Damage to agricultural plants and forests by diseases and pests - abstract. Mass lesions of agricultural plants by infectious diseases BJD as a branch of knowledge

Epiphytoty is a massive, progressive in time and space, infectious disease of agricultural plants and (or) a sharp increase in the number of plant pests, accompanied by mass death of crops and a decrease in their productivity.

Panphytotia is called a mass plant disease and a sharp increase in the number of plant pests on the territory of several countries or continents.

Epiphytoties include:

· rust of cereals, when affected, yield losses amount to 40–70%;

· Rice pyrocular blight – a disease caused by a fungus, yield losses can reach 90%;

Late blight (potato rot) is a disease that affects the leaves, stems and tubers of potatoes, etc., with a fungus.

Plant death and disease can result from improper use of various chemical substances, for example, herbicides, defoliants, desiccants, which are used to destroy weeds and wild shrubs when developing new lands, removing or drying the leaves of agricultural plants before harvesting, as growth and maturation stimulants.

Locusts cause incomparable damage to agriculture in many countries in Africa, Asia and the Middle East. 20% of the globe's surface is subject to its raids. Locusts, moving at a speed of 0.5–1.5 km/h, destroy literally all vegetation in their path. So, in 1958, one flock alone destroyed 400 thousand tons of grain in Somalia in a day. Trees and bushes break under the weight of settling swarms of locusts. Locust larvae feed 20–30 times a day.

Rodents (marmots, gophers, gray voles, etc.) are serious agricultural pests. During mass reproduction, their numbers can increase 100–200 times. This increased number of rodents requires huge amounts of food, which becomes crops, especially grains.

Outbreaks of biological pests occur constantly. The Siberian silkworm causes great damage to forest plantations. It killed hundreds of thousands of hectares of coniferous taiga in Eastern Siberia, primarily cedar taiga. Termites are extremely harmful to buildings, vegetation and food. There is a known case of the destruction of Johnstown on the island by termites. Saint Helena.

The main actions aimed at preventing plant diseases are deratization, disinsection, biological, chemical and mechanical pest control in agriculture and forestry (spraying, pollination, surrounding pest areas with ditches).

When an epiphytoty occurs, a phytopathological survey is organized, which conducts an examination of agricultural land, places of storage and processing of plant products and the adjacent territory, establishes the type of pathogen and the boundaries of infection zones.

The main measures to protect plants from infectious diseases are:

· breeding and cultivation of disease-resistant varieties of agricultural crops;

· compliance with the rules of agricultural technology;

· destruction of foci of infection;

· carrying out quarantine measures;

· chemical treatment of crops, sowing and planting material and etc.

Rescuers are involved in work in epiphytotic conditions if it assumes threatening proportions.

EPIPHYTOTY

Mass death of wild animals

In the last decade, the Republic of Belarus has seen an increase in natural foci of rabies with a tendency to spread. Epizootics of rabies are widespread among predatory animals (wolves, foxes, etc.). The disease in wolves occurs in the same form as in dogs. Rabid wolves, in a state of excitement, leave their packs and run away from them over long distances. On their way, they attack people (usually in areas of haymaking, harvesting, logging, road construction) and herds of animals. Their state of excitement manifests itself for 3–4 days and ends in paralysis, just like in dogs. In certain years, rabies in foxes occurs as a mass disease with typical manifestations and very high mortality. Mad foxes attack animals and people, which is not typical for healthy foxes. Every year there are cases of disease in hunting dogs as a result of bites from rabid foxes.

For the prevention of epizootics among carnivorous wild animals, oral vaccination, shooting of wild carnivorous animals, aeration of rodent burrows, and the use of poisons and hormonal drugs are carried out.

Oral vaccination of wild animals is the use of food baits in which a capsule with liquid or dry rabies vaccine is placed. Held in February–April and October–December.

Epiphytoty– a mass infectious disease of plants in a certain territory, during a certain period, covering large areas (farm, district, region). Epiphytoties manifest themselves as, for example, ergot of rye, rust and smut of cereal crops, apple scab, late blight of potatoes, etc. Epiphytoties usually arise from individual foci of the disease in the presence of favorable factors (weather conditions conducive to the propagation of the pathogen and the development of the disease, a sufficient number of susceptible plants and etc.).

Mechanism of epiphytoty development

Phytopathogenic microorganisms spread from the source of the disease and infect a large number of plants. The following types of epiphytoties are distinguished: local, progressive and widespread (panphytotia). Local epiphytoty characterized by strong, over several years, development of the disease in a limited area. An example of local epiphytoty is lodging of seedlings caused by a phytopathogen.

