Recently, two overseas parcels from more than 7,000 kilometers away from China were intercepted by the Shanghai Post Office Customs and found containing 239 forest onion snails and large cap snails.
Among them, the covered large snail is listed in China's "List of Quarantine Pests entering china". This is also the second time that Shanghai Post Office Customs has intercepted quarantine snails in inbound parcels after intercepting scattered large snails in 2020.
In July, Beijing Customs also intercepted 29 large covered snails. With more than 26,000 teeth on their tongues, these snails are hermaphrodite, clad in heavy armor made of calcium carbonate, and secrete mucus all around them, which look weak but are incredibly destructive.
<h1 class="pgc-h-arrow-right" data-track="28" > caused serious African snails in China</h1>
For example, the African giant snail, which has been flooded in China, is native to Zanzibar and Pemba Island along the East African coast. The spread of the African giant snail in China, except for Taiwan, gradually spread from Fujian to the Pearl River Delta and the Leizhou Peninsula, Hainan Island, and southern Guangxi around 1935. From the perspective of geographical distribution, the southernmost point is distributed in Sanya on Hainan Island in China; the northernmost distribution is distributed in Binyang in Guangxi and the Yingde area in Guangdong; the westernmost distribution is distributed in the Xishuangbanna and Hekou areas in Yunnan; and the easternmost distribution is distributed in Fuzhou in Fujian and Keelung in Taiwan.
The reason why African large snails can spread so quickly, scientists have shown that the African large snail population grows very fast: under the climatic conditions of Fuzhou, adult snails can lay eggs 4 times a year, with an average annual spawn of about 900 eggs, and can lay more than 6,000 eggs in a lifetime; Eggs laid in April and May, after 10 to 12 days of incubation and about 6 months of growth, can develop into snails and begin to mate and spawn. This ecological feature is one of the main reasons why it is extremely easy to establish populations in new areas, causing serious harm. The south of China is the suitable area for African snails, so African snails can quickly attack the city and flood into disasters.
African giant snails are dangerous pests in agricultural and forestry production, and the literature records that they can harm more than 500 crops, not only that, African large snails eat a large amount of food, the daily food intake is equivalent to one-tenth of their own weight, two characteristics that lead to their great damage to China's agricultural production.
African large snails in Xiamen, Quanzhou, Zhangzhou and other places in Fujian mainly endanger horticultural crops, causing losses generally up to 15% to 30%, and even harvests in severe cases. For example, in some areas of Maguan, Malipo, Hekou and other counties along the border of Yunnan, the cruciferous vegetables planted for a long time in the local area cannot be planted due to the rampant harm of African large snails, and can only be planted with sweet potatoes, taro and other root tubers, changing agricultural organisms and planting systems, and destroying biodiversity.
In addition, the African giant snail is also an intermediate host for Eosinophilus Strong nematode, which can cause mammalian and human meningitis, and in severe cases, cause death. Cases of such deaths have been reported in african large snail distribution areas and countries. It is mainly caused by humans or animals eating food contaminated by African large snails.
<h1 class="pgc-h-arrow-right" data-track="30" > what harm forest onion snails and covered snails do</h1>
The interception of forest onion snails and cover large snails is not small, forest onion snails are mainly distributed in Central Europe, Northern Europe and the United States and other places, endangering a variety of vegetables, melons, fruits, flowers and other crops, when the harm is serious, the newly transplanted vegetables can be eaten in a short period of time. Forest onion snails are mainly transmitted by vegetables, melons and fruits and other agricultural products and asexual propagation materials with eggs and young snails, and can be transmitted over long distances with the help of vehicles and containers.
The large snail shell of the cover is larger, the shell is thick and solid, opaque, oval or spherical, there are 5 to 6 spiral layers, the body snail layer is extremely large and tilted downwards, the spiral part is shorter, slightly protruding, dull, the shell mouth is tilted downwards, the mouth edge is sharp, it is U-shaped, the shell is 38 ~ 45mm high, 45 ~ 50mm wide. It is mainly distributed in some countries in Western Europe and Eastern Europe, and is often called a grape snail because it often lives in vineyards. When they are small, they feed mainly on humus and fresh young leaves of plants. When they grow up, they begin to eat the stems, leaves and fruits of grapes, lettuce, rape and other plants, so once they invade other countries, it will cause serious damage to local agricultural production, which was once introduced from Italy as a edible snail, and then caused harm to local vegetable production.
If these snails enter the country illegally, they are likely to cause a flood in the country, due to the lack of effective predator restraints. Therefore, these snails will establish a population in a suitable environment, and once they form a scale in the natural environment, it is difficult to manage, which will eventually have a negative impact on China's ecology and agriculture.
<h1 class="pgc-h-arrow-right" data-track="37" > summary</h1>
Alien invasion has become a major ecological problem in the 21st century, its scope is all over the world, alien invasion refers to the migration of organisms from the place of origin through natural or artificial channels to new areas, and in the local natural or artificial ecological environment to settle, self-propagate and spread, and ultimately destroy the ecological balance of the region, causing ecological disasters. According to statistics, at present, there are more than 500 species of invasive alien organisms recognized in China, of which more than 100 kinds of large-scale occurrences and serious harms occur. In the past 10 years, China has successively discovered the invasion of dangerous and explosive organisms such as western thrips and trilobites, with an average annual increase of 1 to 2 species.
Studies have shown that alien invasions have significantly exacerbated the competitive substitution of species and the evolution of population status, and even accelerated the loss of species diversity in specific areas. With the rapid development of international trade, the problem of invasion of alien species has become more prominent and the situation has become more and more severe.