Exam 3 Entomology

Bugs are pretty cool I guess

What is the idea behind the insect apocolypse?

citizens are observing trends that there are less insects than in the past.

what is the difference between decrease in biodiversity vs biomass

biodiversity is lost is the amount of different kinds of insects.

biomass loss is the loss of the amount of insects

Name some of the anecdotal observations of the insect apocolypse

1. windshield effect (less bugs on windshield)

2. fireflies less present

3. Less bugs by porchlight

4. eat less bugs while biking

How do we actually assess if the insect apocolypse is real?

use historical data from entomological museums and citizen science programs.

What are the two ways insects deal with adverse situations?

• wait it out

• escape

quiescence

period of delayed development or dormancy in direct response to adverse conditions; development resumes once favorable conditions return

diapause

period of delayed development or dormancy in response to recurring periods of adverse conditons: development resumes in response to a secondary stimuli like daylength

dispersal/migration

tracking suitable environments/resources across space

dispersal is broadly defined as

movement of an individual or population away from its birth site.

migration is broadly defined as

directional movement to more appropriate conditions, usually much farther than dispersal

why is temperature one of the most important stressors to insects?

because insects are poikilothermic and ectothermic

what is poikilothermic?

body temperature varies with ambient temperature

what is ectothermic?

temperature drives the rate of growth and development

What happens if you increase the temperature when an insect is already at it’s optimum temperature for growth?

the growth will steeply drop off because the temperature is hot enough that you are denaturing enzymes that are needed for growth.

what do we predict will happen to insects as temperatures increase?

• faster/more generations per year

• higher survival rate/escape from enemies

• lower survival for those already starting at the temp maximum

• range expansion

What do we suspect will happen to insects with milder winters?

• higher survivorship of diapausing insects

• less snow cover which may freeze insects in the ground

• diapause timing will mismatch with host plants

• range expansion

what kind of experiment do we use to monitor the effects of CO2

FACE

free air carbon dioxide enrichment

Insects are not directly effected by CO2 but how does it effect them vicariously

• Increase in photosynthetic carbon fixation for plants which means more biomass for insects to eat

• faster plant growth

• lower percentage of nitrogen in the leaves when they eat it because it has been diluted down.

• increase in carbon based insect defenses like tannins

what happens when insects feed on lower quality food? and what is this called?

they need to consume more of it to the same threshold.

compensatory feeding

how does low quality food effect their suspeptiability to predators?

they are spending more time in the larvae stage so they are more vulnerable and they are more focused on eating.

how do insects sense humidity

they have sensilla for that

does water availability have a direct or indirect effect on insects

direct effect

Plants also need water so water loss in that sense has an indirect effect on insects. what are some ways this happens

• plant growth rate decreases

• plants have a higher amount of free amino acids (nitrogen) in the plant

• increase in plant chemical defenses (toxins)

• physical defenses such as resin decrease

what hormones does drought effect?

ABA which interacts with JA and SA which are all used in plant defenses. ABA is highly activated with drought response, so plant defenses go up.

what is the definition of a pest to humans?

an organism that reduces the quality/quantity/value/availability of some human resource

when was the first agriculture setting?

in about 8000 BCE Sumner had agriculture instead of traveling to follow plants.

What are some key aspects of the era of traditional approaches to pest managment?

• goal was to manage not eliminate insects

• used a diversity of approaches

• based on knowledge of insect ecology and biology

What are the different types of control?

1. chemical control (difficult and dangerous, can be plant derived)

2. physical control (stomping, burning)

3. biological control (ants in crops)

4. cultural control (harvesting dates)

5. varietal control (selecting for resistant plants)

What are some key aspects of the era of pesticides

• was initialized by DDT

• the nexus of the problem was that pest managment shifted from an ecological problem to a chemical problem

• the focus was eradication rather than management

What are the 4 reasons the era of pesticides had problems

• evolution of resistance

• pest resurgence due to lack of predators

• secondary pest outbreak because ecosystem has shifted

• publishing of silent spring

within 20 years of DDT how many species were resistant?

