The hot season and the outbreak of pest

The hot season and the outbreak of  pest

The hot season and the outbreak of pest : The silk weaver pest is the result of years of mismanagement in the selection and planting of non-scented trees, inappropriate changes in the use of forests, forest destruction, indiscriminate cutting of trees and dozens of other destructive factors. Refused.

Larvae weave short and awkward web while feeding and changing the host during pre-pupation and pupation. Male and female insects are different from each other due to the clearly defined difference in appearance as well as the color and pattern of the wings. This pest is called awkward silk moth.

The appearance of full-fledged insects of this pest depends on the weather conditions and the height of the region above sea level, and in forests, this appearance usually occurs in the hot season of summer.

Due to the weight of the body, the female butterfly is not capable of long flights, and it is active around the place of exit from the pupa, and by crawling on the ground, it changes its location from one tree to another. Unlike the female butterfly, the males have the ability to fly well. The male butterfly flies mostly during the hot hours of the day and its tendency towards light is high, so they can be hunted at night.

Male moths identify their opposite sex by the female’s sex pheromone, which spreads from the end of its abdomen, and starts mating. Since this sex pheromone has attractive properties from a long distance and attracts the male butterflies of this pest, American researchers have tried to fight this pest by artificially producing female sex pheromone and launched their product under the brand name Disparlure.

biology

The spawning place of this pest is in the first 2 meters of the tree trunk. This pest usually chooses the evangelical tree for spawning due to the smooth bark of the trunk, and in the forests, this insect spawns on the trunks of oak, evangelical, mermarz, azad and tesca trees more than other trees.

Spawning takes place in the southern and sunny directions of the trees and in a period of 3 to 8 days and in many batches, each of which carries 100 to 1000 eggs. The development of the fetus and its various stages also ends after 20 to 30 days.

The hosts

When feeding, this pest prefers private trees and shrubs over other species. Broad-leaved trees can be mentioned in order:

oak, beech, evangelical, birch, poplar, willow, maple, elm, and alder.

Among conifers, freshness of needles is important and plays a major role during selection and feeding. and in fruit trees;

Pears and apples are more affected by pests than other trees. But in addition to the mentioned species, this pest feeds most of the plants during flooding.

The manner of damage

The damaging stage of this pest is related to its larvae, and the larvae feed on the leaves of the host trees and make them devoid of leaves, so that it is thought that the tree has fallen and dried up.

If the trees are affected by this pest at the beginning of the growing season, they are able to repair themselves with gradual growth and produce new leaves, and if the trees are infected in the middle of the growing season, they will not be able to repair themselves and the damage is more severe.

Coniferous plants are much more damaged than broadleaf plants and they will not be able to repair themselves during the same growing season. This pest usually prefers pure oak or mixed oak forests to other forests and usually attacks light-loving species more than shade-loving ones. And if the damage of the pest continues for several years, it will lead to the death of the tree or its contracting various diseases, and then we will witness the spread of wood-eating and bark-eating pests.

The amount of economic losses

Since the silk weaver pest usually feeds on tree species that have high economic value, it is necessary and important to pay attention to the economic losses of this pest. Therefore, the results obtained from the statistics show that the tree species of boxwood, walnut, lilac, mulberry, fig and eucalyptus were not fed by the larvae and no damage was observed on their leaves. On the other hand, the bases of the tree species of plum, angeli, oak, and hemlock compared to other tree species (Oja, maple, larg, white pellet, and alder) were most likely to be damaged, so that the majority of the tree bases of these species (more than 80% of the bases) They completely lost their leaf cover.

Insect pest damage is more than fire damage

Some researchers have estimated that the damage caused by insect pests is greater than the damage caused by forest fires. A forest tree is not safe from the attack of pests at any stage of its life, even the seed may be destroyed when it is on the mother tree due to the attack of insects.

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After sprouting, the resulting trees are exposed to the attack of all kinds of pests and insects throughout their life, each type of which is appropriate to the size and living conditions of the tree. And it is these insects that often allow fungi to enter trees. In such a way that they either carry the spores or mycelium of the fungus into the tree or open the way for them to enter by creating a hole in the tree.

Also, some insects, such as leaf-eaters, attack forest trees only to obtain food, and some, such as wood-eaters, use the tree as a breeding ground in addition to food.

Therefore, the forest cannot be completely free from pests, but the problem occurs when the pest becomes rampant and their number becomes very large.

