Contents
Organic Farming: Plant origin Insecticides
After witnessing the shortcomings of green revolution, the world agriculture has realized the importance of organic farming and has began its transition phase towards organic agriculture
You may also like to read –
Green Revolution: Shortcomings
Organic farming: Concept and objectives
One of very important components of Organic farming is Plant protection. In organic plant protection chemicals are to be replaced by naturally made or natural origin pesticides
Given in this article, is the information of plant origin insecticides
What are plant origin insecticides?
The Insecticides extracted from extracted from seeds, flowers, leaves, stem and
roots, are termed as plant origin insecticides
They are also called as botanical insecticides or natural origin insecticides
Why plant origin insecticides are not very popular?
Although, the plant origin Insecticides unlike are safer to use but since they are expensive and lack residual toxicity, they are not very popular
Plant origin insecticides information
Neem (Azadirachta indica)
Neew is a Perennial tree distributed in tropical, subtropical, semi-arid and arid zones
Properties of neem
It posses medicinal, insecticidal, insect repellent, antifeedant, growth regulatory,
nematicidal and antifungal properties
Useful Chemicals present in Neemseed extract oil
Azadirachtin, salannin, nimbin, epinimbin, nimbidin that gives insecticidal, insect repellent, ovicidal, Antifeedant and growth regulator characters.
How neem disrupts moulting in insects?
Chemical present in neem is Azadiractitin which disrupts moulting by antagonizing the insect hormone ecdysone.
Oral LD50 dose of Azadiractitin
Azadiractitin Acute oral LD50 for rat is 5000mg/kg, Acute dermal for rabbit is
>2000mg/kg.
Procedure for Preparation of Neem Seed Kernel Extract (NSKE 5%)
Step 1 – Take 50 g of powdered neem
seed kernels soak it in one litre of water for 8 hours and stir the contents often.
Step 2 – Squeeze the soaked material repeatedly for better extraction of the azadirachtin in the aquous suspension
Step 3 – Filter the contents through muslin cloth and make the filtrate to one litre.
Step 4 – Add 1ml teepol or triton or sandovit or soap water (2%) and spray
Prepartion of Neem Cake Suspension
Step 1 – Soak one kilogram of neem cake in 5 liters of water for 2 days and filter It through
muslin cloth
Step 2 – Dissolve 200 g of soft soap in the filtrate and make upto 10 L of water
before spraying.
This controls tobacco cutworm, leaf miners of citrus, groundnut, tomato and beans etc.
Uses of Neem
Dried powder of neem leaves are used against stored grain insect pests.
Leaf extracts showed insecticidal property against,Plutella xylostella,Aproaerema
modicella; Spodoptera litura etc.
Desert locust Schistocerca gregaria avoids feeding onneem leaves.
Neem leaves are found as attractants to white grub Holotrichia adults.
Neem seed/ kernel extract showed insecticidal properties against a number of sucking pest.
Neem oil can be used against storage insect pests @ 1 to 2% and field insects @
(0.2 -0.4%, 1 to 2% 5% or 10% neem oil)
Neem products are safer to honey bees,
parasitoids, predators.
Trade names of Neem formulation
Some of the neem formulations are Margosan, Neemark, Neemrich, Achook, Bioneem, Neemazal, Neemax, Nimbicidine,Vepacide, Margocide ,
Neemgold etc
Commercial formulations of neem are available in 10000 ppm, 1500 ppm and
300 ppm the market.
Nicotine
Nicotine is found in the leaves of Nicotiana tabacum and N.rusticafrom 2% to 14%
Insecticide prepared form Nicotine
Nicotine sulphate has been mainly used as a contact insecticide with marked fumigant action in the control of sucking insects viz., aphids, thrips, psyllids, leafminers and jassids.
Nicotine Sulphate
Nicotine sulphate is more stable and less volatile.
It is a nerve poison being highly toxic when absorbed through the cuticle taken in through the tracheae or when ingested.
It affects the ganglian blocking conduction at higher levels.
Nicotine sulphate containing 40% alkaloid, is safer and is more convenient to use and the free alkaloid is liberated by the addition of soap lime or ammonium hydroxide to the spray solution.
Dust formulation of nicotine sulphate releases nicotine in the presence of moisture.
It is also used in aerosols.
Tobacco decoction
Tobacco decoction is useful for controlling aphids, Thrips etc. can
Preparation of tobacco decoction
It can be prepared by boiling 1kg of tobacco waste in 10 lts of water for 30 minutes or steep it in cold water for a day.
Then make it up to 30 litres and add about 90gm of soap
Addition of soap improves wetting, spreading and killing properties.
Nicotine does not leave any harmful residue on treated surface.
Dosage of nicotine
LD50 for rat oral is 50-60 mg/kg.
