Biopesticide

A biopesticide is a biological substance or microorganism that is used to control pests. Invertebrates and macroorganisms used to control pests are usually categorised as biological pest control agents.

Biopesticides are traditionally obtained through bioprospecting from organisms including plants, microorganisms, etc.^{[1][page needed][2]} They are components of integrated pest management programmes, and are used as substitutes for synthetic pesticides.^[3]

Definitions

• the EU defines biopesticides as "a form of pesticide based on micro-organisms or natural products".^[4]
• 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".^[5]
• invertebrates (parasitoids, nematodes, predatory mites, and other beneficials) and other macroorganisms) are registered by the authorities in the US^[6] and Europe as biological control agents very differently to biopesticides.^[7] In the scientific literature, however, they are sometimes referred to as biopesticides. Similarly microorganisms may also be described as biological control agents.^[8]

Types

Biopesticides are biodegradable and renewable. Organic farming systems adopts some of these methods (microbial and bio-derived chemicals) and disallows others (GM-crops and RNAi) .^[9]

Biopesticides can be classified thusly:

• Microbial pesticides consist of bacteria, entomopathogenic fungi or viruses (and sometimes includes the metabolites that bacteria or fungi produce).^{[10][11][12][page needed]}
• Bio-derived chemicals. Pesticidal chemicals or mixtures containing them obtained from plants and microorganisms. In commercial use are pyrethrum, rotenone, azadirachtin, neem oil, and various essential oils which are naturally occurring substances that control (or monitor in the case of pheromones) pests and microbial disease.^[13][9]
• Plant-incorporated protectants (PIPs) incorporate genetic material from other species (i.e. GM crops). They are banned in most European countries.^[14]
• RNAi pesticides, some of which are topical and some of which are absorbed by the crop.

RNA interference

RNA interference (RNAi) uses segments of RNA to fatally silence crucial insect genes.^[15] In 2024 two uses of RNAi have been registered by the authorities for use: Genetic modification of a crop to introduce a gene coding for an RNAi fragment and spraying double stranded RNA fragments onto a field.^[16] Monsanto introduced the trait DvSnf7 which expresses a double-stranded RNA transcript containing a 240 bp fragment of the WCR Snf7 gene of the Western Corn Rootworm.^[17] GreenLight Biosciences introduced Ledprona, a formulation of double stranded RNA as a spray for potato fields. It targets the essential gene for proteasome subunit beta type-5 (PSMB5) in the Colorado potato beetle.^[16] Other applications against insects, mites, fungi, viruses, and plants are still in the research and development phase.^[18]

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.^[19]

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, Metarhizium, and Steinernema carpocapsae 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.^[10]
• 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.^[20]
• 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^{[21][citation needed]}. Products based on plant extracts such as garlic have now been registered in the EU and elsewhere^{[22][citation needed]}.

Applications

Microbial agents, effective control requires appropriate formulation^[23] and application.^[24][25]

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.^{[citation needed]}

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.^{[citation needed]}

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.^[26]

Market research

The market for agricultural biologicals was forecast to reach $19.5 billion by 2031.^[27]

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