"It is more important to investigate the number of Dendrolimus punctatus on a tree than to eliminate them." Yan Guozeng, chief engineer of Beijing Forestry Protection Station, told the reporter. It turns out that in order to reduce the environmental damage caused by spraying pesticides, Beijing has adopted biological control methods in pest control. The premise of biological control is to predict the severity of pests. Yan Guozeng said: "We even use' biological missiles' to deal with pests-using Trichogramma carrying viruses to spread' plague' among pests."
The reporter learned from the forestry protection station that with this "funnel" device, coupled with the eight tricks of biological pest control introduced by Beijing in the past two years, the trees in Beijing have been fully protected.
"Funnel" Device Works Miracles
Caterpillar can't escape "golden eye" when playing "slick"
The principle of "funnel" device is actually very simple. It ties a "funnel" with a plastic film on the trunk of Pinus tabulaeformis to stop it on the "only way" for Dendrolimus tabulaeformis to dive and overwinter in autumn, so as to investigate the occurrence of Dendrolimus tabulaeformis larvae and make the accuracy of forecasting the occurrence of Dendrolimus tabulaeformis more than 95%. In the past, the accuracy of traditional survey methods was only 20%.
Pinus tabulaeformis is a common tree species in Beijing, and Dendrolimus punctatus is the most harmful to its growth. The tender pine needles in May are delicious food for Dendrolimus punctatus, which is different from the fact that broadleaf trees are only affected by pests. Eating pine needles by caterpillars is equivalent to killing Chinese pine.
Dendrolimus punctatus is a moth larva that lays eggs on pine needles. In autumn, the caterpillar will climb down the tree and spend the winter in the grass, and wait until the next spring to "harm" the Chinese pine.
The traditional investigation method is that when Dendrolimus punctatus overwinters under the tree, forestry workers rummage under the tree. However, the caterpillar is very cunning. Some of them hide under weeds and litter under trees in winter, while others hide in cracks in bark. Although the staff hate that they can't all have "golden eyes", there will still be many "fish that slip through the net".
"In the past, we have been investigating under the tree, but next spring we will find that we have been fooled. In the second year, the number of Dendrolimus punctatus on the tree was much more than that in the first year. " Wang Xiaojun said. So he began to think: "What should be done to cure them?" !
Researchers can easily calculate the number of caterpillars by "waiting for insects"
"The trunk of Pinus tabulaeformis is the only way for caterpillars to get down the tree. As long as a trap is set on the trunk, the caterpillar has nowhere to escape. " Wang Xiaojun said. At first, his idea was to tie the bottom of the hard plastic film to the trunk and make it face up to form a "funnel" shape to prevent caterpillars from passing through.
However, he just tied the lower end of the plastic film to the trunk with a thin iron wire, and when a gust of wind blew, the plastic film stuck to the trunk with the wind. "What if I put a skeleton on the funnel? "Wang Xiaojun continued to" improve "his funnel. In this way, no matter how the wind blows, the direction of the funnel mouth can't be changed, and the funnel stubbornly opens its mouth to meet the caterpillar's "arrest".
As the temperature dropped, Dendrolimus tabulaeformis began to overwinter. But at this time, there is a "funnel" waiting for them in the middle of the trunk of Chinese pine. The Dendrolimus punctatus, which fell into the trap, was caught and hanged by researchers before it could climb the tree to hide. Generally, it lasts about half a month, and Dendrolimus punctatus on the tree completes their "migration". Researchers only need to "wait for the rabbit"-accumulate the number of caterpillars under the tree every day, and they can calculate the caterpillar base of this Chinese pine.
Eight Techniques of Biological Pest Control
The first trick: biological missiles go straight to the nest of pests.
It's not just Dendrolimus punctatus that harms Beijing's forests. Yan Guozeng introduced that, for example, Zhou moth specifically harms poplar leaves, and two kinds of Chinese fir beetles suck the juice of Chinese fir trees. For all kinds of pests, forestry workers have developed various biological control methods, and even used "biological missiles".
If Trichogramma dendrolimi, a parasitic wasp of Dendrolimus punctatus, is allowed to carry the virus that can kill Dendrolimus punctatus and spread among Dendrolimus punctatus populations, Trichogramma dendrolimi carrying the virus will become a special "biological missile". When it parasitizes Dendrolimus punctatus, the diseased Dendrolimus punctatus will set off a "plague" in the whole population.
The second measure: artificially raise gray magpies to eat insects.
Yan Guozeng introduced that if the number of Dendrolimus tabulaeformis on a pine tree is less than five, it is a mild hazard, and this situation can be ignored. However, if the number exceeds 6, measures need to be taken to prevent it. If it exceeds 20, it is a serious hazard. "If there is moderate harm, we will give it a' natural enemy'." Yan Guozeng said.
Gray magpie is widely used as the natural enemy of Dendrolimus punctatus. Wang Xiaojun introduced that Miyun Reservoir Management Office, which is surrounded by Chinese pine forest, specially uses domesticated grey magpie as the "guardian" of Chinese pine.
"We introduce magpie chicks from other places and domesticate them artificially-whenever we want to feed magpies, the breeder will blow the whistle. When magpies grow up, they are put into China pine forest to hunt caterpillars. After the work, all the magpies will fly back. "
Due to the high cost of artificial breeding, the Miyun Reservoir Management Office released the grey magpies into nature and let them breed on their own after they were domesticated successfully. Up to now, more than 2,000 grey magpies have been released to control pests such as Dendrolimus punctatus around Miyun Reservoir. And a grey magpie can kill 400 Dendrolimus punctatus every day.
