Forelle is an attractive, medium-size pear that requires special management and skill to grow it to perfection. The pears need sunlight to remain red throughout their development and obtain the red blush at harvest.
Bas van den Ende
In Australia, growing Forelle pears can be highly profitable, provided the pears are blushed and have good size and shape. To achieve this, and to produce 30 to 35 tons per hectare (bins per acre) each year, is no mean feat.
The pear’s white, melting, juicy flesh, and absence of grit cells, make Forelle a culinary favorite.
Forelle is a small pear, and probably the most difficult pear to produce. Pruning, pollination, and development of a distinctive deep-red blush are critical factors for producing perfect pears. Fruit that is not exposed to the sun will not develop color. A difference in day and night temperatures is not enough to create a red blush.
Forelle is predominantly a spur-bearing variety. The trees are vigorous, show strong apical dominance, do not bear on one-year-old wood, and are not willing to branch.
Transplant shock often delays tree development.
Since Forelle is self-sterile, and the trees flower earlier than most other pear varieties, another early flowering pear variety, plus honeybees, are required for adequate cross-pollination, fruit set, and good fruit shape. An even distribution of seeds in the pears is associated with symmetrical development of the fruit.
Forelle is very susceptible to infection by bacterial blossom blast (Pseudomonas syringae) and fireblight (Erwinia amylovora).
When these traits are understood and the trees are managed properly, Forelle can consistently yield well and produce pears of good size, shape, color, and taste. Here are some hints on how to achieve this.
- Buy large, unheaded trees of high quality with good root systems.
- Prevent or minimize transplant shock (see “Prevent transplant shock,” Good Fruit Grower, April 15, 2011).
- Use Open Tatura with cordon (see “Open Tatura with cordon: A new way to grow fruit,” Good Fruit Grower, April 15, 2005), or Open Tatura with four leaders (see “Use Open Tatura to grow superb apricots,” Good Fruit Grower, July 2009). Make rows 4.5 meters (15 feet) wide and plant trees 1 meter (3 feet) apart on a diagonal. This means that on one side the trees are 2 meters (6 feet) apart. The space between the two lines of trees is 0.5 meter (18 inches). Since Forelle is very susceptible to fireblight, the cordon and four-leader methods allow minimal mutilation of the tree when fireblight strikes.
- Plant two Ya Li (Chinese pear) trees as pollinizers at every trellis frame—i.e., no more than 15 meters (45 feet) apart. Alternatively, graft fruiting units over to Ya Li, alternating trees left and right every 7 meters (20 feet).
- When the canopy is established and trees are not yet in production, spray Ethrel (ethephon) in summer and fall to terminate extension growth, promote development of fruit buds, and keep buds shut. The rate is usually between 200 and 300 milliliters per hectare (about 3 to 4 fluid ounces per acre in the United States), depending on ambient temperature. Sprays might have to be repeated several times.
- When trees are in production, spray with a rest breaker, such as 3 percent Dormex (hydrogen cyanamide) six weeks before anticipated full bloom. The rest breaker condenses the period of flowering, and causes spur leaves to emerge early, resulting in uniformly large fruit at harvest.
- Place five beehives per hectare at 5 percent full bloom.
- Natural fruit set might not guarantee a full crop. But if you spray 15 ppm gibberellic acid per hectare (as ProGibb SG) at about 80 percent full bloom, you can be assured of a good fruit set and full crop. GA3 can result in heavy fruit set, which requires fruitlets to be hand thinned. Thinning allows you to select large fruitlets with the best shape.
- Hand thin fruit early (40 to 45 days after full bloom). Thin to mostly singles and a few doubles in a cluster, removing small and misshapen fruitlets first. Fruit must be medium to large at harvest.
- In summer, keep canopy height at 60 percent of the actual width of the rows. If rows are 4.5 meters (15 feet) wide from center to center, the actual width between opposite trunks in the row is 4 meters (13.5 feet). Maximum tree height is therefore 2.4 meters (8 feet) measured vertically.
- Remove or stub strong shoots in spring and summer to keep the canopy thin and open. Dappled sunlight must reach the ground at all times. Good light distribution throughout the canopy allows fruitlets to continue synthesizing and accumulating anthocyanin, which is the red pigment in the skin. The fruitlets will then remain red throughout their development, and will obtain the attractive red blush at harvest. Redder fruitlets with high concentrations of pigment lose color more slowly during hot weather than do fruitlets with less red pigment.
- Apply NAA (naphthaleneacetic acid) three to four weeks before anticipated harvest, to prevent preharvest drop. A second spray at half strength might be necessary one week before harvest.
- Harvest pears when firmness is between 6.4 and 6.8 kilograms force, or 14 and 15 pounds (use an 8-mm plunger), and sugar is 13° Brix or more. Markets prefer large fruit to be packed in 6-kilo (13-lb) single trays containing 30 large pears or 33 medium pears. If pears are picked too early (i.e., preclimacteric), the normal ripening process might not be induced. The 15/15 rule has been used in South Africa to determine optimum harvest maturity. When the pressure decreases to 15 pounds and the sugar level reaches 15°⁰ Brix, Forelle is ready to be harvested. Make adjustments to this rule if 15° Brix cannot be reached.
- Harvest pears with stems intact.
- Hold Forelle pears in cold storage for at least 12 weeks to ensure that the pears ripen evenly and acquire an acceptable eating flavor. Forelle is a winter pear and needs a longer chilling period in storage before it develops the ability to ripen at room temperature than do summer pears. If the minimum chilling period of 12 weeks is not met, fruit will ripen abnormally, shrivel at the stem ends, develop maturity-related defects, and be of poor eating quality. The amount of chilling needed is influenced by stage of maturity at picking. Pears picked at an early stage need a longer chilling period than do pears picked at a more mature stage. After cold storage, Forelle pears need seven to ten days of room temperature to ripen properly.
- In winter, trim spurs to strong upright buds. Encourage spur systems to grow horizontally and to face into the rows to allow spur leaves to capture most of the sunlight early in the season and fruit to hang freely. The quality and age of the fruit buds can influence the color development of the fruit. Allow small one-year-old pencil-size shoots to bud up, so they can replace aging spurs.
Growing perfect Forelles is not for the faint-hearted. It requires significant financial inputs, dedication, and enthusiasm. Only then will growing this attractive pear become highly profitable.
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Bas van den Ende is a tree fruit consultant in Australia’s Goulburn Valley.