224

What did the publication of silent spring show?

that not much of the chemical was reaching its target. that it was persistant in the environment, and that it is biologically persiant and causes endocrine disruption

why was the EPA created

in response to the DDT issue and the Ohio river fire

What was the federal IPM thrust

by Nixon, it suggested careful use of selective chemicals in combination with non-chemical agents and methods

What did president carter do for IPM

focused this issue as an ecosystem approach to manage pests rather than eradication.

What is IPM

a pest managment strategy that integrates the use of multiple tactics for optimizing control of insects in an economically and ecological manner

what is the keystone for IPM

economics

what is DDT

an organochloride

Injury

what the insect does to the plant

damage

how the plant responds to the injury usually in a measurable loss of utility to the grower

Not all injury causes _________

damage

Not all damage causes ________

economic loss

economic damage

when the value of yield lost is greater than the cost of management

economic injury level (EIL)

minimum number of insects that will cause economic damage

Economic threshold

pest density at which managment action is taken to prevent an increasing pest population from reaching the EIL

what are the two broad categories of insecticides

natural- produced or refined natural substances

synthetic- synthesized by chemically joining compounds

what is the warning label order from least dangerous to most

caution → warning → danger

what do we use to estimate acute toxicity to humans

LD50 (lethal dose that kills 50% of the population)

a higher LD50 means

the substance is less toxic because it takes a higher dose to kill you

What are some natural product insecticides

Soaps (from refined plant oil or animal fat removes protective wax coatings on insects and dries them out)

Mineral Oil (refined petroleum oil that suffocates insects)

Botanical Compounds (neem oil, plant derived, many types and effects)

DDT

is an organochlorine

• broad spectrum

• highly toxic to insects

• Mode of Action= neurotoxin

Concerns of DDT

• Danger warning label

• hydrophobic so persistent in the environment

• chronic effects on vertabrates

Organophosphates

• Broad spectrum

• less persistant than DDT

• AI = Neurotoxin

Problem with organophosphates

they are more toxic to mammals than organochlorides (warning label)

Carbamates

• broad spectrum

• low persistence in the environment

• neurotoxin

problems with carbamates

• toxicity to pollinators and parasitoids

• caution

allelochemical

a compound used to defend themselves against herbivores

Pyrethrum

• most widely used botanical pesticide

• low environmental persistence and toxicity to mammals

• Neurotoxin

• requires a synergist to be prevent the insects from detoxifying it

Pyrethroids

synthetic analog of pyrethrum

• more stable than pyrethrum

• higher toxicity

• very toxic to fish and non-target invertabrates

What three things can you do to reduce selective pressure to insecticides?

1. avoid prolonged exposure to a single insecticide

2. raise economic thresholds

3. use insecticides with different modes of action

Nicotine is a _________

botanical insecticide

what is dangerous about nicotine as an insecticide?

• highly toxic through all exposure

• mimics acetylcholine and keeps neurons firing which causes paralysis, tremors, paralysis, and death.

What is the most widely used insecticide in the world?

Neonicotinoids

What are neonicotinoids?

they are a synthetic version of nicotine that blocks insect nerves but not mammals

What are three benefits of neonicotinoids

1. low toxicity to vertabrates with a high toxicity to insects

2. Flexible Use (powder, liquid, etc)

3. Systemic activity vs contact, the plant becomes toxic

What is a problem with neonicotinoids?

• they are bad at killing mites so mite secondary outbreaks are common

• can have off-target effect on pollinators due to plant droplets, necter, dust, water

What are some restrictions to help reduce off target effects of neonicotinoids?

• don’t spray on flowering plants

• do it after sunset

• inform local bee keepers

Does pesticide lead to mutation?

no but it selects for it

what are three things that promote resistance?

1. prolonged exposure to a single pesticide

2. low economic threshold (so applying often)

3. using only one mode of action

biological control def

purposeful manipulation of natural enemies to obtain reduction in pest status

Predator def

• free living organism that feeds on prey

• often eats many types

• some are predatory only in one lifestage

Parasitoid def

• live and feed on or in a host

• often more specialized for a species lifestage

• individual parasite only kills one or less insects

• Most are from hymoptera

pathogens def

bacteria or virus or fungus or nematode

• BT uses soil pathogen

• Nematodes enter and use bacteria to disolve the host