Proper flower and fruit management during longan cultivation

1) Releasing bees for pollination.

Longan is a dichogamous insect- and wind-pollinated flower, mainly pollinated by insects. Bees are most active within a radius of 250 m, so bee colonies are best kept dispersed throughout the orchard. For every 0.46-0.53 sq km of longan orchard, one bee colony (8-10 hives) should be provided. In large longan bases, use 50 colonies as one group, with one group of colonies placed every 500 m. The colonies used for pollinating fruit trees should be strong colonies with new queens, and their feeding and management should be strengthened to promote colony growth and increase bee activity. The colonies should be moved to the orchard and set up two or three days before longan flowering. During the bee release period, spraying of insecticides should be suspended in this orchard and in nearby orchards, vegetable gardens, and crops.

2) Artificial pollination.

During the peak blooming period of male flowers, repeatedly dab a clean damp towel lightly over the anthers to make the pollen adhere, then quickly rinse it into water; once a relatively large amount of pollen has accumulated, immediately spray it onto the female flowers with a clean sprayer. Pollen must not remain immersed in water for more than 20 minutes; if it exceeds 30 minutes, the pollen will germinate and become ineffective. When immersing whole clusters of blooming flowers in water to wash off pollen, several people should collect flowers at the same time, wash out the pollen quickly within 1-2 minutes, filter it through nylon mesh gauze, and then spray it immediately. If rainy weather prevents pollination, pollen should be collected in advance and stored in a low-humidity, dry container, then diluted in water and sprayed quickly once the weather improves.

3) Fruit thinning.

Fruit thinning is best done from mid-June to early July. Thin early for early-maturing cultivars and later for late-maturing cultivars. For trees with more than 1/4 of the terminal new shoots bearing no fruit, do not thin out fruit clusters; for trees with too many fruit clusters (80%-100% of vigorous fruiting mother branches bearing fruit), remove 10%-30% of the fruit clusters and leave only 60%-70% of the vigorous fruiting mother branches. Cut off overly dense fruit clusters, fruit clusters at the top of the canopy, fruit clusters with too few set fruits, and fruit clusters damaged by pests or diseases, leaving fruit clusters in the middle and lower parts of the canopy shaded by branches and leaves.

After cluster thinning, fruit can also be carefully thinned cluster by cluster, because under the same cultivar and the same cultivation conditions, single-fruit weight and flesh sugar content are greatly affected by the number of fruits per cluster. When the thickness of the main cluster stalk is the same, the more fruits set per cluster, the smaller the individual fruit; when too many fruits are set, the sugar content of the flesh is also reduced.

The method for thinning fruits per cluster is to first cut away overly dense spikelets, remove small fruits, pest- or disease-damaged fruits, and double fruits, and also appropriately thin out excessive fruits on spikelets, until the number of fruits retained matches the number that should be retained for the thickness of the fruit cluster. Generally, for large-fruited types, retain 20-30 fruits per cluster; for medium-fruited types, retain 30-50 fruits per cluster.

4) Bagging fruit clusters.

Bagging fruit clusters helps prevent damage to the fruit by stink bugs, yellow (black) wasps, bats, and others, makes the fruit skin smooth and bright yellow, reduces fruit cracking, and improves commercial quality. Trials have shown that bagging longan fruit clusters with plastic mesh gauze bags not only allows ventilation but also provides a certain degree of shading, can lower the fruit surface temperature at noon by 0.2-1.5°C, reduce the occurrence of sunburn on young fruits, and serve to prevent insects and bats.