Large pine weevil: a description of the pest, what is dangerous and methods of control
The spread of the large pine weevil in coniferous forests leads to the death of young trees. Since the beetles live and breed for up to 6 years, the pest population is constantly growing. Insects infect the bark, roots, bast. Spruces, larches, pines are affected to a greater extent, deciduous trees are sometimes affected, especially in mixed forests. Urgent action is needed to save the plantations.
How to spot a pest
The large pine weevil, or elephant, has a dark brown body from 6-7 to 13-14 millimeters long. Belongs to the Coleoptera order, the weevil family.
The insect received the name "elephant" for its elongated long head ending in a likeness of a trunk, at the end of which on both sides there are cranked mace-like antennae. Folded antennae beetles are placed in the grooves on the sides of the proboscis.
The body is covered with scales and reddish hairs. Transverse interrupted dressings on the elytra of a bright yellow hue. On the back are small concave points, turning into longitudinal deep furrows. 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 old individuals. Old beetles have a dark brown body.
Gender 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 - a squeezed look.
Distribution area
Insects are distributed throughout the area where coniferous trees grow. The large pine weevil causes damage to plants in Europe, Siberia and Japan. They are found on the plains and in the mountains, they can rise to a height of up to 2 thousand meters above sea level.
Growth and development
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.
Insect larva is large, 1.0-1.5 centimeters, curved in the form 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 chrysalis up to 1.4 centimeters long with 2 spines on the extreme part of the abdomen.
From a larva to an adult, a large pine weevil develops in 13-14 months in a favorable climate. The rate of development depends on temperature indicators, nutritional quality and humidity levels. The middle lane 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.
At first, the pest beetle hibernates as a larva, by the middle of summer the larva pupates, 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.
Expert opinionZarechny Maxim ValerievichAgronomist with 12 years of experience. Our best gardening expert.Ask a QuestionImportant: the large pine weevil is considered the most dangerous pest of young coniferous plantations.Adult beetles cannot stand bright light, they are active in the dark. Elephants can fly, this ability is preserved in insects of different ages. They spend the day in cracks in the bark, can burrow into the ground, but prefer to hide at the roots of trees in moss or litter. Beetle years begin in late April-May, depending on the weather.
When and where does it breed
Egg-laying females are placed at the roots of coniferous trees, under the bark of fresh stumps, in areas after fires. Eggs are laid in a hole gnawed in the bark, after which the female seals the passage. The fully formed larva gnaws its way out.
Egg laying continues in warm climates from May to September, and in colder climates from May to late July.Due to the long period of growth, larvae of 5 different instars occur simultaneously. The beetles that appeared in the autumn overwinter in the vacant holes for pupae or in the litter near the tree trunk. Before the onset of cold weather, they occasionally leave their shelter to find food. They start breeding in the next season.
What is dangerous for a tree
Most dangerous for young conifers 3-10 years old. The large pine weevil feeds on the bark of young coniferous trees. When the bark is damaged, increased resin flow begins. The needles turn yellow, the tree dies or deforms. Prevents landings from restarting.
The beetle can feed on the bark of deciduous trees, although it prefers pine, infects mountain ash, apple, hazel and even grapevine. The presence of the beetle can be detected by the abundance of wormholes on tree trunks and increased threshing. In autumn, pest-affected plantings are easy to detect by yellowed needles.The insect is especially dangerous when distributed in forest nurseries.
Methods of struggle
To prevent the spread of the large pine weevil, you must:
- avoid logging near forest nurseries; the appearance of clearings provokes the spread of the elephant;
- uproot stumps;
- carefully inspect plantings from April to September, when beetles are actively breeding;
- carefully inspect the places 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, pyrethroids. For prophylactic purposes, seedlings are treated with chemical pesticides (" Dimilin 250" suspension; "Bitiplex" suspension).
Heavily infested trees are cut down and burned, and the stumps should also be uprooted and destroyed. At a depth of 20-30 centimeters, stakes are buried in an inclined position, in the fall they are burned along with the discovered beetles. Build trapping belts.
Attracting birds is another way to control the great pine weevil. Magpies, jays, nightjars, woodpeckers will eat pests with pleasure.
In order for an adult tree to grow from a small seedling of a spruce or larch, you need to make a lot of effort. Preventing the appearance of a pest and protecting trees from a large pine weevil is one of the stages of planting care.
