Caterpillars destroy hundreds of hectares of pine forests in Nghe An
For about a month now, the caterpillar epidemic has caused hundreds of hectares of pine forests in Nghi Loc district to be stripped of their leaves and at risk of drying out.
Epidemic risk
In mid-August 2024, we followed the staff of Nghi Loc Forest Protection Management Board into the pine forest to trap caterpillars. This work has been carried out by the forest protection force for the past month, since the caterpillar problem began to spread rapidly. Light traps are one of two solutions that Nghi Loc Forest Protection Management Board has deployed to prevent this caterpillar from harming pine trees.
According to forest rangers, the growth of pine caterpillars in Nghi Loc district is very complicated, negatively affecting forest development. Currently, there are larvae of the third generation/2024. Particularly in the eastern area from National Highway 1A down to Nghi Yen, Nghi Tien, Nghi Quang, Nghi Xa communes, larvae grow and develop strongly. Specifically, up to 300 hectares of pine forest are heavily infected with a density of 350 - 400 larvae/tree, which have now been bitten and damaged, causing the canopy to be bare. In addition, there are 450 hectares of forest that are less infected, with an average density of 150 - 200 larvae/tree.
In the pine forest area of Nghi Dong and Nghi Hung communes, the density of worms is 20-30 worms/tree, distributed locally by region, unevenly, mainly concentrated above the storm...
Mr. Tran Van Truong - Deputy Head of Nghi Loc Protective Forest Management Board said that since the beginning of the year, the weather conditions have been warmer than the average of many years, so it is favorable for some pests to develop, especially pine caterpillars. The development of pine caterpillars is complicated and at risk of developing into an epidemic, so the unit has focused human and financial resources on preventive and control spraying. However, the investigation and forecasting of the development of caterpillar generations is very difficult because the forest area is large, pine forests of age V-VI cover a large area, the average height of trees is from 20 - 25 m, so it is difficult to determine the density of caterpillars accurately. Other factors such as climate and terrain also change the formation and development of caterpillar generations. The spraying site is high, steep, precarious hills, with dense bushes and vines, making it very difficult to spray. Up to now, the unit has sprayed insecticide on an area of over 150 hectares.
Caterpillar trap lamp
Along with spraying pesticides, in recent days, Nghi Loc Protective Forest Management Board has also deployed a solution to trap caterpillars with lights. According to Mr. Vo Hien Tuan - Head of Science Department (Nghi Loc Protective Forest Management Board), like many other species of caterpillars, adult pine caterpillars will crawl into cocoons, after a short time they will transform into butterflies and fly out, continue to lay eggs, and reproduce very quickly. "We call these butterflies adult caterpillars, they really like the light of ultraviolet lamps. So trapping with lights is also very effective," said Mr. Tuan.
To trap caterpillars, in recent days, every evening, 4 forest rangers have divided into 2 groups, carrying a lot of equipment, and headed to the pine forests that are being eaten by caterpillars. In addition to ultraviolet lamps, the traps also include tarps to hold water right below the lamps. The location of the trap must be in an open space, so that the caterpillars in the pine forest can see the light. To have electricity to light the lamps, they have to bring hundreds of meters of electric wire, connecting to nearby houses. The location of the trap must not only be open but also not far from the houses, so that the electric wire can reach them. With this light, the caterpillars can be seen from a distance of 1km or less.
At first glance, trapping caterpillars seems easy, but it is quite complicated. The canvas is filled with water and a little oil is also poured in, so that when the adult caterpillars fall down, they will not be able to fly up. After seeing the ultraviolet light, the adult caterpillars will fly down. The light is installed right on the canvas containing water, so the light will be reflected there. "After the caterpillars fly down, they see the light reflected in the water, thinking it is a real light, so they rush towards it. That is how they get caught in the trap," Tuan explained.
Compared to spraying pesticides, trapping caterpillars with lights is not much work. After setting up the trap, just wait for the caterpillars to be attracted. However, for fear of losing the equipment, the forest rangers dare not go home to sleep, and many nights have to stay up all night to keep watch.
“These devices are not expensive, but leaving them there all night without anyone watching is scary. Especially the hundreds of meters of electrical wire,” said Mr. Tuan.
Every night, nearly 20 light traps are set up. Each light trap can catch about 3kg of adult worms. There are so many worms that some people say that trapping one by one is not enough. However, this is a fairly effective prevention solution. Because each adult worm, if not trapped, will lay thousands of eggs a few days later, starting a new cycle.
In particular, according to these people, trapping worms with lights is also less difficult, and does not require going around the forests to spray pesticides. “Spraying pesticides is not simple, because we have to research beforehand, what age the worms are in this forest before we can spray. We only spray when the worms are at the age of eating the most, because that is when it is easy to eat the pesticides stuck to the leaves. In addition, we also have to isolate the area to spray promptly, because the speed of worms eating is very fast, today the pine forest is still green, but tomorrow they may have eaten all the leaves. On the days of spraying pesticides, each person has to carry nearly 30 kg on their back, the terrain is mainly mountainous, so it is very tiring. Even though we wear protective clothing, there are so many caterpillars, so many times they crawl into our bodies. Each time like that, it takes several days to recover from the poison,” added Mr. Vo Hien Tuan.
To spray pesticides effectively and reduce the workload for staff, Nghi Loc Protective Forest Management Board also thought of renting a flycam. The unit also contacted a number of places, but they quoted a price of 800,000 VND to 1 million VND/1 hectare, while the unit is managing thousands of hectares of pine forest, not enough money to rent, so staff still have to endure the hardship of going deep into the forest to spray./.
