Perform "transsexual surgery" on trees and cover the ground with organic matter...
Prevent pollen and stay away from "breathing pain"
Our reporter Du Peng
Spring brings revival and vitality to all things, but it is a difficult season for people with allergies.
At this time, some people start to sneeze, rub their eyes, and go out wearing hats, sunglasses, and masks. Looking around, more and more people are suffering from allergies, and some patients are suffering from allergic rhinitis, allergic asthma, atopic dermatitis, etc. It is estimated that the number of patients with allergic diseases in my country may be in the hundreds of millions.
Pollen, flying catkins, etc. may trigger spring allergies, but due to the widespread distribution of the trees that produce them, prevention and control work is very difficult.
However, in recent years, with the help of advanced scientific and technological means, prevention and treatment work has achieved results, allowing more "allergy stars" to stay away from "breathing pain" and no longer look forward to the "spring".
Wind-pollinated flowers are the culprit of allergies
Pollen allergy mainly refers to the allergic reaction of the human body to pollen, which usually includes nasal congestion, red and swollen eyes, itchy skin, etc. In severe cases, it can induce respiratory diseases such as asthma.
There are many types of pollen. Common spring ornamental flowers such as peach blossoms, pear blossoms, apricot blossoms, lilacs, crabapples, etc. are insect-pollinated flowers. The pollen grains of these flowers are large, viscous and heavy, and are not easily dispersed by the wind. They are mainly spread by insects and rarely cause allergic symptoms.
Pollen that can cause allergies mostly comes from anemophilous flowers, which are flowers that rely on wind for pollination. The characteristics of wind-pollinated flowers are small flowers, light weight and large quantity of pollen. When the wind blows, it can easily be carried to distant places by the wind. The flowers of many trees are wind-pollinated.
In northern my country, common tree pollen in spring includes pollen from juniper, sycamore, ash, poplar, willow, elm and other trees.
Among them, juniper pollen is the “number one killer” causing spring pollen allergies. Pollen monitoring results over the years in urban Beijing show that the main pollen in the air in March is pollen from Cupressaceae plants. It appears in early March, reaches its peak concentration in mid-March, and gradually disappears in April. The amount of this type of pollen accounts for about 1/3 of the total spring pollen in Beijing.
In addition to Cupressaceae plants, Salicaceae plants are also "accomplices" in causing pollen allergies. Ye Caihua, deputy director of the Beijing Meteorological Service Center, said that poplar and willow trees are dioecious, and the main source of pollen for Salicaceae trees is the pollen produced by male plants when they bloom. The caterpillar-like things you usually see on poplar trees are the male inflorescences of poplar trees, which are the source of pollen. Poplar tomentosa, poplar Xinjiang, poplar poplar, dry willow, tapestry willow, steamed bun willow, dragon's claw willow, etc. that are widely planted in northern areas all produce pollen.
In addition to producing pollen, Salicaceae plants can also produce annoying catkins. In spring, the female plants of Salicaceae plants will grow inflorescences in order to reproduce their offspring. The inflorescences will burst when they grow up, revealing cotton-like seeds. These seeds are spread by wind and can pose a threat to people with allergies.
In addition, the plane tree, commonly known as the plane tree, will also produce a certain amount of flying catkins. From late March to April every year, as the temperature rises, the fruits of the sycamore tree mature, the fruit balls crack, and the inner fluff will fall with the wind.
Inject and spray poplar and willow trees
As common urban greening tree species, the problem of poplar and willow catkins is particularly common in northern cities in my country. In order to solve this problem, many areas have tried different prevention and control methods.
Performing "gender reassignment surgery" on poplar and willow trees is an important method to suppress flying catkins. The principle of "gender reassignment surgery" is not complicated. It involves cutting off the branches of female trees and grafting the male branches onto the female trees so that the male branches can grow instead of the female branches to achieve the purpose of reducing catkins.
"Reassignment surgery" sounds simple, but there are many details that need to be paid attention to during the implementation process. First of all, the trees should not be too old. Generally, trees under 10 years old have the highest grafting success rate. At this time, the trees are in a vigorous growth period, and the grafted male branches have a high survival rate. Secondly, after the operation, the "transformed" poplar and willow trees will need about three years of maintenance before they can restore their original landscape functions. If the grafted male branches do not survive, the entire tree will still be female, and the female branches will continue to grow and produce flying catkins. In addition, the cost of "gender reassignment surgery" is relatively high, and the implementation efficiency is relatively low. A skilled worker can graft less than 10 trees a day.
