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Blue sea and blue sky, beach coconut grove, this is our impression of Hainan. But you know what? The coconut grove here has suffered a huge disaster: more than 10 years ago, a small beetle invaded and spread in groups, nibbling on palm plants such as coconut trees and betel nuts, sounding a red alarm for the invasion of alien organisms. In the process of exploring the prevention and control of invasive beetle hazards, the introduction of natural predators has become the most cost-effective method.
Nowadays, the coconut shadow on Hainan Island is fragile, the harm of the invading beetle plague has almost disappeared, and the biological control has fought a beautiful "resistance war".
On the outskirts of Danzhou, Hainan, there is an "arsenal" that specializes in producing "secret weapons" to block an invading beetle. The "Arsenal" is about 200 square meters and consists of 7 ordinary houses. Although it is small in size, it is mysterious enough: the windows are tightly sealed with screens inside and out, and the screens are as dense as gauze; the room is constantly temperature and humidity, and there are neat transparent plastic boxes on each iron frame; under the fresh coconut leaves in the box, there are little black insects squirming.
The plastic box is the birthplace of the "secret weapon" Ji Xiao Bee and The Ding Xiao Bee. Workers collect beetles from the wild and place them in boxes, wait for them to breed larvae or pupae, and then lure bees into the box. The black bees, which are smaller than sesame seeds, lay their eggs in the beetle pupae in the box. The bee larvae are able to grow by sucking on the nutrients in the pupae.
A few days before the bees pupated out, the dried beetle pupae were sent to coconut farmers across the island through logistics. The coconut farmer hangs the flyer and puts in the pupae. A few days later, the bees broke out of the pupae and rushed to the battlefield, saw the insects to kill the enemy, and launched a "blocking war" to prevent and control the coconut leaf beetle and defend the coconut tree.
Small beetles "nibble" off hundreds of millions of yuan of output value, coconut trees "white head"
How much harm can a slender beetle, as big as a sunflower melon seed, bring? The answer for coconut farmers in Hainan is that when the disaster was severe, each coconut farmer lost nearly half of their coconut production.
The small beetle is called the coconut heart leaf beetle (coconut heart leaf beetle), not the indigenous "islander", but the "outsider" who came by the downwind boat. The coconut leaf beetle is native to Indonesia and Papua New Guinea. In 2002, the coconut leaf beetle first broke out in Haikou and Sanya, and then spread rapidly to cities and counties across the island in the following years. Wherever the little beetles went, coconut and betel nut trees were severely damaged.
"One coconut tree after another on the side of the road looks like a white head, the tip of the tree is white, and the white leaves are surrounded by scorched yellow dead leaves." Huang Zhongsheng, an old Haikou resident, recalled the scenes on both sides of the streets of Haikou at that time, and he still remembered it vividly, "thinking that the coconut trees were about to die." The coconut tree is the symbol of Hainan, which is both an urban landscape tree and a cash crop in the countryside. The coconut trees scattered all over the island have become a natural canteen for invading beetles.
The coconut heart beetle, as its name suggests, feeds on the newborn young leaves of the coconut tree heart. Beetles are picky eaters, specializing in nibbling on young leaves, and after gnawing on the young leaves of one coconut tree, they will fly to the next coconut tree to continue eating. The young leaves are gnawed clean, the old leaves wither, and the coconut tree becomes "bald", losing the coconut leaves for photosynthesis and can only die slowly. According to local coconut farmers, coconut trees originally had a coconut lifespan of 20 to 30 years, but when the disaster broke out, the young coconut trees could only live for one year, and the old coconut trees could not live for two years at most.
"There are no effective natural enemies in Hainan, and the beetles themselves have a particularly strong reproductive ability." Peng Zhengqiang, a researcher at the Institute of Environment and Plant Protection of the Chinese Academy of Tropical Agricultural Sciences, is very familiar with the habits of small beetles. Since the outbreak of the disaster, the team led by Peng Zhengqiang has been engaged in the prevention and control of coconut leaf beetles.
According to Peng Zhengqiang, the average lifespan of the coconut leaf beetle is about 4 months, and it can breed 4 to 5 generations a year in Hainan, with overlapping generations. Each female insect can lay more than 100 eggs at a time, and a single flight reaches more than 180 meters, "Hainan has a warm and humid climate, and beetles can reproduce and grow almost all year round, which is very easy to become a disaster."