Progressive epiphytoty– a massive infectious disease of plants, which affects more than 50% of their surface. It covers a wider area and has been developing for many years. For example, progressive epiphytoties of powdery mildew, cereal rust, etc. Panphytotia (widespread epiphytoty) – mass plant diseases covering several countries or continents. An example of panphytoty is the spread root sponge, covering coniferous plantations planted in all European countries.

The most common epiphytoties are: ergot, smut and rust of cereals, late blight of potatoes.

Ergot of rye. The causative agent is the fungus Claviceps purpurea. Harm from ergot is associated with the toxicity of the sclerotia. Bread made from flour containing ground sclerotia causes convulsions, headaches, and stomach damage. The fight against ergot is carried out by clearing sclerotia from rye crops.

Late blight of potatoes– a dangerous disease of potato tubers and tops, which is caused by the protist late blight. The disease manifests itself in the fall: all parts of the plant turn black and quickly die. The fight against it is carried out by spraying plants with special chemicals and spreading resistant varieties in the crop.

To combat fungal plant diseases, it is cost-effective to use chemical pesticides - fungicides and cultivation of crops based on intensive technologies.

Biological pesticides for agricultural plants

pathogenic microbes, in which the active principle is the spores of stem rust of wheat, rye, yellow rust of wheat and potato late blight, as well as insects that carry these microbes or pests that can cause mass destruction of agricultural crops.

EdwART. Glossary of terms of the Ministry of Emergency Situations, 2010

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Every year, crop losses from damage to agricultural plants by bacteria and pests amount to about 30% and about 20% of products die during storage.

More than 68,000 species of pathogenic microbes and plant pests are known.

Let's consider the basic concepts that are used to assess plant diseases and pests.

A plant disease is a disruption of the normal metabolism of cells, organs and the whole plant under the influence of a phytopathogen or unfavorable environmental conditions, leading to a decrease in plant productivity or its death.

Phytopathogen – an animal pathogen that secretes biologically active substances that affect metabolism and the root system.

Epiphytoty– a massive infectious plant disease progressing in time and space.

Enphytotia– local spread of infectious diseases of agricultural plants.

Panphytotia- mass plant disease and an increase in pests on the territory of several countries and even continents.

Plant diseases are classified according to the following criteria:

Place and phase of development (seed diseases, seedlings, seedlings, adult plants);

Place of manifestation (local, local, general);

Course (acute, chronic);

Cause of occurrence (infectious or non-infectious)

Non-communicable diseases plant diseases are caused by an imbalance or deficiency of individual microelements in the soil, climatic and weather conditions.

Infectious plant diseases Mainly caused by bacteria, viruses, fungi.

All pathogenic changes in plants manifest themselves in the forms: rot, mummification, wilting, necrosis, plaque, growths, etc.

The most common in the Republic of Belarus different kinds rot (36 items), mold (15), rust (9), spotting (47), necrosis, cancer, plaque, etc.

To the most dangerous diseases viral character include: mosaic (affects grains, fruit trees, vegetables), jaundice (affects beans, beets, strawberries).

Bacterial nature: rot, spotting, wilting, burn (affect grain and vegetable crops).

Gribkovogo nature: rust, late blight, spotting, powdery mildew, mold affect the stems and leaves of plants.

The most dangerous pests p asthenia are: some types of beetles, mites, slugs, rodents, butterflies, flies, ground beetles, cicadas, bedbugs, fleas, etc.

5. Biological pollutants as sources of emergency situations

Outbreaks of infectious diseases in humans and animals are mainly associated with natural processes in space or other environments, as well as with unsanitary conditions in some areas.

Anthropogenic pollution environment cause genetic mutations in biological systems.

The suppression of some biological species and the growth of others, and the emergence of new, previously unknown pathogenic microbes is a new source of biological and social emergencies.

Biological pollution is the entry and impact on wildlife various living organisms, their metabolic products, leading to disruption of the biological and ecological balance in nature and characteristic of situations of environmental distress.

There are natural and artificial biological pollutants.

TO natural biological pollutants include:

Microorganisms and their metabolic products,

Competitor plants;

A sharp increase in the number of animals and insects;

Human. Large crowds of people lead to changes in the atmosphere, hydro- and lithosphere.

Artificial biological pollutants include:

Medicines, food additives, microbiological industry waste;

Intensive development and decomposition of biota (a set of biological species in one territory);

Imported animals, insects and pests;

Population explosions.

The greatest danger to humans are microorganisms and their metabolic products.

