How to prevent and control citrus fruit cracking? Master these cultivation techniques

Every year in June and July, after the second physiological fruit drop, citrus generally does not drop fruit, but then fruit cracking of varying degrees occurs. The peak period of fruit cracking generally occurs in early August and in the two periods from late August to early September. Citrus fruit cracking is one of the important physiological diseases of citrus during the fruit-swelling period. It occurs commonly in all regions, causes fruit drop during the fruit-swelling period, often results in large-scale yield reduction, and can also induce pests and diseases, causing citrus fruit to rot and fall off.

Analysis of the causes of citrus fruit cracking: First, differences among varieties. In the same orchard, different varieties have different degrees of fruit cracking, with uneven peel thickness; in particular, varieties with thinner peel at the top of the fruit are most prone to cracking. Second, drought causes it; sudden rainfall or irrigation after a long drought is the main triggering factor. If there is long-term drought during the fruit expansion period, the fruit peel contracts and grows slowly. After rain, the flesh absorbs a large amount of water and grows quickly, while the peel growth has not yet fully recovered and grows more slowly than the flesh, causing the peel to split under the swelling pressure of the flesh and producing mechanical fruit cracking. Third, the influence of soil moisture. If the soil moisture content remains in a saturated state for a long time, it causes asphyxiation and death of new roots, and fruit cracking can be triggered when the rain stops and the weather suddenly clears; earlier water accumulation in the soil can further aggravate the occurrence of fruit cracking. The control methods are introduced as follows:

1. Maintain a relatively high but moderate moisture content in the soil, so that the water supply to citrus will not undergo drastic changes. During drought, irrigate in a timely manner. Generally, if there is no rain for half a month, irrigate once thoroughly to resist drought. In hot and dry seasons, irrigation is required once every 10 days. Spread grass over the tree disk to increase coverage and prevent soil moisture evaporation. During waterlogging, open ditches in a timely manner for drainage, and carry out shallow intertillage after heavy rain. Do not fertilize immediately after rainfall following a long drought.

2. Apply more phosphorus and potassium fertilizer and frequently apply foliar fertilizer. In late July or early to mid-August, apply 50-70 kg of decomposed human and livestock manure water per plant, plus 0.3 kg of urea and 0.2 kg of potassium chloride. After fertilizing, cover the soil and irrigate in a timely manner. For citrus trees with too much fruit set, apply more nitrogen fertilizer to increase peel thickness. During drought periods, alternately spray different types of foliar fertilizers every 7-10 days. For example, in the early stage of drought, spray Guoguang triacontanol plus urea; afterward apply potassium dihydrogen phosphate and Guoguang amino acid potassium; during the stable high-temperature stage of the drought period, use wood ash extract; and 48-52 days before harvest, spray a foliar fertilizer with ammonium molybdate, such as Guoguang amino acid molybdenum, “Hongyoutian”, etc., which can both reduce fruit cracking and promote fruit expansion.

3. Keep the growth and development of the peel and flesh in balance. During the fruit expansion period of citrus, if there is a long drought without rain, Guoguang Lieguobizhi can be used for comprehensive control. Spray a 600-fold solution of Lieguobizhi in the evening on the fruit-bearing parts of the canopy. The middle and lower parts of the canopy, which are prone to fruit cracking, are the key areas for spraying. Spray once a week for three consecutive times, and add one more spray before heavy rain. Its fruit-cracking prevention effect is more than 95% higher than other methods and can basically solve the impact of fruit cracking disease. Its principle is: Lieguobizhi contains a variety of highly active substances and a variety of chelated nutrient elements (such as potassium, phosphorus, boron, calcium, rare earths, etc.), is easy to absorb, and can provide comprehensive and balanced nutrients and regulating substances for the growth of the fruit and flesh, promote their balanced growth, regulate the synchronous development of peel and flesh, and prevent the occurrence of fruit cracking.

4. For fruits that have already cracked, remove them promptly to avoid continuing to consume nutrients and water from the tree body, and at the same time prevent the invasion of pests and diseases.