Unrelenting management during the flowering period ensures high yields and a bountiful harvest of apples.

Increasing apple fruit set and preventing flower and fruit drop are essential prerequisites for achieving high yields and a bountiful harvest; therefore, in production practice, it is imperative to employ multiple strategies to enhance both flower pollination and fruit retention.

1. Thinning flowers and fruits

Thinning flowers should begin at the stage when flower clusters are separated and be completed before flowering. Leave one flower cluster every 20–25 centimeters, removing weak branch flowers, axillary flowers, and apical flowers, while retaining more flowers on short shoots. At each flower cluster, eliminate the marginal flowers, keeping only the central flower. Fruit thinning starts one week after peak bloom and is finished 25–30 days after flowering, taking about 20 days in total. Typically, leave one fruiting spur every 20–25 centimeters, with only one central fruit per spur. Pay attention to selecting well‑shaped fruits with a high fruit‑shape index, free from diseases and pests, and growing in a drooping position on medium‑to‑long fruiting spurs; remove young fruits that point upward, have irregular shapes, or show poor development.

2. Artificial pollination

Immediately after the morning dew has dried, collect buds or freshly opened flowers, bring them indoors, and use tweezers or gently rub the two flowers together to release the pollen. Remove any remaining stamens, petals, and other debris; for larger quantities, employ a specialized pollen‑extraction machine to remove the filaments and other impurities. Spread the anthers on clean white paper and place them in a well‑ventilated, shaded area, maintaining an indoor temperature of 20–25°C and a relative humidity of 60%–80%. After 1–2 days, the pollen sacs will naturally split open, releasing yellow pollen grains. Store the pollen—still enclosed in its sacs—in a dry container for later use. Typically, one apple inflorescence yields 1–2 flowers, which both thin the cluster and avoid compromising pollination and fruit set on the tree. Manual pollination should be carried out on a clear day between 9 a.m. and 4 p.m. The stigma’s ability to accept pollen is at its peak on the second day after flowering, resulting in the highest fruit‑set rate.

3. Bee release during the flowering period

Bee pollination

Modern fruit tree production advocates the use of honeybees for pollination; placing beehives in apple orchards during bloom can significantly increase fruit set. Two to three days before flowering, introduce the hives into the orchard to allow the bees to acclimate to their surroundings. With a foraging radius of approximately 50 meters, one hive per 5 to 10 mu of orchard is sufficient to provide effective supplemental pollination.

Mason bee pollination

Common species of mason bees include Osmia cornuta and Osmia rufa. Mason bee pollination is not only simple to implement but also highly effective, making it an efficient method for improving apple fruit set today. Mason bees are easy to rear, have a wide foraging range, and exhibit activity levels 70–80 times greater than honeybees; they can visit 10–15 flowers per minute. Placing 60–80 mason bees per acre of apple orchard yields pollination results that surpass those achieved with honeybees.

4. Frost protection during the flowering period

Before frost sets in, irrigate or spray the ground to regulate near-surface air temperature, slow the decline of tree‑body temperature, delay phenological development, and mitigate frost damage. Alternatively, use crop residues, chopped weeds and leaves, sawdust from pruned branches, and other organic materials as fuel; pile these up at the upwind edge of the orchard to form smoldering smoke piles, and ignite them when temperatures drop to 2°C to disperse cold air and raise orchard temperatures.

5. Pinching the growing tip

For varieties with low fruit set, pinching the secondary shoots on the fruiting spurs about 10 days after flowering can help curb competition for nutrients between these shoots and the developing fruits, thereby improving fruit set.

6. Pinching and bending branches

Perform tip twisting, branch spreading, and branch pulling on the shoots. Fully open the branch angles to shift growth from vegetative to reproductive development, promote nutrient accumulation, enhance the fullness of floral buds, and improve bud quality.

7. Strengthen fertilizer and water management

Strengthen post‑flowering soil, fertilizer, and water management to enhance flower bud quality. Fruit set rate is largely determined by the quality of flower buds, which in turn depends on the tree’s nutritional status during bud formation. Therefore, to produce high‑quality flower buds, first ensure a robust vegetative growth foundation in the early stages: promote timely cessation of new shoot elongation, maintain moderate tree vigor, and accumulate ample organic reserves. Second, apply a sufficient base fertilizer in autumn, combine this with irrigation, and supplement with a late‑autumn foliar spray of 0.3%–0.5% urea to delay leaf senescence, extend the period of photosynthesis, and increase the tree’s stored nutrient reserves, ultimately resulting in large, plump, and superior flower buds.

8. Prevention and control of diseases and pests

During the flowering period, pests that damage flowers and leaves include leaf‑rolling caterpillars and Japanese beetles; timely spraying with appropriate pesticides is essential. At this stage, biopesticides should be prioritized, or manual removal may be employed. Diseases that harm flowers and leaves include blossom blight, powdery mildew, and early leaf drop; prompt preventive measures and timely control are crucial to minimize damage and promote healthy fruit development.