week 8 Flashcards
what is a parasitoid and how do you disinguish it from normal parasites?
Parasitic while immature
Free-living as adults
Normal parasites are usually parasitic for entire life
Ultimately kills host to complete its own life cycle
(how to distinguish from other parasites)
are parasitoids parasites?
yes
what percent of described insect species are parasitoids
10%
what percent of hymenoptera species are parasitoids
75%
what percent of diptera species are parasitoids?
25%
what insect orders are parasitoids present in
hymenoptera, diptera, strepsiptera, neuroptera, trichoptera, lepidoptera
are there any underscribed parasitoids?
Enormous number of undescribed species
Especially in hymenoptera
what do tachinid flies attack
Primarily attack caterpillars and sawflies
Also attack stink bug pests
how many tachinid fly species
More than 10000 described species
Second largest family of flies
how many staphylinid beetle species? how many are parasitoids?
61000 described species
Only a small number are parasitoids
Some both predators and parasitoids
what species do braconid wasps atack
Braconids mainly attack holometabolous insects or hemiptera
what do Ichneumonid wasps attack
Ichneumonidae attack broad range of insects, spiders, centipedes
how many species of Braconid and Ichneumonid wasps? what is special about them?
Likely most diverse animal and insect family
60000-100000 species
Some have very extreme morphology
Long ovipositors
how many chalicnid wasp species and families? what is special about them?
Superfamily
Estimated >500000 species worldwide
22000 described so far
Contains about 20 families
Most very small
what are ectoparasitoids
Larval parasitoid feeds from outside of host
what are Endoparasitoids
Larval parasitoid feeds from inside of host
what are solitary parasitoids
One larva per host
what are gregarious parasitoids
Multiple larvae per host
Results from multiple eggs deposited
what are polyembryonic parasitoids
Multiple larvae per host result from one egg that undergoes fission
Identical clones
what does idiobiont mean
(idio = single; biont = life)
what are idiobiont parasitoids
Host growth stops at time of parasitism
Venom injections by female stop development and paralyse host
what are some common behaviours and characteristics of idiobiont parasitoids
Usually larva develops externally on host
-Ectoparasitoids
Contact of developing parasitoid with host immune and hormonal systems limited
Generalists
Concealed hosts
what are some examples of idiobiont parasitoids (2)
Dahlbominus
-Parasitoid of sawfly pupa
Rove beetle species with parasitic larvae
what does koinobiont mean
(koino = shared; biont = life)
what are koinobiont parasitoids
Host continues to feed, develop and moult
-Injections may alter immune system however
-Growth doesn’t stop but still sometimes affected
what are some common behavoirs and characteristics of koinobiont parasitoids
Usually larva develops internally in host
-Endoparasitoids
Parasitoid must avoid host immune responses
Interactions of host and parasitoid endocrine systems often occur
Specialists
Exposed hosts
what are some examples of koinobiont parasitoids
Braconid parasitoids of lepidopterous larvae
Diptera: tachinidae
-larviposition
-Microtype eggs
what are microtype eggs
Very tiny eggs laid on vegetation, host eats
what are egg parasitoids
special class of koinobiont
Parasitoid develops internally in egg
what is special about egg parasitoids? What are they used for by us?
Egg has no effective immune system
-generalists
Egg rapidly undergoes embryogenesis
Interactions of host and parasitoid endocrine systems in doubt
common in biological control
what is a hyperparasitoid
Host is another parasitoid
Easier to attack because primary parasitoid already dealt with host defenses
Ex.
Hyperparasitoid wasp laying eggs into parasitoid wasp pupae
what are commmon host immune responses when eggs are deposited into hymolymph of host?
Hemocytes may adhere to and from capsule around egg or young larvae
Specialized cells to encapsulate eggs
Capsule can melanize to prevent successful hatching by suffocation
what are 2 counter adaptions by endoparasitoids to overcome host immune responses?
venom
Polydna viruses
what does parasitoid venom do when injected into a host
Venom actions varied
Paralytic activity
Disrupt hemocyte adhesion
Prevent host molting in ectoparasitoid koinobiont
Severe metabolic alterations
Make host more nutritious
what are polydna viruses
Carry dna of wasp that effect defenses of host
Integrated into wasp genomes
Replicates in wasp ovaries
what do polynda viruses do when injected into a host by parasitoids
Cause immune response breakdown upon injection into host
Disrupts encapsulation
Prevents nutritive uptake
what is a pest
Anthropocentric point of view (human at the centre)
Insects that are in conflict with our welfare, aesthetics or profits
what are direct effects of pests (2) and examples of each
Vectors of human disease
Mosquitos ticks, fleas
Allergic reactions
Lady Beetles
what are some indirect efffects of pests (3) and some examples of each?
