Allelochemicals have inhibitory effects on the growth and development of pests. Thus, farmers are using as alternatives of chemicals for control and management of pests.
There are several types of pests in agricultural sector that compete with main crop for moisture, nutrients and space as well as they damage crop. As a result of that physiological functions of crop plants not work properly. In such case, growth and development of crop plant effects badly. This creates a hurdle to achieve full potential yield of many crops.
These pests include weeds, insects and diseases. Weeds are plants which are out of place and in the crop lands. Weeds compete with crop for nutrients, moisture and space as well as they release some chemicals which reduce the growth and development rate of crops. Insects feed on the crop by sucking their cell sap and by chewing the plant parts. They also cause many diseases to attack on crop plants because many of them are carriers of diseases.
Many chemicals are common to use for control of these pests. About 4 million tons of chemicals are in use against these pests of which more than half are herbicides only. But, these chemicals have bad effects not only on environment sustainability but also on human health.
When we apply these chemicals in crops these not only kill the pest but also a lot of species of beneficial insects are killed. These chemicals have their residual effect on food. Which on consumption by human causes many diseases and disorders in their body. Continuous use of these chemicals against these pests helps them to generate resistance against them. It makes them very difficult to control and keep them under threshold level.
Allelochemicals as chemicals alternative
The miracle in which the metabolites produced by bacteria, virus, fungi, other microorganisms and plants is called allelopathy. These metabolites are called as allelochemicals that may negative or positive effects on the functioning of other living organisms.
Allelochemicals which have inhibitory effects on the growth and development of these pests can be used as alternatives of chemicals for their control and management. However, the use of pesticides cannot be totally stopped. But may reduce upto certain extent at which they may have no hazardous for environmental sustainability.
There are several plant species which release certain type of allelochemicals from their different parts like flowers, buds, roots, stem and leaves. Sorghum, tobacco, corn, wheat, sunflower, mustard and some other plants having more height release inhibitory allelochemicals that suppress the growth of pests.
Management of weeds can practice through allelochemicals in many ways:
- use of crop residues and stubbles as organic mulch and use of spreading type crops as a cover crop,
- there should be an addition of such type of crops in crop rotation plan which have inhibitory allelopathic effect on weeds,
- allelopathic crops need to be grow as a mix or strip cropping,
- by using the extract of crop which have some allelopathic nature.
To enhance the efficiency of these crop extracts they mix up with other herbicides to control weeds. Many researchers have conclusion from their studies that when use in combination with allelochemicals, this will reduce herbicide dose upto 55-75%. Their results shows that weed control is the same just like full dose of these herbicides. So that, by using these organic allelochemicals will reduce the residual effects on herbicides in food.
Benefits of allelochemicals
By using the allelochemicals, production cost will reduce. Synthetic chemicals are very expensive which poor farmers can not afford. To get extract from plant parts is very easy and cheap as well. Plant parts are chopp in small pieces and then air dry. After drying they boil in water in a suitable quantity. After boiling when extract become viscous they are ready for the control of pests.
The use of these organic nature allelochemicals does not affect the sustainability and diversity of environment. Allelopathic strategy can also reduce the risk of diseases in human beings due to residual effect of synthetic chemicals. Synthetic chemical also contaminates water, air and soil that affects aquatic life, air quality and edaphic fauna. So that, by suing non-toxic allelochemicals all these effects will reduce.
There is still need to create awareness to the farmers about the role, production, and use of allelochemicals. The supply of these allelochemicals should made on commercial scale to make their supply easy to the farmers. There is need of more research in this field against pests and also to increase the growth and yield of crops. Thus, we can achieve full potential yield and minimize the yield gap.
This article is jointly written by Nasir Ali1, Imdad Ullah1, Nadeem Akbar1, Muhammad Ishfaq1, Muhammad Rashid Fayyaz2. The authors are from 1 Department of Agronomy, University of Agriculture Faisalabad, and 2 Department of Parasitology, University of Agriculture Faisalabad.