Detailed Explanation of Key Points on Seedless Lychee Cultivation Techniques
Regarding lychee, I think what everyone usually eats more of is seeded lychee, or small-seeded lychee, while seedless lychee is still relatively rarely seen. When it comes to lychee, I think everyone will think of “a galloping horse raises dust as the imperial concubine smiles, no one knows it is the lychee that arrives”, and below let's learn about seedless lychee together.
What Is Seedless Lychee
Seedless lychee was introduced by the Dongguan Forestry Science Research Institute, and has the advantages of early fruiting, high yield, stable yield, relatively good quality, and being seedless. In order to optimize and adjust the lychee variety structure in Zhuhai, provide a scientific basis and guarantee for the large-scale promotion of seedless lychee in Zhuhai, and avoid losses that might be brought to fruit growers by blindly introducing varieties directly for production, the Zhuhai Fruit Tree Science Research Institute began "Research on the Introduction and Cultivation of Seedless Lychee" in 2000, and achieved very good results. On June 14, 2003, an expert review panel headed by Professor Lin Shunquan, director of the Institute of Horticultural Biotechnology of South China Agricultural University and doctoral supervisor of the College of Horticulture, unanimously approved the project acceptance.
The seedless lychee fruit is obliquely heart-shaped, with an average single fruit weight of 30 grams and a maximum single fruit weight of 42.3 grams. The mature fruit peel is bright red, the soluble solids content is 16%, the edible rate is about 80%, the seedless trait of the fruit is stable, the seedless rate is 97%, and the flesh is crisp, smooth, and juicy, with medium quality. In Zhuhai, the initial flowering period of seedless lychee is around late March, the flowering period is about 24 days, and the fruit ripening period is from mid-to-late June to early July. From flower drop to fruit ripening, the entire fruiting period is about 75 days. Tests show that under the high-temperature and high-humidity climate conditions of Zhuhai, seedless lychee shows very good adaptability, early fruiting, and high yield, has no strict requirements for soil, can grow vigorously and quickly from planting until fruiting, can resist the effects of rainy weather during the flowering period, and the fruit is basically not harmed by the lychee stem-end borer.
Seedless Lychee Cultivation Techniques
1. Proper close planting
Adopt dwarfed close planting, with row spacing of 3.5×4.5 m and 42 plants per mu. The planting hole is 1 m in length, width, and height. Use 3.5 kg of cake fertilizer, 40 kg of farmyard manure, 30 kg of green manure, and 1 kg of lime, mix evenly with topsoil, and fill in layers. At planting, use one-year-old strong seedlings about 60 cm tall, with a trunk diameter of about 1 cm, 3-4 main branches, no pests or diseases, and well-developed roots.
2. Scientific fertilization
1. Soil fertilization: for young trees that have not yet fruited, frequently apply thin decomposed organic fertilizer water, watering 2-3 times per flush of shoots, to ensure each flush emerges quickly, neatly, and robustly. For trees that have already fruited, generally apply 30 kg of decomposed organic barnyard manure per plant, split into two applications, at flower drop and before and after fruit harvest. In addition, before flowering, during fruit development, and during autumn shoot emergence, apply an appropriate amount of decomposed quick-acting peanut bran cake fertilizer. The application amount is generally determined according to each period, tree vigor, and canopy size.
2. Foliar topdressing: spray leaves with 1% peanut bran water to increase the nutrients needed by the plant.
3. Reasonable soil drainage and irrigation
During the fruit development period and the emergence period of each flush of shoots, if dry weather occurs, use the already installed micro-sprinkler irrigation system to irrigate and spray water timely and appropriately. During the full blooming period of female flowers, when dry-hot southwest winds occur, spray clear water 1-2 times every early morning onto the blooming female flower panicles; when controlling winter shoots in winter, use soil loosening and root cutting measures to control water; during the fruit ripening period, when severe drought is followed by concentrated rain, drain promptly to prevent fruit cracking.
4. Scientific tree management
1. Shaping and pruning of non-fruiting trees: 1-2 year old trees are basically allowed to grow freely, some trees with too many branches are appropriately thinned, and branches that are too weak need appropriate shaping and pruning.
2. Tree management of fruiting trees
① Timely and moderate pruning, and timely shoot release. Because fruiting trees are still relatively small, mainly light pruning is used. 7-10 days after applying post-harvest fertilizer, mainly prune diseased and pest-damaged branches, slender weak branches, and shaded crossing branches. After pruning, the new shoots that emerge should be thinned, leaving 1-2 strong shoots per branch, and 2-3 flushes can be released. Generally, the last flush is released in early October and controlled to mature in early December.
