Organisms are considered to be pests of the forest, which in the process of their activity damage the tissues of trees and shrubs. As a result, there is a decrease to one degree or another of the growth and fruiting of plants, or such a destructive effect leads to the death of forest growth.
Pest classification
The vast majority of pests in the forest are insects. To a much lesser extent, they may be some ticks and vertebrates, such as hares and rodents. Pests belong to the forest fauna, like other organisms, therefore, their existence in a natural forest is quite organic, and their vital activity does not lead to irreparable consequences.
However, forest management, which man manages, pests can cause significant inconvenience, interfering with the rational use of forests. 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 quantities over vast areas, which cause substantial harm to the economy;
- species of limited distribution that form local breeding centers;
- species that can cause significant harm, but do not do so in 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, wood pests of the forest are insects, which are classified into specialized groups depending on the method of nutrition, the damage caused and their habitat. And this:
- needles and leaf-eating - prefer healthy plants;
- stem pests - feed on weakened plants;
- soil or root pests;
- fruit-seed pests.
And now about each group in more detail.
Pests of leaves and needles
Insects feeding on foliage and needles of healthy plants are very numerous. The bulk of them are caterpillar pests, which are butterfly larvae. They are incredibly voracious and can destroy a large number of foliage until they have wings.
Less commonly in this group you can find sawfly larvae. And there are very few cases when a forest pest is a beetle from the leaf beetle family. In some instances, other insects may also be foliage and pine needles eaters.
In the larval stage, almost all lead an open lifestyle, and only some species can hide inside the leaf. Therefore, forest pests of this group are affected by climatic conditions.
Sharp changes in numbers to varying degrees are characteristic of certain types of pests of this group. For example, butterflies, weavers and sawflies are highly susceptible to such fluctuations. And elephants, boils and leaf beetles - to a much lesser extent. Pockets of population growth are mostly formed in young shoots, protective stands and parks under favorable conditions.
The outbreak of quantitative growth, as usual, covers about seven generations of insect pests of foliage and needles. There are 4 phases of increase in numbers:
- initial, when the number of individuals grows slightly;
- increase in numbers when foci form;
- a flash of an increase in insects when there are already a lot of pests and they substantially eat crowns;
- crisis, when the flash attenuation occurs.
Dark coniferous plants (fir, cedars, spruce) are most sensitive to damage by pests. They needles loss of 70% leads to the death of the tree. An ordinary pine tree will calmly tolerate a single overeating, and a larch - a double eating of needles. Hardwoods show the greatest resistance to crown loss from pest invasion.
Types of Caterpillars
There are a huge variety of tracks that damage foliage and needles. They suck out the nourishing juice, causing curling and drying of the green mass of plants. These pests hibernate in the leaves, and with the advent of spring, hordes of caterpillars hatched from eggs migrate to the trees, destroying young foliage. Among other types of caterpillars, one can name a moth, hawthorn, silkworm, leafworm, etc. But in more detail it is worthwhile to dwell 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 their eggs. But their larva - silkworm caterpillar - a real monster, preferring the foliage of apple trees, linden, birch. Hiding from the sun, caterpillars crawl to the ground during the day. The genus of silkworms includes several species:
Unpaired grows up to 6 cm in length, it is densely covered with dark gray hairs, in front of it there are five pairs of blue warts, in the back - six red ones. These tracks are the most dangerous. Their nutrition can serve more than 300 species of different plants. Different sizes of male and female served as the name of the pest. This pest lays eggs in the butt part and can withstand temperatures down to -60 ° C. Butterfly begins to fly in July.
- Mulberry prefers mulberry foliage. He makes a cocoon where the caterpillar becomes a butterfly. The finest cocoon thread is used to make expensive silk fabric. Caterpillars of dark brown color, growing up to 8 cm, brighten to white with gray spots. Their butterflies are large, dirty white, with a thick abdomen and short antennae.
- Nun - black and white butterfly with serrated antennae. Its caterpillar grows up to 6 cm, has 16 legs and a dense hairline. It feeds mainly on needles, but will not refuse foliage of birch, oak, apple and beech.
