2. What is biological control of plant
diseases ?
Biological control involves the use of
one living organism to control
another.
This management technology has
received much attention in recent
times.

3. Pros
•Specific to a
particular pest.
•Cheap after startup.
•It works most of
the time.
Cons
•Does not have a
broad-spectrum as
insecticides.
•Expensive at
startup.
•Doesn't completely
destroy a pest

4. A
Parasitoids
Biological
Control Agents
B
Pathogens
C
Predators
Entomopathogenic micro-organisms (Bacteria,
Fungi, Viruses ,Protozoa and Nematodes).
Antagonists of Plant Diseases
D
E

5. Parasitoids
Each parasitoids requires only one host, which it kills for its development
into a free living adult.
Parasitoids are of the same size as the hosts , or sometimes even smaller.
Mechanism
The Female parasitoid lays eggs inside or on an insect host.
Legless larva on hatching feed on the hosts internally or
externally.
Many adult parasitoids feed on nectar or pollen and serve as
important pollinators.
Eggs of female Trichogramma chilonis
Examples
Trichogramma,Ichneumoid,Scelionoid,Braconid,
Encryrtid,Eulophid,Chalcid wasps and Tachinid Flies

6. Revolution of Trichogramma chilonis
Trichogramma chilonis has been successfully released in
Jammu & Kashmir, Himachal Pradesh, Punjab, Haryana, Gujrat , Uttrakhand ,
Uttar Pradesh, Bihar , Karnataka, Tamil Nadu ,Maharashtra and few other
states.
It has given 56-82% protection against the sugarcane tissue borers.

7. Pathogens
Pathogens are disease causing organisms e.g. Bacteria, Fungi, Viruses
,Protozoa and Nematodes in Insect Pests which kill their host or debilitate the
future generation.
Mechanism
The infected insects are unable to feed properly ,remain
stunted, lose their body colour and get paralysed. Dead
insects are often found hanging on the plants, or a fungal
growth on the body of dried insect could be easily located in
the field.
Caterpillar, Pseudoplusia includens , killed
by entomopathogenic fungus
Nomuraea rileyi , white-disease in soybean
crop.

8. Predators
These are free living and larger in size than their prey, requiring several
preys to complete their life cycle. Some smaller predators release a powerful
poison, use a trap or hunt in groups to be more effective.
Mechanism
Green lacewings (very common and important
predator of crop pests).
The female lays small pale green, oval shaped
eggs at the end of long silken stalks, which
ultimately turns grey.The larva have well
developed legs and pincer like jaws with
which they suck the body fluids from the prey

9. Antagonists of Plant Diseases
The microorganisms used in biological suppression of plant diseases which
grow in association with plant diseases are termed as antagonists.
An antagonist microorganism adversely affects the disease causing
organism by following:-
Competition:- the competition which takes place between two
organisms in terms of nutrients etc.
Antibiosis:-an association between organisms that is injurious to one of
them.
Antibiosis, is provided by marigold (Tagetes species) roots,
which release terthienyls, chemicals that are toxic to several species of
nematodes and fungi.

10. Hyperparastism:-the parasitic habit of one species upon another parasitic
species which is harmful to one of them.
Mycoparasitism:-a parasitism of a fungus(host) by another
fungus(mycoparasite). Trichoderma harzianum, used as seed treatment against
pathogenic fungus(Sclerotium rolfsii) on chickpea and sugarbeet

11. Field Release Methods
Inoculative Release:- The release of relatively small
numbers of natural enemies that are expected to colonize,
reproduce, and spread naturally throughout an affected area.
Augmentation(growing larger) of Natural
Enemies:- It is a method of increasing the population of a
natural enemy that attacks a pest. This can be done by mass
producing a pest in laboratory and releasing it into the field a
the proper time.
Application of microorganisms:-Antagonists like
Trichoderma and Glicladium spp. introduced with planting
material such as seeds and seedlings of vegetable crops to
suppress damping off and root rots are one kind of
inoculative release.