Domestic animals
Cattle flies
Crops
Armyworms, aphids, leafhoppers
b
Timer species
Bark beetles
why is it a bad idea to just spray for pests regularly or apply pest control measures as soon as you see a pest?
Don’t want to spray if
Don’t have a problem
Insects aren’t pests
Insects are pests but not high enough numbers to pose problem
spray is harmful and costly
what is the Economic Injury level (EIL)
Minimum number of pests that reduce yield equal to the gain threshold
Lowest number of pests that cause economic damage
what is Integrated Pest management (IPM)
A comprehensive pest technology using combined means to reduce status of pests to tolerable levels while maintaining quality environment
what is the philosophy of Integrated Pest management (IPM)
limit economic damage to crop
Minimize adverse effects on non-target organisms and on consumers of produce
ie. Manage all pests and minimizing adverse effects
what is the gain threshold and what does it tell us?
The cost to manage pests (per acre) divided by the value of crop (per acre)
Tells you how much extra yield (bushels per acre) you need to profit from pest management
what is a problem with using the gain threshold to decide whether or not to manage pests?
Problem is you Don’t know the market value in the future (when you sell crop)
what is the damage boundary? should you manage pests once you cross it?
Amount of decreased yield that is significant enough to attribute to insects
When you pass damage boundary, still doesn’t cost enough to use pest control
what is the Economic threshold (ET)? whats the difference between it and the EIL? why is it important?
Number of insects that should trigger a management action
Amount of insects you need to apply control measure before pest numbers reach EIL
Gives some time to apply pest control
what are 2 ways of managing pests
insecticides
biological control
what are the 2 types of insecticides? how are they made and what is pros/cons of each?
natural
Come from plants that develop defenses from herbivores
Very expensive
synthetic
made synthetically
Some Mimic natural products
cheap
often more harmful
what are 5 issues with insecticide
toxicity to humans
biomagnification
disruption of regulation by natural enemies
secondary pests
selection for resistant pests
how many cases of pesticide poisoning per year
1-5 mil
how many pesticide deaths per year
20000
what percent of insecticide deaths come from developing countries? what percentage of insecticides do they use? why is this?
99% of deaths in developing countries
Protective equipment is expensive
Don’t ban toxic products
They only use 25% of pesticides
why is it hard to prove how harfmful insecticides are to humans?
Severe sub-lethal effects
what is biomagnification
Concentration of pesticides on higher trophic levels
Animals higher on the food chain have higher concentrations of pesticides in tissue
what is Disruption of regulation by natural enemies caused by insecticide use and an example
Kill all arthropods including natural enemies
Usually pest that survives
Increased use of insecticide lead to larger areas affected by brown planthopper due to disruption of natural enemies
how can pesticides cause secondary pest problems
Pest species that increase due to pesticides affecting their natural enemies
Weren’t pests before, but now are because natural enemies killed
what is biological control
Use of living organisms to control pest populations
what are the three types of biological control
Classical BC
When we have invasive pest species
Importation and establishment of exotic natural enemies
Augmentation BC
Periodic release of natural enemies
Conservation BC
Enhance populations or impact of natural enemies already present
what are Ecosystem services
Services provided by natural ecosystem functions that support human and other organisms survival/well being
what are 4 ecosysem services provided by insects and their costs per year
Estimates for united states
Dung burial: 0.38 bil/year
Pollination wild insects: 3.07 bil/year
Pest control of native herbivores: 4.49 bil/year
Food for wildlife(fishing, hunting, etc.): 49.96 bil/year
what happened with the soybean aphid in NA
Invasive species detected in 2000 in wisconsin
Rapidly spread
40-50% yield losses
Potential virus vector
Economic control is needed
what was found from experimental methods researching soybean aphid control
Found that parasitoids didn’t affect aphid populations
only natural predators such as asian lady beetles
what are 6 other pest control methods
Host plant resistance
Physical control
Cultural control
Pheromone and other insect attractants
Genetic manipulation of insect pests
RNA interference (RNAi)
what is an example of host plant resistance to pests
Resistance to orange wheat midge
Most important pest of wheat in canada
Loses 3-300 mil/year
Controlled by sm1 resistance gene
what yield did soybeans have with no aphids vs predators vs parasitoids?
no aphids and predators had same yield. Parasitoids and no predator/parasitoids had lower yield
why do we get insect habitat loss and fragmentation? Why is this a problem for agriculture?
Agriculture simplifies and fragments habitats
Creates ideal situation for pests of crops
what are some resources and things beneficial insects need to complete their life cycles
Overwintering sites
Alternative prey/hosts
Nectar or pollen resources
Moderated microclimates
Host plants
Aggregation sites
Refuges from agricultural disturbances
why do beneficial insects need refuges from agricultural disturbances
Agricultural fields are very harsh environments for most insects
High temperatures
Dry
Harvest, spraying, tilling
why is landscape ecology important when studying the effects of pest control?
