Pear Production in Ontario
Table of Contents
This Factsheet will provide growers with an update on new developments in pear production based on research from the results of the 1996-2007 CanAdapt-funded pear trial and from other sources around the world.
To ensure consistent commercial production, grow pears in areas that have some moderating effect from one of the Great Lakes or on a site with a slope that allows for good air drainage.
Traditionally, pear trees were predominantly planted in poorly drained, shallow, clay-based soils and took several years to come into full production. Although pear trees tolerated these conditions, fruit size was often too small, and trees suffered a high mortality rate. Trees planted at six different grower sites in the CanAdapt trial performed best (tree growth, overall yields and fruit size) in deep, loam-type soils.
Tile drainage is also critical for tree performance and should be installed between rows prior to planting. Reducing the excess moisture, especially in spring and fall, reduces the risk of root disease such as phytophthora collar rot. Occasionally, some land levelling is necessary to correct severe wet spots.
Test nematode levels, as some sites require fall fumigation. If the season permits, consider a fall planting of a green cover crop to build up the organic matter prior to the spring of planting.
Traditionally, pears were grown at a wide spacing - usually 6 m between rows and 5-6 m between trees (270-300 trees per hectare (109-121 trees per acre)). Trees were also grown to a roughly open centre system, which typically resulted in a very tall tree requiring ladder work for all operations.
A higher density "Central Leader" planting system was used in the CanAdapt trials with 5.5 m between rows and 3, 3.4 or 3.7 m between trees (500-600 trees per hectare (202-242 trees per acre)). By increasing the tree density, production per acre increased, especially in the earlier years of the orchard (Figure 1).
Figure 1. Higher density Central Leader system
The Central Leader system allows for excellent light interception and results in less ladder work, as more pruning, thinning and harvesting can be done from the ground. Most of the ladder work can be accomplished by using just one move into the top of the tree. Trees trained with the Central Leader system can also lend themselves to mechanization with the use of aids for hand labour operations. Most of the fruiting spurs in the lower parts of the trees are retained during the life of the tree due to the good light exposure within the canopy. Since the tree has only one dominant leader and moderate growth, fewer large cuts are necessary in the dormant season.
Other orchard systems from around the world result in increased production and reduced labour costs. These newer, higher-density systems usually require some trellising support and very intensive management. They include:
Figure 2. "V" trained trees
Early training of branches is critical to the development of the tree system and setting fruit spurs early in the life of the orchard. After planting, spread new branches to wide angles while they are growing when tissue is soft and flexible. Small wooden toothpicks can be used to spread branches. Other methods to spread or tie branches down can be used later in the season when the branches are stronger.
It is better to do the tree training during the growing season rather than removing branches with poor angles when pruning during the dormant season. Excessive pruning will stimulate too much growth, and fruiting spurs will develop much later.
Mechanical platforms are currently being developed for higher density orchards to assist in intensive labour operations such as pruning, thinning and harvesting (Figure 3).
Figure 3. Adopting mechanical aids
Brief descriptions of the major pear cultivars and those that show promise when grown in Ontario follow. Unless otherwise indicated, a cultivar is generally satisfactory in tree growth, hardiness, and cropping and fruit quality characteristics such as size, colour, shape and internal quality. These appraisals apply only to Ontario conditions.
Anjou is a good tasting dessert pear with long storage and shipping life. The skin remains light green through to maturity. The flesh is very mild, aromatic and fine-textured. Lack of fruit-set is a common weakness of this cultivar. The tree is more resistant to fire blight than the Bartlett cultivar. Anjou pear plantings have not fared well in Ontario, and most plantings have been removed because of small fruit size and the fruit's poor appearance under Ontario conditions.
This cultivar comprises about 75% of total pear production in North America. In Ontario, it is the leading cultivar in hectares and number of trees. Bartlett trees are productive and adaptable to a wide range of soils and climatic conditions. Careful orchard management is required to avoid fire blight and still obtain satisfactory yield and quality. Swiss Bartlett is a strain of Bartlett that has similar tree and fruit characteristics.
A red budsport of Bartlett known as Max-Red Bartlett has been planted in very small quantities in Ontario. Max-Red is similar to Bartlett except for its red colour and maturity. It ripens 1 week after Bartlett.
