L34

Question 1

reasons for biocontrol

Answer 1

• reduce the pop. of organisms or their propagules naturally or through manipulation of biotic and/or abiotic factors e.g. rabbit pop.
• expansion of agricultural product while containing cost
• avoids selection of pesticide resistant pathogens
• pollution free control

Question 2

2 main philosophies of biocontrol

Answer 2

• conservation biocontrol
  
  • modification of the environment or existing practices to protect + ehance (biostimulation) specific enemies or other organisms to reduce the effects of pests
• augmentation bicontrol
  
  • release of an organism as an agent with the expectations that it control the pest either directly or after multiplication- inoculation and inundation

Question 3

procedure for biocontrol

Answer 3

1. control pathogen starting unit no.s
   
   • prevention of inoculum formation- destruction of pathogens + manipulation of properties of the pathogen
2. utilise friendly microbes to protect against infection
   
   • protection of planting material/food items (e.g. inoculate with antagonists: antiobioric producers)
   • protection of wounded tissue: pre-emptive colonisation by weak pathogens/saprophytes
3. increase host resistance
   -mild strains of pathogens may be used (immunisation with attenuated strains, e.g. smallpox eradication in china)
   
   • phytoalexin (low weight antimicrobial compounds synthesised by + accumulated in plants after exposure to microbes) in plants- production is induced by organisms closely related to pathogens + may protect plants from pathogen
   • mycorrhizal colonisation of plants often confers protection against pathogens: mycorrhiza may trigger production by plant of antifungal substances
4. integrated approach
   
   • combination of chemical + biological methods
     -e.g. armillaria pathogen: removal of ifnected roots or fumigration of soil with carbon disulphide to control armillaria (fungal ifnecting plant roots) then add trichoderma (which attacks + parasitizes + otherwise gain nutrition from other fungi, evolved from numerous mechanisms for both attack of other fungi and for enhancing plant + root growth)

Question 4

explain probiotics

Answer 4

• live microbial preparations which mediate beneficial effects for the host
  e.g. primary cause of travellers diarrhoea is enterotoxigenic e.coli, treatment with antibiotics destroys most gut flora leading to further diarrhoea, its then reduced by dosing patient with a mix of antibiotics
  -e.g. lactobacillus acideophilus species to inhibt intestinal + vaginal bacterial + yeast infection production of lactic acid + other antimicrobials
• probiotics outcompete pathogens during formation of biofilm

Question 5

use microbes to protect against infection