Agriculture Flashcards
Economic injury level
The smallest number of insects (amount of injury) that will cause yield losses equal to the insect management costs (i.e., if you didn’t spray because you wanted to save $50, you’re going to end up losing $50, if not more, due to damage).
Economic threshold aka action threshold
Pest population size at which management will provide an economic return
Economic damage
the amount of injury which will justify the cost of artificial control measures
Damage boundary aka damage threshold
lowest level of injury that can be measured
Nominal threshhold
Subjective threshold established by practitioners based on experience
Cultural control
Strategy relying on manipulating the environment to reduce pest and disease incidence
Categories of genetic resistance to pests in plants
1) Induced resistance: traits that are triggered by environmental factors and lower pest fitness;
2) Constitutive resistance: traits whose expression is not triggered by environmental factors
Types of host plant resistance agains pests/pathogens
1) Antixenosis: disrupts behavior (e.g., less attractive to pest)
2) Antibiosis: disrupts physiology and increases mortality
3) Tolerance: withstanding capabilities
Genetic directions of genetic resistance
Vertical (oligogenic): controlled by one gene
Horizontal (polygenic): controlled by multiple genes
Intercropping
Growing two or more crops in close proximity to promote synergistic interactions
Crop rotation
Growing different crops in succession; increases soil fertility and reduces disease and pest incidence; for some diseases rotation has to be extended for several seasons
Push-pull strategy
Making the protected crop unattractive (push pest away) and pull them into an attractive crop where the pest is killed
e.g., trap crops
Classical biological control
Introduction of an exotic NE aiming for permanent establishment
Responsive insecticide applications
Need-based; EIL should be considered
Broad spectrum insecticides
Toxic to a variety of insects
Selective insecticides
Insecticides that minimize effects on non-target organisms
Biopesticides
Pesticides developed from other plants or animals; less toxic
Mechanisms of insecticide resistance by pests
Metabolic resistance; Altered-target resistance; Behavioural resistance; Penetration resistance; Cross resistance (resistance to A confers resistane to B)
Metabolic resistance to insecticide (mechanisms)
1) Recognition and hydrolysis;
2) Conversion into non-toxic
3) Excretion
Altered target site resistance to insecticides
Binding site of insecticide is molecularly modified
Behavioral resistance to insecticide
Pest switches feeding are (e.g., underside of leaf without insecticide on it)
Penetration resistance to insecticides
Outer cuticle develops barriers
Strategies to manage insecticide resistance by pests
1) Reduce use (rely on other strategies)
2) Mixing insecticides with different modes of action (can backfire into multiple resistance)
3) Short-persistence insecticides (reduce selective pressure)
4) Insecticide rotation (reduce selective pressure)
Semiochemicals aka infochemicals
Chemicals that mediate relationships between two organisms
Behavioural control of pests
Manipulate the behavior of the pest (e.g., pheromone trapping and mating disruption);
Herbivore-induced plant volatiles
Integrated pest management
Approach to pest management that relies on a combination of practices (includes cultural, chemical, biological, and resistance control strategies + pest monitoring)
Plant disease triangle
host, pathogen, environment
Pulses
Annual crops harvested solely as dry grains;
peas, beans, and lentils
Annual crop
Crops that grow and die in a year; must be replanted each season
Perennial
Crops that do not die at the end of the growing season; harvested annually without replanting
Clubroot
Disease of crucifers caused by the protist Plasmodiophora brassicae; Causes malformation and stunted growth; gets transmited through contaminated soil
Blackleg
Fungal pathogen of canola caused by Leptosphaeria maculans; Causes stem thinning, leaf and ste lesions
Sclerotinia
Fungal pathogen of canola that produces brown, watery lesions and bleached stems
Crop diversification
Growing a larger variety of crops; reduces suceptibility to pests and disease; avoid reliance on just a few crops
Principles of integrated disease management
Exclusion (quarantines, certifications, sterilization);
Eradication (destruction of indected plants);
Protection (prevent a disease from becoming worse);
Resistance (resitant crops)
Crop certification
Seeds are screened for pathogens and only those that meet the standard are marketed
Agricultural Pest Act
Legislation resonsile for establishing pest control measures in Alberta; Enforced y agricultural fieldmen
Alberta Agriculture and Forestry
Legislation that provides education and training
Agricultural Service Board
Committees addressing agriculture concerns in local jurisdictions
Fusarium head blight
Important fungal pathogen of grasses (cereals)
Biosecurity
Procedures designed to minimize spread of infection and pests
Canadian Food Inspection Agency (CFIA)
Responsible for controlling the safety and food (including crops and livestock) in Canada
Tillage
Field preparation involving plowing of discarded crop materials into the soil; can increase soil erosion;
Clean tillage: tillage performed many times
Conservative tillage: Incorporates only a portion of plant material to the soil
Zero Tillage
Allowing stubble to remain in the field; increases moisture and soil organic matter
Seed treatment
Seeds are coated with chemical or biological pesticides
Crop residue burning
Effective for disease control, but material is lsot to admosphere; causes air pollution
Liming
Decreasing soil pH to hinder pathogen development
Biological control (broad definition)
Supresson of pest organisms with another organism
Chemical control (broad definition)
Use of chemical compounds that are toxic to a pest
Correct dose
Adhering to manufacturer guidelines when using a pesticide; Aims to reduce pesticide resistance
Induced systemic resistance
Resistance mechanism in plants activated by a pest or pathogen, resulting in an increase in defensive mechanisms
Pestice clasifications based on mobility
1) Contact (remains on plant surface)
2) Sytemic (absorbed into the plant)
3) Trans-lainar (spreads across leaf surface to the other side, but not through vascular tissue)
Yield potential
Maximum amount of yield from a crop under ideal conditions
Check strip
Section of a crop that does not receive a pest or disease treatment; used to compare treated vs untreated
Pest
Unwanted organism that directly or indirectly interferes with human activities.