- Siberian silkworm (cocoonworm) is considered very dangerous. Its butterfly is large, from light brown to black. Distributed from the Urals to Primorye. The female lays eggs on needles, branches and trunks. Caterpillars are up to 7 cm long, feed on needles and winter under the cover of foliage and needles on the ground.
Measures against pine and leaf-eating insects
Protecting the forest from pests of this group includes, in addition to preventive measures, chemical methods of treating the forest with insecticides, carried out during the growth period. Biological measures include the attraction of insectivorous birds, the protection and spread of forest ants, parasitic fungi, bacteria, viruses and other diseases to which these pests are exposed.
Xylophagus
Another group of "bad" insects is stem pests, or xylophages. They are also numerous. The bulk is a detachment of beetles, represented by forest pests such as bark beetles, barbel, goldfish, and weevils. In this group there are hymenoptera weevils, as well as mothworms and vitreous butterflies. Less significant are drillers, grinders, etc.
Insects of this group lead a hidden lifestyle, only adults allow open existence. Development takes place under the bark, in stem wood, branches, where they gnaw through numerous passages in the bast, cambium and in live sapwood, which cause significant harm. The vital activity of such pests leads to the drying of the tree or its damaged part. Wood that has been attacked by a forest pest is losing its value.
Healthy and viable trees and shrubs are less susceptible to infection than weakened by factors such as:
- drought;
- flooding;
- fires;
- dust or gas emissions;
- attacks of leaf and pine needles;
- poor sanitation;
- dead wood and other weakening 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.
Xylophagus Control Measures
Protection of forests from pests and diseases caused by the vital activity of insects of this group is mainly of a preventive nature. It is as follows:
- increasing the sustainability of stands by creating mixed crops with undergrowth;
- selection of rocks appropriate to climatic conditions and the nature of soils in certain areas;
- artificial plantings should be made from species resistant to disease and pest attacks;
- correctness of the cutting system;
- compliance with sanitary standards;
- timeliness of clearing clearings from felling residues;
- laying out of trap trees in stands, such as tumbled down by the storms, sick and weakened, on which pests are specially attracted a month before the start of summer and in summer when the first pest beetles appear (after settling, such traps are burned);
- the use of therapeutic and chemical agents;
- the spread and attraction of natural enemies of bark beetles, among which are parasite 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 lamellar beetles (grubs), wireworms, false-stalked black beetles and many other species that lay eggs in the soil, where they develop and feed on roots.
Adult individuals are selected to the surface for additional feeding and mating, then the females again plunge into the ground, where they arrange masonry and die. The most attractive for such pests nurseries and young artificial plantings.
Soil conditions, grass cover, predatory insects, mammals and birds affect the number of root eaters. May beetles, Khrushchev love to settle on unfinished clearings, where after their appearance a new forest does not grow for a long time. The June lamellar beetle, whose Latin name sounds like Amphimallon solstitalis, prefers to live in the roots of conifers, but does not disdain hardwood, which lives on clearings and clearings.
Pests of fruits, seeds, cones
To lovers of fruits, cones and seeds, a large group of insects can be attributed, among which:
- butterflies - leafworms and moths;
- dipterans - mosquitoes and flies;
- beetles - weevils and many others.
In addition to insects, this group also includes mammals, such as mouse 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 alternating crop years with lean years. Each year, a significant part of cones and fruits are destroyed by pests of this group, and in lean years they eat them completely.
Thus, serious damage is caused to forestry, the reproduction of tree species is slowed down, as generative organs are destroyed by pests. The struggle with insect pests of this group is difficult, because for the most part they are hidden inside the fruit.
Pests of young animals and nurseries
Young plants are preferred for all types of pests, which are very different from each other in terms of nutrition, degree and nature of the harm done, as well as in lifestyle.
Within this group, it is possible to distinguish soil insects that damage the root system, and those who eat the aerial part of plants.
As the plant grows and develops, pests of young growth replace each other. However, there is joint wrecking and destruction of a young forest.
