W13: Biocontrol (Post-release Evaluation Of Weeds) [Dr. Nic]

Question 1

Evaluation/Monitoring?

Answer 1

= measuring the result of the introduction of one or more biocontrol agents on a target weed.

Question 2

Possible outcomes for Biological control of a weed? (3)

Answer 2

• Weed is no longer a problem.
• Other control methods are needed at lower rates.
• Weed is still as much of a problem as before.

Question 3

“Weed is no longer a problem” attributes? (2)

Answer 3

• Project has been a complete success.
• No other control methods needed.

Question 4

“Other control methods needed at lower rates” attributes? (2)

Answer 4

• Project has been a substantial success.
• Weed is still a problem but not so bad (now what?).

Question 5

“Weed is still as much of a problem as before” attributes? (2)

Answer 5

• Project has been a failure.
• Other control methods are needed as before.

Question 6

Reasons to evaluate? (5)

Answer 6

• Provide a historical record of what happened.
• Determine if additional biological control agents are needed.
• Select agents compatible with already-established agents.
• Decide if other types of control (mechanical/chemical) should be used and, if so,
• Develop effective integrated control prigrammes.

Question 7

What are the different scales of Water hyacinth biocontrol covered? (3)

Answer 7

• Landscape.
• Leaf level.
• Seed production.

Question 8

Water hyacinth biocontrol @ Landscape scale?

Answer 8

Satellite imaging was used to view impact on water hyacinth.

Question 9

Water hyacinth biocontrol @ Leaf scale?

Answer 9

Feeding by weevils on water hyacinth.

Question 10

Water hyacinth biocontrol @ Seed production scale?

Answer 10

Solanum bud weevil reducing seed production of bugweed.

Question 11

Ultimate measures of a weed biocontrol programme? (2)

Answer 11

• Reduction in weed density.
• Reduction in weed rate of spread.

Question 12

Impact of biocontrol on selected species in SA?

Answer 12

Shows what would have happened if prickly pear was not introduced in shaded section of graph.

Question 13

Biocontrol of invasive cacti graph? (2)

Answer 13

• Biocontrol using cochineal.
• Good eg of a new equilibrium.

Question 14

Outcomes of biocontrol during stages of an alien invasion Graph 1? (8)

Answer 14

• x-axis = Time.
• y-axis = Area.
• Sigmoid shape from bottom to top.
• 1 = Weed introduced (bottom).
• 2 = Weed invades all available habitat (top).
• 3 = Biocontrol agent introduced.
• 4 = Current date.
• 5 = Area currently invaded.
• 6 = Difference between actual & potential invaded area due to biological control.

Question 15

Outcomes of biocontrol during stages of an alien invasion Graph 2? (6)

Answer 15

• x-axis = Time.
• y-axis = Extent of invasion.
• Category A, B and C from bottom to top.
• Sigmoid shape.
• Tolerable threshold between Category A & B.
• Reversal threshold between Category B & C after biocontrol is initiated.

Question 16

Biocontrol of sesbania (Multiple agents) attributes? (5)

Answer 16

• Eg of what happens when you release multiple agents.
• 1st agent = sesbania flower weevil (bud feeder).
• 2nd agent = seed feeding weevil (seed feeder).
• 3rd agent - stem boring beetle (stem borer).
• All 3 agents together led to the successful biocontrol of sesbania.