Chemical Control
Chemical Control:- Chemical control of plant diseases refers to the use of variety of chemicals that have been designed to control plant diseases by inhibiting the growth of or by killing the disease-causing pathogens.
Types of Chemicals used:-
1. Bactericides (To control Bacteria)
2. Fungicides (To control Fungi)
3. Nematicides (To control Nematodes)
1. Bactericides:-
> Bactericide in an application or product that help stop bacterial infection in Plants.
> Bactericides can be liquid or powder form, organic or non-organic.
> Some of most effective bactericides rely on copper to kill bacteria.
> They help treat conditions ranging from bacterial leaf spots to powdery and downy mildew, as well as early and late blight in range of fruiting plants, such as cucumbers, onions, tomatoes.
> Examples of these products include Camelot and Kocide 3000.
> Indoor-grown plants are sensitive to copper, and application of this type of bactericide should be carefully considered.
> No form of bactericide has proven 100% effective in all instances of killing plant damaging bacteria.
2. Fungicides:-
> Also called as antimycotic, any toxic substance used to kill or inhibit the growth of fungi.
> Most agricultural fungicides are applied as sprays or dusts.
> Seed fungicides are applied as protective covering before germination.
> Systemic fungicides are applied to plants where they become distributed throughout the tissue and act o eradicate existing disease or to protect against possible disease.
> Fungicides kill pathogenic or parasitic fungi by disrupting their critical cellular processes. E-g Many fungicides bind with specific enzymes to interrupt the metabolic pathways involved in cellular respiration.
> Examples: Bordeaux mixture, cadmium chloride, cadmium succinate etc.
3. Nematicides:-
> Nematicide is a type of chemical pesticide used to kill plant-parasitic nematodes.
> E.g. Aldicarb a carbamate insecticide. It is important in potato production, where it has been used for control of soil borne nematodes.
> A common natural nematicide is obtained from neem cake, the residue obtained from cold pressing the fruits and kernels of neem tree.
Classes of Chemical Treatments:- There are three major classes of chemical treatments:
1. Soil Treatments
2. Seed Treatments
3. Foliar Sprays
1. Soil treatment:-
i. Soil Drenching (Fungicides are mixed with water at definite concentration & applied to soil surface).
ii. Furrow application (Fungicides are applied as granules or with water at the time of planting).
iii. Broadcast (non-volatile fungicides are mixed with soil or fertilizers) d. Fumigation.
2. Seed Treatment:-
> It is the treatment of seeds with chemicals, typically antimicrobial or fungicidal, prior to planting.
> Color can be added to seed to make treated seed less attractive to birds
3. Foliar Sprays:- It is the method of applying chemicals by spraying them directly on the leaves.
Advantages:-
i. Relatively low cost.
ii. The ease with which they can be applied and their effectiveness.
iii. Availability and stability.
iv. Chemical pesticides are generally fast-acting, which limits the damage done to crops.
Disadvantages:-
i. Chemical pesticides are often not just toxic to the organisms for which they were intended, but also to other organisms.
ii. Non-selective products are the most harmful, because they kill all kinds of organisms, including harmless and useful species.
iii. Accumulation:- If sprayed plants are eaten by an organism, and that organism is then eaten by another, the chemicals are can be passed up the food chain.