"April snow" is actually related to gender imbalance? Henan is formulating the first technical guide for prevention and control

In early summer, the catkins of willow trees in Zhengzhou city float on the pine trees.

"The east wind does not stop the poplar catkins from flying, and they flutter in the faces of passers-by." The poetic sentiment in ancient poems is actually the trouble in real life.

Willow catkins, also known as snow in April, have caused great trouble to Henan residents at the turn of spring and summer this year. The reason behind the catkin disaster is the serious imbalance in the sex ratio of willow trees. The vast majority of poplar trees in Henan Province are female trees that produce catkins.

The "Technical Guidelines for Poplar and Willow Catkin Control (Draft for Comments)" has ended the solicitation of comments. This will also become the first technical guideline for poplar and willow catkin control in our province, which will help promote the scientific and standardized prevention and control of poplar and willow catkins. On August 28, a reporter from Dahe.com conducted an exclusive interview with the relevant person in charge of the drafting group of the standard.

Cause: The sex ratio of poplar trees is seriously unbalanced

Although several months have passed, the flying catkins of willows in Zhengzhou city in early summer this year still left a deep impression on the citizens.

Fan Wei, chief engineer of Henan Academy of Forestry Sciences, said that this spring, the weather in our province was dry and the low temperatures continued for a period of time, followed by a sharp rise in temperature, resulting in an increase in willow catkins compared with usual years and a concentrated period of flying catkins, which had a certain impact on the public's travel and normal life.

Poplars and willows have the characteristics of rapid growth, wide range of uses, outstanding carbon sequestration function, and significant economic value. They have long been an important tree species for afforestation in our province. Every spring, after the female inflorescence is pollinated, the mature capsule will split open, and the white flocculent hairs carrying the seeds will break out of the shell and spread with the help of wind. This is also the cause of the flying catkins of poplars and willows from March to May every year.

"The reason for the catkins disaster of poplars and willows is the serious imbalance of the sex ratio." Fan Wei said that poplars and willows are dioecious, and the ratio of male and female plants is normal in nature, but because most of the poplar varieties promoted and used in production in the previous stage are female plants, the imbalance and serious catkins phenomenon have occurred. Female plants produce catkins, and the proportion of female trees in our province accounts for the vast majority of the total.

Rule: Poplar catkins are the "protagonist"

Before preventing and controlling poplar and willow catkins, a detailed investigation of the catkin source is required. The person in charge of the drafting group of the "Technical Guidelines for Prevention and Control of Poplar and Willow Catkins" said that catkins are mainly produced by female plants, but in some places, male plants are also controlled when preventing and controlling catkins. The formulation of standards is to provide scientific standards and work norms for relevant departments. Only by understanding the basics of poplar and willow catkins can prevention and control work be targeted.

According to relevant information and survey results, there are mainly the following types of flying catkins of poplars and willows in our province: one is the flying catkins produced by the seeds of female plants of Populus tomentosa, one is the flying catkins produced by the seeds of female plants of Populus americana, and the other is the flying catkins produced by the seeds of female plants of Willow.

The above-mentioned person in charge said that the catkins of poplars and willows in spring and summer are mainly the second type. On the one hand, the number of white poplars in our province is extremely limited, and on the other hand, the sex ratio of willows is within the normal range, and they are mostly distributed by rivers, so their number does not account for the absolute majority.

Based on the long-term experience of the members of the compilation team in preventing and controlling catkins, combined with the feedback information from investigations and visits in various places, and after consulting literature and comparison, the forestry department of our province summarized the three main stages of poplar and willow catkins: early April is the flying catkins of white poplar, mid-to-late April is the flying catkins of willow, and late April to early to mid-May is the flying catkins of European and American poplar. Sometimes the flying catkins of the three types of trees overlap, resulting in continuous flying catkins from April to May. However, the start and duration of flying catkins in the same area are also affected by multiple factors such as location, altitude, and microclimate.

Guidelines丨Provide scientific standards for prevention and control work

A reporter from Dahe.com learned that for a long time, due to the lack of unified guidance on willow catkin prevention and control technology, although all parts of the province purchased a large amount of willow catkin prevention and control materials every year, invested a lot of manpower, material and financial resources, and adopted a variety of prevention and control technical measures, the prevention and control results have been unsatisfactory.

At present, the prevention and control of poplar and willow catkins are mainly divided into greening measures, physical measures, chemical measures, etc. In terms of greening measures, the main ones are adjusting the tree species structure, applying female varieties, high grafting, etc.; physical measures are the back-end work, mainly including retention and deflocculation, spraying and deflocculation, humidification and deflocculation inhibition, etc.; chemical measures are mainly injection of finished preparations that inhibit the differentiation of poplar and willow flower buds.

Relevant personnel from the Henan Academy of Forestry Sciences said that developing technical guidelines and standards for the prevention and control of willow catkins and promoting scientific and standardized prevention and control of willow catkins can effectively reduce the harm caused by willow catkins to society and minimize the impact on people's lives and travel, which is of great guiding significance for the scientific and orderly prevention and control of willow catkins in our province.

The draft for comments proposes to take multiple measures, treat both the symptoms and the root causes, reduce the total amount and prohibit the increase, and achieve the goal of harmony between people and catkins and no catkins disasters through greening measures, physical measures, chemical measures, etc. The amount of catkins in key prevention and control areas will be reduced by more than 80%, and catkins will be occasionally visible in the field of vision without affecting the comfort of outdoor activities. There will be no obvious catkins pollution problem, no fire caused by catkins, and the residents' satisfaction will reach more than 80%.

In this regard, the relevant person in charge of the standard drafting group of the "Technical Guidelines for Prevention and Control of Willow Catkins" said that they have received a lot of opinions in this regard, and will further optimize the demarcation of key prevention and control areas, the proportion of reduction in the amount of catkins, and the standards for residents' satisfaction in the future.

Plan丨Establish a real-time poplar and willow catkin monitoring system

When the phenomenon of poplar and willow catkins cannot be effectively eradicated, if we can predict the occurrence of catkins in advance, we can take preventive measures. This year, meteorological departments and gardening departments in many parts of our province issued forecasts for poplar and willow catkins, reminding people to reduce outdoor activities and take protective measures during the peak period of catkins.

Relevant personnel from Henan Academy of Forestry Sciences said that they are also considering establishing a real-time monitoring and reporting system for poplar and willow catkins. On the one hand, it can scientifically evaluate the development trend of poplar and willow catkins in the current year, so that prevention and control departments can adjust their response measures. On the other hand, it can also monitor the occurrence of poplar and willow catkins in different regions in real time, so as to facilitate scientific prevention and control in different regions.

"This is the first technical guide for poplar and willow catkin control in our province." The above-mentioned person from Henan Academy of Forestry Sciences said that in the next step, they will further improve the technical guide based on the opinions and suggestions collected. After industry review, it will be publicly released by the market supervision department. By then, as a local standard of our province, this technical guide will provide long-term technical support for the comprehensive prevention and control of poplar and willow catkins in the province.