How do apples chemical thinning of flowers and fruits?

How do apples chemical thinning of flowers and fruits?

1 types and characteristics of flower thinning agents

1.1 Stone sulfur mixture

Self-made: the concentration of stone-sulfur mixture made by fruit growers is 0.5% Baume; the concentration of 45% crystal sulfur mixture for commercial use is 150% 200 times, and it is sprayed for the first time at the early flowering stage (that is, 75%-85% blooming of the central flower). At full bloom (that is, 75% of the flowers of the whole tree bloom), spray for the second time.

Function: it can burn pollen, stigma and inhibit pollen germination.

Disadvantages: stone sulfur mixture has adverse effects on bees and products in the orchard.

1.2 Organic calcium compounds

Calcium is one of the necessary mineral elements for fruit trees. Calcium fertilizer is often used to improve the quality, storage resistance and stress resistance of apples. In recent years, flower thinning experiments on Fuji and other varieties have been carried out with a variety of calcium compounds, which has been proved to have different degrees of flower thinning effect. This agent is non-toxic and harmless, does not have any pollution to the environment, has low cost and good effect, and can be used in organic cultivation. At the initial stage of full flowering (that is, 75% of the central flower is in full bloom, 85% of the central flower is in full bloom), it is sprayed for the first time, and at full flowering (that is, when 75% of the flowers of the whole tree is in bloom), it is sprayed for the second time (figure 1). The concentration is 150-200 times each time, which mainly plays the role of flower thinning.

1.3 vegetable oil

Such as olive oil. When used on Hongxing apple varieties, the flower can be thinned and the fruit will not increase. The dosage is 30g / L. Shake the sprayer constantly to make the oil and water mix evenly.

Fig. 1 opening state of central flower of single plant

2 types and characteristics of fruit thinning agents

2.1 Carbaryl

It was originally a kind of carbamate insecticide with high efficiency and low toxicity, which has a good effect on the control of fruit tree heart borer. Registered in the United States in 1958. It was found that it had fruit thinning effect in 1960, and the effect was mild and stable. It was once the best fruit thinner in the United States. But the American study did not solve the problem of how to preserve the central fruit, sparse-edged flowers and axillary flowers and fruits. According to the research of scientific and technological workers in China and Japan, the effective spraying period is 1-4 weeks after full flowering, and the best spraying effect is 2-3 weeks after full flowering, that is, it is sprayed for the first time 10 days after full flowering (the diameter of central fruit is about 0.6 cm). Spray for the second time 20 days after flowering (0.9-1.1 cm in diameter). The suitable concentration is 2.0 ~ 2.5 g / L. It is not easy to produce fruit fruit, abnormal fruit and drug damage. at present, this agent is widely used as a good fruit thinning agent in China and Japan. [Jishan Huayao]

Mechanism: it has the function of internal absorption, after entering the vascular bundle in the tree, it interferes with the transport of nutrients and hormones in young fruits, hinders the transport of nutrients, and makes some young fruits fall off due to the lack of nutrients needed for development. this interference first occurs on the fruits with weak growth, causing fruit drop.

Advantages: relatively safe, low toxicity to humans and animals, not easy to accumulate in the body, no adverse effect on fruit, wide range of effective spraying period and suitable concentration, fruit thinning and pest control at the same time.

2.2 Naphthylacetic acid, sodium naphthalene acetate and similar substances

The mechanism of action is synthetic plant growth regulators, which interfere with the metabolism and transport of some hormones in the tree, thus promoting the formation of ethephon and leading to fruit drop. The suitable concentration of naphthylacetic acid and sodium naphthalene acetate were 1020 mg / kg and 30mg / kg, respectively, and the suitable concentration of naphthylacetic acid and sodium naphthalene acetate were 10 mg / kg, 20 mg / kg and 30 mg / kg respectively. Varieties with more axillary flower buds can be sprayed once at the end of blooming (that is, when more than 95% of the flowers are in full bloom).

Advantages: strong fruit thinning effect

Disadvantages: flower thinning and fruit thinning is unstable, which can easily cause serious sequelae such as upper leaf growth, deformity and inhibition of fruit growth.

2.3 ethephon

Thinning mechanism: it can inhibit the elongation of pollen tube, produce ethylene by self-dissociation, promote the formation of detached cells of young fruit stalk, and lead to fruit shedding. The general concentration is 0.3% 0.5 g / L, which can be sprayed about 10 days before or after blooming.

Advantages: ethephon can thinning both flowers and fruits, which is suitable for varieties with high fruit setting rate, serious size and difficulty in thinning.

Disadvantages: the fruit thinning effect is strong at high concentration, and there is a danger of excessive thinning in case of high temperature weather.

3 usage and matters needing attention

3.1 experiment and demonstration first

When chemical thinning of flowers and fruits is applied for the first time, a small area demonstration should be carried out.

3.2 Select the sprayer

Determine the amount of liquid used per mu: wash the sprayer with clean water before spraying, check the sprayer pressure and see if the spray head has a good atomization effect. The knapsack sprayer uses a long rod, from top to bottom, from the inside to the outside, the spray head is aimed at the flower or young fruit spacing of about 25 cm, and the amount of liquid per mu is controlled at 7500kg.

3.3 depends on the weather

It is suitable to be sprayed in sunny or cloudy days, and the suitable temperature is 20-28 ℃. If the daytime temperature during flowering is continuously lower than 10 ℃ or higher than 30 ℃, or during strong wind, chemical flower thinning is not recommended.

3.4 depends on the amount of flowers and fruits

If the number of flowers is small, chemical thinning of flowers and fruits can be avoided; if the tree is strong and the number of flowers is large in that year, which belongs to the orchard of apple production or normal year, you can use medicine to thinning flowers and fruits.

3.5 depends on the variety

The sensitivity of different varieties to chemical flower thinning and fruit thinning agents is different. In Gala, Jinshuai, Wanglin, American No. 8 and other varieties, the opening period between central flower and edge flower is longer, the lower concentration is easy to remove edge flower, and the concentration can be appropriately reduced. Fuji varieties have a short interval between the opening period of central flower and edge flower, the application concentration should be appropriately increased, and attention should be paid to the spraying period.

3.6 depends on the configuration of the pollination tree

Chemical flower thinning is not suitable for orchards without special pollination trees or pollination varieties. For orchards with pollination trees in the ratio of 1 to 8, chemical flower thinning agents can not be used for pollination trees, but chemical fruit thinning agents can be used for pollination trees. Chemical flower and fruit thinning agents can be used in orchards with the same amount of pollination trees.

3.7 strict use of drugs

The solution should be used whenever you want, except that calcium preparations such as stone sulfur mixture can not be mixed with other pesticides, other chemical flower and fruit thinning agents can be mixed, and the suitable concentration is the same as that when flower thinning or fruit thinning alone, but it can not be mixed with other pesticides or foliar fertilizers, let alone increase the dosage of flower and fruit thinning agents at will. If you use the medicine for thinning flowers and fruits several times in the orchard, you should master it flexibly, preferring to remove the deficiency rather than going too far, and require the user to decide the amount of fruit to be retained according to the target output of his orchard, and check the effect after each use. and then decide when to use it next time.

3.8 Chemical flower and fruit thinning should be combined with artificial flower thinning.

After chemical flower thinning and fruit thinning, artificial fruit setting is carried out according to fruit setting and expected yield, and the effect is better (figure 2).

Fig. 2 effect of chemical thinning of flowers and fruits on Fuji varieties