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Kumar P.,  Kumar, S., and Kumar V. (2021) Botanical insecticide fulfilling their promise in the present scenario. Food and Scientific Reports. 2 (9) 26-29.

ABSTRACT

Botanicals are applied from the ancient time when or where farmers may not be able to afford synthetic insecticides and the traditional use of plants and plant derivatives for the protection of stored products is long-established. Pyrethrum and neem are well established commercially, pesticides based on plant essential oils have recently entered the marketplace, and the use of rotenone appears to be waning. It might be long term alternatives to synthetic chemical insecticides for pest management because; botanicals reputedly pose little threat to the environment or human health. Recently, researchers report that nano-encapsulation botanical insecticides are safer to use, increase soil fertility, improve the pesticide potential to ecological sound with pest management active compounds.

Keywords: Botanical insecticides, Uses, environmental concern and Present scenario

 

Substances used to kill or control insect pests can also be referred to as pesticides, though the latter word has a wider scope of application since other non-insect pests also exist. Insecticides in wide use are mostly synthesized organic compounds, though there are some organic compounds of plant origin referred to as "botanicals", in addition to inorganic compounds of natural and synthetic origin. Synthetic pesticides effectively relegated botanicals from an important role in agriculture to an essentially trivial position in the marketplace among crop protectants (El-Wakeil, 2018). Botanicals had been used since the Vedic period for pest control (Kareru et al., 2013). Farmers traditionally use botanical insecticides in developing countries, where they may not be able to afford synthetic insecticides to protect their valuable crops and stored products. Many plant substances have been considered for use as insect antifeedants or repellents, but apart from some natural mosquito repellents, little commercial success has ensued for plant substances that modify arthropod behaviour. Several factors appear to limit the success of botanicals, most notably regulatory barriers and the availability of competing products (newer synthetics, fermentation products, microbial) that are cost-effective and relatively safe compared with their predecessors. In the context of agricultural pest management, botanical insecticides are best suited for use in organic food production in industrialized countries but can play a much greater role in the production and postharvest protection of the food in developing countries (Isman, 2020).

1. The problem of pests in 21^st-century

i) Pest Resistance

It is defined as a change in the sensitivity of a pest population to a pesticide, failing a correct application of the pesticide to control the pest. Resistance can develop when the same pesticide or similar ones with the same mode of action are used over and over again.

 

ii) Pest resurgence or Secondary pest outbreak

Pest resurgence is the rapid reappearance of a pest population in injurious numbers, usually brought about after the application of a broad-spectrum pesticide has killed the natural enemies, which normally keep a pest in check. A well-known example in rice cultivation is the resurgence of brown planthopper (BPH), whiteflies in mustard cultivation.

 

iii) Health hazards

A pest is any animal or plants harmful to humans or human concerns. Some animals are disliked because they bite or sting; snakes, wasps, ants, bed bugs, fleas and ticks belong in this category. Humans have modified the environment for their purposes and are intolerant of other creatures occupying the same space when their activities impact adversely on human objectives.

 iv) Climate change

Climate change is one of major factor play an important role to the spread of pests and diseases, along with increasing global trade. However, when temperatures and precipitation levels get too high, this can slow the growth and reproduction of some pest species and destroy them by washing their eggs and larvae off the host plant.

v) Pest behaviour

An insect behaviour refers to the various actions of an insect in response to a stimulus or its environment. It covers a wide range of activities, including locomotion, grooming, feeding, communication, reproduction, dispersal, flight, learning, migration, host or prey selection, diapauses, and various responses to environmental hazards such as temperature, humidity, parasites, and toxins. 

vi) Introduction of invasive pest

Invasive (Exotic) species are pressures to agricultural biodiversity as well as human and animal health. These species are non-native or exotic species that have great power of dispersal and adaptation. They are introduced unintentionally into a new area where they get a favourable climate increase in number and establish.

 2. Expectation from Botanicals

Botanicals referred to insect pest management without harming the non-target pest, environmental disturbance, short life spans; once applied and are less poisonous to humans and livestock. It does not harm the natural enemies of the pests and pollinators. It may also use in organic food production, both in the field and in controlled environments for export to developed countries. Botanicals might be a better way to crop protectant rotations, especially in light of the documented resistance of the diamondback moth to Bacillus thuringiensis and spinosad due to overuse.

It might be long term alternatives to synthetic chemical insecticides for pest management because; botanicals reputedly pose little threat to the environment or human health. Many plant substances have been considered for use as insect antifeedants or repellents, but apart from some natural mosquito repellents, little commercial success has ensued for plant substances that modify arthropod behaviour. Based on a recent analysis, the proportion of all botanical insecticides dealing specifically with botanicals has risen from less than 2% in 1980 to over 21% in 2011.

 3. Advantages and Disadvantages of Botanicals

Advantages

·  Relatively safe to users, safe to natural enemies, cheaper & renewable

·  Other uses like household insect repellent and medicinal uses

·  Quickly inhibiting feeding behaviour.

·  These products are stomach action, more selective to insect pests, rapidly decomposed and are not phytotoxic. 

·  Botanicals are non-toxic to mammals, birds & fishes.

·  Botanicals are different modes of action like insecticidal antifeedants, repellent, IGR, oviposition deterrents.

·  Since most of these products have a stomach action and are rapidly decomposed they may be more selective to insect pests.

·  Botanicals prevent Resistant & Resurgence.

 Disadvantages

·  Rapidly degraded by UV light so that their residual action is short.

·  At a global level, the legal registrations establishment process is slow.

·  Not all recommendations followed by growers have been scientifically verified.

·  Botanicals have poor water solubility & generally, botanicals are non-systemic actions.

