Causes and countermeasures of Korla pear falling flowers and fruits
Atunguri Maimaiti
Korla pears have long been loved by the public for their excellent quality, but they face a major problem in the cultivation process, that is, it is difficult to obtain high yields through self-pollination (Fig. 1). Therefore, in cultivation practice, in addition to taking effective measures to improve fruit set rate and reduce falling flowers and fruits, it is also necessary to cultivate corresponding pollination varieties to achieve their high-yield and high-quality cultivation goals.
Fig. 1 Korla pear blossoming
1 Reasons why Korla pears fall flowers and fruits
1.1 The impact of administrative problems
1.1.1 Improper allocation of pollinator trees Although the scale of development in korla has been large enough, management measures have not been followed, especially the number of pollinator trees is relatively small, which also leads to the inability of pear trees with large pollination demand to be fully pollinated, and ultimately reduces its overall fruit setting rate.
1.1.2 Improper cultivation management Reasonable cultivation management is the premise and necessary measures for high yield and quality. However, in the process of field management, due to the lack of correct understanding of the growth characteristics and fertilizer need characteristics of pear trees, it is impossible to carry out reasonable fertilization. Unreasonable fertilization can easily lead to the growth or growth of pear trees, or the phenomenon of few flower buds and low flowering and fruiting rate due to lack of nutrients. Especially in the process of flower bud management, the relationship between reproductive growth and vegetative growth cannot be well coordinated, resulting in a low overall flower bud fruit setting rate; during the flowering period and the young fruit stage, it is also easy to have a serious phenomenon of falling flowers and fruits; there is also the phenomenon of unreasonable use of pesticides and chemical fertilizers. In addition, like most fruit trees, they face pest and disease problems, which is one of the most likely reasons for the reduction of production. Once the tree is infected with various diseases and insect pests, it will lead to insufficient nutrient supply for flowers and fruits, and the fruit setting rate will be greatly reduced.
1.2 Influence of climatic factors
1.2.1 Low temperature of late frost The low temperature of night frost is the main reason for the flowering and young fruit stages. The temperature is often at -1 ~ -3 °C during frost, when the flower and young fruits are very susceptible to frost damage, affecting pollination and fertilization, and it is difficult to achieve results. Temperature is the main factor affecting the growth of pear blossoming, usually the first flower to full flowering period and the full flowering to falling period are 4 to 7 days and 6 to 12 days, respectively, and the flowering period duration is about 14 days. Pollination and fertilization are usually affected by the flowering period, and the shorter the flowering period, the easier it is to cause the flowers to fall off.
1.2.2 Rainfall during flowering Increased rainfall and humid air during flowering are also not conducive to pollination. Because pollen usually needs to be spread by insects in a suitable environment, and bad weather, in addition to affecting insect activities, is also easy to directly affect pollen transmission and lead to pollen rupture.
1.2.3 Dry and hot air during flowering The occurrence of dry and hot air during flowering is also easy to cause the phenomenon of pear scorched flowers. It is also more difficult to spread pollen on the dry stigma, especially when the stigma is covered with sand and dust, pollination is more difficult.
1.2.4 Lack of water in the tree The buds of the pear tree usually begin to differentiate in June, that is, during the summer drought, and the flower buds will differentiate better during the drought. However, the drought in Korla region lasted too long in June and August, and the lack of water in the tree body seriously affected the absorption and supply of nutrients, reduced the quality of flower bud differentiation, and easily led to flower without stigma or short stigma, affecting pollination and fruiting.
1.2.5 The temperature is not suitable 2 to 4 days after flowering and 15 to 25 °C is most suitable for pollination and fertilization, and 5 to 7 days after flowering, the stigma is dried up, and pollination and non-fertilization will occur. Pollen does not germinate at 10 °C, the elongation of pollen tubes at 10 to 14 °C is hindered, and the stigma is easily dried up in temperatures above 30 °C, which will adversely affect pollination and fertilization. Abnormal weather lasting 2 to 4 days may also adversely affect pollination and fertilization of Korla pears.
2 Measures to improve fruit set rate
2.1 Strengthen the comprehensive management of orchards
It is necessary to do a good job in the cultivation and management of pear trees, provide sufficient nutrition to ensure the normal growth of the tree, and improve the drought resistance and low temperature resistance of the tree, so as to effectively improve the flowering and fruiting rate of Korla pears, and then improve fruit yield.
2.1.1 Strengthen fertilizer management On the basis of traditional fertilization, it is necessary to combine the phenological period and tree growth state, soil fertilizer level and other factors to rationally apply chemical fertilizers, trace elements, etc., the types and proportions of fertilizers must be scientific and reasonable, and the use of extra-root topdressing to ensure the strong demand for fertilizer during the growing season of fruit trees. Irrigation can be carried out if the soil is too dry during the phenological period of Korla pear growth.
2.1.2 Reasonable pruning During winter pruning, it is impossible to accurately distinguish leaf buds and flower buds, so on this basis, pre-flowering re-pruning can greatly improve the fruit set rate. It is best to re-prune after budding and end before flowering. The influence of flower amount control on the fruit of the big year tree is more obvious, and the weak remains strong, and the string of flower branches is shortened in the way of flower exchange, leaving 2 to 3 flower buds. Summer pruning should not spare the branches and flowers, nor can it be killed, but the relationship between the vegetative growth of fruit trees and reproductive growth should be coordinated.
