chemical control of Plant diseases

2. 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
i. Bactericides (To control Bacteria)
ii. Fungicides (To control Fungi)
iii. Nematicides (To control Nematodes)

3. 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.

4. …Contnd
 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.

5. 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.

6.  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.

7. 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.

8. Classes of Chemical
Treatments
There are three major classes of
chemical treatments
 Soil Treatments
 Seed Treatments
 Foliar Sprays

9. Soil treatment
a. Soil Drenching (Fungicides are
mixed with water at definite
concentration & applied to soil
surface)
b. Furrow application (Fungicides are
applied as granules or with water at
the time of planting)
c. Broadcast (non-volatile fungicides
are mixed with soil or fertilizers)
d. Fumigation

10. 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

11. Foliar Sprays
 It is the method of applying chemicals
by spraying them directly on the
leaves.

13. Advantages
 Relatively low cost
 The ease with which they can be
applied and their effectiveness,
 Availability and stability.
 Chemical pesticides are generally
fast-acting, which limits the damage
done to crops.

14. Disadvantages
 Chemical pesticides are often not just
toxic to the organisms for which they
were intended, but also to other
organisms.
 Non-selective products are the most
harmful, because they kill all kinds of
organisms, including harmless and
useful species.
 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.