Application of plant growth regulators on fruit trees--Apple

1.  Root growing
Naphthalene acetic acid (NAA) ，
According to the test, using 500mg/L Naphthalene acetic acid (NAA) powder, dipping the apple dwarfing stock M4 and M2, the root rate was 50% and 25% respectively;   After soaking in 50mg/L Naphthalene acetic acid (NAA)  solution for 24 hours and inserting the rod, the rooting rate was 35.7%.

2.  Promote branches growth
Cytokinin: Apply 600~800mg/L cytokinin directly on the buds. Apply the amount of ointment to each bud the size of a red adzuki bean. The appropriate concentration for use during the growing season is 600~800mg/L. Applying it to full buds can effectively increase the number of branches of saplings, which is beneficial to accelerating growth and ripe early. It can also speed up the reproduction of improved seeds, but it should be use on strong trees. It is base on good health and management, and the best use period is during the growing season.

3.  Inhibit the growth of new shoots
Paclobutrazole (Paclo) soil application.
After picking the apples, apply 25g of 15% paclobutrazol wettable powder in the ditch around the rhizosphere of each tree to control the shoot length and increase the number of short branches, thereby enhancing photosynthesis and improving the fruit setting rate.  After applying Paclobutrazole (Paclo), the length of new shoots decrease by 10.7%~46.5% and the yield increase by 31.8%~202.6% in the second year.   In the third year, the length of new shoots decreased by 10.8%~62.6% and the yield increase by 83.3%~141.7%.   It also makes the leaf color darker, the leaves thicker, and the crown dwarfed and compacted.   Paclobutrazole (Paclo) is suitable for foliar spraying in early May.   The concentration of 215~300 mg/L has the best effect.   The inhibitory effect is obvious that year, and the effect can last for 3 years. The inhibitory effect of foliar spray is weaker than that of soil application.

Paclobutrazole (Paclo) apply to branches
20~30 days after flowering, apply 1000mg/L liquid to the trunk, which can slow down the growth of new shoots, dwarf the plant, increase the number of flowers, improve the fruit setting rate and yield, make the fruit uniform in size, good in color, improve the quality of the fruit, and promote the growth and development of the root system, reduce disease and fruit cracking losses.

4. Improve fruit setting rate, preserve flowers and fruits, and enhance plant growth.
Compound sodium nitrophenolate (ATN) is sprayed twice with 6mg/L liquid in the apple flower bud differentiation stage and young fruit stage, which can increase the fruit setting rate by 15% to 20%, increase the mineral elements in the leaves and fruits, and also make the fruit harder.    Increase、extend the storage period .

Diethyl aminoethyl hexanoate (DA-6)
spray once with DA-6 by 8~15mg/L during the initial flowering stage, after fruit setting, and during the fruit expansion stage. It can preserve flowers and fruits, increase the fruit setting rate, and make the fruits uniform in size and good in color.  Sweet taste, ripens early, increases yield.

Gibberellic Acid 
Spraying 10mg/L gibberellin during the flowering period can increase the fruit setting rate of apples.

Brassinolide can increase the chlorophyll content in apple tree leaves, increase photosynthesis, and improve the fruit setting rate, yield and quality of apples.  The concentration of 0.03mg/L has the best effect. However, during production, attention should be paid to thinning flowers and fruits to ensure fruit quality.  It is also necessary to strengthen the management of soil, fertilizer and water in orchards, strengthen the prevention and control of pests and diseases, and adopt comprehensive technical supporting measures such as shaping and pruning to achieve the goal of high yield and high quality.

Ethephon 
spray a mixture of 125mg/L ethephon and 1000mg/L butyric hydrazide twice during the vigorous growth period of new shoots, which is beneficial to the formation of flower buds in the current year and can also increase the yield in the second year.

5. Thinning flowers and fruits
Ethephon has a thinning effect within 50 days from the flowering stage to the full blooming stage.  It can thinning both flowers and fruits.  Use a concentration of 300mg/L and add 20mg/L naphthalene acetic acid.  Spray twice during the early flowering stage and after the full blooming stage.  The effect is significant.

6. Enlarge fruits, prevent pre-harvest fruit cracking and fruit drop, and improve fruit quality.

Naphthalene acetic acid(NAA)
To use Naphthalene acetic acid (NAA) to prevent pre-harvest fruit drop, it should be apply 30 to 40 days before harvest.  The spray concentration of Naphthalene acetic acid (NAA) should be controll at 20 to 30 mg/L, with 20 mg/L  better,  For some fruit drop, For varieties that appear earlier in the season, if the effect of one application is not stable enough, you can spray twice.

Compound sodium nitrophenolate (ATN),
after the apples set fruit, spray 4 mg/L liquid Compound sodium nitrophenolate (ATN) 6 times every 10 to 20 days.  The yield increase effect is extremely significant, and the weight of the single fruit increases by 10% to 12%.  Level 1 Fruit yield increases by 45%~48%.