The key to a high-yielding pear tree lies in good blossom-period management
1. Fertilizer and water management. When pear trees bloom, insufficient nutrients affect fruit set and the swelling of young fruit, so urea should be applied 10-20 days before flower buds break. The amount applied is generally determined by tree age, tree vigor, yield and the nutritional status of the first half of the year. Spraying a 0.20%-0.50% boric acid solution during the flowering period and after flowering can increase the fruit-setting rate.
2. Flower thinning. The main purposes of flower thinning: first, to reduce nutrient consumption during the flowering period, increase the fruit-setting rate and overcome alternate bearing; second, to ensure a moderate fruit load, with large and uniform fruit and fewer cull fruits. Usually thinning flower buds is better than thinning flowers, thinning flowers is better than thinning fruit, and thinning early is better than thinning late. The method to use is then decided according to the year's flower quantity, tree vigor, weather and pollination and fruit set. For example, where there are many flowers, the tree is vigorous, the weather is good and the workload is heavy, flower buds and flowers can be thinned early, with final fruit thinning last. Conversely, only one final fruit thinning is needed, and fruit thinning must be completed within 4 weeks after petal fall.
3. Supplementary pollination
3.1 The necessity of pollination. Most pear cultivars are self-unfruitful. When the flowering period encounters adverse weather such as strong winds, dry hot wind and sand, overcast rain, low temperatures during flowering or frost, the activity of pollinating insects is affected, or the floral organs are damaged, all of these markedly affect pollination and reduce the fruit-setting rate. Because bees collect pollen while moving along rows, the probability of crossing between rows is only 27%-30%, which is especially unfavorable for pollination in densely planted pear orchards where pollinizer trees are planted in rows. Moreover, pear pollen cells only begin to form in early spring, in February-March. In pear orchards with poor management the previous autumn or in an on-year, insufficient stored nutrients cause poor pollen development or abortion the following spring. Even if pollinizer cultivars are planted, poor natural pollination still occurs. If artificial supplementary pollination is used, the fruit-setting rate can increase by 1-5 times, and the yield can exceed 1.50-4 times.
3.2 Pollination methods (1) Pollination by bees: place 1 hive per 10 mu of pear orchard, putting it into the orchard 2-3 days before flowering. In orchards without pollinizer trees, pollen collected in advance can be placed at the entrance of the hive so that bees become covered with it as they come and go, thereby transferring pollen. (2) Rolling pollination with a feather duster: in orchards with pollinizer trees, at full bloom, first roll a feather duster over the flowers of the pollinizer trees to pick up pollen, then transfer it to the main cultivar and gently roll to pollinate, repeating 1-2 times. (3) Manual spot pollination: where there are no pollinizer trees, or the pollinizer trees are in an off-year with insufficient flowers, or the weather during flowering is poor, manual spot pollination can be used. The spotting tool can be a paper spill made by tightly rolling newspaper, or a piece of bicycle valve tubing inserted onto a handle. Each time pollen is picked up, more than ten flowers can be spotted. (4) Dusting and spraying pollination: for pear orchards or years requiring pollination over a large area, a small duster or liquid sprayer can be used for pollination. When dusting, generally 1 part pollen is mixed with 20-30 parts dry starch and used immediately. The liquid spray formula is: 50 g of pollen with anther shells placed in 25 kg of water to make a suspension, and after filtering out the anther shells it is ready for use. Or 15 g of pure pollen added to 25 kg of water, with 0.10% boric acid and 10% sucrose, mixed and sprayed. It must be sprayed within 2 hours.
3.3 Pollen collection methods. Choose cultivars with strong compatibility and a large amount of pollen as pollinizer cultivars. Collect anthers that are mature and about to split or have just split, spread them thinly on smooth paper, and dry them in diffused light or in a shaded place at a room temperature of 23-25°C to make the anthers split. When collecting pollen in large quantities, it is advisable to go 1 week earlier to the southern regions, where the flowering period is earlier, to collect flowers and obtain pollen. Store the collected pollen under low-temperature, dry conditions for later use.
4. Pest and disease control. The period when pear flower buds break is exactly when adult pests such as the pear psylla, pear two-spotted aphid, pear lace bug, hawthorn red spider mite, pear fruit borer and pear star caterpillar emerge from overwintering. Soil pests such as scarab beetles and pear fruit sawflies also begin to emerge. Before flowering, pathogens such as pear scab and brown spot also begin to infect and spread. Insecticide types include “omethoate EC at 1500 times dilution, isocarbophos EC at 1000 times dilution, and fenvalerate EC at 3000 times dilution; fungicides include: 50% carbendazim wettable powder at 600-800 times dilution, 70% thiophanate-methyl wettable powder at 800-1000 times dilution, and 70% mancozeb wettable powder at 400-500 times dilution. Insecticides and fungicides can be mixed for use.