Lecture 2 Flashcards
How many described insect species?
1 million
How many insects are pests?
9000 insects and mites
How many different species of weeds?
8000
How many different plant pathogens?
50,000
What is a pest?
-Anthropogenic term, loose
- Insects become pests when they interact with human welfare, aesthetics or profits (physical, medical, economic)
-No particular ecological significance
What is a parasite?
- Lives on or inside another organism, the host, causing it some harm
-Reduces animal health
-Younger animals often more susceptible
What percentage of wheat is lost globally?
21.5%
What percentage of rice is lost globally?
30%
What percentage of maize is lost globally?
22.5%
Insects as pests
-Herbivores
-Transmit disease
-Allergic reactions
Why do invertebrates become pests?
-Accidental introduction to areas outside native range
-Become a vector of disease
-Move from native plants to introduced ones eg. crops
-Simplified monoculture ecosystems
-Other farming and cultivation practices
Why o invertebrates become pests in simplified monocultural ecosystems?
-Dense aggregations of food resources = proliferation of certain generalist and specialist pests
-Less natural enemies
Why do invertebrates become pests in other farming and cultivation practices?
-Continuous cultivation without fallow = build up of pests
-Prolonged insecticide use = less natural enemies, insecticide resistance
Types of pest control?
-Cultural
-Mechanical/Physical
-Biological Control
-Chemical Control
History of Pest Control
- Cultural Control (manipulation of husbandry practice- ‘pre-historic’)
- Mechanical/Physical Control (exclusion /removal /destruction - ‘Pre-historic’)
- Biological Control (deliberate manipulation of ‘natural enemies’)
- Resistant Crops (use of inherited genetic resistance)
- Chemical Control
Chemical Insecticides
-Deceloped during and after 2nd world war
-Initially effective and cheap
-Replaced traditional forms of chemical, cultural and biological control
-Insecticide “boom”
Why is an increase in pesticide use not effective?
-Despite increased insecticide use, damage by insect pests has increased dramatically
-Eg. prop crops damaged by pests doubled 7-13% from 1950 to 1985 in the US
Imbalances between pest problems and control?
-Human trade and movement of pests
-High yield varieties more susceptible to pests
-Monocultures with reduction in sanitation and rotation
-Aggressive commercial marketing
Limitations on the use of pesticides?
- Target resistance (in insects, plant pathogens and weed species)
- Target Resurgence (pest returning after beneficial natural enemies killed)
3.Residues (in food crops)
4.Induction of Secondary Pest Problems (former non-pest species that were controlled by natural enemies) - Environmental contamination (affecting wildlife and pollinators as natural enemies)
6.Chronic Occupational Exposure/ Human Health
What is Insecticide resistance?
-Selection of individuals predisposed to survive insecticide
-Cross resistance
-Multiple resistance
Why move towards less insecticide use?
-Problems with insecticide resistance
-Cost of insecticides
-Strong consumer backlash against environmental and human heath concerns (non-target organisms)
-Development of alternative controls
Integrated Pest Management
-First promoted in 1960’s following failure of insecticides in cotton
-Philosophy is to limit economic damage and simultaneously minimise
>Adverse effects on non-target organisms
>Adverse effects on consumers
>Adverse effects on environment
-Ecologically based. Combines:
>Physical control
>Cultural control
>Biological and chemical control
>Use of resistant varieties