Landscape around fields matters for studies
More fields around likely means less natural enemies
what is a landscape
Area that is spatially heterogeneous in at least one factor of interest (differs)
Not defined by surface area
Size of landscape depends on organism you study
what is a patch
Surface area that differs from surroundings in nature or appearance
Typically by vegetation
what is fragmentation
Breaking up of habitat or cover type into smaller, disconnected parcels (patches)
what is a cover type? give some examples
Category within a classification scheme defined by user that distinguishes among different habitats, ecosystems or vegetation type on landscape
Classification of patches
Ex. forest, cornfield, etc.
what is landscape quantification
To quantify how different or variable a landscape is
what are the 2 measures we use for landscape quantification
Composition
-What a landscape is made of
-Proportion occupied by different habitats
-Relative habitat richness habitat diversity
-Habitat diversity
Configuration
-How a landscapes parts are spread out
-Habitat connectivity
-Habitat fragmentation
what is special about complex landscapes vs simple landscapes
Higher % deciduous forests
Lower % area cover by crops
Smaller fields
-Smaller patches
Wider field borders
Taller vegetation in border
Richer tree species in border
Higher % of trees/shrubs in border
what makes complex landscapes better for beneficial insects
Predators/parasitoids have more refuges
Can move between areas easier through borders
Results in more parasitoids/predators
what is the history and distribution of cereal leaf beetle (CLB) and what crop does it attack
Native to europe
Found first in southern michigan in 1960s
In canada: manitoba, sask, alberta BC
55% yield loss on spring wheat
23% yield loss on winter wheat in NA
what pest control method did we use to control CLB
Classical biological control with the parasitoid: Tetrastichus julis
Native to europe
how well did Tetrastichus julis work at controlling CLB? Where was it used
very well in states so we brought it to establish in BC, Alberta and Sask
Current releases include West Manitoba
what was the landscape analyzed when studying the effects of pest control on CLB
Digital maps using ARC MAP 10
Proportion of different habitats and habitat diversity
4 circular sectors from 0.5 to 2 km
what did we notice when studying pest control of CLB at the .5km scale? how did this change when we moved to the 2km scale?
At 0.5km scale
The more diversity of crops results in less CLB
More parasitoids results in less CLB
At 2 km scale
More canola and alpha fl resulted in more parasitoidism
what is the result of predators arriving early to crops vs late compared to aphids? What conclusions can we draw?
Much less aphids when predators early vs late
Means natural enemy habitats closer to fields result in less aphids
what were the two main things found to reduce CLB abundance?
Crop diversity reduce CLB abundance
More difficult to find cereal fields in diversified landscapes
Parasitism reduce CLB abundance
what was found to increase CLB parasitism?
Flower providing crops (alfalfa, canola) increase CLB parasitism
what were 2 things that helped with melon aphid control in australia
Alfalfa area related with higher aphid suppression
Early predation increased aphid suppression
-Facilitation of natural enemy movement can enhance pest control services across a range of agricultural landscapes
how much money do natural enemies save several states per year in aphid control?
239 mil / year
what were the 2 main things measured when studying Landscape effects on soybean aphid predation in NA? how?
Landscape characteristics
-Landscape composition - 2km radius
-Digitally quantified: ArcGIS 10
-Habitat diversity (Aimposon’s diversity indices)
Natural enemy movement
-30 bi-directional malaise traps
-Between soybean and adjacent habitats
-Lady beetles, minute pirate bugs, damsel bugs, brown lacewings, green lacewings, hover flies
do natural enemies suppress soybean aphids in manitoba? why?
Natural enemies suppress soybean aphid in manitoba
Natural enemy movement from neighboring habitats explains levels of aphid suppression
what crop is the best for controlling aphids? why?
Proportion of cereal (wheat, granola) had negative association with aphid populations at highest spatial scale
They aren’t sprayed with insecticide so more natural enemies
what natural enemies are the best for aphid suppression
Green lacewings and lady beetles had negative association with soybean aphid population
what type of landscape is best for beneficial insects and why?
Complex landscapes affect beneficial insects by providing resources from non-crop habitats
what affect does complex habitats have on natural enemy populations? what effect does this have on pests?
Natural enemies increase abundance in complex habitats
Pest suppression in complex landscapes usually higher
what is the best way to plant your crops to prevent pest population rise?
Crop diversity can decrease some pest populations
is it only complex landscapes that effect predator/parasitoid populations?
no, Some crops may also be source of predators and parasitoids
what is a way being studied to enhance natural enemy impacs
Adding flower resources at edge of fields to help natural enemies
