Module 10 - Sustainable Insects-Human Interactions II

Question 1

The use of chemical insecticides improves global crop production and pest management, but comes with its own set of risks such as pollution and contamination, as well as the “three R’s”. What are the three R’s?

Answer 1

Resurgence, replacement, and resistance

Question 2

Biological control

Answer 2

A pest management approach where natural enemies are manipulated.
- takes advantage of natural trophic interactions; predators, parasitoids, pathogens, and even herbivores of pestiferous plants or weeds

Question 3

Cultural control

Answer 3

• Environmental factors are manipulated to reduce pest development, survival, and reproduction to restrict pest access to essential resources

Question 4

Four basic trophic levels

Answer 4

1st: Autotrophs (“producers”)
- create their own food; can obtain energy from inorganic chemicals or other energy sources

2nd: First-order consumers
- obtain energy by feeding on autotrophs
- herbivores

3rd: Second-order consumers
- obtain energy by feeding on first-order consumers
- carnivores

4th: Top predators
-feed on other carnivores

*many organisms do not fit neatly into these categories

Question 5

In most pest management situations, what is the management target?

Answer 5

Herbivores
- kept in check by natural enemies in the third trophic level

Question 6

Natural enemies

Answer 6

predators, parasitoids, parasites, and pathogens such as bacteria, viruses, and fungi

Question 7

Biological control agents; 4 types

Answer 7

When natural enemies are recruited or managed by humans in order to reduce pests populations
1. Predators
2. Parasitoids
3. Pathogens
4. Herbivorous insects

Question 8

What is the most widely used biological control agent?

Answer 8

Parasitoids

Question 9

Parasitoids

Answer 9

Insects that are parasitic as larvae, and eventually kill the arthropod host
- contrast to parasites, which don’t normally kill the hose to complete life cycle
- only larval parasitoids parasitise the host; adult parasitoids are free-living and do not feed on the host

Question 10

Where does a female parasitoid lay her eggs?

Answer 10

On or inside the body of a host, after which the larvae hatch and feed on the host’s internal organs and hemolymph- killing the host
- some postpone death of host by feeding on non-essential organs and tissues

Question 11

What makes parasitoids effective control agents in IPM systems?

Answer 11

• affect fewer non-target species than chemical insecticides
• specialized host-finding

Question 12

Downside of using parasitoids in IPM?

Answer 12

Only ovipositing female parasitoids search for hosts, and their reproductive capacity is dependant on host availability

Question 13

What order are most parasitoids in?

Answer 13

Hymenoptera and Diptera

Question 14

How can parasitoids be categorized?

Answer 14

Based on where they occur on the host during feeding stages of their life cycle. Can also be categorized by impact they have on the host.

Question 15

Endoparasitoids

Answer 15

Parasitoids that develop within the hose
- feed on tissues within host, and have specialized adaptations for living within another organissm

Question 16

Ectoparasitoids

Answer 16

Feed from outside the host and live on the host during larval development

Question 17

Koinobiont parasitoids

Answer 17

Develop while the host continues to feed and grow

Question 18

Idiobiont parasitoids

Answer 18

Paralyze and inhibit the development of their hosts
- conceal hosts in a burrow
- most are ectoparasitoids

Question 19

3 parasitism strategies that involve more than a single parasitoid larva within the host

Answer 19

1. Superparasitism
   - when a host is attached multiple times by individual parasitoids of a single species
2. Multiparasitism
   - multiple species parasitise a single host
   - interspecific competition results in only a single species completing development
3. Hyperparasitism
   - the parasitoid larvae or pupae serves as a host for another parasitoid species
   - only occurs at the fourth trophic level

Question 20

Parasitoids: Dealing with the Host’s Immune Response

Answer 20

Endoparasitoids live within host and are at the mercy of the host’s immune system = developed adaptations.

1. Host response: encasing parasitoid with hemocytes to form a cover in a process known as ENCAPSULATION
   Adaptation: hijack capsule and use as a protective shealth; form a respiratory funnel
2. Adaptation: carefully place offspring in regions with weak immune response (Ex. ganglia)
3. Adaptation: suppress host immune responses and even host beahviour

Question 21

Predators

Answer 21

Free-living organisms that feed on other animals, killing their prey more rapidly than parasitoids
- used as biological control agents
- attack and kill several animals in lifespan = great biological control agents
- feed on multiple prey species
- predators in both larval and adult stages, unlike parasitoids

Question 22

3 examples of predators

Answer 22

1. Ladybird beetle
2. Predatory mite
3. Lacewing larva

Question 23

What does the effectiveness of generalist predators depend on?

