Pest control

Question 1

What are different types of pest control?

Answer 1

Chemical

Resistant crop plants (GM)

Cultural Techniques

Biological control (use of natural antagonists)

Question 2

What does the german Plant protection law state?

Answer 2

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

Question 3

What are some sources of natural insecticides? Give some examples

Answer 3

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

Question 4

What are some side effects of insecticides? With examples

Answer 4

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

Question 5

What is the definition of host-plant resistance/resistant crop plants in the context of pest control?

Answer 5

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

Question 6

Give some characteristics of plant genetic engineering

Answer 6

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

Question 7

What are some important transgenic varieties of crop plants?

Answer 7

soybean, maize, rapeseed, cotton

Question 8

What are some advantages of transgenic Bt-crops?

Answer 8

Systemic protection of plant in all growth stages

Control of insecticide resistant pests possible

Application of insecticides may be unnecessary

Question 9

What are some problems and risks of transgenic Bt-crops?

Answer 9

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

Question 10

What are some categories of cultural techniques for pest control?

Answer 10

Temporal modifications:
- Crop rotation
- Planting dates

Spatial modification
- Planting density (ex in wheat, to reduce weed competition)
- Soil cultivation (tillage vs no-tillage)

Question 11

What is biological pest control ?

Answer 11

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)

Question 12

Give an example of an issue with bio pest control and invasive species

Answer 12

Harmonia axyridis=> introduced as pest control agent

Strong impact on native ladybeetle species

however beneficial for agriculture

Question 13

What are some important antagonist used in biological pest control?

Answer 13

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

Question 14

Are more natural enemy species more effective in controlling a pest, compared to only one species?

Answer 14

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

Question 15

What are 3 main strategies of biological control?

Answer 15

Use major antagonists of pests

Augmentative biological control

Conservation biological control

Question 16

What is augmentative biological control?

Answer 16

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

Question 17

What are 2 types of augmentative control?

Answer 17

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

Question 18

What is conservation Biological Control?

Answer 18

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

Question 19

What is the push-pull system?

Answer 19

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

Question 20

What are some extra benefit of the push-pull system using desmodium and napier grass?

Answer 20

Desmodium: leguminose, enhanced soil fertility and allelopathic effects on Striga weed

Napier grass: animal fodder

=> Leads to increased yields

Question 21

What are examples of conservation biological pest control at the field border level?

Answer 21

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