This cultivar is a high-quality, flavourful dessert winter pear with excellent keeping and shipping quality. Bosc is widely grown as a dessert pear in the western U.S. It is an important and well-adapted pear in milder regions of Ontario. The trees can be very productive but come into bearing late and are susceptible to fire blight. They are difficult to train due to their spindly growth habit and lack of branching. There are several strains that are superior to the standard Bosc, such as the Golden Russet® strain, with a distinctive golden appearance and fine net-like russet that warrants testing by growers in Ontario.
This cultivar is an attractive, large, productive, good-quality pear. It matures 2 weeks ahead of Bartlett. Pick the fruit when they attain sufficient size, at least 10 days before full maturity. Failure to harvest fruit at the proper stage of maturity results in rapid core breakdown. The tree is vigorous, bears early and regularly, does well on heavy soils and is very cold-hardy. However, it is very susceptible to fire blight.
This is the hardiest cultivar available for colder districts of Ontario. Flemish Beauty is susceptible to scale insects and fire blight. The tree is very productive and vigorous. The fruit are high in quality, but require careful timing of harvest to obtain full flavour and avoid breakdown.
This is an old cultivar. French Bartlett resembles Bartlett in shape and colour but tends to be larger and rougher. Trees come into bearing early, but breakage of branches is sometimes a problem. It is not as good in quality as Bartlett but is quite acceptable. It ripens with or just after Clapp's Favorite.
This is an early summer pear of good quality and medium size. When picked at the correct stage of maturity, it keeps well. It is suitable only for limited commercial planting as an early roadside and farm market cultivar.
AC Harrow Crisp (formerly HW 610)
This is a very attractive pear with red blush on smooth yellow skin. The cream-white flesh is smooth, grit-free and firm even when fully ripe, with a mild sweet flavour. The fruit, which is similar in size to Bartlett, matures just after Bartlett and can be picked over a 2-week period. Early picked fruit can be stored for about 2 months, but storage life is reduced with later picking. If kept too long or picked too late, it will deteriorate internally without external signs. Ratings of both fresh and processed (halves) fruit have been good to very good. The tree has excellent resistance to natural fire blight infections. Precocity of AC Harrow Crisp is similar to Bartlett, trees coming into production about 4 years after planting. AC Harrow Crisp is protected under the Plant Breeders' Rights Act.
AC Harrow Gold (formerly HW 616)This cultivar has an attractive yellow fruit, with good size, smooth skin, fine texture, very good flavour with a good balance between sweetness and acidity. It is exceptionally juicy. Fruit are picked about 10 days before Bartlett, between Harrow Delight and Harvest Queen. As with many other early-season pears, the fruit will not store for very long (probably no more than 4-6 weeks) in common cold storage, but is excellent for roadside stands. AC Harrow Gold has excellent resistance to natural fire blight infections. Precocity in a second test planting appears to be similar to that of Bartlett. AC Harrow Gold is protected under the Plant Breeders Rights Act.
The fruit of this variety are smaller than Bartlett, greenish-yellow with a red blush. The cultivar ripens 2 weeks before Bartlett and is resistant to fire blight. Pick fruit while still green, otherwise a high percentage of the fruit will drop to the ground.
The fruit of this variety resemble Bartlett in shape, colour, texture and flavour, but are smaller than Bartlett. Thinning will improve fruit size and reduce the tendency toward biennial bearing. Harvest Queen ripens 1 week before Bartlett and is as resistant to fire blight as Kieffer. Fruit hangs well on the tree, and size will improve with delayed picking.
Fruit size of this variety is comparable to Bartlett, colour is yellow with a red blush at maturity, and taste is sweet, juicy and excellent. The cultivar ripens 3½ weeks later than Bartlett; trees show good resistance to fire blight. Harrow Sweet is protected under the Plant Breeders Rights' Act.
Harovin Sundown (formerly HW 614)
This cultivar is picked about 3 weeks after Bartlett. The large fruits have a smooth yellow-green skin with a light blush, and the flesh is cream-white with good texture. While flavour is generally good, there can be some astringency in the skin, which is reduced by storage for 3-4 weeks. This pear stores very well for about 3-4 months. The tree has good fire blight resistance. It has a tendency to secondary flowering but this has not resulted in increased fire blight infections. In second test plantings, precocity and productivity have been similar to Bartlett. Harovin Sundown is protected under the Plant Breeders' Rights Act.
