BIOPESTICIDES IN AGRICULTURE

INTRODUCTION

It has been truly said that ‘survival of the fittest’. The importance of this line in

this contest is that man has realized the harmful effects of the chemical

fertilizers and the pesticides. In an attempt to save the earth and to make

himself feel safe to live in the earth it has developed the bio-pesticides and has

been successfully utilized in the field of agriculture. There has been a

significant development toward the development and application of bio-

pesticides in agriculture.

WHAT ARE BIO- PESTICIDES

'Biopesticides' are certain types of pesticides derived from such natural

materials as animals, plants, bacteria, and certain minerals. These include for

example; fungi such as Beauveria sp., bacteria such as Bacillus sp., neem

extract and pheromones. Similarly Canola oil and baking soda have pesticide

applications and are considered as biopesticides.

The use of these materials is widespread with applications to foliage, turf, soil,

or other environments of the target insect pests. In a much simpler way we

can say that these are pest management tools that are based on beneficial

microorganisms (bacteria, viruses, fungi and protozoa), beneficial nematodes

or other safe, biologically based active ingredients. Benefits of biopesticides

include effective control of insects, plant diseases and weeds, as well as

human and environmental safety. Biopesticides also play an important role in

providing pest management tools in areas where pesticide resistance, niche

markets and environmental concerns limit the use of chemical pesticide

products

The market for biopesticides is expanding rapidly: growing at some 10% per

year, by 2010 global sales are expected to hit the $1 billion mark and make up

4.2% percent of the overall pesticides market. Much of this rapid growth is

due to the fact that, perhaps surprisingly, more than 80 % of biopesticides are

used, not by organic farmers, but by producers employing conventional

farming practices. Orchard crops hold the largest share of total biopesticides

use at 55%.

Biopesticides in general-

(a) have a narrow target range and a very specific mode of action.

(b) are slow acting.

(c) have relatively critical application times.

(d) suppress, rather than eliminate, a pest population.

(e) have limited field persistence and a short shelf life.

(f) are safer to humans and the environment than conventional pesticide.

(g) present no residue problems.

Advantages of Using Biopesticides

25 million cases of acute occupational pesticide poisoning in developing

countries are being reported each year (WHO, 1990). 14% of all known

occupational injuries and 10% of all fatal injuries are caused by pesticides

(ILO, 1996). Obsolete pesticides are being stored in developing countries-

20,000 tonnes in Africa alone. Pesticide residues in agricultural commodities

are being the issue of major concern besides their harmful effect upon human

life, wild life and other flora and fauna. Equally worrying thing is about

development of resistance in pest to pesticides. The only solution of all these

is use of 'Biopesticide' that can reduce pesticide risks, as-

(a) Biopesticides are best alternatives to conventional pesticides and usually

inherently less toxic than conventional pesticides.

(b) Biopesticides generally affect only the target pest and closely related

organisms, in contract to broad spectrum, conventional pesticides that may

affect organisms as rent as birds, insects, and mammals.

(c) Biopesticides often are effective in very small quantities and often

decompose quickly, thereby resulting in lower exposures and largely avoiding

the pollution problems caused by conventional pesticides.

(d) When used as a fundamental component of Integrated Pest Management

(IPM) programs, biopesticides can greatly decrease the use of conventional

pesticides, while crop yields remain high.

(e) Amenable to small-scale, local production in developing countries and

products available in small, niche markets that are typically unaddressed by

large agrochemical companies.

Types of Biopesticides

Biopesticides fall into three major classes:

(1) Microbial pesticides consist of a naturally occurring or genetically

controlled

Microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active

ingredient. These pesticides can control many different kinds of pests,

although each separate active ingredient is relatively specific for its target

pest(s). For example, there are fungi that control certain weeds, and other

fungi that kill specific insects

They suppress pest by-

(a) Producing a toxin specific to the pest.

(b) Causing a disease.

(c) Preventing establishment of other microorganisms through competition or

(d) Other modes of action.

An example of a most widely used microbial pesticide is subspecies and

strains of

Bacillus thuringiensis or "Bt". It is a naturally occurring soil bacterium that is

toxic to the larvae of several species of insects but not toxic to untargeted

organisms. BT can be applied to plant foliage or incorporated into the genetic

material of crops and as discovered, it is toxic to the caterpillars (larvae) of

moths and butterflies. These also can be used in controlling mosquitoes and

black flies. Several strains of BT have been developed and now strains are

available that control fly larvae. While some BT’s control moth larvae found on

plants, other Bt's are specific for larvae of flies and mosquitoes. The target

insect species are determined by whether the particular Bt produces a protein

that can bind to a larval gut receptor, thereby causing the insect larvae to

starve.

(2) Plant-Incorporated-Protectant

(PIPs) is pesticide substances that plants produce from genetic material that

has been added to the plant. For example, scientists can take the gene for the

Bt pesticide protein, and introduce the gene into the plant's own genetic

material. Then the plant, instead of the Bt bacterium, manufactures the

substance that destroys the pest.