Answer 23

The population density of the pests
- most effective when pest pops are low; when high cannot keep up (in these cases specialists may be more effective)

Question 24

Pathogens

Answer 24

Include microorganisms such as bacteria, fungi, and viruses
- important natural enemies that kill arthropod pests
- bacterial pathogens commonly used in formulation of microbial insecticides for biological control; ex. Bacillus thuringiensis (Bt)

Question 25

Bacillus thuringiensis (Bt)

Answer 25

- most widely used bacterial biological control agent - multiple strains = toxic to different pests = targeted control - once ingested (to control plant-feeding insects), Bt produces crystals containing endotoxins which damage and paralyze midgut = death by starvation and infection as gut contents leak into hemocoel - applied in a variety of ways; emulsified concentrates, wettable powders, granular formulations, genes

Question 26

Fungal pathogens

Answer 26

- also used as biological control agents - they can penetrate intact insect cuticle!!! - once spores land and attach to exoskeleton, they germinate and penetrate the cuticle, infecting the hemocoel - many produce toxins that incapacitate the insect and kill them before the fungal growth does - ex. Beauveria bassiana

Question 27

Pathogens: Viruses

Answer 27

- Used as biological control agents - Infect and replicate within the cells of a living organism, and can kill them in the process; as the insect falls apart, viral particles are released onto surrounding surfaces to infect other insects - Many only attack specific insects and break down quickly in enviro = can be used effectively in IPM systems - Microbial insecticides made up of viruses, bacteria, fungi are becoming increasingly important; easy to mass produce for wide scale application

Question 28

Baculoviruses

Answer 28

A group of viruses that have been formulated to target specific insect pests

Question 29

Other Biological Control Agents: Manipulating Endosymbionts

Answer 29

- relatively novel way to manage pest pop is to manipulate the symbiotic microorganisms already carried in their bodies - community of microorganisms = microbiome; protects host against diseases, produces essential vitamins, and assists in digestion - disturb or manipulate microbiome to inflict effects on pests; decreased growth rates, diminished reproductive success, reduction in ability to transmit disease

Question 30

3 techniques used to manipulate endosymbionts

Answer 30

1. Introduction of novel microorganisms into an insect's microbiome 2. Genetic modification of the microorganisms already present within the pest species 3. Targeted elimination of microorganisms essential to the pest's survival

Question 31

Other Biological Control Agents: Herbivores

Answer 31

- Herbivores or plant pathogens can be employed as biological control agents to control weeds (aka unwanted plants that grow in comp w/ other plants and crops) - Consume different parts of weedy plants

Question 32

3 major categories of biological control

Answer 32

1. Important/Classical biological control 2. Augmentative biological control 3. Conservation biological control

Question 33

Important/Classical Biological Control

Answer 33

Involves the introduction of non-native biological control agents to control non-native pest species in its expanded range - reaches high population levels due to the absence of natural enemies in new region - goal is that they become self sustaining - preferred approach to biological control for invasive pests on non-cultivated land, but may work against pests on cultivated land as well - intended to control not eliminated invasive pest species

Question 34

Augmentative Biological Control

Answer 34

- Involves the active manipulation of populations of biological control agents to control pest species that can be either native or invasive - Not expected to become fully established in the area; requires mass production and semi-regular release - 2 methods of application: inoculative and inundative - Require commercially available control agents

Question 35

Inoculative augumentative biological control

Answer 35

- Involves the release of small numbers of natural enemies at well-timed intervals throughout the activity period of the pest species, and sometimes prior to pest activity - expected to reproduce and additional applications support population - ex. Encarsia formosa

Question 36

Inundative augmentative biological control

Answer 36

- Involve the release of large numbers of natural enemies to immediately reduce pest populations during or just prior to an outbreak - more of a corrective measure than preventative, since the goal is for the natural enemy to quickly overwhelm the pest population - control agents not expected to become established - Ex. microbial insecticides, such as Bacillus thuringiensis (Bt)

Question 37

Conservation Biological Control

Answer 37

- The manipulation of specific variables in the environment to enhance the efficiency and persistence of natural enemies already present - can either reduce factors that interfere with the success of natural enemies or by enhancing resources necessary for their survival or by enhancing certain habitat features that provide refuge and resources for natural enemies

Question 38

Banker plants

Answer 38

- Non-crop plants deliberately infested with a non-pest herbivore that acts as an alternative food supply for natural enemies in the cropping system - Support natural enemies - Can be used for conservation biological control - Can also be used to support biological control agents introduced into the system