This is a very high-quality, attractive, productive, small, late pear. The core tends to break down near harvest. In Ontario it has been used for pickling. Seckel should be planted only in home gardens and for specialty markets in Ontario.
Pear rootstocks belong to several species of pear (Pyrus), and a few are even in different genera (Cydonia, quince; Crataegus, hawthorn; Sorbus, mountain ash). In the past, Bartlett pear seedlings (Pyrus communis) have been used exclusively in Ontario as the standard rootstock for pear orchards.
Pear rootstock selection depends mainly on three factors:
Most of the pear trees in North America are grown on open-pollinated seedlings of Bartlett. These seedlings produce vigorous trees and are adaptable to a wide range of soil and climatic conditions but they are all susceptible to fire blight in the nursery and orchard. Trees of Bartlett-on-Bartlett seedling rootstock are moderately vigorous and strong. The root system is composed of numerous roots that are well distributed and provide good anchorage. The fruit tend to be medium in size, fairly well shaped and high in soluble solids.
Bartlett seedling is still the preferred rootstock for pear in Ontario.
Old Home x Farmingdale Clones (OHxF)
The clonal selections OHxF 40, 69, 87 and 97 have been classified as semi-dwarfing in vigour by nurseries on the West Coast but compared to trees with standard Bartlett rootstock from the CanAdapt demonstration trials at various climatic locations in Ontario, the cultivars on these rootstocks proved to be just as big as the cultivars on standard rootstocks. Trees on OHxF clones 40, 69, 87 and 97 produce crops earlier in the life of the tree and have large yields. Fruit size was also considerable larger than the fruit on standard Bartlett rootstocks. These clones are all highly resistant to fire blight, suckering and winter injury. OHxF clones are now being planted as the main rootstocks in the pear producing areas on the West Coast.
The following OHxF clones were tested in the CanAdapt pear trials in Ontario.
Although it has only limited testing, early observations indicate that early production can be achieved.
Reports from the West Coast indicate that varieties on this rootstock may produce a tree approximately 70%-80% the size of a standard pear seedling.
This rootstock is the highest producer of the Old Home series. It has demonstrated the ability to set fruit early and bear heavily.
Trees on this rootstock are roughly the same size as Bartlett seedling trees but highly precocious. It is winter hardy, compatible with most cultivars and resistant to pear decline.
More precocious dwarfing rootstocks suitable for intensive pear plantings are in development. Pruning and training systems must be amended for these rootstocks to ensure the size-controlling affect.
Pear growers have been limited to quince selections (Cydonia oblonga) for use as dwarfing rootstocks.
This rootstock has not been as successful in grower orchards as it was in some research trials. It is reasonably winter hardy (to -26°C), tolerates excess soil moisture but not standing water, restricts vegetative growth of the pear scion cultivar and induces fruit production at a younger age. It is not unusual to have fruit on 2-year-old trees in the nursery or orchard. However, the tree requires good sandy soils for root development, needs staking for support, early fruit thinning to prevent stunting of the tree, irrigation to keep the tree from going under stress and mulching for additional water management benefits.
Since the standard Bartlett is incompatible on quince, Swiss Bartlett, a strain of Bartlett, which is compatible with Quince A, is used directly on quince roots. Bosc is also incompatible with Quince A.
Trees on Quince rootstock require superior management practices and conditions for success in the orchard.
Under Ontario conditions, commercial pear cultivars are considered self-unfruitful, consequently, cross-pollination with a suitable pollenizer cultivar is required. The pollenizer cultivar should bloom annually, flower at the same time as the cultivar to be pollinated and be cross compatible. Choose cultivars of commercial importance that are suitable for the market requirements of the grower as pollenizers. Do not choose pollenizer cultivars that are biennial in bearing habit or unusually susceptible to pests, disease or other problems that might interfere with the pollenizer function.