(3) Biochemical pesticides are naturally occurring substances that control

pests by nontoxic mechanisms. Conventional pesticides, by contrast, are

generally synthetic materials that directly kill or inactivate the pest.

Biochemical pesticides include substances, such as insect sex pheromones

that interfere with mating as well as various scented plant extracts that attract

insect pests to traps. Man-made pheromones are used to disrupt insect mating

by creating confusion during the search for mates, or can be used to attract

male insects to traps. Pheromones are often used to detect or monitor insect

populations, or in some cases, to control them.

Farmers in their traditional wisdom have identified and used a variety of plant

products and extracts for pest control, especially in storage. As many as 2121

plant species are reported to possess pest management properties, 1005

species of plants exhibiting insecticide properties, 384 with antifeedant

properties, 297 with repellant properties, 27 with attractant properties and

31 with growth inhabiting properties have been identified. The most

commonly used plants are neem (Azadirachta indica), pongamia (Pongamia

glabra) and mahua (madhuca indica). 2-5 % neem or mahua seed kernel

extract has been found effective against rice cutworm, tobacco caterpillar, rice

green leafhopper, and several species of aphids and mites. The efficacy of

vegetable oils in preventing infestation of stored product pests such as

bruchids, rice and maize weevils has been well documented. Root extracts of

Tagetes or Asparagus as nematicide and Chenopodium and Bougainvillea as

antivirus have also been reported.

Potential of Biopesticide

The efficacy of many of the biopesticide can equal that of conventional

chemical pesticides.

However, the mode of action will be different. With many of the biopesticides,

the time from exposure to morbidity and death of the target insect may be 2 to

10 days. Understanding the fundamental differences in the mode of action of

biopesticide vs. traditional pesticides is important since the use patterns of a

biopesticide may be different from traditional pesticides to control a

particular pest species.

It is important to be careful when using any pesticide, even organic or natural

or biopesticide.

Even if this product is considered to be organic in origin, it is still a pesticide.

Just because a product is thought to be organic, or natural, does not mean that

it is not toxic. Some organic pesticides are as toxic, or even more toxic, than

many synthetic chemical pesticides. Organic pesticides have specific modes of

action; just as do synthetic pesticides have specific modes of action, just as do

synthetic pesticides. While some organic pesticides may be nontoxic or are

only slightly toxic to people, they maybe very toxic to other animals. For

instance, the organic pesticide ryania is very toxic to fish. Also, some organic

pesticides may be toxic to beneficial insects, such as honeybees, if they are

combined with other materials, such as combining pyrethrins with rotenone.

The use of an Integrated Pest Management Program (IPM) is important to

insure success.

Challenges and Opportunities for Biopesticides

Biopesticides offer powerful tools to create a new generation of sustainable

agriculture products. They are the most likely source for alternatives to some

of the most problematic chemical pesticides currently in use that are under

ever-increasing scrutiny. Biopesticides may also offer solutions to concerns

such as pest resistance to traditional chemical pesticides, public concern

about side effects of pesticides on the surrounding environment and

ultimately, on human health. The overriding challenge for the biopesticides

industry is to live up to the promise that the field holds. As the discussion of

specific technologies and products above indicates, there are unanswered

questions and un-examined assumptions about them with which those

involved must contend. Challenges to biopesticides stem from questions about

their efficacy and safety, public and grower confusion about the wide

spectrum of biopesticide products on the market, and current market

conditions that paradoxically both hinder and favor the field’s growth. Specific

challenges and opportunities to intervene and advance the promise that

biopesticides offer include the following:

Challenges and Opportunities

Challenges Opportunities

Efficacy

• Do they work?

Efficacy

• Demonstrations: More field trials,

agricultural

extension outreach, collaborative

R&D

Safety:

• For humans

• For the environment

Safety:

• Deeper testing (more inter-

disciplinary environmental

health science-based testing)

• Rapid screening and throughput

(borrow techniques

from pharmaceutical companies using

broader

ecological assays)

• Wider testing of both Active and

Inert ingredients

(using cutting edge environmental

health sciences)

Transparency:

• User education

• Public Understanding

• Questions about products

Transparency:

• Industry Standards and Ecolabels:

better

communication on efficacy and safety

of products to

(both active and inert

ingredients)

public, growers, and policy makers

• Multi-stakeholder dialogue on

choices and tradeoffs

in pest management techniques and

products,

including biopesticides

Market Issues:

• Small producers vs.

Economies of scale

• Niche products vs. Broad

Scale

Market Issues

• Shift the playing field:

• Phase out pesticides of greatest

concern;

• Award the innovators

• Create multi-disciplinary “Pesticide

Innovation Teams”

to develop and test urgently needed

replacements,

test across environmental and health

endpoints.