Pests, like forest trees, need special weather conditions in order to survive and grow optimally; Therefore, weather conditions limit the spread of pests. Therefore, for each pest, there are limits in terms of temperature, outside of which the life of the insect will be shortened or it will die.

In general, more species of pests and insects are found in hot and low-altitude areas than in cold and high-altitude areas.

The best thing for forest health is prevention

Abiotic factors such as dryness, heat and light play a significant role in the increase of this pest. Drought causes a decrease in water in the chemical composition of the leaves, and parallel to this decrease, the amount of sugar that is used directly by the larvae increases, and as a result, the larvae get more nutrients. In addition to the dryness factor, heat and light or the combination of these three factors cause the reproductive period of this insect to be shortened, and as a result of this shortening, the risks caused by predators, pathogens, etc. during the growth period of this insect are reduced, and finally insects produce more.

Regarding the increase in the population of Najor silk weavers in recent years, it is necessary to mention that as a result of the destruction of the forest and the conversion of forest areas into agricultural lands, gardens, residential units and other unauthorized uses, parts of the forest that cannot grow due to darkness and temperature conditions And the appearance of the silk weaver pest has been at its minimum. By opening up the space, brightening the forest and entering the light, reducing the humidity and changing the temperature, suitable conditions for the reproduction of this pest in the destroyed and changed forests will be provided.

forest diseases and pests

Some experts also believe that forest diseases and pests cannot be ignored and the best thing for forest health is prevention. One of the preventive measures is that the planting of any plant should be appropriate to the situation of that area, and the import of seeds and seedlings should be taken seriously, as well as the control and quarantine of plants.

Also, the monoculture of the forest is one of the factors that make it vulnerable to pests, and the forest should be mixed, i.e. composed of different plant species. According to these experts, one of the ways to fight against pests is to support the natural enemies of that pest. For example, prevent the hunting of forest birds that feed on pests and build nests for them.

Because if the pest covers a large area, the programs prepared for forestry and forestry as well as wood extraction will be disturbed.

Man, the cause of problems

There is a very complex and regular relationship between the different factors in the forest, and interfering with it and removing even one low-value factor causes changes in the entire ecosystem.

The problems caused by the occurrence of pests and diseases in the forest begin when humans enter it and disrupt the balance with actions such as over-harvesting and removing native species and opening the forest space and planting non-native species.

Therefore, destructive factors in the forest are divided into two categories of non-living factors, such as adverse weather conditions and mixing of soil elements and living factors.

The living factors that are effective in damaging the forest are the pests and diseases that include many species of animals, viruses, bacteria, parasitic and semi-parasitic plants.

A healthy plant performs various activities such as cell division and tissue formation, photosynthesis, absorption and transfer of water and nutrients, and any living or non-living factor that disrupts these activities causes the plant to be called sick.

If the cause of the disease is a living organism, it is called a pathogen or pathogen, any abnormal and harmful physiological phenomenon caused by the proximity and continuous stimulation of a pathogenic agent in the plant is called a disease.

Pests also include those animals that damage plant organs in some way and often include insects, mites, rodents, and molluscs.

Pests feed on different plant organs depending on their behavior and living environment and the type of food they need and the external shape of their feeding organs (mouthparts) and cause damage.

Leaf eaters, root eaters, wood eaters, bark eaters, seed eaters, bud eaters, flower eaters, fruit eaters, stem eaters, ring eaters, root eaters, sap eaters are the most important pest groups in forests.

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In general, all plant organs, from the most terminal part of the branches and buds to the most basic parts of the plant, i.e. the roots in the soil, are attacked and fed by these damaging agents.

In addition to the above-mentioned injuries that are directly inflicted on plant organs, sometimes the damages caused by them appear indirectly. He points out: the creation of scabs on plant organs (scab-causing bees), the creation of complications in leaves and plant organs (wasps), the deformation of plant organs, the secretion of honeybees and the accumulation of dust and soot on leaves and organs (aphids and weevils) and Transmission of some pathogenic agents is one of the indirect damages.

Pests and forest diseases never appear permanently, but periodically appear for short periods and then subside. About the reason for this, it can be said: compared to the agricultural and garden ecosystem, the forest ecosystem is more stable and resistant and can protect itself to some extent.

Therefore, one of the necessities of the forest’s immunity from pests is the benefit of expert forces who are sensitive to any unexpected changes in the forest and report it. Because the lack of expert personnel in executive departments makes it difficult to identify and fight against forest pests.