Lecture 5 Part 1 Flashcards
End-use products contain one or several ____ and _____
Active ingredients and formulants
What is an active ingredient?
Substances or micro-organisms, including viruses, having general or specific action against harmful organisms on plants, parts of plants or plant products, and constituting a product to which is linked the pesticide’s effect.
What is a formulant?
Any substance or group of substances other than the active ingredient that is intentionally added to a pest control product to improve its characteristics
Pesticides are classified by their target organism, give two examples
- Herbicide for plants
- Fungicides for fungi
Plant protection product: products consisting of or containing active substances, safeners or synergists, and intended for one of the following uses: (5)
- Protecting plants or plant products against all harmful organisms
- Influencing the life processes of plants
- Preserving plant products
- Destroying undesired plants or parts of plants
- Checking or preventing undesired growth of plants
Broadly what are the three main reasons why fungicides are used?
- To control a disease during the establishment and development of a crop.
- To increase productivity of a crop and to reduce blemishes.
- To improve the storage life and quality of harvested plants and produce.
What is principle 5 of IPM
Principle 5 is to target-specificity and minimization of side effects of pesticides
What are the three main selection criteria for PPP’s
- Human helath
- The environment
- The Efficacy
In terms of efficacy as a consideration for selection of pesticide criteria what three main things do we need to take into account?
- MoA (Mode of action) Spectrum and risk of resistance
- PhMoA/PMoA (Physical mode of action) activity and use of pesticide
- Risk of resistance (Principle 7)
What do we consider in regard to the MoA?
Site and mechanism of action: cellular components subject to the fungicide action (target sites) and mechanisms that made the fungicide effective.
What are three types of MoA fungicides?
- Multi-site fungicides (have more sites and modes of action)
- Site-Specific fungicides (have only one site and one mode of action)
- Spectrum fungicides (range of fungi hit by the fungicide; could be broad spectrum fungicides or specific fungicides)
What does PMoA describe?
the effect of a fungicide with respect to the time of its placement in relation to the host-pathogen interaction.
What are the three main things that PMoA considers?
- Fungicide activity
- Fungicide localization with respect to the plant
- Duration and degree of the fungicide activity
what are the four activities in which fungicide activity considers?
- Pre-infection activity (preventative)
- Post-infection (curative)
- Pre-symptom
- Post-symptom (eradicant)
What are the two groups that fungicides can be broken up into?
- Protectant (non-penetrative)
- Systemic (Penetrative)
Penetrant fungicides are systemic to different degrees, what are they (4)
- Locally systemic
- Fully systemic
- Xylem systemicity
- Phloem systemicity
Five main attributes of contact fungicides
- Not Absorbed
- Not-mobile
- Preventative
- Multi-site of action
- No or few resistance
Five main attributes of penetrative fungicides
- Absorbed
- Mobile
- Preventative + curative
- Often single site of action
- Fungi can develop resistance
After a fungicide is applied, fungicide residues progressively decrease over time due to: (5)
- Weathering
- Chemical deterioration
- Microbial activities on plant surface
- Redistribution over the plant
- Fungicide dilution by plant growth
Discuss decay kinetics
A constant decay is very rare, they are usually exponential
7 Fates of the fungicide after treatment
- Adhesion of the droplets
- Drying out
- Redistribution on the surface with leaf wetness
- Redistribution in the vapor phase
- Redistribution with rains and wash-off by rains
- Uptake by the plant
- Endophytic movement and dilution
6,7 are for penetrative
Rainfastness:
The time required between application on the plant surface and rain for the product to be effective in controlling the target organism.
Fungicide tenacity
Is the ability of the fungicide to resist to rainfall wash-off.
Attenuation factor
Disappearance of canopy applied fungicides from plant tissue
What do we know about the attenuation factor when graphed and measured
- Fungicide residue disappears much more quickly post-infection rather than pre-infection
Wash-off by rainfall
In case of rainfall, the fungicide residue on the plant surface is reduced based on the precipitation amount
What is principle 7 of IPM
Application of anti-resistance strategies
How do we get resistance
The extensive use of pesticides has often resulted in the development and evolution of pesticide resistance in insect pests, plant pathogens, and weeds.
Define fungicide resistance
Stable, inheritable adjustment by a pathogen to a fungicide, resulting in reduced sensitivity of the pathogen to fungicide
First of five origins and development of fungicide resistance
- Resistant fungal strains are already present in the pathogen population, caused by naturally-occurring genetic variability and mutations
Second of five origins and development of fungicide resistance
Fungicide applications select for these resistant pathogen biotypes: fungicides kill the fungicide-sensitive population and only resistant biotypes survive
Third of five origins and development of fungicide resistance
Repeated use of the particular fungicide exerts selection pressure in the fungal population
Fourth of five origins and development of fungicide resistance
As a consequence, the population of resistant pathogen biotypes increases and replaces the sensitive population
Fifth of five origins and development of fungicide resistance
Further applications of the fungicide fail in disease control
What are the two types of resistance build-ups
- Qualitative
- Quantitative
What is qualitative resistance build-up? (3)
- Fast occurrence
- Associated with site-specific fungicides
- Complete loss of disease control
What is quantitative build-up? (3)
- Develops over time
- Associated with multi-site fungicides
- Varying degree of disease control
A fungicide has a specific target site where it acts to disrupt a particular biochemical process or function. If this target site is somewhat altered, the fungicide no longer binds to the site of action and is unable to exert its toxic effect.
This is the most common mechanism that fungi use to become resistant.
Mutated target site
Overexpression
Overexpression of the target site (e.g. a protein) increases the concentration of fungicide necessary for inhibition.
5 Fungicide resistance mechanisms
- Mutated target site
- Overexpression
- Removal
- Detoxification or metabolism
- Reduced uptake
A fungal cell may rapidly export the
fungicide before it can reach the target site of action.
Removal
Metabolism within the fungal cell is one
mechanism a disease pathogen uses to detoxify a foreign compound such as a fungicide. A fungus with the ability to quickly degrade a fungicide can potentially inactivate it before it can reach its site of action.
Detoxification or metabolism
The resistant pathogen simply absorbs the fungicide much more slowly than the susceptible type.
Reduced uptake
What is the Combined risk of fungicide resistance pyramid made up of (4)
- Fungicide risk
- Pathogen risk
- Agronomic risk
- Overall resistance risk
Pathogen population that is resistant to one fungicide within a group develops resistance over other members of the same group
Cross resistance
Pathogen population shows resistance to fungicides from more than one chemical group
Multiple resistance
