The causes of Fruit trees falling Flowers and fruits and the measures to improve the Fruit setting rate

The causes of Fruit trees falling Flowers and fruits and the measures to improve the Fruit setting rate

1 the reasons for falling flowers and fruits

1.1 genetic factors of tree species and varieties

There are differences in genetic characteristics among different species and varieties of fruit trees. In the cultivation and management of fruit trees, ignoring these characteristics will easily lead to serious flower and fruit drop. Dioecious tree species, such as kiwifruit and ginkgo biloba, should be pollinated by males in order to bear fruit. Monoecious tree species, such as walnut and Chinese chestnut, although male and female flowers grow in the same plant, there is a phenomenon of heterogeneity between female and male flowers in most varieties. the flowering period of female flowers and male flowers is very short, and male flowers can not pollinate female flowers. Self-flowering is unfruitful, and most fruit trees can differentiate into complete flowers, but many varieties of self-flowering are unfruitful or have low self-flowering seed-setting rate, for example, most apple varieties have low self-flowering seed-setting rate, and some even self-flowering unfruitful (Marshal varieties). Among the cultivated varieties of abortive flowers and fruit trees, there are varieties with high pollen abortion rate, which can not be used as pollination trees. For example, peach varieties Cangfang Zaosheng, Annong water honey. Cross-pollination affinity, fruit trees cross-pollination generally have affinity, but there is a great difference in pollination affinity, such as apple variety Jinguan × Fuji, the fruit setting rates of orthogonal and reverse cross varieties are very high; Fuji × American No. 8, the fruit setting rate of orthogonal Fuji is very high, while that of reverse cross American No. 8 is low.

1.2 problems in fruit tree management

① is short of water and fertilizer, extensive management, few flowers, poor quality of flower buds, flowering and fruit drop due to lack of nutrition. Improper fertilizer and water management, watering too frequently, partial application of nitrogen fertilizer, excessive vegetative growth, due to nutrient competition, resulting in flower and fruit drop. Improper pruning of ②, overpruning or leaving too many flower buds result in the imbalance between vegetative growth and reproductive growth, affecting flowering and fruit setting. ③ florescence and young fruit stage are sensitive periods for pollination, fertilization and young fruit development. A little improper management of fertilizer, hormone and pesticide spraying can lead to abnormal flower and fruit drop. ④ disease and insect damage, resulting in root damage, branch decay, leaf lesions, incomplete and even deciduous leaves, affecting the growth and development of fruit trees, affecting flowering and fruit setting. Flowers and young fruits are infected, and their development is hindered or even stiff and shedding. For example, flower rot infects, causing buds or flowers to wither; young fruits become brown and rotten and dehydrated into stiff fruits. The flowering period is often harmed by hairy beetles, small golden beetles, aphids, pear wasps, etc., gnawing (sucking) flower eaters and young fruits.

1.3 influence of climatic factors

① florescence and young fruit stage, late frost low temperature is one of the main reasons for flower and fruit drop, late frost low temperature, easy to frostbite floral organ and young fruit, resulting in floral organ can not be pollinated and fertilized, young fruit can not continue to develop. ② flowering period is rainy, the air humidity is high, the pollen is easy to break when soaked in water for a long time, Rain Water scours the stigma, the pollen is difficult to spread elegantly, and the pollination insects slack off because of wet and cold work, which is disadvantageous to pollination. ③ florescence dry and hot wind, causing scorched flowers (such as jujube flowers), stigma dry, can not touch pollen; dust storm, dust cover stigma, affecting pollination. Absolute low temperature, drought and waterlogging in ④ special year affect flower bud formation, flower bud quality, flowering and fruit setting.

(2) measures to protect flowers and fruits

2.1 strengthen the comprehensive management of orchards

Strengthening the comprehensive management of orchards, improving the nutrition level of trees, promoting the growth of fruit trees and improving stress resistance are the basic measures to differentiate flower buds, blossom and fruit. ① soil management. The orchard soil is deeply turned to expand the hole, the mountain orchard does a good job of soil and water conservation, and the sandy or clayey orchard is improved by pressing soil or mixing sand. ② fertilizer and water management. Pay attention to the application of organic fertilizer, according to the growth of fruit trees, soil conditions and growth period, pay attention to the combined application of different element fertilizers. Pay attention to extra-root topdressing in the growing season. According to soil moisture and fruit tree growth period, reasonable irrigation, so that drought can be watered, waterlogging can drain, tree plate covered with grass or plastic film, soil moisture and grass control. Reasonable pruning of ③. Winter pruning and summer pruning are used to adjust the relationship between growth and development; to prevent heavy pruning, it is also necessary to put an end to light pruning of sparse branches and flowers. ④ pest control. According to the occurrence law of the main diseases and insect pests in the orchard, formulate the pest control calendar; usually pay attention to observation, investigation, make a good forecast, spray or adopt other measures to control in the critical period. Promote the comprehensive control of chemical control, biological control, artificial control and other measures. Pesticides are prohibited during flowering, and pesticides are used cautiously in young fruit to avoid abnormal flower and fruit drop.