2.1.3 Disease and pest control According to the occurrence of the main pests and diseases in orchards, a scientific control calendar should be formulated, and comprehensive control should be carried out in combination with prediction and forecasting. (1) The beginning of April is the best booby trap period for heart-eating insects, you can choose a special trap or a vagus tube for booby traps, and control the drug distance to obtain the best booby trap effect. (2) Booby-trap and kill the spotted borer in early April. Kill emulsion or high-efficiency cypermethrin emulsion with a suitable proportion of sweet and sour liquid or enemy, and depending on the severity of the pest, choose the appropriate dose or concentration. (3) In early and mid-March, use yellow plates (armyworm plates) to trap pear stem bees. Pesticides cannot be used during the flowering and young fruit stages to avoid abnormal flowering and fruit drops.
2.2 Measures to promote pollination and fertilization
Korla pear has a low self-flowering fruiting rate, so it needs to be supplemented by pollination varieties or artificial pollination, otherwise the fruit set rate is low and high yield cannot be achieved, specific measures include:
2.2.1 Allocation of pollination trees In the planting and orchard planning of Korla pears, it is reasonable to select the pollination varieties such as duck pears and crisp pears that have earlier flowering periods than Korla pears or the same pollination varieties, and the proportion is controlled at 1:4 to 5.
2.2.2 Assisted pollination In the case of no or too little configuration of pollination trees, auxiliary pollination can be carried out by manual pointing, shaking, liquid spray pollination, etc. Flowering is best in 1 to 2 days, pollination within 3 days can make the fruit set rate exceed 70%, and the pollination rate on days 4 to 5 and 6 of flowering is reduced to 30% to 50% and less than 15%, respectively. 10:00-14:00 is the best pollination time of the day, high temperature affects pollination, 15 ~ 25 °C is the most suitable. (1) Manual teaching method (Fig. 2): Use a brush, pencil with an eraser head, paper stick, etc. to dip pollen. When ordering, use the tip of the rubber head to dip a little pollen, and lightly tap on the stigma of the flower, and each dip of pollen can be ordered to 5 to 7 flowers. (2) Jitter pollination method: mix pollen with starch in a silk bag with fine holes and scatter on top of the pollinated flowers. (3) Liquid spray pollination method (Figure 3): 10, 20, 30 and 500 grams of borax, pollen, urea and sugar are dissolved in 10 kg of water and sprayed with an ultra-low volume sprayer within 2 hours.
Figure 2 Artificially assisted pollination
Figure 3 Spray liquid pollination
2.2.3 Grafted pollination varieties In the spring, the preferred east-west and good-growing interlayer secondary branches are grafted between the main branches of the 1st and 2nd layers on the central trunk of the pear tree, and the pollination varieties are mainly duck pears or Stony pears, and the fruits on the grafted branches are removed after the flowers are dueling to avoid their nutrient consumption.
2.2.4 Hanging branches The branches of pollinator trees with buds are hung in small buckets or water bottles for natural pollination in the middle and upper northwest directions of the pear tree.
2.2.5 Orchards are introduced into the colony at a density of 1 box/10 acres 2 to 3 days before the flowers, but the pyrethroid pesticides should be banned during this period.
2.3 Spray foliar manure
In the bud to full blooming period, you can choose 0.1% borax or 0.2% boric acid or 20.5% Hefeng boron or 0.3% urea, supplemented by a little honey spray, the pear fruit set rate can be greatly improved.
2.4 Fruit thinning
The fruit thinning of korla pear trees with too much fruit set in that year can maximize the size and quality of individual fruits. When fruit thinning, the amount of fruit thinning is determined according to the conditions of various aspects of the tree. Fruit thinning usually follows the following principles: weak trees and trees with large flowers should be thinned early and more sparsely, while wang trees should be less sparse and late. 5 to 6 short branches leave 1 fruit, the outer strong branches leave more fruit, and 1 short branch leaves 1 fruit. In general, the sooner the fruit is thinned, the better. Fruit is thinned 10 to 15 days after flowering and ends within 14 days after flowering has withered.
2.5 Prevention of severe weather
Spring in Korla is often accompanied by extreme weather such as frost, high temperature, floating dust, and high winds, which can easily cause flower buds and young jelly damage, thereby reducing the fruit setting rate. Therefore, the following measures can be taken to deal with severe weather:
2.5.1 Anti-low temperature frost Temperature drops to -1 °C ~ -3 °C often frost, after receiving the frost forecast, two measures can be taken to prevent the occurrence of frozen flowers: one is to immediately irrigate the whole orchard, which can delay or prolong the flowering time; the other is to spray boron-containing micro-fertilizer. After the frost, artificial assisted pollination measures were taken to improve the fruit set rate of flowers that did not occur frost damage.
2.5.2 Prevent high temperature, high temperature plus dry hot wind from affecting pear pollination, fertilization and fruit setting, and the heavy flower stigma is dried and shrunk, and even the flower is damaged. Precautions: Spring water during flowering, or spray water on trees, to lower the temperature of the entire orchard.
2.5.3 Sand and dust Prevention Sand and dust adhering to the stigma of flowers can affect pollination and fertilization. Countermeasures: After the sand and dust weather, wash the sand and dust on the flowers with water or with a boron-containing micro-fertilizer solution.