The third measure: bionic preparation to end the life of pests.
If the investigation base of Dendrolimus punctatus has reached serious pests, spraying bionic chemicals by plane is the best way to deal with Dendrolimus punctatus.
After all the Dendrolimus punctatus trees were planted in early April, the plane began to spray bionic chemicals. After pine needles stained with bionics are eaten by Dendrolimus punctatus, the bionics will destroy the enzymes that control the growth of "skin" (the outer skin of the caterpillar) in the caterpillar. Dendrolimus punctatus undergoes seven molts from egg to adult, and its growth process is actually a continuous molting process. After eating pine needles soaked in bionic preparation, the caterpillar will not shed its skin again, and the life of the worm will be over.
Chief engineer Yan Guozeng introduced that due to long-term adherence to biological control of Dendrolimus punctatus, the area of damaged Pinus tabulaeformis forest in Beijing has been reduced from 6,543,800 mu to 30,000 mu, mainly distributed in Pinggu, Huairou, Changping, Miyun and Mentougou.
The fourth measure: copy the virus "fight poison with poison"
In the virus laboratory of Biological Control Center of Beijing Forestry Bureau, the staff also developed gypsy moth virus and Popeye moth virus to control these two pests.
Different from "biological missiles", these viruses are extracted from dead insects, inoculated into artificially propagated healthy gypsy moth adults, and then toxins are extracted from a large number of body fluids infected with pests.
After the toxin is diluted, the staff will spray it by plane. This method can not only kill insects in a large area, but also has no harm to the environment.
Yan Guozeng introduced that toxins extracted from body fluids of pests and diseases have the characteristics of "specificity", which can cause "epidemic situation" among pests similar to pests and diseases, and have no harm to other insects.
The fifth measure: artificially raise swollen-legged bees to eat longicorn larvae.
There is a kind of bee with stout hind legs, which can absorb nutrients from the larvae of Monochamus alternatus, which harms trees, and thus kill Monochamus alternatus. Researchers call this little bee "swollen-legged bee".
The larvae of Anoplophora longicorn are fat and tender, much larger than the "swollen-legged bee". However, as long as it is stung by a "swollen-legged bee" with an "anesthetic", the larvae of longicorn beetles will be easily caught.
Hou, an assistant engineer at the Biological Control Center, said that it was purely accidental to find that "swollen-legged bees" could kill the larvae of longicorn beetles. In the 1980s, two Chinese fir trees on the Western Hills of Beijing were harmed by longicorn beetles. Groups of longicorn beetles got into the trunk and ate the tree into a hole.
The staff of the center cut down the hollow trees eaten by longicorn beetles and brought them back to the research center. After the research, I was surprised to find that this kind of bee with thick hind legs can absorb the nutrition of longicorn larvae through "parasitism" and make them "die young" "So, we will breed this' swollen-legged bee' on a large scale and send it to the disaster-stricken areas of the Anoplophora longicorn disaster."
The sixth measure: 500 million "Zhou's biting bees" went into battle.
The natural enemy of moths that harm a large number of trees in this city is "Zhou's biting wasp". This kind of bee is only 1 mm long, but it has strong flying ability and parasitic ability, and can keenly find pests hiding in various hidden places and pupating. Can be used for preventing and controlling LEPIDOPTERA pests, such as Popeye, Poplar Moth, Willow Moth, Ulmus pumila, Marsupial Moth, etc.
Because of the "appetite" of "Zhou's biting bees", Beijing forestry department has released 500 million "Zhou's biting bees" in Daxing, Tongzhou, Pinggu, Shunyi, Huairou, Changping, Fangshan and other 12 suburban counties. During the pupation of moths, the staff will fix the "Zhou's biting bee" parasitic in silkworm chrysalis on the tree and release it. "Zhou's biting bees" were released to nature, just like a group of horses going straight to the moth nest to kill moths that are still pupating.
The seventh trick: ladybugs eat up the pests in Zizhuyuan.
Ladybugs in colorful clothes are natural enemies of pests-aphids. The green bamboo in Zizhuyuan was once troubled by aphids, and the "depressed" and withered leaves won the victory by relying on the natural enemy ladybug of aphids.
According to Hou of the Biological Control Center, last year, after learning that the green bamboos in Zizhuyuan Park were damaged by aphids, the Biological Control Center urgently allocated 50,000 ladybugs to Zizhuyuan. The easiest way for ladybugs to deal with aphids is to eat with their mouths open. Aphids with thin skin and juicy juice are undoubtedly a good meal for ladybugs. In just over a month, the green bamboo has grown new leaves.
Eighth measure: plastic "circle" to prevent pests from climbing trees.
Another pest control method is to wrap a tape about 20 cm wide in the middle of the trunk, just like putting a plastic "ring" on the tree.
This method is often used to control grass scales. Grass borers can be regarded as "elders" among pests. It is the earliest pest in Beijing, which not only harms trees and fruit trees, but also seriously disturbs people.
According to the observation for many years, grasshoppers began to move in the middle and late June of 65438+ 10, and moved up and down the trees with the daily temperature change. By February and March, larvae will enter residential areas and families, interfering with the normal life of residents.
The method of controlling this insect is relatively simple. Before the grass grows on the trees in the middle and late June of 5438+ 10 every year, the rough skin of the old trunk is scraped and wrapped with 20 cm wide adhesive tape or plastic film. The smooth plastic film makes it difficult for grasshoppers to crawl, and most insects will gather under the plastic film. Every three to five days, when they gather to a certain scale, they can be manually erased 1 time or scalded with boiling water, which will have a good control effect.