MINISTRY OF EDUCATION OF THE REPUBLIC OF BELARUS

EE "Mogilev State University"

them. A.A. Kuleshova"

Department of Physics and Technical Disciplines

ABSTRACT

Damage to agricultural plants and forests by diseases and pests

Mogilev 2010

The concept of epiphytoties

Forest pests and diseases

Pests of agricultural plants

The concept of epiphytoties

Infectious plant diseases differ significantly from each other not only in the characteristics of pathogenesis and external manifestation, but also in the nature of their development in nature. Some diseases are ubiquitous but rare and their incidence rates remain the same. Other diseases are more common, but also little subject to fluctuation; Mass development of these diseases over large areas and severe damage to plants, posing a threat to crops or plantings, are not observed. Such diseases include many types of stem rot of tree species, damping off of seedlings and a number of other diseases.

At the same time, there are diseases whose distribution and development in a certain area or within the entire range is inconsistent and subject to sharp fluctuations. These include many types of rust and powdery mildew, some types of vascular diseases and root rot of tree species, a number of viral and other diseases.

The massive development of an infectious plant disease in a certain area over a certain period of time is called epiphytoty. The study of epiphytoties is occupied by a special section of phytopathology - epiphytotiology. This is the study of the development of pathogen populations within host populations of plant diseases that arise as a result of their interaction under the influence of the environment or human intervention.

The role of the pathogen, host plant and environment in the development of epiphytoties

The emergence, development and attenuation of epiphytoties, as well as the dynamics of diseases in general, obey certain patterns and depend on the interaction of three components involved in the epiphytotic process: the pathogen population, the disease, the host plant population and the environment. If this interaction turns out to be favorable for the development of the disease, it progresses and epiphytoty occurs. If, during the course of epiphytoty, conditions are created that prevent its further development, its gradual attenuation occurs, and the outbreak of the disease stops. Each of these components plays a specific role and is equally important.

The role of the pathogen. The role of the pathogen is extremely important. For epiphytoties to occur, it is necessary that the pathogen be highly aggressive and virulent in relation to the host plant growing in the area and that the reservoir of infection be sufficiently large. The decisive prerequisite for epiphytoties may be the emergence of a highly aggressive pathogen new to the area, which has high fertility and the ability to accumulate in nature.

The higher the rate of reproduction of a pathogen, the easier and faster it spreads, the longer it can survive without losing viability, the greater the threat of epiphytoties. And, conversely, a reduction in the supply of infection, a decrease in the reproductive energy and speed of spread of the pathogen, and a decrease in its aggressiveness are the most important prerequisites for the attenuation of epiphytoties.

The role of the host plant. It is also very significant. Mass development of the disease occurs only if many susceptible plants are concentrated in a certain area. The importance of this factor increases when the development cycle of the pathogen occurs on two different feeding plants, as is observed in rust fungi of different hosts. In this case, for epiphytoty to occur, the presence of both host plants in sufficient quantities is necessary. Therefore, removal of the intermediate host may be a decisive condition for stopping further development of rust.

Weeds play a very important role in the accumulation of infection and the development of epiphytoties, on which pathogens of diseases of cultivated plants and forest species can multiply and persist. The role of the host plant during introduction is especially great: if the introduced plant species turns out to be susceptible to local pathogens, then over time the development of these diseases on the new host can acquire the character of epiphytoties. The same thing happens if a pathogen enters new areas and finds new susceptible hosts there.

The host plant can also play an important role in the attenuation of epiphytoties. If epiphytoty is seasonal, then its attenuation can be facilitated by age-related changes in plants or their tissues, due to which the plants acquire resistance, as is observed, for example, with lodging of seedlings or powdery mildew of oak.

A factor in the attenuation of epiphytoties may also be a general increase in the stability of plantings under the influence of changes in external conditions or as a result of natural selection, since the most stable or hardy individuals survive in the population. Finally, epiphytoty can stop when resistant species or forms of plants are introduced into the culture.

The role of the environment. This role often turns out to be decisive. Especially great importance have climatic conditions of the area and weather conditions of a given year, sometimes several recent years. The determining factor in this case is, as a rule, not one factor (for example, optimal temperature or humidity), but the optimal combination of many factors that favor the mass reproduction of the pathogen, its accumulation and spread, and infection of plants. Environmental factors can contribute to the occurrence of epiphytoties even if they have an adverse effect on the host plant, causing it to weaken and thereby reducing its resistance to the disease. And, conversely, any conditions that prevent the accelerated reproduction and persistence of the pathogen in nature, its rapid spread and infection of plants, as well as all factors that increase the viability and resistance of the host plant, can be factors in the attenuation of epiphytoties.

