Lecture 4: Insecticides Flashcards
what is the story about how Pyrethrum was commercialized?
A german women notcied dead insects nean an old bouquet of Tanacetum flowers
when and where was pythrum grown commercially
1820s in southern europe and was introduced to Japan in 1881
Today where is the most commerial pordicution occur
Africa, ecuador and more recently Australlia
where is the insecticidal product concentrated in pyrethrum?
flowering heads which are hand harvested
What are the insecticidal properties of pyrethrum? and what do they do?
pyrethins - are contact incecticides that are neurosensor blockers; they help keep sodium channels open, which result in repeate firing of the nerve cells and eventual insect paralusis
What is the toxicity of pyrethrins to birds and mammals? and why should ground contamination be avoided
low - but ground water contamination should be avoided since pyrethrins are toxic to fish
A semi senthetic version of pyrethrin?
transfluthrin - 10X more effective than naturally occuring pyrethrins
what is pyrthrum used for?
as a “natural” garden insecticid; to control animal ectoparasites - flea collars for pets and insecticidal dips for domestic animals; commonly in mosquito coils
where is neem found and what environments does it live in?
native to indian subcontinent and widely planted in the Middle East, Africa, and China. It is frost-intolerant and perfers hot arid environements and sandy soils - grows well in humid tropics
What is the neem tree according to Hindu mythology?
divine origin
How long ago was neem used in India
4000 ya
In Aurvedic medicine what were the leaves, fruit, oil, and twigs used to treat?
Leaves - chewed for general health; tonics and teas to treat feavers, intestinal worms, and ulcers
Fruit - treat leprosy, intestinal worms, and urinar infections
oil - treat skin problems, leprosy, and ulcers
twigs - dental hygiene to brush and clean the teeth
What was neem used for in India
neem oil and leaves to deter insects in granaries
how was neem oil extracted in the early years that was considered inefficient?
using water as a solvent
What did the germal scientist observe that lead him to believe neem was a natural insectide?
neem trees planted in Sudan were unaffected by locust swarms - this lead researchers to investigate the insecticidal prperties of neem in the 1960s
what was needed before the commercialization of neem?
a method for efficient extraction and stailixation of the active ingredients
When was the commercialization of neem? and by who
W.R. Grace comany in 1992 - issued a US patent for a simple extration technique using ethyl ether, a lipophilic solvent
why did the commercialization of neem in the US lead to accusion of biopiracy?
American patent law does not recognize oral tradition meaning that companies in India with a long history of established use would be completely excluded from the American market
- There was also questions as to whether lipophilic solvent extraction could be considered an innovation as required under American patent law
What are the active components of neem?
tetracyclotriterpenoids known as limonoids - particularly the compound azadirachtin
What causes the insecticidal properties of azadirachtin?
the compound inhibits normal growth and development, blocks normal feeding behaviour, and inhibits reproduction in insects
What types of insects is azadirachtin most effective on and where does it show potential protection?
locusts, moths, beetles, aphids, and mosquitos
- it shows potential protection against fungal, bacterial, viral, and nemetode disease. it is not harmful to mammals
Why have neem insecticides proven less commercially successful than expected?
expensive to produce, are slow acting, efficay of neem varies considerably (very effective on tocust but other pests can be unaffectied or rapidly desensitized
- it also is not commercially approved in canada, austraillia and many eurpoean contries
what have various specie of leguminous vines been used for?
fish poisons and/or insectisides
what is the active principle in the fish poison species?
isoflavonoid rotenoide
- first isolated from species of Lonchocarpus form south america
where is rtenoine concentrated
roots and rhizomes
how does rotenone kill fish?
by inhibiting respiratory enzymes which disrups respiratory function - within 10 mins
- inverts and mammals are unaffected
how does Rotenone work as an insecticide?
insect mitochondiral poison; it stops energy production by blocking the e- transport chain
- must be ingested by the insect
where were commercial plantations of Lonchocarpus established and when. where does rotenone now come form?
in peru in the 1940s but most comes form venezeula and peru - known as cube root
Today, what is rotenone mainly used for?
to reclaim lakes and ponds for game fishing and as an insecticide in organic farming operations
what are plant essential oils mixtures of and where are they obtained from
monoterpenes and sesquiterpenes obtained form steam distillation of aromatic plants
what are essential oils widely used for?
fragrances, flavourings in the food industry and in aromatherapy and herbal medicine
- long used in southern europe and asia as fumigants to deter insects in granaries
what is the mode of action of essential oils?
not really known, but terbenoid mixtures are knwon broad -spectrum insect neurotoxins
- non-toxic to mammals, fish and birds
what is the result of essentail oils widely used by the processed food industry and therefore are exempt from registration and regulation?
a number of companies esp in the USA are developing insecticides based on essetial oil mixtures
- terpinoids from rosemary, thyme and cloves are the most commonly used