After the outbreak of the disaster, according to the statistics of the agricultural and forestry department of Hainan Province, the total number of plants of the insect-infected palm family in Hainan Province reached more than 3 million, and the direct economic loss exceeded 100 million yuan.
The introduction of exotic parasitic wasps to kill insects, the cost of control from 40 yuan per tree to 1 yuan
The little beetle ate happily, which became a disaster for the coconut tree. In accordance with the strategy of "first saving trees, then studying, while studying, and applying", the agricultural and forestry departments of Hainan Province and scientific research experts began to conduct a comprehensive study on the prevention and control of coconut leaf beetles.
Initially, in order to save the trees first, the urban agriculture and forestry department adopted emergency prevention and control methods, organized manpower to use machinery and tools, and cut down and shoveled the infected coconut leaf branches one by one, and sprayed them tree by tree using pesticides. When the amount of insects on coconut leaves is small, artificial emergency control has certain results, but after the insect infestation, the insect removal effect becomes worse. Especially in rural areas with many large areas and many trees, tree-by-tree treatment requires a lot of manpower, and it is difficult to cover the prevention and control forces.
Just when manual prevention and control was at a standstill, two species of small bees caught the attention of experts. "In 2003, our team checked foreign data and found that in Vietnam, Indonesia and other places where beetle disasters have occurred, there have been successful cases of natural enemy prevention and control." Peng Zhengqiang compared Chinese and foreign cases and found that the natural environment in Vietnam and other places is similar to Hainan, and the introduction of natural enemies of beetles may be a feasible method, "At that time, it was uncertain whether it could effectively control beetles, and it was necessary to observe and study the two kinds of natural enemies wereps in the early stage."
The two species of wasps are smaller than mosquitoes, with a body length of only 1/3 of the size of black sesame seeds, called Ji Xiao Wasp and Ding Xiao Wasp. When the bees breed their offspring, they like to use the larvae and pupae of the coconut leaf beetle as a "nest", and the eggs are specially laid in it until they grow until the adults feather and fly out. The beetle larvae and pupae that are "targeted" by the wasps are basically equivalent to declaring death and can no longer grow into adult beetles.
In 2004, after more than a year of laboratory observation and field demonstration, it was basically determined that two parasitic wasps were suitable for the ecological environment of Hainan and could effectively control the outbreak of coconut leaf beetles. "Only parasitic coconut leaf beetles, harmless to humans and animals." After making a discreet environmental report, Peng Zhengqiang's team began to introduce Ji Xiao Wasp and Ding Xiao Wasp, and tried artificial breeding.
Since 2005, Hainan has begun to release ji and beets in the wild on a large scale. By the end of 2014, 5.4 billion wasps and beetles had been released from captivity and in the wild across Hainan Island, fundamentally controlling the coconut leaf beetle epidemic. At present, Hainan Has a total of four artificial breeding bases for small bees, including the Institute of Environment and Plant Protection of the Chinese Academy of Tropical Agricultural Sciences, the Coconut Research Institute, the Hainan ForestRy Science Research Institute, and the Danzhou Forest Disease and Pest Control and Quarantine Station, with a daily production capacity of 1.5 million wasps and 500,000 wasps.
Every year, after the local agriculture and forestry department and the grower purchase the bee larvae from the base, they first estimate the number of local coconut forest insect pests, and then release the small bees to the coconut forest and betel nut forest according to the ratio of 10:1 bee insects. "The wasp is effective, no longer have to worry about coconut yield reduction." Fu Shiheng, a villager in the eastern suburbs of Wenchang, Hainan, said that the coconut grove in the eastern suburbs is a well-known coconut production area in Hainan, and the use of bees to control beetles is cost-effective and popular among the villagers.