Rotenone
It is extracted from the roots of Derris plant which many contain 4 to 11% rotenone depending on the variety.
Rotenone is reported from 68 species of leguminous plants
Rotenone occurs in Derris roots (4-9%), Lonchocarpus (8-11%)
It is oxidized to non-insecticidal compound in the presence of light and air and hence
rotenone residues are difficult to find after 5 to 10 days in normal sunlight.
How rotenone kills insects?
Insects poisoned with rotenone show a steady decline in oxygen consumption followed by paralysis and deaths.
It is very specific being highly toxic to fishes and to most insect species but almost harmless to warm blooded animals except pigs
Dose of rotenone
LD50 to white rat is oral-130 to 1500
Commercial use
Dust or spray containing 0.5 to 1.0 per cent and 0.001 to 0.002 percentrotenone are used commercially.
Plumbagin
Plumbagin is naturally occurring napthoquinone of plant origin from the roots of Plumbago europea L. (Plumbaginaceae)
It is named so in 1828 by Bulong d’ Astafort
Plumbagin is known for its medicinal, antifertility, antimicrobial, molluscicidal,
nematicidal and other pharmacological properties on diverse fauna.
The yield of plumbagin ranges between 0.5-3.000 percent on dry weight basis.
The elucidation of structure of plumbagin and its synthesis in 1936 led to detailed studies.
More recently, its IGR properties viz., inhibition of chitin synthetase and ecdysteroid titres have been demonstrated (Kubo et al., 1982)
The cold alcoholic extract (5%) of roots of P. zeylanica L was toxic to Euproctis fraterna larvae as contact spray.
Contact toxicity of 5% petroleum ether
extracts of P. zeylanica root against Spodoptera litura, Dystercus
koenigii, Dipaphis erysimi was also reported
Pyrethrum
It is extracted from dried flower heads of Chrysanthemum cinerariaefolium (Asteraceae).
Chemical ingredients
The actual chemical ingredients having insecticidal action are identified as five esters
They are Pyrethrin I, Pyrethrin II, cinerins-I and cinerin-II and Jasmoline, which are predominately found in achenes of flowers from 0.7 to 3 %.
The esters are derived from the, Two acids – Chrysanthemic acid and Pyrethric acid and
Three alcohols – Pyretholone, Cinerolone and Jasmolone
Active principles/Esters
Pyrethrin I = Pyrethrolone + Chrysanthemc acid
Pyrethrin II = Pyrethrolone + Pyrethric acid
Cinerin I = Cynerolone + Chrysanthemc acid
Cinerin II = Cynerolone + Pyrethric acid
Jasmolin II = Jasmolone + Pyrethric acid
Properties of pyrathroids
Highly unstable in light, moisture and air.
Have no residual effect
Paralyse by more contact
Gains entry through spiracle and cuticle
Act on central nervous system
Having rapid knock down effect
Practically no mammalian toxicity
Good insecticides against household and cattle pests
Pyrethrum Powder
Pyrethrum powder is prepared by grinding the flowers.
The powder mixed with a diluent such as talc or clay is known as pyrethrum dust.
It is prepared just before use Otherwise it gets deteriorated rapidly.
It is also used as emulsions, solutions, and
aerosoles
Pyrethrum is unstable to light, air moisture and alkali.
The residues deteriorate very rapidly after application.
How pyrethrins kill the insects?
Pyrethrins are powerful contact insecticides but appear to be poor stomach poisons.
A characteristic action of Pyrethroid is the rapid paralysis or ‘knock down’ effect and substantial recovery that follow it.
This recovery is due to rapid enzymatic detoxification in the insect
To bring about mortality equivalent to
knock down effect three times increase in dosage may be required
Compounds such as piperonyl butoxide, propyl isome and sulfoxide are known to
inhibit the detoxication enzyme and increase the toxicities of pyrethroids
These synergists are used at 10 parts to 100 part of pyrethroid.
Dosage of pyrethroids
LD50 for white rat oral-200 dermal for rat-1800
Uses
Pyrocon E 2/22 (1 part of pyrethrin + 10 parts of piperonyl butoxide) is used for the control of coconut red palm weevil.
In household sprays and as a repellent against external parasites of livestock pyrethrum is useful.
It is also mixed with grains in storage to protect from stored grain pests.
Its use alone or in combination with piperonyl butoxide as food packages has been permitted by the food and Drug
Administration in the U.S.A. and no other chemical has been approved.
Further readings and references
Handbook of Agriculture
IUPAC (2006). “Glossary of Terms Relating to Pesticides” (PDF). IUPAC. p. 2123. Retrieved January 28, 2014
Murray B. Isman “Botanical Insecticides, Deterrents, And Repellents In Modern Agriculture And An Increasingly Regulated World” Annual Review Of Entomology Volume 51, pp. 45-66