World agriculture has progressed dramatically since early 1970s as a result

of research and development based policy support. High yielding varieties and

hybrids along with intensive inputs, particularly the chemical fertilizers,

pesticides and water have resulted in such a phenomenal growth. Developing

countries, being largely agriculture based economies, benefited substantially

from these advancements achieving food self sufficiency, improved rural‐

incomes and higher overall economic growth. While the gains have been very

impressive, the input intensive agriculture has resulted in some undesirable

effects on the environment and the overall sustainability of the farming

systems.

Adverse effects of chemical pesticides have been reported on both the abiotic

and biotic components of the environment. The former are exemplified by

residues in soil, air, water, food etc. and the latter by phytotoxicity, residues,

vegetation changes etc. in plants and physiological deformities, diseases,

mortality, population changes, genetic disorders etc. in mammals, avian,

insects and other organisms. Entry of pesticides into the food chain coupled

with their bioaccumulation and biomagnifications trigger effects of

unforeseen consequences. Chemicals like methyl bromide,

chlorofluorocarbons etc. are established culprits for depletion of the ozone

layer.

Indiscriminate use of fertilizers, particularly the nitrogenous, has led to

substantial pollution of soil, air and water. Fertilizer contamination of ground

waters has led to eutrophication of lake and river waters causing depletion of

oxygen and even death of aquatic life, nitrate pollution, increased emissions of

gaseous N and metal toxicities. The presence of nitrates in potable water has

been blamed for health hazards such as birth defects, impaired nervous

system, cancer and methaemoglobinemia (the blue baby syndrome).

With an increasing awareness about the harmful effects of synthetic plant

protection and production agrochemicals, the demand for technologies and

products based on biological processes has been increasing steadily

worldwide. Biopesticides, comprising living organisms or natural products

derived from them are exemplified by plants (ex. pyrethrum Chrysanthemum

sp., neem Azadirachta or Melia sp. etc.), macrobials (ex. Trichogramma

parasitoid a ‐

protozoan, Cryptolaemus montrouzieri a coccinellid predator etc.),‐

microscopic animals (ex. nematodes), microorganisms including bacteria (ex.

Bacillus thuringiensis), viruses (ex. nucleopolyhedrosis virus), fungi (ex.

Beauveria sp.) and the transgenic plants containing a pest combating gene (ex.

Bt cotton).Their key advantages include safety to mammals and other non‐

target organisms, environment compatibility, target specificity, lower

exposure to pests, supplemental role to chemical pesticides enabling their use

in integrated pest management and acceptability for use in organic

agriculture. Similarly, biofertilizers, or bioinocculants comprise environment

friendly microorganisms which are beneficial to agriculture to improve soil

fertility or crop productivity. They supply nutrients (ex. nitrogen) as well as

improve availability of the unavailable forms of certain others (ex.

phosphorus) and are comprised by several bacteria, fungi, actinomycetes etc.

Rhizobia, Azotobacter, Azospirillum, blue green algae, Azolla and phosphate

solubilizers (several bacteria and fungi) are the key examples. Their role in

supplementing nutrition makes them ideally suitable in integrated nutrient

management systems.

In view of their several advantages, the demand for natural pesticides and

fertilizers has been rising steadily. It is estimated that the total global market

for synthetic pesticides which was valued at US$ 26.7 billion in 2005 will

decline to US$ 25.3 billion in 2010i. On the other hand, the global market for

biopesticides will increase from US$ 672 million in 2005 to over US$ 1 billion

in 2010. While Europe, at an average annual growth rate (AAGR) of 15

percent, is projected to lead the growth in biopesticide use, Asia will be no far

behind with an average AAGR of 12 percent. Worldwide data for biofertilizer

market are not available though the sale volume is estimated to be US$ 3

billionii.

Organic farming, a production system that tends to skip the use of synthetic

pesticides, fertilizers and other additives, relies heavily on biopesticides and

biofertilizers. The current global market for organically raised agricultural

products is valued at around US$ 30 billion with a growth rate of around 8

percent. Nearly 22 million hectares of land is now cultivated organically. The

organic cultivation represents less than 1 percent of the world’s conventional

agricultural production and about 9 percent of the total agricultural area. This

only highlights the tremendous potential in the growth of biopesticides and

biofertilizers.

Conclusion

Biopesticides are a set of tools and applications that will help our farmers’

transition away from highly toxic conventional chemical pesticides into an era

of truly sustainable agriculture. Of course biopesticides are only a part of a

larger solution; sustainable agriculture is a broad and deep field. But helping

farmers move from their current chemical dependency to organic agriculture

and beyond requires tools for the transition and tools for a new era.

Biopesticides can and will play a significant role in this process.

By definition, green chemistry is about continuous improvements aimed at

reducing or eliminating hazard. Fully defining hazard is difficult. Even

products hailed by green chemistry and regulators alike as safer for human

health may turn out to have unforeseen negative environmental health

impacts- for example, Spinosad, a green chemistry award winning

biopesticide, is significantly safer for humans than other treatments but is

toxic to bees. We must encourage pest management solutions and regulations

to continuously evolve and ensure that multi-disciplinary teams, including

green chemists, environmental health sciences and other sciences, approach

these products systemically to both discover and refine them.