Most popular pear cultivars flower at about the same time, and there is often satisfactory bloom overlap for effective cross-pollination among cultivars. The bloom season for pears, as for other fruit crops, varies among cultivars, from season to season and between locations. The long-term data collected at Vineland show an average full-bloom date of between May 15 and 17 among different cultivars. Full-bloom dates, however, are not useful for predicting the exact full-bloom period for this crop from year to year.
Cross-incompatibility (the inability of pollen from one cultivar to set fruit on another) is seldom found among diploid pear cultivars. The only exception of importance is the cross-incompatibility of Bartlett pollen with Seckel. There may be other causes of functional incompatibility among pear cultivars. The flowers of Bartlett and Bosc have abundant pollen and are satisfactory pollenizers of each other, as well as of other cultivars. Flemish Beauty has shown the highest degree of self-fertility among pear cultivars grown in Ontario. Pollinated by Anjou, Flemish Beauty is a good pollenizer for Bartlett and Bosc.
In standard orchards, the pollenizer cultivar should not be more than two trees away from the main cultivar, i.e., at least one tree of a pollenizer cultivar for every eight trees of the main cultivar. Because pear pollen grains are relatively large, little transfer of pollen by wind occurs. Honeybees, bumblebees and large flies are the major agents responsible for transferring pollen among pear cultivars. Having two beehives per hectare in mature orchards is considered the minimum, and four hives per hectare is optimum for pollination. Several hives can be placed together in a protected area. Research has shown that a great deal of pollen transfer occurs within the hive. Place the hives in the centre of every 2 hectares by the time 10%-20% of blooms have opened. Hive openings should face south for best exposure to the sun to stimulate early bee activity.
The nectar of pear flowers contains about 10% sugar as compared to the bloom of some weeds and fruit crops, which may contain up to 60% sugar in their nectar. For this reason, pear flowers are relatively unattractive to pollinating insects. Mow the orchard just prior to bloom to remove alternative nectar sources attractive to bees. Avoid spraying with insecticides during bloom and remove hives as soon as possible after bloom to avoid damage to bees from post-bloom sprays.
Bosc is an ideal pollenizer for Bartlett and is adequately pollinated by Bartlett as well. Anjou is a satisfactory pollenizer for Bartlett. Pollen compatibility of new introductions has been assessed using pollination records from the breeding program and from a limited number of crosses made specifically for this purpose. Generally, a fruit set of greater than 20% is required for commercial fruit production, whereas fruit set less than 10% suggests incompatibility. Results have been inconsistent over the years, and, in some cases, fruit set has varied widely from year to year.
AC Harrow Crisp (formerly HW 610) tends to be a poor pollinator and will not consistently pollinate Bartlett, but Bartlett will pollinate AC Harrow Crisp to a limited extent. Good fruit set has been obtained in some years when AC Harrow Crisp was self-pollinated or pollinated by Flemish Beauty, Bosc, Swiss Bartlett and Harovin Sundown (formerly HW 614). AC Harrow Crisp pollinated Bosc, Anjou, Flemish Beauty, AC Harrow Gold and Harovin Sundown with limited fruit set on Bartlett, Swiss Bartlett and Clapp's Favorite.
AC Harrow Gold (formerly HW 616) can pollinate Bartlett, Bosc, Flemish Beauty and Anjou, but results have been variable from year to year. Pollination of AC Harrow Gold by Bartlett, Bosc, AC Harrow Crisp and Flemish Beauty has been variable, while Harovin Sundown has been more consistent.
Harovin Sundown has successfully pollinated Bartlett, Bosc, Clapp's Favorite, Flemish Beauty, AC Harrow Crisp, AC Harrow Gold and Swiss Bartlett. Cultivars that have successfully pollinated 'Harovin Sundown' include Bosc, AC Harrow Crisp, AC Harrow Gold and Swiss Bartlett, whereas 'Bartlett' pollen does not consistently produce adequate fruit set for commercial production. There is also some evidence from controlled pollination trials for self-compatibility in 'Harovin Sundown.'
While pollination requirements of recent introductions have not been fully determined, it should be noted that fruit set in the CanAdapt plantings has been adequate for full commercial crops of all cultivars (Bartlett, Swiss Bartlett, AC Harrow Gold, AC Harrow Crisp, Harovin Sundown and HW 620).
