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 of 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 destroyed, causing the canopy to be dry and 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 spraying for prevention and control. 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, trees have an average height of 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 for prevention. Up to now, the unit has sprayed insecticide on an area of more than 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 divided into 2 groups, carrying a lot of equipment, headed to the pine forests that were being eaten by caterpillars. In addition to the ultraviolet lamp, the worm trapping tools also included tarps to hold water right below the lamp. 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 lamp, they had 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. 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 the adult caterpillars will not be able to fly up when they fall down. 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 and 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 of a hassle. After setting up the trap, just wait for the caterpillars to be lured in. However, for fear of losing the equipment, the forest rangers dare not go home to sleep, but 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 electric wire,” said Mr. Tuan.
Every night, nearly 20 light traps are installed. Each light trap can catch about 3kg of adult worms at night. 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 all over the forest to spray pesticides. “Spraying pesticides is not simple, because we have to research beforehand to see what age the worms are in this forest before we can spray. We only spray when the worms are at their most feeding age, because that is when they are most likely to eat the pesticides stuck to the leaves. In addition, we also have to zone 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 that they crawl into our bodies many times. 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 the staff still have to work hard to go deep into the forest to spray./.
