Insecticides 3

Question 1

what are botanicals, and what are the general properties?

Answer 1

natural insecticides derived from plants; easily metabolized, rapidly degraded in environment

Question 2

Nicotine mech of tox?

Answer 2

nicotinic receptor agonist– mimics ACh at autonomic ganglia and NM junctions; has high affinity for synaptic ganglia (CNS) of insects; highly toxic to mammals (twitching/ CV collapse)

Question 3

neonicotinoid insecticides general info

Answer 3

most widely used class of insecticides today; three chemical classes

Question 4

three chemical classes of neonicotinoids?

Answer 4

n-nitroguanidines (e.g. imidacloprid); nitromethylenes (e.g. nitenpyram); N-cyanoamidines (e.g. acetamiprid)

Question 5

mech of tox ac of neonics

Answer 5

nicotnic ACh receptor agonist; bind strongly and activate nic receptors; at low conc: nervus stimulation (e.g. muscle twitching, convulsions);
at high concs: nic receptor blockage that leads to paralysis and death

Question 6

what are the advatanges of neonics?

Answer 6

low toxicity to vertebrates–>more selective for insect nic receptors; also effective against organisms resistant to OPs or carbamates;
they are also water soluble, which means they are readily absorbed by plants via roots and leaves–>this transports them through ALL of the tissues–>highly systemic activity–>can protect all parts of the plants from insect activity
flexible use–used as a seed dressing, foliar sprays, bait formulations, granular formulations, soil drench, inject into timber, and topically applied
possible economic benefits

Question 7

disadvantages of neonics?

Answer 7

1. absorption into target crop is very low–16-20% of the active ingredient in the seed dressing–>traditional sprays exceed 50% uptake;
2. persistent in soil– different neonics will have different properties influencing persistence, but will mostly be persistent; soil type will also influence persistence; may have half lives of 200-1000 days
3. potential for bioaccumulation;
   may contaminate other environments (ground water, surround crops containing non-target plants)
4. Toxicity across taxa–insects are most sensitive but are gaining resistance–> birds are also sensitive; risks to granivorous verts
5. impact on pollinators– neonics found in pollen and nectar–> affect bees, hoverflies, butterflies, etc
6. Indirect ecological impact–>reduction in invert pops

Question 8

rotenone general info—whre it’s produced, uses, toxicity, enviro kinetics

Answer 8

produced in roots of derris and lonchocarpus; used to control leaf-eating caterpillars; used in home and garden; used as a piscicide (neutralized by KMnO4); moderately toxic to mammals; rapidly photodegraded;

Question 9

rotenone mech of ac?

Answer 9

strong inhibitor of ETC–>inhibs complex I of ETC (NADH DH complex); no ATP = no energy to keep up cell structure = oxidative stress

Question 10

what is pyrethrum?

Answer 10

extract from flowers of tropical Chrusanthemum species –> a mixture of four compounds–> Pyrethin II and Cinerin I and II

Question 11

pyrethrum general info–uses, kinetics, disadvantages

Answer 11

very unstable in sunlight, t1/2 = 8.5, 12-13h on soil; requires synergist (e.g. piperonyl butoxide) to be toxic; used in household insecticides sprays and pet products; has low mammalian toxicity

Question 12

why is pyrethrum not very toxic to animals?

Answer 12

rapidly metabolized in animals; can cause allergic reactions in humans

Question 13

what are the synergists of pyrethrum?

Answer 13

piperonyl butoxide and sesamex

Question 14

piperonyl butoxide and sesamex general info?

Answer 14

not toxic/insecticidal by themselves–>inhibit CYP450 enzymes (pyrethrum would be inactivated by CYPs if they weren’t inhibited); these synergists only work with insecticides inactivated by CYPs

Question 15

first gen pyrethroids time, e.g., and advantages

Answer 15

1949, allethrin, and more stable than parent, cinerin 1, but requires synergist

Question 16

second gen pyrethroids time, e.g., and advantages

Answer 16

1965, tetramethrin, resmethrin (common in household sprays); greater efficacy but still requires synergist

Question 17

third gen pyrethroids time, e.g., and advantages

Answer 17

1972, fenvalerate/permethrin; stable in sunlight and does not require a synergist;
first agricultural pyrethroids

Question 18

fourth gen pyrethroids time, e.g., and advantages

Answer 18

1985; cypermethrin, decamethrin; photostable, long resisdual effect and high efficacy; no synergist needed

Question 19

mech of ac of pyrethroids

Answer 19

all affect Na channels, but differently; 
Type 1 (1st and 2st gen)--> cause repetitive neural discharge (holds Na channels open for a longer than normal tim-->produces inappropriate APs/neuronal irritation)
type 2 (3rd and 4th gen): no repetitive discharge; instead holds Na channels for an even longer time--> causes persistent depolarlization (inceases refractory period of the neuron, cause inappropriate firing firing, then prevents subsequent firing)

Question 20

toxin produced Bacillus thuriningiensis (Bt)

Answer 20

used as insecticide; must be ingested to kill; alkaline gut activates the pro-toxin (good for us with our acidic gut –> non-target species not killed); gene for Bt toxin inserted genome of crops to kill insects that infects the crop;

Question 21

three main serovarieties of the Bt toxin

Answer 21

kurstaki; israelensis; tenebrionis;

Question 22

what is the kurstaki toxin used for?

Answer 22

used for lepidoptera larvae; ag, home, and forestry

Question 23

what is the israelensis toxin used for?

Answer 23

selective for mosquitoes and blackfly larvae; some midges (type of black fly); applied directly to water where larvae are found

Question 24

what is the tenebrionis toxic used for?

Answer 24

targeted for the colorado potater beetle

Question 25

What are the classes of avermectins?

Answer 25

Ivermectin
Abamectin
Emamectin

Question 26

Ivermectin use?

Answer 26

Soil nematocide; pet-livestock anti-helminthic and for ticks/fleas

Question 27

Abamectin use?

Answer 27

Controls fire ants and mites

Question 28

Emamectin use?

Answer 28

Pesticide of choice to treat sea lice in Canadian salmon farms

Question 29

Avermectin toxicity and mech of AC?

Answer 29

Unstable in enviro–photolysis;

Produces rapid paralysis–slow death; may be a gaba agonist–atom gaba release, or open GABA-gates Cl channels