Pest control Flashcards
What are different types of pest control?
Chemical
Resistant crop plants (GM)
Cultural Techniques
Biological control (use of natural antagonists)
What does the german Plant protection law state?
Integrated Crop Management is part of good agricultral practice
Combining different practices with PRIORITY to biological, biotechnical, crop breeding and management practices
While pesticides have to be kept to the absolute minimum
Good agricultural practices does not affect negatively nature and is in line with nature protection
What are some sources of natural insecticides? Give some examples
Plants
- approx 2400 spcies, mainly secondary plant metabolites => ex: nicotine from nicotiana species
Microorganisms
- Toxins of the bacterium Bacillus Thuringiensis (BT)
- Toxin destroys gut wall of insects
- Different Bt species produce specific toxins, which are active only against certain insects
What are some side effects of insecticides? With examples
UNSPECIFIED MODE OF ACTION
- Killing or behavioral disorders of non-target species
- Residues in food products
- Poisoning of humans due to misuse and ignorance
Ex: DDT in the food chain => concentration higher when higher in the food chain. Affected
INSECTICIDE RESISTANCE
- Evolutionary process based on mutation and selection
- Mutations in individuals of a pest population
- Regular application of an insecticide eliminates the non-resistant individuals The resistant ones survive and reproduce
- Requires continuous development of new insecticidal agents
What is the definition of host-plant resistance/resistant crop plants in the context of pest control?
Collective heritable characteristics of a wild or cultivated plant to resist damaging insects compared to a plant of the same species w/o these characteristics
This can vary a lot between varieties
Give some characteristics of plant genetic engineering
Introduction of genes into organisms of a different species
=> leads to new heritable characteristics
Plants possessing DNA from other species are called transgenic plants
=> resistance against herbicides and/or insects
What are some important transgenic varieties of crop plants?
soybean, maize, rapeseed, cotton
What are some advantages of transgenic Bt-crops?
Systemic protection of plant in all growth stages
Control of insecticide resistant pests possible
Application of insecticides may be unnecessary
What are some problems and risks of transgenic Bt-crops?
Bt-toxins are specific to certain insects
=> not always a complete substitute of insecticides
Risk of pest resistance to transgenic plants
Potential of Bt-gene transfer to wild or cultivated plants
Toxicity to non-target species including beneficials
What are some categories of cultural techniques for pest control?
Temporal modifications:
- Crop rotation
- Planting dates
Spatial modification
- Planting density (ex in wheat, to reduce weed competition)
- Soil cultivation (tillage vs no-tillage)
What is biological pest control ?
Use of living organisms to limit the density of pest populations in order to reduce or prevent damage of crops
=> Does. not include the use of resistant plants, natural insecticides, pheromones
=> Important component of Integrated Pest Management (IPM)
Give an example of an issue with bio pest control and invasive species
Harmonia axyridis=> introduced as pest control agent
Strong impact on native ladybeetle species
however beneficial for agriculture
What are some important antagonist used in biological pest control?
Hymenoptera
=> parasitoids
Insectivorous vertebrates
=> Bats and birds
=> ex: bats and birds regulate stinkbuf population in macadamia plantation
=>ex: great Tits reduces butterfly damage in apple plantations
Are more natural enemy species more effective in controlling a pest, compared to only one species?
Not necessarily
Predation and competition among antagonists can reduce biocontrol
ex: sparrow feeding on hoverfly larvae=> reduced biocontrol of aphids
However,
Synergistic effects can enhance biocontrol ( presence of parasidoids, predators in the vegetation, predators on the ground)
=> key is FUNCTIONAL COMPLEMENTARITY
What are 3 main strategies of biological control?
Use major antagonists of pests
Augmentative biological control
Conservation biological control
What is augmentative biological control?
Augmentation of antagonist under artificial conditions and their periodical release in high numbers ( in the field or in greenhouses)
=> Released antagonist species need to have a high preference for the pest species to control
=> Timing and numbers of released individuals need to be adapted to the pest situation
What are 2 types of augmentative control?
1) Inundation
Released organisms do not establish (do not reproduce) and need to be introduced each time when needed
ex: predatory mites against spider mites
ex: bumblebees=> system for biopesticides spread in the crops , Entomo-vectoring
2) Classical: released organisms reproduce and persist permanently in the target area. Usually for control of exotic (= accidentally introduced) pests using antagonists of the region of origin
ex: california’s citrus industry nearly ruined due to infestation by cottony cushion scale (originates from Australia) => Coccinellid beetle R Cardialis was imported as antagonist and became established permanently
What is conservation Biological Control?
Conservation or enhancement of antagonists in order to increase their numbers in agroecosystems for a more effective pest control
Based on management and modifications of the habitat structures within and around the agroecosystem
=> within fields, next to the fields, landscape scale
=> Wild plants within and around the agroecosystem can serve as additional food sources or refuge habitats for antagonists. Soil cover by wild plants, undersown crops or mulch can increase density of certain antagonists
What is the push-pull system?
Pushing away the insect by introducing repellent plant inside the rows, and pulling the insects outside the field by introducing trap plants
ex: naper grass outside corn fields, desmodium between corn rows
What are some extra benefit of the push-pull system using desmodium and napier grass?
Desmodium: leguminose, enhanced soil fertility and allelopathic effects on Striga weed
Napier grass: animal fodder
=> Leads to increased yields
What are examples of conservation biological pest control at the field border level?
Field borders and flower strips
Field borders: increased beetle banks=> predators/antagonists
Flower strips=> also other ecosystem services such as predation, pollination…
- Large flower fields enhance biocontrol of aphids