(The picture shows researcher Peng Zhengqiang hanging a small bee releaser in the wild)
According to Peng Zhengqiang's calculations, compared with manually spraying potions from trees and hanging medicine packs to control beetles, the use of natural enemies and wasps to control beetles can reduce the cost of prevention and control from 40 yuan per coconut tree to 1 yuan. "In densely forested areas, after 4 to 6 bees were released in half a year, the wasps form a population that can reproduce naturally and suppress insect outbreaks for a long time." Peng Zhengqiang introduced that the bee releaser developed by their team contains small bee larvae, and after the larvae feather and break the shell, they naturally fly out of the bee releaser, "the number and range of release can be controlled, the operation is simple, and both urban and rural can be used."
Start from the source of prevention and control, protect the local ecology, and improve the "resistance"
Unknowingly sneaking in secretly, quietly settling down and growing freely, gradually evolving into a threat to native species after disasters – this is the conventional routine of alien invasion. Although the coconut leaf beetle is controlled in Hainan, the hidden dangers brought to Hainan's economy and ecology have existed for a long time.
Although the two species of wasps control the coconut leaf beetle as natural enemies, they do not completely "drive away" the beetle.
In the wild, beetles are the breeding space for the offspring of small bees, and small bees and beetles form a food chain to rely on, which can only control the outbreak of insect infestations. As an invasive organism, beetles are bound to occupy the living space of native species in Hainan. Experts believe that the prevention and control of alien invasion must start from the prevention and control of the source of entering the island.
"As an island province, Hainan is surrounded by the sea and seems to be alone, but in fact it is difficult to set up checkpoints on the long coastline." The relevant person in charge of the Hainan Entry-Exit Inspection and Quarantine Bureau said that with the development of the economy, due to frequent exchanges and exchanges between personnel, logistics, commerce and trade, and other reasons, the threat of invasive alien species to Hainan is increasing, which is manifested in the characteristics of accelerated invasion frequency, many types of invasion, and heavy harm.
In addition to being susceptible to the invasion of alien species, Hainan is also prone to becoming a "transit station" for alien pests. Because it is in a tropical area, the environment is high temperature and high humidity, which is very suitable for the growth of some foreign animals and plants. The invasive species that "settled" in Hainan will "transit" to other provinces through forests, seeds, agricultural products, trade and other channels, expanding the invasion area and causing multiple regional victimization.
Taking the coconut leaf beetle as an example, when and where to enter Hainan Island is still inconclusive. Experts speculate that it may be accompanied by palm family timber and vegetation transport inputs. At present, not only the coconut leaf beetle has been found in Hainan, but also in Guangdong, Guangxi and Fujian. Peng Zhengqiang's team, South China Agricultural University, Hainan Provincial Forest Disease and Pest Control and Quarantine Station, Guangdong Academy of Forestry Sciences and other units are actively summarizing the experience of prevention and control of the two kinds of natural enemy wasps, and promoting prevention and control methods to other regions.
"Natural enemies to control coconut leaf beetles is currently the most environmentally friendly and effective method, but before using it everywhere, it is necessary to be cautious." Peng Zhengqiang explained, "Alien predators are also alien creatures. Whether the introduction of alien organisms will adversely affect local organisms must be carefully tested and observed. At first, there was also a parasitic bee predator that entered Peng's team's experimental range as an alternative, but it was abandoned because it would cause harm to other native beetles on the island.
In addition, Hainan biological prevention and control experts believe that the expansion of invasive alien organisms is also related to the degree of damage to the local ecological environment, and the crazy growth of invasive alien animals and plants will also select the environment and choose a place where the "resistance" of local animals and plants is weak.
"For example, in some environments with intact forest vegetation on Hainan Island, invasive alien plants rarely grow wildly in large areas; on the contrary, in some woodlands where trees have been cut down or in deserted fields, it is easy to find the presence of invasive alien plants." Huang Qiaoqiao, an associate researcher at the Invasive Biology and Weeds Research Laboratory of the Institute of Environment and Plant Protection of the Chinese Academy of Tropical Agricultural Sciences, gave the example of the original forest shrub vegetation in Yahouling, Shiguan Village, Longguang Town, Lingshui County, causing the invasive plant Tome to multiply vigorously.
The harm caused by invasive alien species is not only the consequences of foreign trade and species introduction, but also the warning and punishment of human sabotage by the ecological environment. Therefore, protecting the local ecology and improving the "resistance" of the ecological environment is one of the effective strategies to prevent invasive alien species.
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