How nature regulates insect pest damage using fragrances?

Fragrance and smell has always remained integral part of communication since life exists. Who know well about it than teens and adults in schools and colleges emptying bottles of perfumes & deodorants to entice opposite sex-partners. Even smell of once's body is a factor of attraction in physical intimacy. You might be heard that wife caught her husband's physical relationship with someone else smelling husband's cloth/body. Anyway your mother might have caught your smoking habit while washing cloths if you smoke sometimes. 

Not only fragrance and smell play important role in human relationships, it plays vital role in all kind of natural life exists around. Whole animal kingdom primarily insects communicate through chemical smells known as pheromones. At the same time it is extensively documented that plants also deploy chemical trails as communication channels along with mycorrhizal fungal networks as part of defense mechanisms.

Historically farmers have been observing these principles and mechanisms while growing food and to regulate insect-pest damages naturally using numerous permutations and combinations of plants (guilds). They have been observing nature keenly and, her way of doing and managing the things. Diverse set of designs and combinations operates in nature to regulate the life and destruction.

A diverse range of food herbs, flowers and oil crops have always been grown with pulses and grains in integration to keep soil infertility and various biotic damage at bay. This polyculture model promotes a lot of direct and indirect benefits from food self-sufficiency to no-use of harmful synthetic chemicals. Few leaves could be taken out of natural designs to grow food without harmful chemicals in fun way.

In this brief piece of information without much diverting I am trying to convince that such models/designs can be tried/experimented to grow food both at garden and farm level without deploying harmful synthetic chemicals. Designs simply include growing plants or a group of plants in such a combination (guild) that insect population remains below EIL (economical injury level) technically.

How it works?
In nature life operates as a cycle of procreation and death. At lower rang of animal kingdom, particularly in insects, this play-game is more profound and intense. Insects reproduced hundred thousand of pro-genies in short period of life span. A small proportion of them reach to maturity just like a tree produced hundred thousand of seeds but very few reach up to matured tree.

Similarly maximum of insect babies get simply predated and used as someone other insect's food in hierarchy of wood-web. When diverse range of multi-crops are raised on a small plot or big-sized farm it attracts diverse range of insects where with crop damaging insects their predators come into picture in first place and, second numerous fragrant and smelly plants disturb the communication network/pheromone trails to check the reproduction rate. Some plants also attract particular type of insect predators to let them feed upon other crop damaging insects e.g. mustard, legumes (grams, fenugreek, peas) and coriander is being grown around wheat fields from ages. 

In this bio-mimicked design mustard traps the aphid population and at the same time promotes the lady-red-beetle population (one lady red beetle eat around 5000 aphids in his life span roughly) to predate upon aphids. Coriander's fragrance hinders the pheromone induced mating mechanism operates in aphids to check reproduction rate. Legumes fix atmospheric nitrogen and act as ground cover, and thrive soil life. This is the simple example of linear design deployed by farmers traditionally through out ages but there are many such cyclic designs connecting with each other operates in natural eco-systems.

What you can do?

• Little you can do try to bring maximum of diversity of crops/seeds into your food garden/plot using permaculture guilds.
• Grow fragrant herbs and oil giving plants along with food crops, veggies and salads, and fruit trees (moreover you can make concoction of herbs and use them as pest repellent sprays).  
• Try to get hands dirty with practice of wild-gardening/natural farming/forest gardening. 
• Think how food is being grown in natural ecosystems without any human or technological intervention?
• Read bio-mimicked designs/permaculture to grow food naturally with pledge to not use harmful chemicals damaging whole range of eco-systems. 
• Use native diversity of food and deploy traditional mechanisms of food growing being practiced in farms since ages.

What's take out?

• Nature raise food using and deploying various cyclic mechanisms for numerous life-forms unlike modern linear food-system.

• You can grow healthy food as fun and without any use of synthetic-chemicals bringing-in diversity of food.