12. Control methods for pests and diseases

Question 1

What structure in bacteria do most antibiotics target?

Answer 1

Bacterial ribosome - where proteins get manufactured

Question 2

What key properties make a pesticide/drug?

Answer 2

• must be toxic to the pest/parasite
• must be harmless to us
• targets some metabolic difference - need to find difference bw parasite and us

Question 3

What knowledge of the parasites do we need to design a pesticide?

Answer 3

• lifecycle
• weak points
• are there predators?
• are there parasites?

Question 4

What 2 hormones are involved in insect molting?

Answer 4

JH: Juvenile hormone

MH: Molting hormone

Question 5

Moulting hormone

Answer 5

• constant at each moult
• induces growth of new cuticle
• begins molting process
 - partial absorption of old cuticle
- inflation of body to crack cuticle

Question 6

Juvenile Hormone

Answer 6

•reduces with each moult
• determines form of next stage
- zero JH produces adult

Question 7

Methods used for biological control (other than predatos)

Answer 7

•drain pools and swamps - for mosquito larvae
• monolayer dispersants on water surface
• traps baited with food smell (Tsetse fly)
• traps/tubes with female pheromone
(Cabbage moths)

Question 8

What are desirable features of predators?

Answer 8

• fairly specific as to the prey it eats
• same habitats as pest
• rapid rate of increase
• disperse easily
• population size not kept low by environment
• survives when pest is at low levels
• easily cultured

Question 9

What are wolbachia?

Answer 9

bacteria that live inside insect cells

Question 10

How does wolbachia spread into insect populations?

Answer 10

• get into immature spermatids and eggs of the insects
• if sperm from infected insects fertilises uninfected eggs the offspring die but infected eggs produce offspring
• this means by adding enough infected, can take over the population

Question 11

Best way to reduce the number of pests?

Answer 11

• impose a genetic load

* spread the genetic load through the population

Question 12

Improved methods of spreading a genetic load?

Answer 12

• recombinant DNA technology
• delayed sterility
• conditional lethal genes (activated by certain conditions ie cold weather)
• more sexually active males
• meiotic drive
• introduce an incompatible competing strain

Question 13

How do you reduce a pest by introducing an incompatible competing strain?

Answer 13

• A strain that produces dead offspring if it reproduces with wild types
• but it can reproduce with itself, and you can select the alleles it has
• using Wolbachia or compound chromosomes