Plant path lab 7

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Plant path lab 7
2015-10-12 12:42:21
Plant path lab
Plant path lab 7
Plant path lab 7
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  1. What is a pesticide?
    • any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest
    • Are a class of biocide
  2. What is the Bordeux mixture?
    • Copper sulfate + Lime
    • Broad-spectrum (biocides). Very general mode of action
    • Pathogen specific. More specific mode of action
    • Most are applied tofoliage and otherabove-ground parts ofplants
    •       – ex: fungicides to protectfrom apple scab
  3. Protectant Fungicide
    • Has localized action: effective only in the plant areaapplied, they are not absorbed or translocated by theplants (non-systemic)
    • They must be present prior to arrival of the pathogen
    • Coverage important
    • “often difficult to predict infection events”
  4. Systemic Fungicides
    • Have some mobility in the plant
    • Can have limited ability to “cure” an infection, “eradicant”
    • Move within vascular tissues
    • Coverage not as critical
    • Can be applied up to several days after an infection event,giving growers more flexibility in timing fungicide applications-Translaminar Move to other side of leaf Fungicides
    • Some fungicides have antisporulant activity– prevent formation ofspore bearingstructures
  5. Fungicide Resistance
    • Non-specific, protectant fungicides generallyhave fewer problems with resistance
    • Fungicide resistance important problem withsystemic, specific fungicides
    • Application of fungicides places strongselection pressure on pathogen population
    • Pathogen responds by evolving resistance tothe fungicide
    • Good example of evolutionary process -“evolution in action”
  6. Fungicide Resistance Management
    Any practice that reduces selection pressure onpathogen population for fungicide resistance willslow resistance evolution
  7. How do you reduce selection pressure?
    • 1) Reduced numbers of applications
    • 2) Reduced fungicide doses
    • 3) Alternating fungicides with different modes of action
    • 4) Mixtures of fungicides with different modes of action
  8. Integrated Pest/Disease Management
    use of several different disease control methods to reduce reliance on fungicides (eg. sanitation, host resistance)
  9. Benomyl mode of action
    Binds to beta-tubulin interfering withmicrotubules development- disrupt celldivision and cellular transport in plantpathogenicfungi
  10. Benomyl mechanism of resistance
    • single nucleotidechange in beta-tubulin gene results in singleamino acid change in beta-tubulin protein
    • Mutations are generally found in codons 198,199, 200, 240 of the beta-tubulin protein infield isolates of plant-pathogenic fungi
    • Botrytis cinerea - substitution of a cytosine foran adenine in codon 198 changes codon fromGAG (glutamic acid) to GCG (alanine)
    • Alanine at this position confers a highlyresistant phenotype