·  Botanicals are not easily available everywhere.

·  Some botanicals do not quickly knock down the effect against insects.

·  They are not necessarily available season long.

 4. Current Botanicals in Use

At present, there are four major types of botanical products used for insect control (pyrethrum, rotenone, neem, and essential oils), along with three others in limited use (ryania, nicotine, and sabadilla). Additional plant extracts and oils (e.g., garlic oil, Capsicum oleoresin) regional uses in various countries, but these are not considered here. The botanical pesticides are divided into two generations:

·  The 1^st generation included: Nicotine, Rotenone, Ryania, Pyrethrum.

·  The 2^nd generation included: Synthetic Pyrethroids and Neem Products

·  Potential new plant extract oils: Annonaceous Acetogenins, Sucrose Esters

 1. Pyrethrum

The "oleoresin" is extracted from the dried flowers of the pyrethrum Tanacetum cineraria folium (Asteraceae). The flowers are grind into a powder form and then mixed with hexane or a similar non-polar solvent; removal of the solvent yields an orange-coloured liquid that contains the active principles. The insecticidal action of the pyrethrins is characterized by a rapid knockdown effect, particularly in flying insects, and hyperactivity and convulsions in most insects.

Pyrethrum is naturally derived, acts on the nervous system of a wide spectrum of insect pests,   professional-grade pesticides. It is registered as suitable for organic and non-organic farming as it kills pests quickly, leaves no toxic residue and edible food crops can be safely harvested only 24 hours after application. Pyrethrum accounted for 74% of all botanicals used that year, but only 27% of that amount was used in agriculture. 

2. Nicotine

The nicotine extracted from the leaves of the tobacco plant which are effective against soft body insect, their mode of action is contact and fumigants in nature. Nicotine sulphate a commercially available nicotine-based product acts upon the central nervous system of insects. It has both contacts as well as fumigation action. 

3. Indian Neem (Azadirachta indica)

The commercial product of neem first time developed from USA and Germany Neem-based insecticides are available in many less-developed countries in Africa, the Caribbean, and Latin America, a consequence of the nearly pantropical introduction of neem trees for their provision of shade, use as firewood and use as a source of natural pharmaceuticals. Both neem seed kernel  EC formulation and neem oil-based  EC formulations have been registered and being used in agriculture for various insect pest management viz., sucking pest complex in tomato, cotton, brinjal, bhindi leaf folders, mite etc.

The ease of seed collection and production of crude seed oil has facilitated their use as insecticides. However, in most regions, it has enjoyed limited commercial success, even in its native India, where there are a plethora of registered neem products. Both neem seed kernel  EC formulation and neem oil-based  EC formulations have been registered and being used in agriculture for various insect pest management viz., sucking pest complex in tomato, cotton, brinjal, bhindi leaf folders, mite etc.

5. Nanotechnology in botanicals

Nanotechnology has been applied in numerous fields such as food, food biofuel, plant protection, and agrochemical industries to create novel products with a wide range of applications. Nanoparticles (NPs) of Ag, Cu, SiO₂, and ZnO have significant properties of pest control as well as reducing the capability of water, soil, and environmental pollution. These are applied to protect plants, increase soil fertility, weeds control, and improve soil nutrients. To be precise, nanobotanicals would be safer for use and would have improved pesticide potential, via nanoencapsulation of the products (Reddy and Chowdary, 2021). Nanoencapsulation means nanosized molecules of the active pesticide compound that are sealed by a thin-walled sac. Such offers effective control of pests, preventing the accumulation of residues in the soil and its runoff to water bodies. It also has the advantages of protecting the active pesticide ingredient from degradation, improving the effectiveness, and greatly decreasing the pesticide input to at least 10–15 times less than those applied with classical formulations.

 Others promising plants showing insecticidal action

Plants	Active principle	Plant part used	Target insect
Plumbago	Plumbagin	Root	Red cotton bug
Karanja	Karanjin	Seed	Thrips, Mites etc.
Goat weed	Precocenes 1& 2	Leaves	Antijuvenile hormones
Garlic	Dially sulfide	Rhizome	Mosquito, Red cotton bug
Black pepper	piperine	Seed	H. zea
Soybean	Pinitol	Pod	Rice weevil
Congress grass	Parthenin	Leaf extract	Tobacco caterpillar, red cotton bug

 6. Barriers to Implementation of Botanicals

In reviewing this topic, I identified some main barriers to commercialization for botanical insecticides:-

·  Sustainability of the botanical resource

·  Standardization of chemically complex extracts

·  Regulatory approval remains the most challenging barrier to the commercialization of new botanical insecticides

·  The burden of registration for new botanical insecticides has become a major constraint, it will take approximately 2 to 4 years respectively, from data submission to approval.

·  Other drawbacks or limitations are the slow actions of many botanicals, growers must gain confidence in insecticides that do not produce an immediate "knockdown" effect and the lack of residual action for most botanicals.

 

References

Isman, M. B (2020). Botanical insecticides in the twenty-first century fulfilling their promise? Annual Review of Entomology. 65, 233-249.

Kareru, P., Rotich, Z. K., Maina, E. W (2013). Use of botanicals and safer insecticides designed in controlling insects: the African case. Insecticides–Development of Safer and More Effective Technologies. 10, 297-309.

 Reddy, D. S and Chowdary, N. M (2021). The botanical biopesticide combination concept is a viable option for pest management in organic farming. Egyptian Journal of Biological Pest Control. 31, 1-10.

El-Wakeil, N. (2018). Retraction: Botanical Pesticides and Their Mode of Action. Gesunde Pflanzen, 65, 125-149. DOI 10.1007/s10343-013-0308-3

 

 

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