Biopesticides, a contraction of 'biological
pesticides', include several types of pest
management intervention: through predatory,
parasitic, or chemical relationships.
The term has been associated historically
with biological control – and by implication
– the manipulation of living organisms.
Regulatory positions can be influenced by
public perceptions, thus:
in the EU, biopesticides have been defined
as "a form of pesticide based on micro-organisms
or natural products".
the US EPA states that they "include naturally
occurring substances that control pests (biochemical
pesticides), microorganisms that control pests
(microbial pesticides), and pesticidal substances
produced by plants containing added genetic
material (plant-incorporated protectants)
or PIPs".They are obtained from organisms
including plants, bacteria and other microbes,
fungi, nematodes, etc.
They are often important components of integrated
pest management (IPM) programmes, and have
received much practical attention as substitutes
to synthetic chemical plant protection products
(PPPs).
== Types ==
Biopesticides can be classified into these
classes-
Microbial pesticides which consist of bacteria,
entomopathogenic fungi or viruses (and sometimes
includes the metabolites that bacteria or
fungi produce).
Entomopathogenic nematodes are also often
classed as microbial pesticides, even though
they are multi-cellular.
Bio-derived chemicals.
Four groups are in commercial use: pyrethrum,
rotenone, neem oil, and various essential
oils are naturally occurring substances that
control (or monitor in the case of pheromones)
pests and microbial diseases.
Plant-incorporated protectants (PIPs) have
genetic material from other species incorporated
into their genetic material (i.e.
GM crops).
Their use is controversial, especially in
many European countries.
RNAi pesticides, some of which are topical
and some of which are absorbed by the crop.Biopesticides
have usually no known function in photosynthesis,
growth or other basic aspects of plant physiology.
Instead, they are active against biological
pests.
Many chemical compounds have been identified
that are produced by plants to protect them
from pests so they are called antifeedants.
These materials are biodegradable and renewable
alternatives, which can be economical for
practical use.
Organic farming systems embraces this approach
to pest control.
=== RNA ===
RNA interference is under study for possible
use as a spray-on insecticide by multiple
companies, including Monsanto, Syngenta, and
Bayer.
Such sprays do not modify the genome of the
target plant.
The RNA could be modified to maintain its
effectiveness as target species evolve tolerance
to the original.
RNA is a relatively fragile molecule that
generally degrades within days or weeks of
application.
Monsanto estimated costs to be on the order
of $5/acre.RNAi has been used to target weeds
that tolerate Monsanto's Roundup herbicide.
RNAi mixed with a silicone surfactant that
let the RNA molecules enter air-exchange holes
in the plant's surface that disrupted the
gene for tolerance, affecting it long enough
to let the herbicide work.
This strategy would allow the continued use
of glyphosate-based herbicides, but would
not per se assist a herbicide rotation strategy
that relied on alternating Roundup with others.They
can be made with enough precision to kill
some insect species, while not harming others.
Monsanto is also developing an RNA spray to
kill potato beetles One challenge is to make
it linger on the plant for a week, even if
it's raining.
The Potato beetle has become resistant to
more than 60 conventional insecticides.Monsanto
lobbied the U.S. EPA to exempt RNAi pesticide
products from any specific regulations (beyond
those that apply to all pesticides) and be
exempted from rodent toxicity, allergenicity
and residual environmental testing.
In 2014 an EPA advisory group found little
evidence of a risk to people from eating RNA.However,
in 2012, the Australian Safe Food Foundation
alleged that the RNA trigger designed to change
wheat's starch content might interfere with
the gene for a human liver enzyme.
Supporters countered that RNA does not appear
to make it past human saliva or stomach acids.
The US National Honey Bee Advisory Board told
EPA that using RNAi would put natural systems
at "the epitome of risk".
The beekeepers cautioned that pollinators
could be hurt by unintended effects and that
the genomes of many insects are still unknown.
Other unassessed risks include ecological
(given the need for sustained presence for
herbicide and other applications) and the
possible for RNA drift across species boundaries.Monsanto
has invested in multiple companies for their
RNA expertise, including Beeologics (for RNA
that kills a parasitic mite that infests hives
and for manufacturing technology) and Preceres
(nanoparticle lipidoid coatings) and licensed
technology from Alnylam and Tekmira.