② Apply girdling technology. After the last autumn flush matures, girdle the main branches to control winter shoots; winter shoots that have already emerged can be removed manually; during the fruit growth and development period, spring and summer shoots that have already emerged can be removed manually.
③ Shake flowers after rain. During the full flowering period in rainy, windless weather, especially when the temperature is relatively high, manually shake the flowers once the weather clears, to shake off water droplets on the panicles and prevent flower rot.
④ Appropriately thin flowers and promptly thin fruit in stages. Cut back or thin overly long and overly numerous flower panicles so that panicle length remains at about 15 cm; because seedless lychee can set fruit through self-pollination, cross-pollination, or without pollination, and can adapt to the effects of adverse weather conditions, the fruit-setting rate is generally relatively high. Excessive fruiting affects fruit size, and in addition some fruits set but never develop flesh and can remain until maturity, becoming empty-shell fruits that consume tree nutrients in vain. Therefore, when the fruit is the size of a broad bean, we carry out the first fruit thinning to remove excess fruit, keeping about 10 fruits. When it can be determined that some fruits are empty-shell fruits, these fruits are removed in the second thinning when the fruit shoulder is slightly red, and finally about 5 fruits are retained per panicle.
5. Integrated pest and disease control
Adopt integrated control methods to keep pest and disease damage below the level that causes economic loss.
1. Agricultural control: combined with pruning, cut off dead branches, shaded branches, and diseased and pest-damaged branches, collect residual branches, fallen leaves, and fallen fruits for centralized disposal, and do a good job of winter orchard cleaning to reduce overwintering pest and disease sources; strengthen cultivation management, fertilize reasonably, enhance tree vigor, and improve the plant's resistance.
2. Physical control: use the death-feigning behavior of scarab beetles and lychee stink bugs for manual capture, and use frequency-vibration insect-killing lamps to predict and trap pests such as scarab beetles and fruit-sucking noctuid moths.
3. Biological and biochemical control: protect and utilize various natural enemies of pests to control pest populations; carry out timely and appropriate control according to different pests and diseases in shoot, flowering, and fruit periods. ① Pest control. In the tender shoot period, flower panicle emergence period, and fruit period, according to specific conditions, alternately use 0.3% neem oil EC at 1000 times, 10% cypermethrin at 1500 times, and 90% trichlorfon at 800 times for spraying. Because the main lychee pest during the fruit period, the lychee stem-end borer, basically does not harm seedless lychee fruit, overall, the number of pesticide applications is very small. ② Disease control. Mainly downy blight, after the beginning of spring when soil temperature becomes warmer, spray Bordeaux mixture or lime under the tree canopy for soil disinfection; during the flower panicle development period, spray fungicides 1-2 times according to disease conditions; during the fruit growth and development period, spray fungicides 1-2 times. Commonly used agents include Bordeaux mixture (1:1:100) and 30% copper oxychloride at 500 times.
6. Timely harvest
When the peel of seedless lychee is bright red and the soluble solids content is above 16%, the fruit is excellent in color, shape, and quality and can be harvested; harvest generally begins in mid-to-late June.
7. Pollution-free cultivation techniques
Throughout the entire production process of seedless lychee, comply with the national operating procedures for green food production and prevent pollution.
Through several years of introduction observation, experimental demonstration, and after planting in Zhuhai, the good variety characteristics of seedless lychee can be fully brought into play. We preliminarily believe that seedless lychee can be propagated and promoted in Zhuhai and will certainly obtain good social and economic benefits.
Is Seedless Lychee Genetically Modified?
No. When talking about seedless lychee, it is easy to think of seedless watermelon. Like seedless watermelon, seedless lychee is not a genetically modified food. It is not completely without a seed; rather, the seed is incomplete and does not form properly during development, and is extremely small.
According to plant science Ph.D. Shi Jun, under normal circumstances, after lychee pollination, the ovule together with the outer integument begins to develop, and the result is the lychee seed we are familiar with. As for the crystal-clear lychee flesh, it is an aril developed from the seed stalk. Why is it called an aril? Because it is not developed from the ovule wall, but from the funicle and placental tissue. Therefore, they are not closely related to the seed, but originate from maternal cells. Thus, as long as the seed does not develop, seedless lychee is formed.
“A galloping horse raises dust as the imperial concubine smiles, no one knows it is the lychee that arrives.” Lychee has a cultivation history of thousands of years in our country. Seedless lychee was originally wild lychee. The reason for its formation may be that during long-term cultivation, some lychee branches produced bud mutations or branch mutations due to environmental factors, causing the lychee seeds they produced to be unable to develop.
In fact, seedless lychee is just like our seedless watermelon. It is only a variety of lychee. Seedless lychee is a kind of wild lychee. Since many people now like to eat seedless things, the market prospect of seedless lychee is very large, and so it is being planted by more and more people.