planted would have reduced gross returns by up to $1,000,000 in the first eight years of their production.

 

2.   The OHxF 87 performed well enough in the D’Anjou and Golden Russet Bosc trials to become the current industry standard semi-dwarfing rootstock until something better comes along.  These data have encouraged the nursery industry and WSU research to pursue better methods of propagating this rootstock, and they are making it much more available to Pacific Northwest pear growers.

 

3.   Bartlett on Pyro 2-33 appears somewhat superior to Bartlett on OHxF 87.  The lower fruit set induced by this root is adequate for good production, but leads to much faster fruit hand thinning, the fruit is consistently larger, and the compact trees are similar in size to those on OHxF 87.  The Pyro 2-33 remains free of diseases, such as pear decline, produces no root suckers, and seems to tolerate very cold winter temperatures.  This root did not generally out-perform OHxF 87 in Bosc or D’Anjou trials in Cashmere and Tonasket, but it was somewhat more dwarfing, and had slightly higher production efficiency in the Hood River D’Anjou trial.

Rootstocks included:

Rootstock
Tonasket Bosc
Cashmere D'Anjou
2002 OHxF 87
X
X
OHxF 40
X
X
Pyrodwarf
X
X
Pyro 2-33
X
X
708-36
X
X
Fox 11
X
X
Fox 16
X
X
 

2005

OHxF 87
X
X
BM2000
X
X
BU-2
No
X
BU-3
X
X
Horner 4
X
X

As this was not considered a training systems trial, there was no effort to study the scion/rootstock behavior in an intensive, on-wire, formal training system. That effort would require many more trees than are available on these specific rootstocks. The 2002 trees were planted 10 feet apart in the row and were trained in a free-standing central leader. To date, the “semi-dwarf” plot trees in this system are generally healthy, but much less vegetatively vigorous than the standards of the industry. Most of the trees appear as if they would have been quite appropriate if planted at 6 – 7 feet in row and 14 – 15 foot row spacing, with no wire support. As this was not considered a training systems trial, there was no effort to study the scion/rootstock behavior in an intensive, on-wire, formal training system. That effort would require many more trees than are available on these specific rootstocks. The 2002 trees were planted 10 feet apart in the row and were trained in a free-standing central leader. To date, the “semi-dwarf” plot trees in this system are generally healthy, but much less vegetatively vigorous than the standards of the industry. Most of the trees appear as if they would have been quite appropriate if planted at 6 – 7 feet in row and 14 – 15 foot row spacing, with no wire support.

 
     

Scaffold limbs have been spread early in the training years, and may be almost as productive as if they had been placed on wire support. In recognition of this, in the D’Anjou trial at Cashmere and the Bosc trial in Tonasket, the 2005 trees were planted at 6 foot row spacings, and were trained to wire starting in 2006 (a year too late). The 2005 D’Anjou rootstock trial in Hood River was planted at the wider spacing standard of this trial, and may serve as a contrast of rootstock behavior on intensive vs. semi-intensive systems. Pruning and training at all four trial sites has been directed or carried out by local experts, with the intention of bringing the trees into early production, while building a proper framework for the free-standing system.

Pear TrellisSince 2002, some survival and root suckering problems have emerged, which may have eliminated some of the rootstocks prior to commercialization. Yields began in the third year, and were significant in the fourth leaf. By 2007, some of the 2002 rootstocks will probably be judged lacking in various important attributes, and the degree of evaluation reduced or dropped entirely. More firm conclusions on the two or three more promising rootstocks will require at least 2007 data, and the sixth and seventh leaf data will likely separate and solidify fruit size differences. The 2005 planted rootstocks will be producing fruit in 2007-2011. Some of these rootstocks have been trained on a 4-wire, 10 foot high trellis. Picture 1. Picture 2.

The trials have been carried through their fifth season; have now reached the years when yield and fruit quality data is most abundant, and constitute a significant investment of time, money and land by grower cooperators and researchers. 2006 fruit data indicates there are both very promising possibilities and potentially serious problems in current commercial rootstocks (see results summary tables). If these trends continue in the older trees, the data will become crucial to nurseries and growers making informed rootstock decisions over the next decade. In the longer term, the quest for the perfect PNW pear rootstock of the future continues. Perhaps that root currently resides in the trial, but that remains to be determined. Positive results from this trial will serve to encourage both the nurseries and the growers to plant rootstocks that have the greatest potential in the intensive pear systems trials that will be planted in the near future. The perfect rootstock does not appear to be available, but we can work with the current choices until something better comes along.

Objectives:

To continue evaluation of 2002 and 2005 planted pear rootstocks, with emphasis on tree survival, root suckering, vegetative growth potential of the scion, fruit yield, and fruit size.

To complete the planting of land provided in 2002 by two grower cooperators. (Done in 2006, these will now serve as pear/trellis training demonstration trials, see pictures below:).

 Bosc, free-standing vs. on wire Bosc tree, 2nd year 
Methods and Materials

Rootstock trial sites will be maintained at a local high standard by grower cooperators, the researchers, and technical employees. Local committees will continue as advisors on management of the trees. Trees will be evaluated on their survival and degree of root suckering, vegetative growth, flowering habit, fruit set, and fruit yields and size by appropriate, timely measurement. Data will be summarized and made widely available to growers in a useful format. As specific tree/rootstock trials are judged to have any significant drawbacks, they will be dropped from the evaluation list. These trees will remain intermingled with the remaining trees, so some maintenance will be necessary. If they appear to have some positive attributes in years six or seven, they could be re-included in the evaluations, but that will be unlikely.

  empty   empty
   
 
  empty   empty

 

WSU Extension, WashCo County, 311 E Hulbert, Pullman, WA. 98164, 509-335-8292, Non-Discrimination, Contact Us