Thus, epiphytoty is a complex complex of interrelated elements that continuously change under the influence of many factors: genetic, environmental, economic, etc. These elements form a kind of continuous chain in time and space, and its individual links and the nature of the connections between them are determined by the specific relationships in the pathogen-host system and the characteristics of the environment.

Dynamics of epiphytoties

Epiphytoty is a dynamic process, in the development of which a number of sequential stages are distinguished: 1) the preparatory stage, or pre-epiphytoty; 2) an outbreak of disease, or epiphytoty itself; 3) stage of depression, or attenuation of epiphytoties.

During the first stage, those changes in the populations of the pathogen and the host plant occur in nature, which then lead to an outbreak of the disease: the emergence of new, more aggressive races of the pathogen or more active, due to optimal weather conditions, reproduction and accumulation of the pathogen already existing in the area , concentration on large areas of susceptible plants (for example, when creating pure forest crops) or reducing the sustainability of plantings for one reason or another; the emergence of favorable conditions for plant infection (for example, due to human economic activity, increased recreational loads or the influence of abiotic factors, etc.). The duration of this stage may vary, but most often it lasts several years.

The second stage (outbreak) is characterized by simultaneous damage large quantity plants, severe damage and death of a significant part of diseased plants, high level of damage caused by the disease. The moment of culmination of the outbreak can be confined to a certain age of plants or to a period with the most favorable weather conditions for the development of the disease.

During the third stage (depression), there is a gradual decrease in the number of diseased plants and the degree of their damage. Usually the zone of distribution of epiphytoties also decreases.

The duration of epiphytoties, as well as its individual stages, depends on many factors and can vary greatly. The epiphytoty of some diseases develops within one season, while others can last for many years.

Processes occurring in interacting populations of pathogens and host plants are described and explained by mathematical models. Mathematical modeling of epiphytoties is considered in the works of Van der Planck and other authors. Models of population changes over time are used to analyze population parameters, assess development and predict epiphytoties.

Types of epiphytoties

Depending on the characteristics of development and the scale of distribution in nature, the following main types of epiphytoties are distinguished:

Local epiphytoties, or enphytoties. They are characterized by the annual (over several years) strong development of the disease in a limited area, sometimes in the form of separate foci. Pathogens of local epiphytoties, as a rule, are constantly present in a given area. They can survive for a long time in the soil, on plant debris, seeds, weeds, etc. The infectious origin of such pathogens usually accumulates slowly in nature and spreads relatively slowly. However, if the infection reserve reaches a high level, then in the presence of susceptible plants and favorable external conditions, epiphytoties often occur. An example of local epiphytoty is the enphytoty of lodging of seedlings, observed annually in nurseries in many regions of the country.

Progressive epiphytoties. Epiphytoties of this type begin as local ones, but over time cover larger areas. They are usually caused by the most aggressive pathogens that have high reproductive energy, form several generations of asexual sporulation during the summer and are able to quickly spread through the air or with the help of insects (for example, epiphytoty of rust, powdery mildew, some vascular and viral diseases).

The cause of progressive epiphytoties may be the transfer of infected planting material from one area to another or the entry of the pathogen into new areas where there are significant areas of susceptible host plants. An example of such an epiphytoty is the epiphytoty of Weymouth pine blister rust, which arose and quickly covered the vast areas occupied by this pine in the United States after the causative agent of the disease was brought to America from Europe.

Progressive epiphytoties often develop over many years. In young pine crops created on vast areas of concentrated clearings in the northern and northwestern regions of Russia, progressive epiphytoties of snow shutter and rust of pine shoots are observed.

Widespread epiphytoties, or panphytoties, are characterized by the massive development of the disease over the territory of an entire country, sometimes several countries or continents. Panphytotia is a rather rare phenomenon, but they can take on the dimensions of a national disaster, as happened during the panphytotia of potato late blight in the mid-19th century. At the beginning of the 20th century. The character of a panphytotia was the massive spread of oak powdery mildew and gooseberry powdery mildew, brought from America to Europe. The widespread distribution of root fungus in many countries of Europe and North America over the past decades has also reached the level of panphytotia.

In addition, a distinction is made between slowly developing, or tardive, and rapidly developing, or explosive, epiphytoties. The former are most often observed when perennial plants (for example, trees) are affected by diseases such as Dutch elm disease or root fungus on conifers. They are characterized by a smooth progression of the outbreak and its gradual attenuation. The latter are caused mainly by pathogens with a high reproduction rate and are characterized by a sharp increase in the outbreak and its rapid attenuation. The course of epiphytoties of this type is often subject to seasonal changes and is largely determined by environmental factors. Examples include epiphytoty of apple scab, lodging of seedlings, powdery mildew, rust, schutte and other agricultural use Law >> Ecology

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