Biological control involves the use of one living organism to control another.

This management technology has received much attention in recent times.

What is biological control of plant diseases ?

•Specific to a particular pest.

•Cheap after

startup.•It works most of the time.

•Does not have a broad-spectrum as insecticides.•Expensive at startup.

• Doesn't completely destroy a pest

Pros Cons

AParasitoids

BPathogens

CPredators

Entomopathogenic micro-organisms (Bacteria, Fungi, Viruses ,Protozoa and Nematodes).

D

Antagonists of Plant Diseases E

Biological Control Agents

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.

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.

Trichogramma,Ichneumoid,Scelionoid,Braconid,Encryrtid,Eulophid,Chalcid wasps and Tachinid Flies

Parasitoids

Mechanism

ExamplesEggs of female Trichogramma chilonis

Revolution of Trichogramma chilonisTrichogramma 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.

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.

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.

Pathogens

Mechanism

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.

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

Predators

Mechanism

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.

Antagonists of Plant Diseases

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

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 at 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.

Field Release Methods