Choosing a rootstock is one of the most important decisions when planning an intensive pear production system. Rootstocks play an integral role in influencing

• tree vigour
• growth habit
• cropping
• resistance to pest and diseases, and
• tolerance to unfavourable conditions in the growing environment.

The performance of a rootstock is influenced by a combination of factors including the choice of scion variety, the quality of rootstock material, grower management practices and the growing environment. It is therefore important that growers have a good understanding of each of these factors as well as rootstock characteristiscs to ensure they choose a combination that provides maximum potential.

Rootstocks for intensive pear production

Quince Rootstocks

Pear (Pyrus) Rootstocks

Availability in Australia

Further Information

References

Rootstocks for intensive pear production

Most European pear species (Pyrus communis) around the world are currently grafted on either clonal (vegetatively propogated) or seedling rootstocks of the Pyrus species (Pyrus communis, P. calleryana, P.pyrifolia, P. betulaefolia) or on quince (Cydonia oblonga).

In the case of intensive production systems, the objective is to use a rootstock that restricts tree vigour, induces early cropping (ie. is precocious) and results in a high yield efficiency. Yield efficiency is usually measured as yield per unit of tree size (trunk cross sectional area).

Quince Rootstocks

Almost all quince rootstocks are clonal and they have been used for pear production for many years, particularly in Europe. The most commonly used are

• BA29
• Quince A
• Quince Sydo
• Quince Adams
• Quince C
  

There have been many evaluations carried out with quince rootstocks. Whilst there is often some variation in results between sites and scion cultivars, generally BA29 is considered the most vigorous followed by Quince A and Quince Sydo (both approximately 75% of seedling) and then Quince Adams. Quince C is the least vigorous at approximately 60% of seedling.

Quince C and Quince Adams have the highest yield efficiency compared to BA29, Quince A and Sydo (which are all similar).

Figure 1: 'Conference' nursery trees in Belgium. On the left trees are grafted onto Quince C and the right is Quince A.

In more recent years three other promising quince clones have emerged - Quince EMH (developed at East Malling), C132 (a selection from the Caucasus region of Russia) and Eline® (a Romanian selection sourced from Fleuren Nurseries in the Netherlands). These rootstocks are generally considered to perform similarly to Quince C in terms of vigour control and yield efficiency (Johson et al 2005, Maas 2006). However in some trials they have exhibited traits that may make them more attractive than Quince C such as improved fruit size (EMH and C132) and reduced russetting (Eline®) (Maas 2006).

See the Gallery for more images of Quince rootstocks

Management challenges

Whilst quince rootstocks provide considerably good vigour control there are still key management challenges associated with their use. 

One major issue  is the incompatibility of quince with many important European pear scion cultivars ('Williams', 'Buerre Bosc', 'Packhams'). This can be overcome with the use of interstems of compatible cultivars such as 'Buerre Hardy' or 'Comice'. 

Quince rootstocks are also susceptible to lime induced chlorosis. Lime induced chlorosis is often assosciated with soils that have high pH and high ligh content. Generally in areas where this is a problem  (such as in many parts of Southern Europe) the more vigorous of the quince rootstocks (such as BA29) or Pyrus rootstocks are preferred.

Limited winter hardiness is also an issue with quince rootstocks, and this has limited their use in areas that suffer severe winters, such as in the US Pacific North West and parts of Eastern Europe. This should not be a major issue in Australia's pear production regions.    

The biggest challenge growers in Australia may face with quince rootstocks is their susceptibility to drought stress. This is potentially more serious on the less vigorous Quince C and Adams. If quince is to be adopted in production systems it is important that growers closely monitor tree performance and ensure optimal irrigation management.

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Pear (Pyrus) rootstocks

Whilst quince is the preferred rootstock in Europe, Pear (Pyrus) rootstocks are still heavily relied on elsewhere. This is largely due to unsuitable growing conditions for quince in these areas. The majority of Pyrus rootstocks used are seedling which often results in very vigorous growing trees, an undesirable trait for intensive production. Trees grown on seedling rootstock can also be highly variable.

In Australia Pyrus calleryana D6 (D6) is currently the most commonly used rootstock for commercial pear production. However, it is an excessively vigorous seedling rootstock that produces very large trees and is unsuitable to modern systems of intensive pear production.

There have been some clonal pyrus rootstocks developed for intensive production and these are outlined below.

