Chemical Control of Plant Diseases

What is a Plant Disease?

A plant disease is something that stops or prevents the plants from growing normally or performing to their maximum potential. It is an impairment of the normal state of the plant that modifies its vital functions or interrupts it. All the plants, irrespective of their species, habitat, etc are affected by the diseases. These diseases vary season to season and depend on the presence of the pathogen, type, and variety of plant and environmental conditions. Plant diseases could be biotic or abiotic. Biotic diseases are caused by living organisms called pathogens. Abiotic diseases are caused by external factors and not living organisms. 

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.

FAQs (Frequently Asked Questions)

 1. How are Plant Diseases Diagnosed?

Ans - Proper diagnosis of diseases is required before suggesting proper control measures. Diagnosis is the first step in the study of any disease. It is largely based on the characteristic symptoms of the plant in which disease is there. Three steps are involved in the diagnosis of the disease - careful observation and classification of the facts, evaluation of the facts, and a logical decision as to the cause. 

2. What are The Advantages of Plant Disease Chemical Control?

Ans - The advantages of chemical control of plant diseases are as follows:

  • It is relatively low cost

  • It can be applied with ease and is effective.

  • It is easily available in the market and is stable.

  • They are fast-acting which results in less damage to the crops.

3. What Are The Disadvantages of Chemical Control?

Ans - The disadvantages of plant disease chemical control are as follows:

  • They are harmful not just to the organisms they are meant for but to other organisms as well.

  • They are generally of two types: selective and non - selective. Non-selective is the most harmful one as it harms all the organisms around it.

  • The selective chemicals have a limited range. They kill only the targeted organisms such as pests, diseases, or weeds.

  • Another major drawback is that it gets passed on to the food chain. If a sprayed plant is eaten by an organism and then that organism by another organism and then it by the other, the chemicals revolve in the food chain. 

  • The most significant threat by the chemical control is the residues of the chemicals on the crop. That may be consumed along with the fruits and is harmful to other organisms including humans. 

4. What are The Categories of Pesticides?

Ans - There are five categories of pesticides:

  • Fungicide - they act against the fungi that harm the plants or crops.

  • Herbicides - they are used against the weeds present with the crops that harm the crops.

  • Insecticides - they act against harmful insects.

  • Acaricides - they help in protecting the plants from mites.

  • Nematicides - they are used to control the nematodes that attack the plants.