Lecture 16 Flashcards
what are the direct effects of pests?
vectors of human diseases (ex: mosquitos, ticks, fleas)
allergic rxns (ex: ladybeetles)
what are the indirect effects of pests?
Domestic animals (ex: cattle flies)
Crops (ex: aphids, locusts, armyworms, leafhoppers etc.)
Timber species (ex: bark beetles)
what costs are involved in applying control measures of pests?
economic costs & envr costs
economic injury level (EIL)
“min number of pests that reduce yield equal to the gain threshold”
or
“lowest number of pests that cause economic damage”
central concept in integrated pest management (IPM)
“a comprehensive pest technology that uses combined means to reduce the status of pests to tolerable levels while maintaining a quality envr”
attempt to maintain envr quality
what are the 2 considerations when applying pest control
how much it costs per unit area to apply an insecticide
how much money you are getting out of each yield
injury
any damage detected on the crop
incres in injury =
decres in yield
what occurs when you reach the gain threshold?
necessary to apply a controlled measure or you will lose money
economic damage & what is necessary when you reach this point?
when you can save some yield by applying a controlled measure
invest money in a control measure when you pass this point
what happens when you cross the damage boundary?
yield reduction
when is it necessary to apply a control measure?
when crossing economic injury level (EIL)
where does noneconomic losses occur?
b/w EIL & Damage boundary
what occurs when applying control in noneconomic losses?
lose money, but if you apply at the damage boundary then you can save money
doesn’t make sense to apply here b/c insects might be controlled naturally
economic threshold (ET)
“number of insects that should trigger a management action” = “action threshold”
the economic threshold is always lower than _____
economic entry level
management activity
where the population passes economic threshold & where insecticide was applied
where you should apply an insecticide
what are the 2 kinds of insecticides?
natural products & synthetic products
natural products
plants produce for defense
but it’s expensive to extract form plants so synthetic products have been used as an alternative
what are exs of natrual products? (4)
alkaloids [nicotine]
rotenone
pyrethrins
neem
synthetic products
same effect as natural products (not the same chemical composition)
what are exs of synthetic products?
nictotinoids or neonicotinoids, pyrethroids, carbamates, organophosphates, organochlorides
what are the advantages of synthetic insecticides?
Can be produced in massive amounts & are cheap
what are the disadvantages of synthetic insecticides?
No natural ways to break them down
what are the issues with insecticides? (5)
- Toxicity to humans
- Biomagnification
- Disruption of regulation by natural enemies
- Secondary pests
- Selection for resistant pests
where do deaths from insecticides mostly occur? & why?
developing countries
toxicity of products: use older & banned pesticides in undeveloped countries (tend to be lethal)
protection of application: manually apply, no equipment
- -> no $ to buy
- -> no enforcement
biomagnification
concentration of pesticides on higher trophic levels
how does biomagnification effect higher trophic levels?
higher mortality
why does increased use of insecticides lead to larger areas affected by brown hoppers?
disruption of natural enemies
describe the cycle occurring when using bbroad-spectrumpesticides
When you spray, you kill both the pests & the natural enemies
Leads to increase resistance of pests
Can kill natural enemies
Leads to the need to apply more & continues the cycle
secondary pests
Pest species, usually at low levels, that increase due to pesticides affecting their natural enemies
Originally, aren’t a pest but become one when exposed to insecticides b/c the insecticides kill the natural enemies
what is an ex of a secondary pest?
mites - not a prob until you spray for aphids
leads to resistant mites
what is the result of applying insecticides?
selecting for resistant pests
How do you delay resistance of insecticides?
rotate pesticides
use diff types of modes of action so you don’t continually select for this type of resistance
biological control (BC)
Use of a living organism to suppress pop density or impact of pest pops
classical BC
importation & est of exotic natural enemies
when is classic BC used?
with an introduced pest
augmentation BC
periodic release of natural enemies
when is augmentation BC used?
Works well in small areas or for greenhouse protection b/c you know they will remain in the same area
doesn’t require further intervening or management
conservation BC
enhance pops or impact of natural enemies already present
done by making the habitat more favourable for the natural enemies
what are the ecosystem services provided by insects?
Predators control the pops of the pests
Provide support to any of our activities
what effect do insecticides have on ecosystems?
lead to a loss of ecosystem functions which then leads to more $$ to replace the function
what are the functions that humans would need to replace if insects weren’t there to fulfill the role?
dung burial
pollination wild insects
pest control of native herbivores
food for wildlife
soybean aphid in NA (4)
invasive species
40-50% yield losses
potential virus vector
economic control is consistent
what are the natural enemies of soybean aphids? (2)
Multicoloured Asian ladybeetle & Minute Pirate Bug control
are predators effective at reducing soybean aphids?
yes
what are other control methods besides chemicals & BC? (5)
Host plant resistance
Physical control
Cultural control (ex: tillage or crop rotation) Disrupts lifecycle of pests
Pheromone & other insect attractants
Disrupts mating – pop won’t reach high levels
Genetic manipulation of insect pests
Replace insects with those that don’t carry disease vectors
do parasitoids have an effect in pop control of soybean aphids?
NO
How is resistance of the orange whet midge managed?
controlled by Sm1 resistance gene (in plants)
–> mix resistant with non-resistant to delay resistance in pest