OHF series

The Old Home x Farmingdale (OHF) series of rootstocks originated in the United States. OHF 40, 51, 69, 87, 217, 282 and 333 are the major rootstocks in this series. Evaluations from different areas have shown a range of vigour and yield efficiency. It is generally accepted however that these rootstocks are too vigorous for intensive production. Some of these rootstocks have been introduced into Australia, however no rigorous evaluation has occurred and they are not readily available from nurseries.

Several trials are underway at the Mid-Columbia Agricultural Research and Extension Center in the US to screen for a dwarfing rootstock from the Horner series. This is a pyrus series developed from crosses of ‘Old Home x Farmingdale’ rootstocks (Mielke and Smith 2002, Mielke and Sugar 2004).

BP1

BP1 originated in South Africa and is reported to have a vigour similar to Quince A and BA29 ( 75% of Pyrus Calleryana) and have a good yield efficiency. There are no reported compatibility issues with BP rootstocks and scion cultivars. These rootstocks are, however, highly susceptible to pear decline and fireblight and are difficult to propagate. Susceptibility to pear decline has particularly limited the use of BP rootstocks in Europe.

The BP1 rootstock is being evaluated in the pear rootstock trial site in the Goulburn Valley and has shown reduced vigour and improved yield efficiency when compared with D6 (for both 'Williams' and 'Packhams'. This rootstock is commercially available in Australia but numbers can be limited. Results from the trial can be found by visiting the APFIP website.

Figure 2: 'Williams' on BP1 in its 5th leaf at the APFIP pear rootstock trial site in the Goulburn Valley. Central leader system with plant spacings of 4.5m x 1.4m (1585 trees/ha)

Pyrodwarf

Pyrodwarf originated from a crossing between Old Home and Bonne Luise d’Avranches. It reportedly has a vigour 50% lower than Pyrus Calleryana D6. It has good graft compatibility with European and some East-Asian pear varieties. It has a low susceptibility to iron chlorosis, is tolerant to waterlogging and is winter hardy. Rootstock evaluations in Europe have however shown it to still be too vigorous for intensive systems.

This rootstock has been introduced in Australia and is hoped to be included in future in the APFIP pear rootstock trial. This should yield information about its performance in local conditions.

Pyriam

Pyriam is a clonal rootstock developed by INRA in France through open pollination of ‘Old Home’. It is seen as a potential replacement for BA29 in south-east France. It reportedly has good graft compatibility with ‘Williams’, a good ability to be propagated, low susceptibility to Fireblight and good growth and habit in the nursery. It induces slightly higher vigour than BA29 but has equal productivity and fruit sizes (Simard and Michelesi 2002) . No published data was available to compare its performance to quince.

BM2000

BM2000 originated in Australia as a result of open-pollination of likely parents ‘Williams’ and ‘Packhams’. It is described as having medium vigour compared to Pyrus Calleryana D6. There is no experimental data regarding precocity, productivity and yield efficiency in the literature.

This rootstock is currently in the APFIP pear rootstock evaluation site and has demonstrated reduced vigour and better yield efficiency than D6 (on both 'Williams' and 'Packhams'). Results from the trial can be found by visiting the APFIP website

Figure 3: 'Williams' on BM2000 in its 5th leaf at the APFIP pear rootstock trial site in the Goulburn Valley. Central leader system with plant spacings of 4.5m x 1.4m (1585 trees/ha)

Fox Series

Fox 11 and Fox 16 are two of the fox series which have plant variety rights. Fox 11 vigour similar to BA29 and is recommended for tree densities between 2000-2500 trees/ha. It also has good compatibility and tolerates high alkalinity. Fox 16 has a vigour slightly greater than BA29 and it has drought tolerance but is less tolerant of high alkalinity than Fox 11.

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Availability in Australia

At present the most widely available rootstock for pear production is D6.  It is expected that Quince A, BM2000 and BP1 should be more readily available in the coming years.

The APFIP pear rootstock trial at present is the only source of rootsock performance data under Australian conditions. Results from the trial can be found by visiting the APFIP website 

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Further information

These Australian and international sites may be useful for growers. However they are intended as an information source only. Any specific chemical or other control recommendations may be outdated or irrelevant for Australian conditions and growers should seek local advice.

Please note: By electing to visit sites linking from this page you will be leaving the intensivepear.com website.

Australian Resources

Rootstock characteristics

• Pear rootstocks - New South Wales DPI AgFact (external link).

Rootstock performance in Australia

• Australian Pome Fruit Improvement Program - pear rootstock trial data from the Goulburn Valley (external link).