Fire blight, caused by the bacterium Erwinia amylovora, is the most serious disease of pears. Not only does this disease reduce yield for the current year, it can kill trees. The bacterium survives in cankers on the wood and is washed into the open flowers when it rains during bloom. Once infection occurs, bacteria move quickly in succulent tissues (1-4-yr-old tissues), especially under conditions of warm temperatures and high humidity. Secondary infections can occur throughout the growing season and arise from the spread of E. amylovora as a result of primary infections in blossoms and shoots, as well as from oozing cankers. Large numbers of bacteria are spread by rain, wind and piercing-sucking insects. Pruning using contaminated equipment can also hasten the spread of fire blight. Secondary infections are usually the most serious and can result in eventual tree losses. Therefore it is critical to control fire blight infections by removing infected wood during winter pruning and by protecting open blossoms during bloom. Several of the new pear cultivars are much less susceptible to fire blight than Bartlett and Bosc.
Pears are also susceptible to fungal diseases such as pear scab and fabraea leaf spot. Both pathogens can infect both leaves and fruit. Seckel and Anjou are more susceptible to these diseases than Bartlett. Both pathogens survive in leaf litter that was infected the previous year. If either disease was a problem the previous year, the most effective way to control them is to spray protective fungicides early in the season to prevent primary infections. Mowing leaves and applying urea to speed up breakdown of leaf litter have proven useful for managing pear scab.
The main insect pest of pear is pear psylla. This insect overwinters as an adult in cracks of tree bark or under debris. On warm sunny days as temperatures reach 10°C, adult psylla may be seen moving around on the bark. As buds develop and new shoots emerge, egg-laying shifts to the margins of leaves and stems of shoots. The eggs hatch to release nymphs that feed by sucking sap from developing buds, leaves and shoots.
Heavy populations of psylla weaken the tree, reduce terminal growth and may influence the following season's crop by reducing fruit bud set. Psylla also may cause wilting, scorching and premature leaf drop due to toxic saliva injected during feeding. Trees weakened by heavy populations may also be more subject to winter injury. Excretion and build-up of honeydew on the foliage and fruit is the most obvious sign of psylla feeding. A sooty mould fungus develops in the honeydew causing a russeting condition of the surface of the fruit that downgrades the quality at harvest. Trees in orchards with a past history of psylla and where large amounts of honeydew have occurred have a characteristic blackened bark due to sooty mould. The impact of psylla can be reduced by maintaining good air drainage in the orchard through proper pruning, good fertility practices and adequate tree spacing. Insecticides are required to control this insect.
Codling moth and oriental fruit moth cause direct injury to the fruit, not just of pears, but also of other tree fruit, including apple and peach. Therefore, pear orchards close to either crop should be monitored for the codling moth and oriental fruit moth. Pheromone traps plus fruit inspection will provide information for timing of insecticide sprays. Mating disruption also provides effective control of these pests.
Water plays an important role for plant development and fruit size. Pears are typically planted in clay, clay loam or loam soils in Ontario and therefore any stress from dry weather will hamper good root growth, resulting in poor shoot growth and small fruit size. Water is necessary for all plant processes, including the uptake of nutrients from the soil. To encourage initial root growth, irrigate newly planted orchards 2-4 times from planting time in the spring until late August (depending upon normal rainfall: 60 mm/month in Ontario). Repeat each year for non-bearing trees to ensure adequate root development and good shoot growth for tree structure.
Once the trees start producing fruit, the timing of irrigation is important for establishing good fruit size. There are two key times to irrigate bearing trees: at cell division (shortly after bloom) and cell expansion (later in the growing season as fruit start to size). However, it is still important to irrigate to prevent water stress throughout the growing season.
Irrigation water can be delivered in several ways. Overhead gun irrigation is common but there is always the risk of spreading the bacterium Erwinia amylovora and promoting the development of fire blight. Trickle irrigation is also used and can be effective, but careful soil monitoring and the right number of emitters is important to ensure that adequate water is delivered to the roots. Trickle irrigation is often applied 2-3 times per week for 4-8 hours per day, depending upon emitter output. In Ontario, under most soil conditions, the soil should be allowed to dry out slightly to prevent soil saturation and any soil disease issues.