Question 39

Advantages of Biological Control

Answer 39

1. Reduced impact biological control methods have on the environment when compared to chemical controls - definitive lifespan - activity is generally dependent on the presence of the pest 2. Addresses growing problem of pesticide resistance - biological control agents can evolve with the pests 3. Movement towards sustainability 4. Economically justifiable - increasing costs of new pesticides - stricter rules governing the use of chemical pesticides - as new tech (ex. mechanized applicators and banker plants) are developed, cost of biological control becomes more affordable - short-term costs are high, but continuous control comes at no additional cost 5. Less likely to cause damage to plants - unlike pesticides applied repeatedly to perennial crops

Question 40

Disadvantages of Biological Control

Answer 40

1. Requires more research regarding the biology and ecology of all species within the habitat = more time to develop - ensures efficiency and helps prevent possible ecological damage 2. Living organisms - require additional resources for survival - activity may be affect by environmental conditions - interact with other organisms in the environment - diet breadth can impact efficiency (may consume non-pests) 3. Natural enemies of different species can interfere with each other - compete for resources or be vulnerable to predation/parasitism 4. Agents need to be compatible with other control tactics used in the managed system 5. Effects are not as instantaneous as with chemical controls - can be problematic in the management of high-value crops, extremely damaging pests, or where ideal conditions can cause quick buildup of pest populations 6. Regulations restricting the movement of living organisms between regions - limits availability of biological control agents

Question 41

Cultural Control/Ecological Mangement

Answer 41

- Involves purposeful manipulation of the environment to reduce the number of pests present and mitigate the damage they cause - encompasses virtually all pest control methods that aren't chemical controls, and do not manipulate natural trophic interactions - need understanding of the biology, behaviour, and ecology of a pest species

Question 42

Methods used in cultural control

Answer 42

1. Reducing Favorability of the Habitat - eliminating suitable pest habitats or restricting pest access to resources, or sometimes modifying environmental conditions - removing refugia, physical barriers, tillage, removal of crop residue after harvest, destroy alternate plant hosts 2. Manipulating Timing - disrupting the chronological continuity btw pests and their hosts - ex. crop rotation; different crops planted in the same area over consecutive seasons; controls pest populations from building up that specialize on one crop - can also disrupt the temporal synchrony between pests and hosts within a single year by having a clear understanding of the PHENOLOGY of both the pest and host - understand timing of insect activity to reduce access to hosts 3. Diverting Pests - techniques that aim to divert or lure pests away from the target resource: trap cropping, intercropping, semiochemical lures - Trap cropping: planting crops adjacent to the main crop that are attractive to the target pest - Semiochemical lures: lures pests with synthetic pheromones to concentrate attack on a trap tree - Intercropping: planting of multiple types of crops in the same area to increase crop yield by making the most efficient use of resources on the land but itcan also be used to make the main crop less attractive to pests. In some cases it is purely physical in others the intercrop may be selected because it is a repellant to pests - outside of agriculture, we regularly divert pests away from animal hosts using insect repellants (ex. DEET) 4. Host Resistance - by reducing host injury to acceptable levels, other pest management techniques can be used at reduced frequencies - host resistance is manipulated through SELECTIVE BREEDING and GENETIC ENGINEERING

Question 43

How can we categorize traits of host resistance?

Answer 43

Based on the way they operate 1. Non-preference plant defence - traits that deter pests from finding or feeding on them 2. Antiobiosis - disrupt a pests metabolism after ingestion 3. Tolerance - yield maintained despite pest damage - inducing compensatory growth in the plant to the point that slightly damaged plants have greater root mass and produce higher yield than undamaged plants

Question 44

How can urban pests such as cockroaches and bedbugs be managed?

Answer 44

By removing REFUGIA available to the insects through cleaning and sealing cracks and crevices.

Question 45

Selective Breeding

Answer 45

- Involves the selection of specific parents that express beneficial traits to pass to offspring - takes several generations

Question 46

Genetic Engineering

Answer 46

- quicker and allows manipulation of targeted genes directly using molecular processes and DNA editing tools - also allows for incorporation of genes from one species to another = transgenic organisms - Bt crops produced by inserting genes from Bacillus thuringiensis into plant genomes (so they produce Bt toxin_ - RNAi (novel tech) to create transgenic crops as an alternative to Bt crops; blocks protein synthesis in the target; can silence genes used to synthesize proteins necessary for pest's survival - also can be used in the STERILE INSECT TECHNIQUE (SIT) = members of the pest species are irradiated or genetically modified to become reproductively sterile