In addition to changing the gender of poplar and willow trees, other methods can also be used to control catkins, such as injecting "contraceptive pills" into trees.
The so-called "contraceptive pill" is actually a growth regulator, usually composed of amino acids, etc., which can make plants reduce flowering or not flower as much as possible, and reduce the production of flying catkins by inhibiting flower bud differentiation.
After growth regulators are injected into poplar and willow trees, they will spread to the crown and other parts of the tree due to transpiration, causing the tissue originally differentiated into flower buds to differentiate into leaf buds. The next year, the trees will not bloom or bloom less. This not only reduces the generation of flying catkins, but also does not affect the normal growth of trees.
"The injection actually converts the nutrients consumed by poplar and willow trees for reproduction into growth, which means that the poplar and willow trees shift from focusing on reproduction to focusing on growth. It is not only harmless to the natural growth of the trees, but also makes them more luxuriant." Xu Qinming, director of Wuxi Landscaping Management Center, introduced.
Injecting "contraceptive pills" into trees is not a one-and-done solution. After the trees are injected in the current year, it can usually only ensure that there will be no or less flying catkins in the following year. If there is a need for long-term prevention and control, annual injections are required. In addition, the dosage of medicine required for each tree is also different. The dosage should be calculated according to the diameter of the tree, and the relevant work needs to be carefully arranged by the gardening department.
In addition to "injections", similar prevention and treatment measures include "taking medicine". You can directly spray pesticides on poplar and willow inflorescences before they form catkins to cause the inflorescences to fall off in advance. This method can effectively control the generation of flying catkins in a short period of time, but it is necessary to pay attention to the amount of drug used and the timing of spraying to avoid adverse effects on the environment and trees.
Scientific selection of hypoallergenic plants
Injections and sprays can be used to deal with flying catkins, but reducing the impact of pollen on people mainly relies on the selection and matching of urban greening tree species.
Wang Cheng, a researcher at the Forestry Research Institute of the Chinese Academy of Forestry, believes that the production of plant-derived pollutants such as pollen is determined by the biological characteristics of plants and is difficult to completely eliminate. Therefore, for plants that are prone to pollution, the degree of pollution can be reduced through reasonable configuration. He suggested that urban greening should choose greening tree species with low allergenicity, and in particular, try to avoid planting allergenic tree species in urban upwind areas, residential areas, public leisure green spaces and other areas. At the same time, attention should be paid to mixed planting of multiple tree species to avoid large-scale planting of plant-derived polluting tree species; male tree species can also be cultivated to gradually replace female tree species with pollution problems.
Regardless of whether they are flying catkins or pollen, their final destination is the ground. The surface conditions and soil structure of woodlands and green spaces directly affect the spread of pollen and flying catkins. Enhancing the adsorption and retention function of soil in woodlands and green spaces can effectively control their spread. Wang Cheng said that organic matter can be used to cover the surface of urban green spaces and landscape woodlands, and attention should be paid to retaining herbaceous plants under trees and understory in ecological forests.
To prevent and control pollen catkins, it is more important to treat the symptoms than the root causes. In recent years, with the continuous advancement of breeding technology, my country has made a series of achievements in the breeding of hypoallergenic plants.
For example, not long ago, the National Forestry and Grassland Administration's Forestry and Grassland Plant New Variety Protection Office announced the third batch of new plant variety rights granted in 2023. Among them, 5 "Harmony Poplar" series varieties were bred by the Populus tomentosa genetic improvement team of Beijing Forestry University. Among them. This variety is a male clone of Populus tomentosa with no or little pollen. It has the characteristics of strong growth, straight trunk, and beautiful tree shape. It can be used as an alternative variety for the management of willow catkins in Beijing and other distribution areas of Populus tomentosa. In addition, the team of Bao Manzhu, a professor at the School of Horticulture and Forestry of Huazhong Agricultural University, introduced, cut and grafted more than 500 special germplasm resources of French plane trees collected, and developed 7 new varieties including "Huanong Qinglong" and "Huanong Lifeng" . Compared with traditional plane trees, the new varieties can reduce lint by 80% to 90%. (Science and Technology Daily)