Accessing rootstocks

Growers should liaise with their nurseries about accessing rootstocks for intensive pear production (external link). 

• Australian Pome Fruit Improvement Program may also provide some guidance on rootstock availability (external link). 

International Resources

Rootstock characteristics

• 'Clonal rootstocks for apples and pears'  - Hortfact (external link).
• Pacific North West pear rootstock trial -  Washington State University site (external link). 

References

Maas, F. (2006). “ Evaluation of Pyrus and Quince rootstocks for high density pear orchards.”  Scientific Works of the Lithuanian Institute of Horticulture and Lithuanian University  of Agriculture 25(3). 13-26

Mielke, E.A., and Smith, L. (2002). “Evaluation of the Horner rootstocks” Acta  horticulturae 596: 325- 330. 

Mielke, E.A., and Sugar, D. (2004). “Initial seven-year evaluation of thirteen Horner pear  rootstocks”. Acta horticulturae 658: 513-517

Johnson D., Evans K., Spencer, J., Webster, T., Adam, S. (2005). “Orchard comparisons of new Quince and Pyrus  rootstock clones.” Acta horticultuae 671: 201-207

Simard M.H., Michelesi J.C. (2002). “'Pyriam': a new pear rootstock.” Acta  horticulturae 596: 351-355.

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The quality of nursery trees is one of the most important factors when establishing an orchard. The profitabilty of any intensive pear orchard is related to its ability to produce early yields of quality fruit. This is highly dependant on trees having good growth and developing an adequate canopy structure in the early years after planting.

An adequate canopy structure is one that allows for optimal light interception and has enough buds with the capacity to produce flowers.  This is best achieved through using high quality nursery trees that already have in place a good canopy structure.

It is also important that nursery trees are healthy - that is free of pest and disease and mechanical injury.

Types of nursery trees

Which tree will give the best result for an intensive system? 

Ordering a nursery tree 

Further information

References

Types of nursery trees

There are a number of different types of nursery tree that can be used when planting an orchards. These include

1. One year old whips - produced through bench grafting of rootstocks in winter, planting in spring and then encouragement of a single bud to grow. These are often unbranched and can lack uniformity.
2. Summer budded trees - produced over two seasons with rootstocks planted in spring and budded in summer. These are headed at the bud in late winter, with the bud growing into a tree the next season.
3. Two year old feathered trees (or 'Knip' trees) - produced over 2 seasons. One year old trees produced through either bench grafting or summer budding are held over in the nursery for another year and in the second winter are headed to the required height (50-75cm). A single shoot is allowed to grow from the top bud and any laterals are removed. The shoot grows very vigorously and produces branches on the current seasons growth (called feathers).
4. Sleeping eye trees - summer budded rootstocks that are cut above the dormant bud and stored for planting in a nursery or orchard.

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Which trees will give the best results for an intensive system?

Many studies from around the world have shown that the use of  highly feathered nursery trees, such as the two year old well feathered (knip) trees  can result in significant yields in the second and third year after planting. This is compared to unbranched trees (or whips) that may take four or five years to produce a yield.   

Highly feathered trees such as the 'knip' trees are the most favoured nursery tree type in many European production systems.  

Generally the best quality 'knip' tree should have   

• A minimum tree height of 1.6m above graft union 
• A minimum stem diameter of 14-16mm measured at least 10cm above graft union
• A number (6-15) of well positioned feathers/laterals with a maximum length of 30cm
• Feathers starting no less than 80cm above the soil.
• Feathers with moderate vigour - that is wtih a  diameter no greater than 30% of the trunk.
• Feathers with wide crotch angles

Figure 1 & 2 : 'Knip' trees in Belgium.

Often these trees require little (or no) pruning at planting, particularly if feathers are already well located around the tree.  

The drawbacks of these trees is that they are produced at a higher cost and therefore will be more expensive than a one year whip.  However the production losses through using cheaper, poor quality trees will cost more money in the long term than the initial cost of using quality trees.  

It is important however that growers understand the requirement of their intended system before deciding on a nursery tree. Often as densities get higher (>4000 trees/ha) and spacings narrower, highly feathered trees become less desirable. Systems such as the super spindle (4000-7000 trees/ha) are often best planted with whips with short branches. These treese should still be of a good quality however (uniform in size and healthy). 

Sleeping eye trees can often be an option to keep tree cost down in very high density orchards. The danger with sleeping eye trees is that the risk of tree loss at planting can be higher. This was demonstrated by Elkins et al. (2008) who found that even though sleeping eye trees were cheaper than 'standard' nursery trees (similar to whips) the cost of replacement and intensive training negated the benefit of the lower purchase price.

