Lecture 4: Insecticides

Question 1

what is the story about how Pyrethrum was commercialized?

Answer 1

A german women notcied dead insects nean an old bouquet of Tanacetum flowers

Question 2

when and where was pythrum grown commercially

Answer 2

1820s in southern europe and was introduced to Japan in 1881

Question 3

Today where is the most commerial pordicution occur

Answer 3

Africa, ecuador and more recently Australlia

Question 4

where is the insecticidal product concentrated in pyrethrum?

Answer 4

flowering heads which are hand harvested

Question 5

What are the insecticidal properties of pyrethrum? and what do they do?

Answer 5

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

Question 6

What is the toxicity of pyrethrins to birds and mammals? and why should ground contamination be avoided

Answer 6

low - but ground water contamination should be avoided since pyrethrins are toxic to fish

Question 7

A semi senthetic version of pyrethrin?

Answer 7

transfluthrin - 10X more effective than naturally occuring pyrethrins

Question 8

what is pyrthrum used for?

Answer 8

as a “natural” garden insecticid; to control animal ectoparasites - flea collars for pets and insecticidal dips for domestic animals; commonly in mosquito coils

Question 9

where is neem found and what environments does it live in?

Answer 9

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

Question 10

What is the neem tree according to Hindu mythology?

Answer 10

divine origin

Question 11

How long ago was neem used in India

Answer 11

4000 ya

Question 12

In Aurvedic medicine what were the leaves, fruit, oil, and twigs used to treat?

Answer 12

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

Question 13

What was neem used for in India

Answer 13

neem oil and leaves to deter insects in granaries

Question 15

how was neem oil extracted in the early years that was considered inefficient?

Answer 15

using water as a solvent

Question 16

What did the germal scientist observe that lead him to believe neem was a natural insectide?

Answer 16

neem trees planted in Sudan were unaffected by locust swarms - this lead researchers to investigate the insecticidal prperties of neem in the 1960s

Question 17

what was needed before the commercialization of neem?

Answer 17

a method for efficient extraction and stailixation of the active ingredients

Question 18

When was the commercialization of neem? and by who

Answer 18

W.R. Grace comany in 1992 - issued a US patent for a simple extration technique using ethyl ether, a lipophilic solvent

Question 19

why did the commercialization of neem in the US lead to accusion of biopiracy?

Answer 19

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

Question 20

What are the active components of neem?

Answer 20

tetracyclotriterpenoids known as limonoids - particularly the compound azadirachtin

Question 21

What causes the insecticidal properties of azadirachtin?

Answer 21

the compound inhibits normal growth and development, blocks normal feeding behaviour, and inhibits reproduction in insects

Question 22

What types of insects is azadirachtin most effective on and where does it show potential protection?

Answer 22

locusts, moths, beetles, aphids, and mosquitos

• it shows potential protection against fungal, bacterial, viral, and nemetode disease. it is not harmful to mammals

Question 23

Why have neem insecticides proven less commercially successful than expected?

Answer 23

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

Question 24

what have various specie of leguminous vines been used for?

Answer 24

fish poisons and/or insectisides

Question 25

what is the active principle in the fish poison species?

Answer 25

isoflavonoid rotenoide

• first isolated from species of Lonchocarpus form south america

Question 26

where is rtenoine concentrated

Answer 26

roots and rhizomes

Question 27

how does rotenone kill fish?

Answer 27

by inhibiting respiratory enzymes which disrups respiratory function - within 10 mins

• inverts and mammals are unaffected

Question 28

how does Rotenone work as an insecticide?

Answer 28

insect mitochondiral poison; it stops energy production by blocking the e- transport chain

• must be ingested by the insect

Question 29

where were commercial plantations of Lonchocarpus established and when. where does rotenone now come form?

Answer 29

in peru in the 1940s but most comes form venezeula and peru - known as cube root

Question 30

Today, what is rotenone mainly used for?

Answer 30

to reclaim lakes and ponds for game fishing and as an insecticide in organic farming operations

Question 31

what are plant essential oils mixtures of and where are they obtained from

Answer 31

monoterpenes and sesquiterpenes obtained form steam distillation of aromatic plants

Question 32

what are essential oils widely used for?

Answer 32

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

Question 33

what is the mode of action of essential oils?

Answer 33

not really known, but terbenoid mixtures are knwon broad -spectrum insect neurotoxins

• non-toxic to mammals, fish and birds

Question 34

what is the result of essentail oils widely used by the processed food industry and therefore are exempt from registration and regulation?

Answer 34

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