There are more than 20 varieties of lychees cultivated in Taiwan, mostly in the central and southern regions, and it is one of Taiwan's important economic fruit trees.
At present, the main planting varieties are "Hak Ip" and "Yu Her Pau". Among them, Yu Her Pau has the advantages of early maturity, early production period, large fruit shape, rich meat quality, and high sugar content. The cultivation area in the southern region is gradually increasing, but Yu Her Pau is often suffering from poor fruit set or inferior fruit quality due to climatic factors or improper cultivation management.
Possible problems and reason during the fruiting period of “Yu Her Pau” lychee:
Low fruit set
1. Panicle size too long cause excessive flowers but less female flowers.
2. Low pollen germination rate, reducing the chance of fertilization.
3. Low temperature and excessive rain may reduce pollen germination rate, affect pollinating insect activity, and further reduce the chance of pollination and fertilization.
4. The peak blooming of male and female flowers did not simultaneously reduce the chance of pollination.
5. Competition for nutrients: When new shoots sprout or fruit grows rapidly on the bunch, inadequate assimilate allocation may cause fruit drop.
Fruit cracking
When the fruit rapidly expands, it can cause the skin to split either radially or transversely. If the soil suddenly becomes dry or wet too much at this period, it will cause the fruit cracking worse.
Diseases and pests
Yu Her Pau lychee is susceptible to damage from the lychee moth, fruit sour rot, and downy blight from the young fruit stage to the mature stage, especially during the rainy season and in environments with poor sunlight and ventilation.
Improvement measures:
Panicle pruning:
In the early stage of flowering, remove weak and diseased branches, control the number of fruit-bearing branches, and provide sufficient sunlight and good ventilation for flowering branches. Moderately removing young leaves can prevent excessive competition for nutrients between leaves and panicle. Thinning panicle can promote their growth and the development of female flowers then increasing fruit set.
Enhancing pollination and fertilization:
Adjusting the flowering time of branches, so that female flowers will bloom in early to mid-March the temperature is more stable during the time, so as to increase the success rate of pollination and fertilization. In addition, by breeding pollinating insects such as bees from the beginning of the small flower blooming until the end of the flowering period to increase pollination opportunities.
Supplementing plant growth regulators:
Spraying plant growth regulators is one of the methods to promote fruit setting, generally used during the flowering or young fruit stage. However, improper use can easily produce malformed fruit reduce fruit quality.
Water management:
Proper use of irrigation during fruit development is necessary to prevent large changes in soil moisture which easily caused serious fruit cracking.
Fertilization management:
The fertilization for Yu Her Pau will be practice after fruit harvest (post-harvest fertilization), from flower bud differentiation to pre-flowering (basal fertilizer), and from young fruit to fruit enlargement period (top dressing fertilizer). For basal fertilizer, choose fertilizers with low nitrogen and high phosphorus and potassium content, and supplement with calcium, magnesium fertilizer, and trace elements as appropriate. During the young fruit period, fertilizers with higher nitrogen content can be applied to promote fruit set and grow. Then post-enlargement stage should reduce nitrogen fertilizer and increase phosphorus and potassium fertilizer to increase fruit sweetness and avoid competition for nutrients, which can cause fruit drop due to the emergence of new sprout during fruit growth.
Orchard maintenance and pest control:
Pruning can increase the plant's ventilation and direct sunlight promotes the plant's healthy growth, flower panicles thinning can prevent diseases. Proper use of pesticides can control pests or using the non-pesticide control to prevent. Good orchard sanitation is necessary to practice, removing fallen or diseased fruits, pruning or elevating fruits near the ground can reduce the density of pathogens and minimize contact with them. |
