Precautions for Using Plant Growth Regulators on Fruit Trees
What should be noted when applying plant growth regulators to fruit trees? Plant growth regulators are synthetic organic compounds that promote, inhibit or otherwise alter a specific growth process in plants. Although they are trace substances, they can produce noticeable effects. But improper use often backfires, while rational use...
What should be noted when applying plant growth regulators to fruit trees?
Plant growth regulators are synthetic organic compounds that promote, inhibit or otherwise alter a specific growth process in plants. Although they are trace substances, they can produce noticeable effects. But improper use often backfires; rational use is the guarantee of fully bringing their growth-regulating function into play.
1. Choose the appropriate type of growth regulator. Different plant growth regulators have different regulatory effects on plants: some promote growth, some inhibit growth, and some retard growth. The type of regulator should be chosen according to the problem that needs to be solved in production, the properties and functions of the regulator, and economic conditions. For example, auxins can be chosen to accelerate growth, and growth retardants can be chosen to control excessive vigor.
2. Pay attention to the responses of different tree species and different cultivars to growth regulators. Different tree species and cultivars have different degrees of sensitivity to regulators, and different types and concentrations of regulators should be chosen accordingly. For example, apricot trees are not sensitive to paclobutrazol, so the dosage should be increased. Another example is the use of paclobutrazol on plum trees: Chinese plum (Prunus salicina) is not suitable for it. The choice must be made according to the responses of the tree species and cultivar.
3. Pay attention to conducting small-scale trials. Because of the influence of various factors such as climate, the quality of the growth regulator and the formulation, a unified standard cannot be followed during use. Crop species differ and cultivars differ; even the same crop and the same cultivar will vary with differences in climate and soil. Before large-area treatment, small-scale trials must first be conducted to determine the appropriate type, concentration and formulation of the regulator, so as to achieve scientific and rational use.
4. The containers used for preparing the solution must be washed clean. Different regulators have different physicochemical properties such as acidity and alkalinity, so the containers used for preparing the solution must be clean. A container that has held alkaline agents, if not cleaned, will render an acidic agent ineffective when it is later placed in it; after holding a growth-inhibiting regulator, it also cannot bring a promoting agent into effect. For example, in production, maleic hydrazide is generally used at a relatively high concentration. If residue remains and is not cleaned, and the container is used to treat at a low dose to prevent fruit drop, it will cause the fruit tree to drop both leaves and fruit, producing the opposite effect.
5. Pay attention to the application stage and time. Growth regulators act at a certain link in plant growth and development, so the application stage must be appropriate; too early or too late will not achieve the desired effect. For example, naphthaleneacetic acid (NAA) used at the young fruit stage has a fruit-thinning effect, while use before harvest can prevent pre-harvest fruit drop. It must be applied at the appropriate stage, and attention should also be paid to the time of use; generally, it is better before 10 a.m. on a clear, windless day, and it should not be used on rainy days.
6. Pay attention to selecting the appropriate concentration and formulation. Growth regulators have strong activity, so an appropriate concentration must be chosen during use: too low a concentration will not work, while too high a concentration will produce the opposite effect. For example, 24-D at low concentration can promote growth and parthenocarpy, while at high concentration it can kill plants. At the same time, a suitable formulation should also be chosen; generally, water-based formulations are used for spraying, and powder formulations are used for soil application.
7. Pay attention to the method of use. Choose the method of use according to the pathway by which the regulator enters the plant body. For example, paclobutrazol is absorbed through the roots and can be applied to the soil; daminozide is stable in soil and has a long residual effect, but it readily enters through the leaf surface, so it can be applied by spraying.
8. Pay attention to the part treated. The part to be treated is determined according to the essence of the problem. For example, to prevent flower and fruit drop with 24-D, the agent should be applied to the flowers to inhibit the formation of the abscission layer; if 24-D is used to treat young leaves, it will cause damage. Another example is using naphthaleneacetic acid or ethephon to stimulate flowering in pineapple: the solution can be poured into the cup-shaped central leaf whorl to directly stimulate flower bud differentiation, rather than being applied by soil drenching or spraying.
9. Pay attention to changes in the vigor of the fruit tree and the climate. Generally, for trees with good vigor the concentration can be slightly higher, for average vigor the conventional concentration can be used, and for weak vigor the concentration should be slightly lower or even not used. Temperature also has a great influence on regulators: at high temperature the response is fast, and at low temperature the response is slow, so the concentration used in winter and summer should differ.
10. Pay attention to the number of applications and the dosage. The number of applications should be decided according to the plant's response. Generally it is once, but if the effect is poor, it may be applied multiple times; for those that are extremely sensitive, a small amount may be applied multiple times. For example, to control excessive vigor and promote flowering in young apple trees with daminozide, it should be applied once every 10 days for 2-3 times. The dosage used must also be controlled; for example, for water-based spraying, the leaves should just be wet.
11. Use multiple agents in combination. Sometimes several problems need to be solved at the same time in production, so they can be used in combination. Those that do not undergo chemical reactions with each other can be mixed for use, achieving the effect of making the most of strengths and avoiding weaknesses, and getting twice the result with half the effort. For example, to advance the supply period of pears, when using ethephon for ripening, it can be mixed with naphthaleneacetic acid to avoid causing fruit drop. However, some agents, such as daminozide, should not be mixed with other alkaline agents, otherwise the effect will be affected.
12. Pay attention to the storage of growth regulators. Many plant growth regulators are not very stable themselves. For example, indoleacetic acid (IAA) decomposes when exposed to light; Fengguole and Xiweiyin become ineffective when they encounter alkali or acid; methyl naphthaleneacetate is volatile. They must be stored properly according to their physicochemical properties, otherwise the efficacy will be reduced.
13. Pay attention to the mutual coordination of various agricultural techniques. Growth regulators act only at a certain link in plant growth and development and cannot replace fertilizers, pesticides and other cultivation measures. To achieve ideal results in their application in agricultural production, they must be coordinated with other agricultural technical measures. For example, when treating cuttings with naphthaleneacetic acid or indoleacetic acid to promote rooting, a certain humidity and temperature must be maintained in the seedbed, otherwise rooting cannot be guaranteed.
In short, when applying growth regulators on fruit trees, one must be "both active and cautious," and consider all factors comprehensively, so as to achieve the goal.
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