Citrus branches can be classified according to their growth time into spring, summer, autumn, and winter shoots. Since spring shoots are relatively neat and tidy, they generally do not need to be thinned. Therefore, the main targets for thinning are summer shoots and autumn shoots, and chemical thinning methods are commonly used. The period from May to July is the time for summer shoots of citrus. Below, we will introduce the methods of chemical thinning using this as an example.
1. Paclobutrazol
(a) Action Characteristics: Paclobutrazol is a triazole-type plant growth regulator that can be used to regulate morphogenesis. Its main function is to inhibit gibberellin synthesis, reduce auxin levels, and slow down shoot emergence and growth.
(b) Application Method: After the flowering of citrus is completed and the spring shoots are mature, the first thinning agent is applied. After 10-15 days, the second thinning agent is applied; Recommended dosage: 25% Paclobutrazol 400-500 times + potassium dihydrogen phosphate 500 times. If the summer shoots have emerged, they need to be removed before spraying Paclobutrazol or spraying shoot-killing agents. Paclobutrazol should be sprayed before the summer shoots emerge for better results.
(c) Precautions:
① During the use of Paclobutrazol for thinning, various nutrients required for plant bud differentiation should be supplemented in time. For trees with vigorous growth, flowering promotion methods such as girdling can be considered.
② For areas with long-term drought, the frequency and concentration of Paclobutrazol should be appropriately reduced to avoid affecting the growth of spring shoots next year. Excessive concentration of Paclobutrazol can also cause phytotoxicity.
2. Flurprimidol
(a) Action Characteristics: Flurprimidol is a contact and local systemic tobacco lateral bud inhibitor, mainly inhibiting plant cell division, thereby inhibiting lateral bud growth, controlling shoot emergence, and promoting nutrient supply to fruits.
(b) Application Method: Flurprimidol is effective for summer shoots below 2 centimeters, cannot kill newly developed leaves, has high safety, and also requires mature spring shoots. After the young fruits turn green, the medication is applied. The medication can control thinning for more than 25 days before the summer shoots emerge. The recommended concentration is 12.5% Flurprimidol 500 times. Spraying around the edge of the canopy is sufficient.
(c) Precautions:
① Do not use gibberellin and other agents within one week after spraying Flurprimidol. Generally, another spray can be applied after 20 days.
② Flurprimidol is generally not suitable for mixing with other pesticides. When spraying, attention should be paid to the method to avoid the liquid drifting onto adjacent crops and causing damage.
Conclusion
In conclusion, the commonly used pesticides for citrus thinning are Flurprimidol and Paclobutrazol. Each of them has its own advantages and disadvantages, so choose the one that suits you. The key is to pay attention to the timing and method of spraying pesticides. Of course, besides chemical thinning, manual thinning, girdling thinning, and nutrient thinning methods can also be used reasonably.
FAQ
1. How do I know if my citrus trees need thinning?
Typically, if your citrus trees are producing too many fruits, resulting in small-sized or poor-quality fruits, it might be an indication that thinning is necessary. Additionally, if the branches are overcrowded and sunlight cannot penetrate through the canopy effectively, thinning might be required to improve air circulation and fruit development.
2. When is the best time to thin citrus trees?
The best time to thin citrus trees is typically after the flowering period and when the fruits are still small and green. For most citrus varieties, this usually falls in the spring or early summer months. Thinning too early may result in fruit drop, while thinning too late may affect fruit size and quality.
3. How do I thin my citrus trees manually?
Manual thinning involves physically removing excess fruits by hand. This can be done by gently twisting or snipping off the excess fruits with pruning shears. It's important to leave space between the remaining fruits to allow for proper development. Avoid damaging the branches or leaving behind jagged cuts that may invite disease.
4. Can I use organic methods for citrus thinning?
Yes, there are organic methods available for citrus thinning. These may include hand thinning, which involves manually removing excess fruits, or using natural plant growth regulators derived from plant extracts. Organic citrus thinning methods are often preferred by growers who follow organic farming practices.
5. Are there any risks associated with chemical thinning?
While chemical thinning can be effective, there are potential risks to consider. Over-application of chemical thinning agents can lead to phytotoxicity, causing damage to the tree or affecting fruit quality. Additionally, improper timing or application methods may result in unintended consequences such as poor fruit set or yield reduction.