There are several ways to monitor moisture in the soil. Soil probes are one of the most reliable methods since they can measure water content of the soil at several different soil depths. This would give a better indication of the soil moisture profile at several locations ranging approximately 15-100 cm deep.
Orchard Ground Cover
Annual grass mixes of ryegrass and fescues are common for most orchards in Ontario. The ground is typically disked and cultivated in the spring and seeded in early July. The grass provides a good ground cover by early September just before harvest. A light mixed fertilizer application can assist in the growth of the grass. Overhead irrigation might be necessary just after planting in some dry years.
A permanent sod of fescue grass might be considered after the orchard is well developed and starts to crop. A permanent sod is more beneficial during wet seasons for traction with spraying and harvest equipment. Do not plant permanent sods too close to the trees since sod is very competitive for moisture.
Take soil tests in the fall prior to the year of planting and apply any adjustments of nutrients or pH in the spring. The ideal pH is 6.0-6.5. Take soil samples periodically over the life of the orchard to monitor any changes in nutrients in the soil.
Nitrogen is not usually needed during the year of planting; however, it is important to start with good organic matter, knowing that there is no nitrogen deficiency in the soil.
Take leaf samples annually to monitor the plant nutrient levels.
Mulch orchards with straw or hay periodically to provide additional organic matter and protection for the roots from extreme winter temperatures and to retain soil moisture in the rooting zone.
The thinning of fruit is particularly beneficial during seasons of heavy fruit set or inadequate moisture. Bartlett and Bosc can set fruit in clusters of three to five fruit per spur, so thinning is essential.
In Ontario, wind machines are primarily used to protect grapes from extreme cold temperatures, spring and fall frosts. Although pears are not as susceptible to extreme winter temperatures, wind machines can still provide some measure of protection from extreme cold temperatures by mixing warmer air 12 m above the orchard with the colder air in the orchard fruiting zone.
Wind machines are probably most useful during cold spring frost events by raising the temperatures just above freezing to prevent blossom damage and eventually crop loss. Wind machines could also be used in the fall prior to harvest to protect fruit from freezing damage.
There are only five to six main cultivars of pears, so the harvest season is late August to early October.
Most pears reach optimum harvest maturity while they are still green and hard, and before they ripen on the tree. Therefore, pears are usually harvested based on fruit firmness. 'Bartlett' pears having 81-90 N (18-20 lb) firmness at harvest are optimum for long-term storage. These values are lower for 'Bosc' and possibility for some of the newer cultivars as well.
Some of the recently released pear cultivars from the Harrow breeding program remain firm on the tree for longer periods of time and can be harvested with less firmness than Bartlett. Some cultivars have fruit that adhere to the spur and are difficult to remove while others fall off quite easily.
Pears are generally picked directly in baskets or bags and gently placed into large bins for storage (Figure 4).
Figure 4. Harvest of Central Leader system
Pears are very delicate and require special post harvest care. A few extra hours in the orchard, rough handling, slow cooling and storage temperatures slightly above optimum are the primary causes for disorder development, shortened storage life and, ultimately, consumer dissatisfaction.
It is essential that pears be cooled quickly. The optimum storage temperature for pears is -1°C-0°C, with 90%-95% relative humidity. It is possible to have good quality pears for 2-4 months. Controlled atmosphere (CA) storage can be used to further extend storage life. Atmospheres ranging in 1%-2% oxygen and 0%-2% carbon dioxide are often used, with specifics depending on cultivar.
SmartFresh is a new product that inhibits the action of ethylene. Application should occur 3 days after harvest, while the pears are in cold storage. SmartFresh slows fruit ripening and greatly reduces the incidence of storage disorders, such as senescent scald, core breakdown and friction marking.
This Factsheet was written by Ken Slingerland, former Tender Fruit and Grape Specialist, OMAFRA, Vineland, and Wendy McFadden-Smith, Tender Fruit and Grape IPM Specialist, OMAFRA, Vineland. The authors would like to thank Dr. David Hunter, Pear Research Scientist, Agriculture and Agri-Food Canada, and Dr. Jennifer R. DeEll, Fresh Market Quality Program Lead - Horticulture, OMAFRA, Simcoe, for their contributions to this Factsheet.
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