Plant diseases are something that stops or prevents plants from growing naturally or achieving their maximum growth potential. It is a type of impairment of the normal state of the plant which modifies its vital functions or interrupts it. All of the plants, irrespective of their species, habitat, etc can be affected by various plant diseases. These diseases vary from season to season and depend on the presence of the type of pathogen, the variety of plants, and the environmental conditions. Plant diseases can be biotic or abiotic. Biotic diseases are caused by living organisms known as pathogens whereas Abiotic diseases are caused by external factors and not living organisms.

Control of Plant Diseases

For the prevention of plant diseases, the use of chemical control plays a critical role. There are numerous specific action fungicides that have been developed since the 1960s and a variety of chemicals are available nowadays which are developed and designed to control plant diseases by inhibiting the increment of or by killing the disease-causing pathogens. There are various types of chemicals used for this purpose such as chemicals that control bacteria (bactericides), that control fungi (fungicides), and chemicals that control nematodes (nematicides). These chemicals should be used in a proper and judicious manner for plant disease control.

How to Control Plant Diseases?

To control plant diseases, we should have a thorough knowledge of the disease cycle and the causal agent, host-pathogen interactions in relation to the environmental factors and the cost. We can control plant diseases by choosing the best variety and seeds. For the harvested crops, disease control can be extended through transport, storage, and marketing. The other approaches for controlling plant diseases are biological, cultural, and chemical methods. Of all plant disease control methods, we will learn about the chemical control of plant diseases in this article.

Chemical Control of Plant Diseases

In the prevention of plant diseases, chemical control plays a critical role. Numerous specific action fungicides have been developed since the 1960s. A variety of chemicals are available nowadays that are developed and designed to control plant diseases by inhibiting the growth of or by killing the disease-causing pathogens. There are various types of chemicals - chemicals that control bacteria (bactericides), that control fungi (fungicides), and chemicals that control nematodes (nematicides). These chemicals should be used properly for plant disease control.

Control of Crop and Forest Disease

The chemicals used for plant disease control are applied to seeds, flowers, fruits, foliage, and soil to reduce or prevent infections. The protectants act as a chemical barrier between the plants and the pathogens. The eradicants are designed to kill the pathogens present in the seeds or vegetative propagative organs such as tubers, bulbs, or corms and in the soil. The therapeutic chemicals are used to combat in-progress infection.

Chemical Control Methods

The soil treatments kill the nematodes, bacteria, and fungi inhabiting the soil. The eradication of these biotic pathogens can be done using steam and chemical fumigants. The nematodes that are born in the soil can be killed by liquid nematicides or granular nematicides. Generally, the soil is treated before plantation, but a few fungicides are mixed with the soil at the time of plantation or after it.

The seeds, bulbs, tubers, and corms are frequently treated with chemicals to get rid of pathogens - fungi, bacteria, and nematodes. This helps in protecting the seeds, bulbs, corms, and tubers from the pathogen present in the soil - mainly the fungi, which is the cause of the decay and the damping off. The seeds are also treated with fungicides which they absorb and get protection for the growing seedling.

The protective dust and sprays are used to prevent infection in foliage and the fruit of crops. There is a wide range of chemical dust and sprays. They are not absorbed by the plant or translocated through the plant, and hence they protect only those parts of the plant treated before invasion by the pathogen. A second spray is always recommended and required as the first layer may be washed away by the wind, rain, or irrigation. There is a possibility of breaking down by the sunlight also.

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FAQs on Chemical Control of Plant Diseases

1. What is the method for control of crop and forest disease?

The chemicals which are used for plant disease control are applied to seeds, flowers, fruits, foliage, and soil to reduce or prevent infections. These protectants act as a chemical barrier between the plants and the pathogens. These eradications are designed to kill the pathogens present inside the seeds or vegetative propagative organs such as tubers, bulbs, or corms and in the soil. The therapeutic chemicals are also used to combat in-progress infection.

2. What are the chemical control methods for plant disease prevention?

The soil treatment is useful to kill the nematodes, bacteria, and fungi inhabiting the soil. The eradication of these biotic pathogens can be achieved using steam and chemical fumigants whereas the nematodes which are born in the soil can be killed by liquid nematicides or granular nematicides. So, the soil is treated before plantation and a few fungicides are mixed with the soil at the time of plantation or after it. The parts like the seeds, bulbs, tubers, and corms are frequently treated with chemicals to get rid of pathogens - fungi, bacteria, and nematodes. This is helpful in protecting the seeds, bulbs, corms, and tubers from the pathogen present in the soil

3. How are plant diseases diagnosed?

The Proper diagnosis of diseases is essential before suggesting proper control measures. Diagnosis is the first and pivotal step in the study of any disease. It is largely based on the characteristic symptoms of the plant in which disease is present. There are three steps that are involved in the diagnosis of the disease, which are careful observation and classification of the facts, evaluation of the facts, and a logical decision as to the cause of the disease.

4. What are the disadvantages of Chemical Control?

There are several disadvantages of control of plant disease by chemical control such as:

They are harmful not just to the organisms they are meant for but to the other organisms as well.
The chemicals are generally of two types: selective and non - selective. Non-selective is the most harmful one as it harms all the organisms in the ecosystem.
The selective chemicals have a very limited range. They kill only the targeted organisms such as pests, etc.
Another major drawback of chemical control is that it gets passed on to the food chain. If the sprayed plant is eaten by an organism and then that organism by another organism and then it by the other, the chemicals accumulate in the food chain.

5. What are the categories of Pesticides?

Pesticides are chemicals that are sprayed on plants to prevent plant diseases. There are broadly five categories of pesticides:

Fungicide - which acts against the fungi that harm the plants or crops.
Herbicides - which are used against the weeds present with the crops that harm the crops.
Insecticides - which act against harmful insects.
Acaricides - which help in protecting the plants from mites.
Nematicides - which are used to control the nematodes that attack the plants.