Pests of the forest are organisms that in the course of their life activity cause damage to the tissues of trees and shrubs. As a result, there is a decrease in varying degrees of growth and fruiting of plants, or such a destructive effect leads to the death of forest growth.
Pest classification
The vast majority of forest pests are insects. To a much lesser extent, they can be some ticks and vertebrates, such as hares and rodents. Pests belong to the forest fauna, like other organisms, so their existence in a natural forest is quite organic, and their vital activity does not lead to irreparable consequences.
However, pests can cause significant inconvenience to human-managed forestry, interfering with the rational use of the forest. In each ecological and economic group there are species that differ in mass, and they can be divided according to the characteristics:
- species that reproduce at regular intervals in significant numbers over vast areas than they bringsubstantial damage to the economy;
- species with limited distribution that form local breeding centers;
- species that can cause significant harm, but do not do so under existing conditions.
Based on the nature of the damage, they can be classified as follows:
- focal - damage concentrated in one place;
- diffuse - dispersed damage.
For the most part, tree pests of the forest are insects that are classified into specialized groups depending on the way they feed, the damage they cause and their habitat. And this:
- needle- and leaf-eating - prefer he althy plants;
- stem pests - feed on weakened plants;
- soil or root pests;
- fruit-bearing pests.
And now about each group in more detail.
Pests of leaves and needles
Insects that feed on leaves and needles of he althy plants are very numerous. The main part of them are pest caterpillars, which are butterfly larvae. They are incredibly voracious and can destroy large amounts of foliage until they develop wings.
Sawfly larvae can be found less frequently in this group. And there are very few cases when the forest pest is a beetle from the leaf beetle family. At some points, other insects can also eat leaves and needles.
In the larval stage, almost everyone leads an openlifestyle and only some species can hide inside the leaf. Therefore, forest pests of this group are affected by climatic conditions.
Sharp changes in numbers are to varying degrees characteristic of certain types of pests in this group. For example, butterflies, weavers and sawflies are highly susceptible to such fluctuations. And elephants, blisters and leaf beetles - to a much lesser extent. The centers of population growth are mostly formed in young growths, protective plantings and parks under favorable conditions.
An outbreak of quantitative growth usually covers about seven generations of insect pests of foliage and needles. There are 4 phases of population growth:
- initial, when the number of individuals grows slightly;
- increase in numbers when foci form;
- an outbreak of an increase in insects, when there are already a lot of pests and they significantly eat the crowns;
- crisis when flash fades.
Dark coniferous plants (fir, cedar, spruce) are the most sensitive to damage by pests. In them, the loss of needles by 70% leads to the death of the tree. Ordinary pine will calmly endure a single overeating, and larch - two-time eating of needles. Deciduous species, on the other hand, show the greatest resistance to crown loss from pest invasion.
Types of caterpillars
There is a huge variety of caterpillars that damage foliage and needles. They suck out the nourishing juice, causing the green mass of plants to curl and dry out. These pests overwinter in the leaves andwith the advent of spring, hordes of caterpillars hatched from eggs migrate to trees, destroying young foliage. Among other types of caterpillars, here one can name moth, hawthorn, silkworm, leafworm, etc. But in more detail it is worth dwelling on silkworms as the most numerous, diverse and dangerous pests.
Silkworm
This is a terribly voracious pest. The silkworm caterpillar is active at night. His butterflies are completely harmless, except for laying eggs. But their larva, the silkworm caterpillar, is a real monster that prefers the foliage of apple, linden, and birch trees. Hiding from the sun, during the day the caterpillars crawl to the ground. The silkworm genus includes several species:
Unpaired grows up to 6 cm in length, it is densely covered with dark gray hairs, it has five pairs of blue warts in front, and six red ones in the back. These caterpillars are the most dangerous. More than 300 species of different plants can serve as their food. The different sizes of the male and female served as the name of the pest. This pest lays eggs in the butt and can withstand temperatures down to -60 °C. The butterfly begins to fly in July
- Mulberry prefers mulberry leaves. He makes a cocoon where the caterpillar becomes a butterfly. The thinnest cocoon thread is used to make expensive silk fabric. Caterpillars are dark brown in color, growing up to 8 cm, brighten to white with gray spots. Their butterflies are large, off-white, with a thick belly and short antennae.
- Nun is a black and white butterfly with jagged antennae. Herthe caterpillar grows up to 6 cm, has 16 legs and thick hair. It feeds mainly on needles, but will not refuse birch, oak, apple and beech leaves.
- Siberian silkworm (cocoonworm) is considered very dangerous. Its butterfly is large, light brown to black in color. Distributed from the Urals to Primorye. The eggs are laid by the female on needles, branches and trunks. Caterpillars up to 7 cm long feed on needles and hibernate under the cover of foliage and needles on the ground.
