Biopesticide

A Biopesticide is a biological substance or organism that damages, kills, or repels organisms seens as pests. Biological pest management intervention involves predatory, parasitic, or chemical relationships.

They are obtained from organisms including plants, bacteria and other microbes, fungi, nematodes, etc. They are components of integrated pest management (IPM) programmes, and have received much practical attention as substitutes to synthetic chemical plant protection products (PPPs).

Definitions

Regulatory positions can be influenced by public perceptions, thus:

• the EU, defines biopesticides 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".

Types

Biopesticides usually have no known function in photosynthesis, growth or other basic aspects of plant physiology. Many chemical compounds produced by plants protect them from pests; they are called antifeedants. These materials are biodegradable and renewable, which can be economical for practical use. Organic farming systems embraces this approach to pest control.

Biopesticides can be classified thusly:

• Microbial pesticides consist of bacteria, entomopathogenic fungi or viruses (and sometimes includes the metabolites that bacteria or fungi produce). Entomopathogenic nematodes may be classed as microbial pesticides, even though they are multicellular.
• 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 disease.
• Plant-incorporated protectants (PIPs) incorporate genetic material from other species (i.e. GM crops). Their use is controversial, especially in European countries.
• RNAi pesticides, some of which are topical and some of which are absorbed by the crop.

RNA interference

RNA interference is under study for use in spray-on insecticides (RNAi insecticides) by companies including Syngenta and Bayer. Such sprays do not modify the genome of the target plant. The RNA can be modified to maintain its effectiveness as target species evolve to tolerate 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 Roundup. RNAi can be mixed with a silicone surfactant that lets the RNA molecules enter air-exchange holes in the plant's surface. This disrupted the gene for tolerance long enough to let the herbicide work. This strategy would allow the continued use of glyphosate-based herbicides.

They can be made with enough precision to target specific insect species. Monsanto is developing an RNA spray to kill Colorado potato beetles. One challenge is to make it stay 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 claimed that the RNA trigger designed to change the starch content of wheat might interfere with the gene for a human liver enzyme. Supporters countered that RNA does not appear to survive 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 undetermined. Other unassessed risks include ecological (given the need for sustained presence for herbicides) and possible RNA drift across species boundaries.

Monsanto 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 Forest 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.

Mycopesticide

Mycopesticides include fungi and fungi cell components. Propagules such as conidia, blastospores, chlamydospores, oospores, and zygospores have been evaluated, along with hydrolytic enzyme mixtures. The role of hydrolytic enzymes especially chitinases in the killing process, and the possible use of chitin synthesis inhibitors are the prime research areas.

Examples

Bacillus thuringiensis is a bacterium capable of causing disease of Lepidoptera, Coleoptera and Diptera. The toxin from B. thuringiensis (Bt toxin) has been incorporated directly into plants via genetic engineering. Bt toxin 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 hyperparasite of grape powdery mildew); Bacillus subtilis is also used to control plant pathogens.
• beneficial nematodes attacking insects (e.g. Steinernema feltiae) or slugs (e.g. Phasmarhabditis hermaphrodita)
• entomopathogenic viruses (e.g.. Cydia pomonella granulovirus).
• weeds and rodents have been controlled with microbial agents.

Various animal, fungal, and plant organisms and extracts have been used as biopesticides. Products in this category include:

• Insect pheromones and other semiochemicals
• Fermentation products such as Spinosad (a macrocyclic lactone)
• Chitosan: a plant in the presence of this product naturally induces 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. Vegetable oils such as canola oil have pesticidal properties. Products based on plant extracts such as garlic have now been registered in the EU and elsewhere.

Applications

Microbial agents, effective control requires appropriate formulation and application.

Biopesticides have established themselves on a variety of crops for use against crop disease. For example, biopesticides help control downy mildew diseases. Their benefits include: a 0-day pre-harvest interval (see: maximum residue limit), success under moderate to severe disease pressure, and the ability to use as a tank mix or in a rotational program with other 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 by 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 rot, damping-off, root rot and seedling blights. They can also be used to control internal seed-borne fungal pathogens as well as fungal pathogens on the seed surface. Many biofungicidal products show capacities to stimulate plant host defense and other physiological processes that can make treated crops more resistant to stresses.

Disadvantages

• High specificity: which may require an exact identification of the pest/pathogen and the use of multiple products used; although this can also be an advantage in that the biopesticide is less likely to harm non-target species
• Slow action speed (thus making them unsuitable if a pest outbreak is an immediate threat)
• Variable efficacy due to the influences of various 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 tolerance to control. If the target population is not exterminated or rendered incapable of reproduction, the surviving population can acquire 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.

Market research

The market for agricultural biologicals was forecast to reach $19.5 billion by 2031.

See also

• Antagonism (phytopathology)
• Bioherbicide
• Biological pest control
• Cembratrienol
• Integrated Pest Management
• LUBILOSA
• Pest resistance management plans
• Plant defense against herbivory
• Use as a population control agent

External links

• Bioinsecticides Market (Acquire Market Research)
• Registered Biopesticides 04/29/02 United States Environmental Protection Agency. Updated 29 March 2002. Retrieved 25 November 2011.
• International Biocontrol Manufacturers' Association (IBMA)