The spread of the large pine weevil in coniferous forests leads to the death of young trees. Because the beetles live and reproduce for up to 6 years, the pest population is constantly growing. Insects attack the bark, roots, and phloem. Spruce, larch, and pine trees are most affected; sometimes deciduous trees are affected, especially in mixed forests. Urgent measures are needed to save the plantings.
How to identify a pest
The large pine weevil, or elephant weevil, has a dark brown body ranging from 6-7 to 13-14 millimeters in length. Belongs to the order Coleoptera, the family of weevils.
The insect received the name “elephant” for its elongated long head ending in the semblance of a trunk, at the end of which there are cranked, club-like antennae on both sides. The beetles place their folded antennae in grooves on the sides of the proboscis.
The body is covered with scales and reddish hairs. Transverse interrupted bandages on the elytra are bright yellow. On the back there are small concave points that turn into deep longitudinal grooves. Juveniles are distinguished by a brighter pattern of elytra. With age, the transverse yellow bands on the back of the insect fade and completely disappear in older individuals. Old beetles have a dark brown body color.
Sexual characteristics
The sizes of females and males are the same, females differ from males in the structure of the abdomen. In females it is more convex, in males it is compressed.
Distribution area
Insects are common throughout the area where coniferous trees grow. The large pine weevil harms plants in Europe, Siberia and Japan. They are found on plains and in mountains, and can rise to a height of up to 2 thousand meters above sea level.
Growth and development
The beetles lay milky white eggs about 1 millimeter long. Each female lays from 60 to 100-120 eggs per season. It takes 2-3 weeks for a larva to develop from an egg.
The insect larva is large, 1.0-1.5 centimeters, curved in the shape of a sickle with a yellowish body and a yellow-brown head covered with bristles. Head with large two-toothed jaws. The larva turns into a pupa up to 1.4 centimeters long with 2 spines on the outermost part of the abdomen.
The large pine weevil develops from larva to adult in 13-14 months in a favorable climate.The rate of development depends on temperature, nutrition quality and humidity levels. The middle zone is characterized by a 2-year development of the pest beetle. A year before the adult, the larva can only develop in a warm climate.
First, the pest beetle overwinters as a larva, by mid-summer the larva pupates, and by the next winter an adult has time to form. In the form of larvae and pupae, the large pine weevil is not dangerous; only adult insects cause harm.
Adult beetles cannot tolerate bright light and are active in the dark. Elephants can fly; this ability is preserved in insects of different ages. They wait out the day in cracks in the bark, they can burrow into the ground, but they prefer to hide at the roots of trees in moss or litter. The beetle's flight begins in late April or May, depending on the weather.
When and where does it breed?
Females lay eggs at the roots of coniferous trees, under the bark of fresh stumps, and in areas after fires. Eggs are laid in a hole gnawed in the bark, after which the female seals the hole. The formed larva gnaws its way out.
Egg laying continues in warm climates from May to September, and in colder regions from May to late July. Due to the long growth period, larvae of 5 different ages occur simultaneously. Beetles that appear in the fall overwinter in the vacated cavities for pupae or in the litter near the tree trunk. Before the onset of cold weather, they occasionally leave the shelter to find food. They begin to reproduce in the next season.
Why is it dangerous for a tree?
The most dangerous for young coniferous trees 3-10 years old.The large pine weevil feeds on the bark of young coniferous trees. When the bark is damaged, increased tarting begins. The needles turn yellow, the tree dies or becomes deformed. Does not allow planting to resume.
The beetle can feed on the bark of deciduous trees, although it prefers pine, and attacks rowan, apple, hazel and even grapevines. The presence of the beetle can be detected by the abundance of wormholes on tree trunks and increased gumming. In autumn, plantings affected by the pest can be easily detected by yellowed needles. The insect is especially dangerous when spread in forest nurseries.
Fighting methods
To prevent the spread of the large pine weevil, you must:
- prevent logging near tree nurseries; the appearance of clearings provokes the spread of the elephant;
- uproot stumps;
- carefully inspect the plantings from April to September, when beetles are actively breeding;
- Carefully inspect the sites of former forest fires; weevils love to breed in such places.
When a pest is detected, urgent measures are taken; trees are sprayed with chitin synthesis inhibitors and pyrethroids. For preventive purposes, seedlings are treated with chemical pesticides (“Dimilin 250” suspension; “Bitiplex” suspension).
Heavily infested trees are cut down and burned, and stumps should also be uprooted and destroyed. At a depth of 20-30 centimeters, stakes are buried in an inclined position, and in the fall they are burned along with the discovered beetles. Construct trapping belts.
Attracting birds is another method of controlling the large pine weevil. Magpies, jays, nightjars, and woodpeckers will happily feast on pests.
In order for a small spruce or larch seedling to grow into an adult tree, you need to put in a lot of effort.Preventing the appearance of the pest and protecting trees from the large pine weevil is one of the stages of planting care.