In 2012 Syngenta acquired Devgen, a European
RNA partner.
Startup Forrest Innovations is investigating
RNAi as a solution to citrus greening disease
that in 2014 caused 22 percent of oranges
in Florida to fall off the trees.
== Examples ==
Bacillus thuringiensis, a bacterial disease
of Lepidoptera, Coleoptera and Diptera, is
a well-known insecticide example.
The toxin from B. thuringiensis (Bt toxin)
has been incorporated directly into plants
through the use of genetic engineering.
The use of Bt Toxin is particularly controversial.
Its manufacturers claim it has little effect
on other organisms, and is more environmentally
friendly than synthetic pesticides.
Other microbial control agents include products
based on:
entomopathogenic fungi (e.g. Beauveria bassiana,
Isaria fumosorosea, Lecanicillium and Metarhizium
spp.),
plant disease control agents: include Trichoderma
spp. and Ampelomyces quisqualis (a hyper-parasite
of grape powdery mildew); Bacillus subtilis
is also used to control plant pathogens.
beneficial nematodes attacking insect (e.g.
Steinernema feltiae) or slug (e.g. Phasmarhabditis
hermaphrodita) pests
entomopathogenic viruses (e.g.. Cydia pomonella
granulovirus).
weeds and rodents have also been controlled
with microbial agents.Various naturally occurring
materials, including fungal and plant extracts,
have been described as biopesticides.
Products in this category include:
Insect pheromones and other semiochemicals
Fermentation products such as Spinosad (a
macro-cyclic lactone)
Chitosan: a plant in the presence of this
product will naturally induce systemic resistance
(ISR) to allow the plant to defend itself
against disease, pathogens and pests.
Biopesticides may include natural plant-derived
products, which include alkaloids, terpenoids,
phenolics and other secondary chemicals.
Certain vegetable oils such as canola oil
are known to have pesticidal properties.
Products based on extracts of plants such
as garlic have now been registered in the
EU and elsewhere.
== Applications ==
Biopesticides are biological or biologically-derived
agents, that are usually applied in a manner
similar to chemical pesticides, but achieve
pest management in an environmentally friendly
way.
With all pest management products, but especially
microbial agents, effective control requires
appropriate formulation and application.Biopesticides
for use against crop diseases have already
established themselves on a variety of crops.
For example, biopesticides already play an
important role in controlling downy mildew
diseases.
Their benefits include: a 0-Day Pre-Harvest
Interval (see: maximum residue limit), the
ability to use under moderate to severe disease
pressure, and the ability to use as a tank
mix or in a rotational program with other
registered fungicides.
Because some market studies estimate that
as much as 20% of global fungicide sales are
directed at downy mildew diseases, the integration
of biofungicides into grape production has
substantial benefits in terms of extending
the useful life of other fungicides, especially
those in the reduced-risk category.
A major growth area for biopesticides is in
the area of seed treatments and soil amendments.
Fungicidal and biofungicidal seed treatments
are used to control soil borne fungal pathogens
that cause seed rots, damping-off, root rot
and seedling blights.
They can also be used to control internal
seed–borne fungal pathogens as well as fungal
pathogens that are on the surface of the seed.
Many biofungicidal products also show capacities
to stimulate plant host defence and other
physiological processes that can make treated
crops more resistant to a variety of biotic
and abiotic stresses.
== Disadvantages ==
High specificity: which may require an exact
identification of the pest/pathogen and the
use of multiple products to be used; although
this can also be an advantage in that the
biopesticide is less likely to harm species
other than the target
Often slow speed of action (thus making them
unsuitable if a pest outbreak is an immediate
threat to a crop)
Often variable efficacy due to the influences
of various biotic and abiotic factors (since
some biopesticides are living organisms, which
bring about pest/pathogen control by multiplying
within or nearby the target pest/pathogen)
Living organisms evolve and increase their
resistance to biological, chemical, physical
or any other form of control.
If the target population is not exterminated
or rendered incapable of reproduction, the
surviving population can acquire a tolerance
of whatever pressures are brought to bear,
resulting in an evolutionary arms race.
Unintended consequences: Studies have found
broad spectrum biopesticides have lethal and
nonlethal risks for non-target native pollinators
such as Melipona quadrifasciata in Brazil.
== See also
