Lecture 11 - Weed Biocontrol Flashcards
biological weed control
control of a weed species by their natural enemies to maintain the weed population below the level of economic injuryty
organisms used a biocontrol agent
- invertebrates
- pathogens
- mammals
- birds
- fish
advantages of weed biocontrol
- permanent solution to weed problem
- self-perpetuating and self dispersing
- risks are known and evaluated
- high benefit:cost ratio
- no harmful side effects
disadvantages of weed biocontrol
- control is slow and eradication is impossible
- establishment may fail
- # of potential agents is low if weed is close to crop
- some risks may not be known and cannot be evaluated
types of weed biocontrol
classical
inoculation
augmentation
inundation
conservation
classical biocontrol
importing an agent from somewhere else
inoculation biocontrol
introduce a natural agent that is already in the country to a new location or environment (rearing and releasing)
augmentation biocontrol
intervention to enhancing or restoring the function of a natural agent that is already in habitat, location, or environment (rearing and releasing)
inundation biocontrol
mass release of native agent into certain environment to quickly suppress a weed infestation
conservation biocontrol
improving agricultural practices to enhance the functioning of natural agents (no rearing or releasing)
2 main requirements for classical biocontrol metho
- invasive (exotic) weed species was freed from its natural enemies when it was introduced to new habitat
- natural agent being imported should not have any enemies in the new habitat
core assumptions of a classical weed biocontrol program
- weed to be controlled has native habitat
- agents can control target weed
- agent should be specific
- agent can be reared in captivity
- agent can find target weed and self disperse
- agent is able to reproduce in new habitat
steps to developing a classical biocontrol program
- determine suitability of weed for biocontrol
- find potential natural enemies
- evaluate ecology of enemy
- select candidate species
- host range testing
- small-scale experimental release
- post-release evaluation
- large-scale general release
natural agents need ______ generations to achieve control in classical biocontrol
6-13
examples of classical weed biocontrol
- moth with prickly pear cactus
- leaf beetles on st, johns wort
- thistle head and stem mining weevil on nodding and canada thistle
- rust fungal pathogen on curly dock
- white amur on waterway weeds
classical biocontrol is likely to fail if:
- agent fails to establish
- agent causes instability in the new habitat
- agent attacks non-target plants after controlling weed
examples of failed classical weed biocontrol
- lantana lace bug did not reduce lantana population
- fireweed couldnt find any agents cause it was to close to native plants
main requirements for inoculative weed biocontrol
- want to expand range of agent
- agents can reproduce
- impact should at least be season long
- further releases are needed if 2nd outbreak occurs
main requirements of augmentative weed biocontrol
- function response of agent might be saturated
- impact should be season long
- further release is needed if 2nd outbreak occurs
main requirements of inundative weed biocontrol
- agent can rapidly suppress populations of the target weed
- timing of application must be right, as agent is not expected to reproduce
- agent should be easy to mass-rear
- impact similar to herbicides
main requirements of conservation weed biocontrol
- no agents are introduced or released into environment
- relies on agents ability to provide mid-late term suppression of weed populations
- focus is on species ecology
nuts and bolts
- insects eat the seed
- embryonic plants are killed
- plants suffer fitness costs