Measures against needle and leaf-eating insects
Protection of the forest from pests of this group includes, in addition to preventive measures, chemical methods of forest treatment with insecticides, carried out during the period of increase in numbers. Biological measures are the attraction of insectivorous birds, the protection and distribution of forest ants, parasitic fungi, bacteria, viruses and other diseases that these pests are susceptible to.
Xylophages
Another group of "bad" insects is stem pests, or xylophages. They are also numerous. The bulk is a detachment of beetles, represented by such pests of the forest as bark beetles, barbels, gold beetles, weevils. There are also hymenoptera weevils in this group, as well as woodworm and glass moth butterflies. Less significant are drillers, grinders, etc.
Insects of this group lead a hidden lifestyle, only adults allow open existence. Development occurs under the bark, in stem wood, branches, where they gnaw through numerous passages in the bast, cambium and living sapwood thancause significant harm. The vital activity of such pests leads to the drying of the tree or its damaged part. Wood attacked by a forest pest loses its value.
He althy and viable trees and shrubs are less susceptible to infection than those weakened by factors such as:
- drought;
- flooding;
- fires;
- dust or gas emissions;
- attacks by leaf and needle-eating insects;
- poor sanitation;
- dry wood and other debilitating conditions.
Artificial plantings are most susceptible to infection by pests of this group, especially if they are located in arid areas - steppes and forest-steppes, where there is a lack of moisture.
Measures against xylophages
Protection of forests from pests and diseases caused by the vital activity of insects of this group is mainly preventive in nature. It is as follows:
- improving plantation resilience by creating mixed crops with undergrowth;
- choice of breeds corresponding to climatic conditions and the nature of soils in certain areas;
- artificial plantations should be made from species that are resistant to diseases and pest attacks;
- correct felling system;
- compliance with sanitary standards;
- timeliness of clearing cuttings from logging residues;
- laying trap trees in plantations, such as fallen by storms, diseased and weakened, for which pests are specially attracted for a monthbefore the beginning of summer and in summer when the first pest beetles appear (after settling, such traps are burned);
- use of medicinal and chemical agents;
- distribution and attraction of natural enemies of bark beetles, including parasitic riders, predatory beetles, woodpeckers.
Root pests
Among the pests of the root part of plants is a large number of insects. For example, larvae of horn beetles, wireworms, black beetles and many other species that lay their eggs in the soil, where they develop, feeding on roots.
Adults come to the surface for additional food and mating, then the females again sink into the ground, where they lay eggs and die. The most attractive for such pests are nurseries and young artificial plantations.
Soil conditions, grass cover, predatory insects, mammals and birds affect the number of root beetles. May beetles love to settle in unfinished clearings, where after their appearance a new forest does not grow for a long time. The June beetle, whose Latin name sounds like Amphimallon solstitalis, prefers to live in the roots of conifers, but does not disdain deciduous species that live in clearings and clearings.
Pests of fruits, seeds, cones
To lovers of fruits, cones and seeds can be attributed a large group of insects, including:
- butterflies - leafworms and moths;
- Diptera - mosquitoes and flies;
- beetles - weevils andmany more.
In addition to insects, this group also includes mammals such as voles and various hares that love to feast on the reproductive organs of plants.
Populations of pests of fruits, seeds and cones are formed only in plantations that are within the fruiting period. Many species have adapted well to these periods with their alternations of good years with lean years. Every year, pests of this group destroy a significant part of the cones and fruits, and in lean years they eat them completely.
Thus, forestry is seriously damaged, the reproduction of tree species slows down, as the generative organs are destroyed by pests. It is difficult to control insect pests of this group, because for the most part they are hidden inside the fruit.
Pests of young animals and nurseries
Young plants are preferred for any type of pest, which is very different from each other in the way they feed, the degree and nature of the damage, as well as in lifestyle.
Within this group, one can distinguish between soil-dwelling insects that damage the root system and those that eat the above-ground part of plants.
As the plant grows and develops, pests of young growth replace each other. However, there is also joint sabotage and the destruction of a young forest.
Protection
Forest pest control can take place in many ways. It is preferable, of course, to take prophylacticmeasures.
When protecting forests from pests and diseases, a whole system of measures is used, which are carried out by specialists from forest protection services or under their vigilant control. Security officers are engaged in constant monitoring of forest lands, during which they establish cases of uncontrolled reproduction of pests. The measures taken can be qualified as preventive or extermination.
Preventive consists of forestry and silvicultural measures, and killer are chemical methods that include:
- mixing seed with insecticides;
- applying insecticides to the soil;
- insecticide treatment of seedlings, cuttings or cuttings and seedlings;
- air dusting of forest plantations against adult pests;
- physical and mechanical methods of destruction.
In general, in each case, its own system of measures is developed, based on ongoing research, to destroy a certain type of forest pests.
Currently, measures have been developed to combat a variety of pests, of which there are countless. Basically, the severe consequences of infection with various diseases occur with forest plantations that a person has planted. However, do not forget that the natural forest is able to heal itself, as it grows according to the rules determined by nature itself.