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Ordering a nursery tree 

When ordering a nursery tree, growers need to consider what tree will give them the best start for their system. This requires a good understanding of the planting site and intended system. If growers want highly feathered nursery trees, they will need to order atleast 2-3 years in advance from the nursery. If whips are the tree of choice, there is less lead time required, but growers should still order with enough time to ensure best chance of starting a system with the highest quality trees.

Fundamentally,growers must develop a good relationship with their nursery in order to get the right tree for their system. Being able to clearly specify the requirements of a tree can make this a smooth transparent process. APFIP has released a guide to nursery tree specifications, a useful reference when ordering trees from a nursery. 

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Further information

These Australian sites may be useful for growers. However they are intended as an information source only. Any specific chemical or other management recommendations may be outdated or irrelevant for Australian conditions and growers should seek local advice.

Please note: By electing to visit sites linking from this page you will be leaving the intensivepear.com website.

Australian Resources

Nursery Tree Specification

• APFIP Nursery Tree Specifications - For information on nursery tree specifications (external link).

Planting nursery trees

• Go to the planting nursery tree page for more information on management of nursery trees at planting

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References

Elkins, R.B., DeJong, T.M., Klonksky, K., and DeMoura R. (2008). "Economic evaluation of high density versus standard orchard configurations; Case study using performance data for 'Golden Russet Bosc' pears". Acta Horticulturae 800: 739-746

 Mostly pears are considered self-infertile (can not produce fruit from their own pollen) and require cross pollination.

Insufficient pollination may result in reduced yields and misshapen fruit. It is important when planning an intensive pear orchard to ensure adequate pollination through

• planting compatible varieties that flower at the same time
• careful planning of orchard configuration for effective pollinizer arrangement
• ensuring satisfactory bee populations in the orchard at flowering
• minimising competition from other flowering plants

Varieties for cross-pollination of pears

Planting pollenisers

Ensuring satisfactory bee populations at flowering

Minimise competition from other flowering plants

Further information

References

Varieties for cross-pollination of pears

It is important that pollinating varieties are compatible. The main variety and pollinator must also have a flowering period that coincides enough to ensure pollen is available as flowers open.

The following table lists compatible pollinators for selected pear varieties.

Table 1: Pollination table (adapted from Campbell (2002))

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Planting pollenisers

The placement of pollenisers in the orchard is particularly important in intensive production systems. Pollenisers need to be placed close to the main variety to ensure good pollenation.

Bees tend to fly down rows an not across them so full row systems of pollenisers (often used in old low density systems) may have limited effectiveness in intensive production systems. 

A more effective layout is one that has pollenisers evenly planted throughout every row.

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Ensuring satisfactory bee populations at flowering

Often growers will need to hire honeybee colonies as populations of wild or feral honeybees are low. Bees can be killed as a result of pesticide application in the orchard so growers will need to ensure they plan pesticide application programs to avoid this.

Suggested stocking rates for pears are provided in the resources below. However growers should consult an apiarist and local expertise to determine honeybee requirements for their orchard. 

Bee activity under hail netting

In order to ensure adequate pollination under hail netting, there are a number of factors that need to be managed. These were outlined by Middleton and McWaters (2002) and include

• Placement of hives under the netting  once flowering has commenced as bees will be less likely to fly into blocks covered by hail netting. If bees are introduced too early they will seek alternative nectar and pollen outside netted area 
• Allowing an adequate gap between the top of the trees and hail net cover for optimum bee flight
• Bees may become trapped in the netting when first introduced. These bees will die and be replaced by younger bees that have acclimatised to the conditions.
• Temporary removal of netting (or sections of netting) during flowering to allow bees to fly in and out and reduce numbers of bees trapped.

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Minimise competition from other flowering plants

Pear nectar is often less attractive to bees due to its low nectar content. This means if there are other flowering plants in close vicinity to the orchard, bees may be drawn away from the pears to forage. It is important to control flowering weeds around the orchard to minimise competition.

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Further Information

These Australian and international sites may be useful for growers. However they are intended as an information source only. Any specific chemical or other control recommendations may be outdated or irrelevant for Australian conditions and growers should seek local advice.

Please note: By electing to visit sites linking from this page you will be leaving the intensivepear.com website.

Australian Resources

Bee Pollination

• Bee pollination benefits for pear and nashi - Department of Agriculture Western Australia Bulletin (external link).
• Honeybee pollination of fruit tree crops - Victorian Department of Primary Industries Ag Note (external link).

