What are the techniques for emasculation of chestnut?

    Chestnut is a monoecious tree species, and the number of male flowers is 1200 to 2000 times that of female flowers. Male flowers open first, 8 to 10 days earlier than female flowers, and the flowering period is longer, lasting 17 to 18 days, with a large amount of pollen. Therefore, under the premise of ensuring pollination, timely thinning out a large number of male flowers to reduce the nutrients consumed by male flowers can improve flower quality and fruit set rate. A simple emasculation technique for chestnut is introduced here.

    I. Emasculation time

    The flowering period of chestnut is about 1 month after sprouting, and the best time for emasculation is when the male inflorescences grow to 1 to 5 cm. The difference between male inflorescences and female inflorescences is: male inflorescences are spike-like inflorescences, while female inflorescences have swollen stigmas with the involucre exposed.

    II. Emasculation techniques

    When the ratio of female to male flowers in chestnut reaches 1:120, pollination needs can still be ensured, so removing 80% to 90% of the male inflorescences is sufficient. ① During winter pruning, pay attention to thinning out weak branches or heavily shortening male flower branches. ② At sprouting, wipe off the buds on the lower part of fruiting branches, remove newly grown male flowers, and pinch off the shoot tips before the fruit. ③ Pay attention to thinning out inflorescences in the inner canopy, and retain male flowers on the top of the crown and peripheral branches to facilitate pollination. ④ At the early stage of inflorescence formation (the whole inflorescence is less than 2 cm), retain 3 to 4 bisexual inflorescences on the upper part of new shoots, and wipe off all male inflorescences on the lower part. ⑤ Use shuxiongchun for emasculation. Experiments have shown that when chestnut male flowers grow to about 10 cm and mixed inflorescences are 2 to 3 cm, spraying shuxiongchun (produced by the Mountain Area Research Office of the Beijing Academy of Agriculture and Forestry Sciences) at 1000 to 1300 times dilution on the leaves gives better results. Three days after spraying, the leaves begin to curl, which is a normal pharmacological response; 5 days after spraying, male flowers begin to drop; 7 to 8 days later, male flower drop reaches its peak, and the effect lasts 10 days. If the effect is not ideal, spray once more. Note that if the spraying concentration is too high, the leaves may be damaged; if the concentration is too low, the male flowers are not easy to drop; the spraying time should not be too early, otherwise the leaves will curl severely. The spraying amount should be controlled so that the spray covers evenly without dripping. For each backpack sprayer, add 1 bottle of 10 ml shuxiongchun to spray 7 to 8 8-year-old chestnut trees.

    III. Precautions

    Chestnut is a wind-pollinated fruit tree, and a single pollen grain can travel farther in strong wind. When the wind is weak, it does not exceed 20 m. Artificial supplementary pollination can be carried out. Stamen pollen has strong vitality and can be stored at room temperature, maintaining germination for up to 1 month.