Types of effects of a pest on a crop
1) Direct (immediate effect such as damage)
2) Indirect (e.g., pest transmitting a pathogen)
Outbreak
Sudden rise in a pest’s population; often exceeds carrying capacity
Monoculture
Large fields planted with a single crop; increases potential for outbreaks
Intensified farming practices (concept)
Practices that increase the poential for pest outbreaks
Top factors causing pest outbreaks
Monocultures,
Highly fertilized crops,
Reduction of naturel enemies,
Agriculture intensification,
Globalization,
Weather conditions,
Crop breeding for yield
Breeding for yield
Breeding plants in order to maximize yield can result in loss of traits providing pest resistance (e.g., loss of trichome hairs)
Planting date and pest management
Practice that aims to disconnect a crop species’ most vulnerable stage from pest emergence (e.g., planting canola late for flea beetles)
Plant density and pest management
This practice can redue pest impact (e.g., tinner stems less likely ot be oviposited on by root maggots; also lower individual/plant ratio)
Host plant resistance (broad definition)
The ability of plants to prevent herbivory via chemical or mechanical defenses; may be accompanied by a decrease in yield
Classes of biological control agents
Predator, parasitoid, pathogen
Types of biocontrol
1) Classical (release and establishment of an exotic species)
2) Augmentation (increase numbers of an existing NE)
3) Innoculation (NE is expected to establish but not permanently)
4) Inundation (mass rlease of a temporary NE)
5) Conservation (protetion and maintenance of NE populations)
Enemy release hypothesis
Hypothesis suggesting that exotic pests are successful due to a lack of NE
Necessary characteristics of IPM
Effective, economical, simple, flexible
Adaptive potential
A measure of the genetic variance needed by a pest to respond to selective pressures; Insects have a high adaptive potential.
Host switching
Pathogen, pest, or parasite changing its host organism
Host range expansion
Pathogen, pest, or parasite adds a new host
Isothyocyanates
Molecules produced by crucifers that attract parasitoids
Insecticide
Natural or synthetic chemical used to kill insects
Insecticide entry categories
1) Contact: Enter insect when it walks over treated surface
2) Systemic: Insecticide is translocated within plant end enters insect via gut
3) Ingestion: Through gut but not necessarilly systemic (e.g., boric acid pelets)
4) Inhalation: Enter insect through tracheal system
Examples of cultural controls for insect pests
Crop rotation, tillage practices, planting date, planting density, intercropping, trap cropping
Insecticide Resistance Action Committee
Organization aiming to increase isnecticide effectiveness by managing strategies
Insecticide mode of action (concept)
The physiological pathway through which it affects an insect
Three common synthetic insecticides in the prairies
1) Organochlorines: Open Na+ channels in nerves
2) Organophosphates: Inhibit acetylcholinesterase in nerve synapse
3) Neonicotinoids: Block nicotinic acetylcholine receptors
4) Pyrethroids: Prevent Na+ channel closure in neurons
Who regulates insecticides in Canada?
Health Canada, via the Pest Management Regulatory Agency (PMRA)
Insecticide resistance definition
reduction in the sensitivity of a population to an insecticide
Multiple toxin approach to insecticides
The use of more than one toxin in tandem makes it harder for a pest to develop resistance
Four management strategies to reduce insecticide resistance
1) High dose strategy: LC99 Lethal concentration that kills 99% of population
2) Refugia concept: allowing the non-resistant pest to survive to dilute resistant genomes
3) Avoid repeated use
4) Use in full recommended doses
Land sparing
Intensifying agriculture with the objective of leaving natural areas for conservation
Land sharing
Relax agricultural practices to be more environmentally-friendly at the potential expense of lower yield and less natural area
Matrix
The spatial and qualitative characteristics of agricultural landscapes
Wildlife-friendly agriculture
Agricultural practices that support biodiverse and heterogeneous agricultural systems
Winners/Losers
Winners are species that benefit from agriculture; Losers are species that decline in relation to agriculture
Jevon’s paradox
The original objective of intensifying agriculture to spare natural habitats encourages further expansion due to high revenue
FAO
Food and Agriculture Organization of the United Nations
Staple crops
Crops that represent a highly important diet component of the human population
Cash crops
Crops with high economic return independent of its usefulness to basic human needs
Land grabs
Land acquisition by transnational corporations or other countries
Sustainable intensification
The goal of increasing yield outputs while at the same time improving environmental and social conditions
