Weeds L6

Question 1

Biological weed control

Answer 1

control of a weed species by their natural enemies to maintain the weed population below the level of economic injury

Question 2

Lotka-Volterra equation/Predator-prey model

Answer 2

Simplified model about predator-prey relationship

Question 3

Economic injury level (EIL)

Answer 3

the lowest pest population density that will cause economic damage equal to the cost of the control

Question 4

Economic threshold (ET)

Answer 4

the level of pest infestation at which management action is justified

Question 5

Types of biocontrol agents

Answer 5

Invertebrates (insects, worms, etc.)
Pathogens
Mammals
Birds
Fish

Question 6

Advantages of weed biocontrol

Answer 6

offers permanent solution to problem
agents are often self-perpetuating and self-dispersing
Risks are known and evaluated before release
Good cost ratio for successful programs

Question 7

Example of unsuccessful biocontrol

Answer 7

Attempt to control beetles in sugarcane with the cane toad. Didn’t work because beetles just flew to tops of sugarcane and toads just ate everything else

Question 8

Disadvantages of weed biocontrol

Answer 8

control is slow and weed eradication is impossible
establishment may fail
# of control agents may be low if target weed is closely related to crop
some risks are not known and cant be evaluated

Question 9

Classical weed biocontrol

Answer 9

The intentional introduction of host-specific natural agents from a different country to achieve control of an invasive weed species (importation)

Question 10

Non-classical weed biocontrol

Answer 10

inoculation, augmentation, inundation, conservation

Question 11

2 main requirements for the classical weed biocontrol method

Answer 11

• invasive weeds species was freed from its natural enemies when it was introduced to the new habitat
• the natural agent being imported should not have enemies in the new habitat

Question 12

it can take __________ years to achieve control (plus millions of dollars)

Answer 12

5-10

Question 13

example of classical weed biocontrol success

Answer 13

Purple loosestrife was brought from Europe/Asia to North America and is invasive to wetlands
Released beetles Galerucella calmariensis and G. pusilla to control it

Question 14

What are the core assumptions of classical weed biocontrol programs that are needed to reunite pest species with their coevolved natural enemies?

Answer 14

Natural agent can control target weed
agent is specific (not attack other plants)
can be reared in captivity
can self-disperse and reproduce in new habitat

Question 15

Steps to developing a classical biocontrol program

Answer 15

• determine suitability of weed for biocontrol
• search for potential enemies
• evaluate ecology of natural enemies
• select candidate species and conduct host range testing
• small-scale experimental releases
• post-release evaluation
• large scale general release

Question 16

Example of successful classical weed biocontrol in North America

Answer 16

Leaf beetles were introduced from Europe to control St. Jon’s Wort Hypericum perforatum in Canada and the USA

Question 17

Example of classical biocontrol in Australia

Answer 17

Moth Cactoblastis cactorum was brought from Argentina to control the Prickly Pear Cactus in Australia

Question 18

Thistle Biocontrol examples

Answer 18

Thistle head weevil and Canada thistle stem-mining weevilintroduced from Eurasia to control thistle

Question 19

Curly dock Biocontrol example

Answer 19

Rumex rust fungal pathogen introduced from Europe to control curly dock

Question 20

Fish biocontrol example

Answer 20

White amur introduced from East Asia to control weeds in waterways

Question 21

When is biocontrol likely to fail?

Answer 21

Natural agent fails to establish, cause ecological instability, or attack/targets non-target plants

Question 22

Inoculative weed biocontrol

Answer 22

Introducing a natural agent that is already in the country to a new location or environment

Question 23

main requirements for inoculative weed biocontrol

Answer 23

agents are able to reproduce
impact is season long
further releases necessary if secondary outbreak of target weed occurs

Question 24

Augmentative weed biocontrol

Answer 24

intervention to enhancing or restoring the function of a natural agent that is already in the habitat, location, or environment

Question 25

Main requirements for Augmentative weed biocontrol method

Answer 25

Impact should be season-long
further releases necessary if secondary outbreak of target weed occurs

Question 26

Inundative weed biocontrol

Answer 26

the massive release of a natural agent into a certain environment to quickly suppress a weed infestation

Question 27

Main requirements for Inundative weed biocontrol

Answer 27

Agent is able to rapidly suppress target weed population
Agent doesn’t have to reproduce
Easy to mass-rear
Impact is similar to herbicide

Question 28

Conservation weed biocontrol

Answer 28

Improving agricultural practices to enhance the functioning of natural agents

Question 29

Main requirements of Conservation weed biocontrol

Answer 29

No bio controls are released
rely on agents ability to suppress weed populations
focus is on the species ecology

Question 30

Weed seed predation

Answer 30

Predators that attack seeds of target weed species

Question 31

Pre-dispersal seed predation

Answer 31

carried out by specialist insects that attack the seedheads and destroy the seeds

Question 32

Post-dispersal seed predation

Answer 32

carried out by non-specialist invertebrates and vertebrates that attack seeds on the soil surface and destroy them