Lecture 5 - DA Flashcards
Name 6 advantages of pesticides.
Name 4 disadvantages.
Advantages -Effective -Fast -Easy to use -Cheap -Broad spectrum -Increases productivity Disadvantages -Toxic to humans -Toxic to non target organisms -Persistent in the environment -Pests develop resistance
Name the 5 groups of pesticides.
Organochlorines Organophosphates Carbamates Botanicals Biologicals
What is the solubility (in water and lipids) of organochlorines like? What about its toxicity? Is it likely to persist in the environment?
Low solubility in water, high in lipids.
Toxicity is low-moderate.
Will bioaccumulate due to lipid solubility.
Which is more toxic, organochlorines, or organophosphates?
Which is more persistent?
Which degrades easier (and how)?
Organophosphates are more toxic.
However, they do degrade easier.
Organochlorines persist more.
Which is more water soluble, organochlorines or organophosphates?
Organophosphates.
Are carbamates more toxic than organochlorines/phosphates?
No, less toxic.
Do carbamates take long to degrade? What does this suggest about its persistence?
No, they degrade rapidly. Therefore, there are no problems with persistence.
What is the solubility of carbamates like?
Is variable.
Where are botanicals derived from?
Are pesticides derived from plants.
Are botanicals moderately toxic, or highly toxic?
Highly toxic.
Name 3 examples of botanicals.
Nicotine, pyrethrum, and pyrethroid.
What are 2 forms of pyrethrin?
Pyrethrum - natural form
Pyrethroid - synthetic form
What is one way pesticides can be classified?
By their mode of action.
How can analogues of juvenile growth hormones be used as pesticides?
Prevents the completion of the life cycle - perpetually in juvenile form.
What are 3 advantages of using juvenile growth hormones as pesticides? Name a disadvantage.
Is highly selective
Rapid degradation
Essentially non-toxic to other organisms
However, it will still affect bees.
What do antimetabolite pesticides prevent? What is a consequence of this? Are they highly specific or is there non-target toxicity?
Chitin synthesis. Failure to survive moulting.
There is some non-target toxicity.
Name 3 examples of biological pesticides (ie parasites, bacteria etc).
Fungi
Nematodes
Bacillus
What are some disadvantages of using biological pesticides?
Toxicity of ecotoxins, and affecting non-target insects like bees.
May also affect genetic stability.
Name 3 kinds of herbicides.
Triazine herbicides
Urea herbicidea
Phenoxy herbicides
What kind (in terms of persistence and selectivity) and dose of herbicide is needed for permanent removal of all vegetation?
High dose of a non-selective persistent herbicide.
What kind (in terms of persistence and selectivity) and dose of herbicide is needed for temporary removal of all vegetation?
Moderate dose of a non-selective non-persistent herbicide.
What kind (in terms of persistence and selectivity) and dose of herbicide is needed for selective removal of some plants, while leaving others?
Low-moderate dose of a selective herbicide.
How are herbicides taken in by plants? What characteristics are needed by the herbicide to be effectively taken up, and why?
Taken in via the leaves and stems above ground, and roots below ground.
Plant is covered by a lipid based cuticle, so the herbicide must be somewhat lipophilic.
Must also be slightly water soluble to be transported once through the cuticle.
What are the 3 selectivities of herbicides?
Differential uptake
Differential detoxification
Differential root growth habit.
What are diuron and linuron herbicides, and what kind of herbicide selectivity do they fall under?
Diuron - binds rapidly at soil surface
Linuron - not intensely bound to soil surface
They fall under differential root growth habit selectivity
What kind root systems are diurons toxic to? What about linurons? Do they leach?
Diurons - shallow root systems. Does not leach.
Linurons - deep root systems. Leaches rapidly.
What are triazine herbicides applied to, where are they taken in, and where are they transported to?
Applied to the soil, taken in by roots, and transported to the leaves.
What effect do triazines have?
Accepts electrons produced during photosynthesis, causing lipid peroxidation, and necrosis.
How are triazine herbicides detoxified?
C1 is replaced with an OH group.
The ring is cleaved.
Where are urea herbicides applied to, and what kind of transport does it utilise?
Applied to soil, utilises apoplastic transport.
What is the binding capacity of urea like?
Different types have different capacities.
The mode of action of herbicides is most similar to what other herbicide?
Similar to triazine herbicides.
Name 2 ways urea herbicides are degraded.
Bacterial demethylation
UV degradation
Are urea herbicides selective or non-selective?
Typically non-selective.
Are urea herbicides diurons or linurons?
Mostly diurons.
Phenoxy herbicides are used to control what weed amongst what crop?
Controls dicot weeds amongst monocot crops
What weed are phenoxy herbicides selective for?
Broadleaf weeds.
What is the mode of action for phenoxy herbicides?
mimics auxin, but isnt degraded.
What is the half-life of phenoxy herbicides? After what period of time will there be negligible amounts left?
Half-life - days to weeks.
Negligible after a year.
Name 2 ways phenoxy herbicides are degraded.
Via microbes and UV light.
Do chlorophenols degrade? What is a problem with degrading them?
They do degrade, but are toxic once degraded.
Order in terms of sensitivity to phenoxy herbicides.
Invertebrates, fish, algae
Algae - resistant
Invertebrates - more sensitive
Fish - sensitive
Is glyphosate toxic to animals? Why/why not?
Is non-toxic, as they lack the pathway it affects.
Is glyphosate volatile? What is its selectivity and solubility?
Non-volatile
Water soluble
Non-selective action
Why was glyphosate once considered to be toxic? Why isnt it anymore?
Early formation was very toxic. Later found to be due to the surfactants and solvents used, which was removed upon discovery.
Can dioxins be degraded by bacteria?
Yes, but a long half-life.
Do dioxins bind tightly to soil? Does it leach?
Binds tightly, and doesnt leach.
Where do dioxins accumulate?
The liver.
What is the major problem with dioxins?
Bioaccumulation, and biomagnification.
