W13: Biocontrol (Constraints To Classical Biocontrol) [Dr. Nic]

Question 1

Constraints to Classical biological control? (7) BDP(^2)ICH

Answer 1

• Biocontrol agent taxonomy.
• Dispersal limited.
• Predation.
• Parasitism.
• Interference from native species.
• Climate incompatibility.
• Host-plant incompatibility.

Question 2

Biocontrol agent taxonomy?

Answer 2

= deals with the taxonomic issues in the identification of weed biocontrol agents.

Question 3

Biocontrol agent taxonomy attributes? (3)

Answer 3

• Taxonomic issues of biological agents can significantly affect the success of biological control programmes.
• Misidentification of species/incorrect classification leads to many issues.
• Important to correctly identify species of biological agents.

Question 4

Issues that the misidentification of species/incorrect classification can lead to? (3)

Answer 4

• Ineffective control.
• Unintended consequences of non-target species.
• Failure of the biocontrol initiative.

Question 5

Egs of Biocontrol agent taxonomy? (2)

Answer 5

• Diorhabda species on invasive Tamarisk species.
• Water hyacinth mirid bug biocontrol agent on water hyacinth.

Question 6

Dispersal limited?

Answer 6

= when the biological control agent is restricted in its movement/dispersion.

Question 7

Why is a biological control agent dispersal limited? (4)

Answer 7

• Limited flying ability.
• Sedentary life stages.
• Host plant dependence.
• Incompatible habitats.

Question 8

Eg of Dispersal limited?

Answer 8

Acacia cyclops & the seed-feeding weevils.

Question 9

Predation?

Answer 9

= refers to the biological control agent being preyed upon.

Question 10

Eg of Predation?

Answer 10

Bugweed lace bug agent on bugweed are preyed upon by generalist insects like mirids.

Question 11

Eg of Parasitism?

Answer 11

Water hyacinth planthopper on water hyacinth.

Question 12

Interference from native species?

Answer 12

= when native predators/parasitoids in the introduced environment may attack the biological agent, reducing its population & effectiveness.

Question 13

Eg of Interference from native species?

Answer 13

Ant predation of Cactoblastis eggs in South Africa.

Question 14

Climate incompatibility?

Answer 14

= when the climate envelope/”niche” of the biological control agent and host plant don’t complement each other, reducing the agent’s effectiveness.

Question 15

Eg of Climate incompatibility?

Answer 15

Bugweeds & weevils, with weevils having a lower thermal range than bugweeds.

Question 16

Host-plant incompatibility?

Answer 16

= the inability of a biological control agent to effectively use a target pest because the pest’s host plant does not support the agent’s life cycle or development.

Question 17

Possible reasons for Host-plant incompatibility? (3)

Answer 17

• Genetic variation in the weed population.
• Different biotypes/strains of weed species.
• Agent specialisation to specific weeds.

Question 18

Eg of Host-plant incompatibility?

Answer 18

“Tree of heaven”.

Question 19

“Tree of heaven”?

Answer 19

Genetically matching mites with the “Tree of heaven” to selectively collect the best agent for your target.