Biological methods of pest management:

Herbivorous insects are said to be responsible for destroying one fifth of the world's total crop production annually [Insect Damage- FAO]. 

Chemical pesticides have been so popular and most common option for pest management and plant protection. 

However, they are not free from hazards that can be poisonous to both harmful pests and beneficial one too. They are hazardous for humans as well as many other organisms surviving in environment, degrading the whole ecosystem in long run if used indiscriminately. So, it's high time that we have to realize such adverse effects of chemical pesticides towards environmental sustainability and seek for the application of eco friendly biological methods of our agricultural problems, specially pest control.

Biological methods of pest control:

In biological pest management method, we use natural enemies of crop pests such as: predators, parasitoids and pathogens. 

According to biological events, biological control means to reduce the number of other organisms by the use of predator, parasitoid or pathogen which is not possible in absence of these whereas in entomology, it means the study and application to reduce the density of pests by the use of natural predators, parasitoids and pathogens. 

In case of arthropods, predators are those organisms that preys on more than one creature to complete its life cycle. Parasitoids are those which depends on only one organism to complete its life cycle. Parasitoids are considered to be more beneficial than predators as predators do not destroy pests when pest population is lower but parasitoids do. Parasitoids are smaller than pest and their life cycle is also shorter. These organisms lay their eggs, on specific life stage of pest ; egg, larva, pupa or adult with their sharp ovipositor, from where larva emerge and start feeding on the pest which results in the death of that pest stage. But predator organisms (insects, spiders) directly feed on specific stage of pest and thus control their number. As some examples of predators we can take some coleopteran insects from families- coccinellidea, cicindelidea and carabidea feed on Aphids, Scales, Mealybugs and Eggs of lepidopterans. 90% of parasitoids are from order- Hymenoptera, for e.g. Trichogramma chilonis of trichogrammatidea family is egg parasitoid of Eggs of sugarcane internode borer, cotton bollworm, rice leaf folder, etc. 

Another effective method of biological pest control is microbial control method. It is defined as the control of pests by the use of microorganisms like virus, bacteria, protozoa, fungi and nematodes, which kill their host or debilitate the future generation. For example, use of Metarhizium anisopliae has been found to be effective on biological control of locust. Similarly, NPV viruses for larva of lepidoptera larvae. Bacterias like Bacillus thuringensis affect various insect larvae/ nymph and adult. Likewise, there are various entomopathogenic Nematodes (EPNs) thata are capable of killing, sterilizing or seriously hampering the

development of insect and completing at least one stage of their life cycle in the

host. Family Mermithidae :(Order: Enoplida), family: Steinernematidae (Order; Rhabditida) and family: Heterorhabditidae are the important groups of EPNs. 

Why to use biological control methods?

(Advantages of biological pest control method): 

1. It doesn't have negative impacts like of chemical pesticides on humans, other organisms and plants as this method uses predator, parasitoid insects and microorganisms for pest control and are host specific. Thus, it is an eco-friendly technique.

2. There is a high chance of killing of natural enemies of crop pests by chemical pesticides and this can allow faster growth of less harmful insects to harmful pests, which may not be a problem in case of biological control used fields.

3. Lesser chances of pest resistance development and insurgence of minor pest to a major pest.

4. Low cost in multiplication or large scale culture and application than chemical pesticides. They are also best suited for crops with high economic value. 

5. It is compatible with chemical pesticides too for Integrated Pest Management (IPM).

Despite of all these advantages, we must be careful about creating the favourable environment for proper establishment of these organisms and control pests in an eco-friendly way. 

Green cheers!! 

Source of image: https://images.app.goo.gl/NMGU8YtPccySrJCt5

http://www.dailymirror.lk/opinion/Sri-Lanka-has-successfully-turned-to-biological-control/172-158760

http://entnemdept.ufl.edu/creatures/nematode/entomopathogenic_nematode.htm