2.2 selection and configuration of pollination trees

The selection of pollination trees is a basic measure to improve the fruit setting rate, especially for dioecious, self-fruiting and unisexual fruiting tree species and varieties. The varieties with easy flowering, more pollen, strong pollination affinity with the main varieties, consistent flowering period and high economic benefits were selected as pollination trees. Some fruit tree species have selected special pollination tree varieties, such as apple and ginkgo biloba. The planting forms of main varieties and pollination varieties are mostly determinant or central planting; when the number of pollination trees is large, the determinant is often used; when the pollination trees are few, the central type is often used. For the varieties with high pollen abortion, more than two varieties should be used as pollination trees, and the pollination affinity between the pollinated varieties should be strong, and the allocation ratio of main varieties to pollinated varieties is generally 3: 6 ∶ 1, and for dioecious fruit trees, the ratio of female to male plants is 100 ∶ 5: 10.

2.3 artificial assisted pollination

Artificial pollination of fruit trees is an effective measure to overcome the bad natural pollination, which is often carried out under the conditions of insufficient or improper configuration of pollination trees, less flower bud formation (small years), disastrous weather and so on. On the varieties with strong pollination affinity and large number of flowers, the big bell flowers are collected from the varieties with strong pollination affinity and large number of flowers, and the flowers should be picked according to the requirements of flower thinning. After rubbing the anther, put it in the room of about 25 ℃ to promote the anther to disperse powder. Pollination is often done manually or sprayed with pollen solution. In artificial pollination, the effect of pollination with mixed pollen of 2 or 3 varieties was better than that of single variety. Tree species or varieties with different flowering time, trees with few flowers or suffering from disastrous weather, diseases and insect pests should be awarded 2 or more times. Storing pollen in natural state has little effect on pollen viability after 1-2 days. If it is not used for a long time, it can be stored in the freezer.

2.4 releasing bees at flowering stage

Releasing bees at flowering stage in orchard (protected area) is an efficient pollination measure. In the past, more bees were released, but now wall bees and bumblebees are often used because of their poor ability to adapt to adverse environmental conditions such as low temperature, high humidity and strong wind, and low flower visiting efficiency. Wall wasps and bumblebees have strong adaptability to adverse environmental conditions, and their work efficiency is 30 to 50 times that of honeybees. It is only about 100 bees in 666.7m2 orchards. Bee pollination and honey can be used to release bees in the flowering period of late-flowering trees such as jujube and pomegranate in field orchards, and a box of strong swarm bees (about 20000) can be placed in 0.6~1.0hm2 orchards.

2.5 use of hormones

The use of plant growth regulators to prevent flower and fruit drop has the advantages of convenient application, low cost, quick effect, obvious effect, no pollution to the environment, no harm to human health and so on. At present, the commonly used regulators are gibberellin (GA3), naphthylacetic acid (NAA), PBO, chlorophenylurea (CPPU) and so on. Spraying GA3 20~30ml/L at flowering stage of jujube, Hawthorn and grape can significantly improve the fruit setting rate. NAA can be used to prevent pre-harvest fruit drop. Marshal apple spray 20~30ml/L NAA 2-3 weeks before harvest can effectively prevent pre-harvest fruit drop. With the application of plant growth regulators, the application period, dosage, times and methods should be strictly grasped according to the growth and development characteristics, growth status, meteorological and environmental factors of tree species and varieties.

2.6 thinning of flowers and fruits

Thinning flowers and fruits, reducing the consumption of tree nutrients, reasonable load, improving the nutrition needed for the development of flowers and fruits, which is beneficial to flowering and fruit setting. The amount of flower and fruit is determined according to tree size, growth status, growth and development habits of tree species and varieties, meteorological factors, management level and so on. Thinning flowers as early as possible, in winter pruning, thinning of overdense and weak fruiting (mother) branches; bell flowering or growing obvious inflorescences begin to thinning flowers (inflorescences), weak flowers (inflorescences), deformed flowers (inflorescences), overdense flowers (inflorescences), and the remaining flowers are evenly distributed on the crown. Fruit thinning is generally carried out twice, the first time is mostly carried out around 7 days after flowering, and the second time is mostly carried out after physiological fruit drop; trees with low fruit setting rate, varieties or orchards with frequent natural disasters such as late frost should be kept more and thinned late. Apple, pear and other large fruit tree species generally leave 1 fruit per inflorescence, grape sparse inflorescence or remove overdense spikelets or fruit grains. Walnut, Chinese chestnut, a large number of male flowers, to remove most of the male inflorescence, can significantly increase the fruit setting rate. Thinning of male flowers is generally carried out when the male inflorescence is long 2~3cm, removing 80% to 90% of the male inflorescence.

2.7 Prevention of disastrous weather

In flowering and young fruit stage, late frost, overcast and rainy low temperature, high temperature and drying are the main reasons for flower and fruit drop. The basic measures to prevent disastrous weather are: ① to strengthen the comprehensive management of orchards and enhance the resistance of fruit trees themselves. ② prevents late frost, especially for early flowering tree species, and late frost seriously affects fruit setting tree species and varieties. The first preventive measure is to postpone flowering, avoid late frost, often use grass cover on the ground, white tree trunks and branches, irrigation before flowering, etc., generally postpone flowering for 3-7 days. The second is to prevent frost damage caused by late frost, mainly by smoking method. According to the weather forecast, smoke piles are set up in the orchard to pay attention to the change of temperature at night. When the temperature drops to 2: 1 ℃, there is a downward trend, and the smoke pile is lit. Generally, frost is formed at 2: 4 in the morning. ③ fruit trees damaged by disastrous weather during flowering and young fruit stage should take various measures to prevent falling flowers and fruits so as to increase the fruit setting rate.