Varieties for cross pollination

• European pear varieties - NSW Department of Primary Industries AgNote (external link).

References

Campbell, J. (2002). ' European Pear Varieties'. Retrieved January 2009 from http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0013/120217/european-pear-varieties.pdf

Middleton, S. and McWaters, A. (2002). ' Hail Netting of Apple Orchards - Australian Experience'. Compact Fruit Tree 35(2) : 51-55

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Intensive production systems offer the advantage of earlier production than traditional low density systems and better efficiency of harvest and management operations.

These advantages come at a cost however - as intensive systems are more expensive to establish and subsequently have a higher financial risk associated with crop loss or failure.

There are many interlinked decisions that need to be made during initial planning for an intensive system that are critical to ensuring success. These decisions will be influenced by a range of site, economic and management factors. These factors will vary from orchard to orchard.  

Making the right choices about system establishment and management depends on growers having a good understanding of 

•  the financial commitment and risks of an intensive production system
• the management commitment needed to ensure maximum potential for high annual yields beginning as early as possible and
• the importance of integrating the 'technical' aspects (variety x rootstock x planting system x management regime) for the best possible orchard outcome 

Financial Commitment

Management Commitment

Choosing the Right Combination

Risks

Key Planning Questions

Financial Commitment

It is crucial that before moving ahead with an intensive orchard, growers have a good understanding of the financial commitment required and the capacity of the business to meet this commitment. This means having a clear idea of the financial position of the business and the cost of intensive system options.

The cost of establishing an intensive system are higher than for a traditional system. The higher cost can be due to;  

• a requirement for higher tree numbers
• the installation of trellis/support systems
• the requirement for more intensive management during the establishment years 
• the cost of interest on borrowed money to establish systems

Often establishment and annual overhead costs can only be reduced to a certain threshold - and not enough to have a significant influence on profitability. Cost cutting in the establishment phase may also impact on the long term performance of the orchard. 

 The key to making money in a new planting is to have these costs paid off as soon as possible. This means early production of high yields of good quality fruit that the market wants.   

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Management Commitment

Intensive orchards often require far more careful management during the early establishment years to ensure good growth and early fruit production. This means paying careful attention to the quality of the planting materials, ensuring optimal site preparation and  tree planting, tree nutrition, irrigation, pruning and training.

Growers need to consider what management commitment they are able or prepared to make to an intensive system and choose a system that will suit their situation. A whole range of different skills or technologies may need to be adopted in order to ensure maximum potential for early and sustained high annual yields of good quality fruit.

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Choosing the Right Combination

When planning an intensive system, it is critical to choose the right combination of rootstocks, varieties, planting systems and management options. It is also important to understand the inherent site characteristics such as soil fertility and climate and their impact on system choice. Mistakes made during the establishment phase such as spacings too wide for the vigour of the site and rootstock will have long term impacts on production.

The following pages on this site outline key information about these areas. It is important to recognise that each orchard will have its own set of  deciding factors - so there is no easy recipe for success. Planting systems that are technically efficient and productive may not be practical for all orchards.

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Risks

The biggest financial risk with an intensive production system is crop loss or failure - particularly in the early years of establishment. There may be a range of reasons for crop loss or failure including extreme weather or poor management decisions. The failure to produce early yields will not only have an immediate financial impact but may also affect yield production in subsequent years.

It is crucial that orchards have in place risk management options right from the beginning. This is particularly imporrtant for  those risks that growers have much less control over - such as extreme weather events.

Any planning for an intensive orchard should include provisions for managing the risk of crop loss  such as  hail netting, frost fans, overhead irrigation for evaporative cooling or even crop insurance. This may mean that the establishment costs are further increased and a further delay in reaching the break even point on the system. It is important however to assess the likelihood of these events occurring and weigh up the cost of risk management options versus the cost of losing a crop.    

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Key Planning Questions:

1. How much will the system cost to establish? 
2. Do I have access to the funds needed to cover this cost?
3. If I choose to borrow money can I afford the cost of interest? 
4. What impact would crop loss or failure have on the ability of the business to cover costs of establishment?
5. What management tools will I need in place to minimise the risk of crop loss?
6. What management skills and tools are required to ensure the system achieves early and sustained yields to help pay off establishment costs? Can I afford to commit to these?
7. Have I got access to all the required resources for an intensive system (eg. varieties, rootstocks, nursery trees, support materials)?

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