Ent 222 Insect Population Dynamics + Sampling + Economical Injury

What factors contribute to the dynamics of insect populations?

1. Population density

2. Dispersion

3. Dispersal

4. Age structure

5. Natality

6. Mortality

What factors influence dispersal?

Flight capacity

Crowding

Nutritional status

Habitat and resource conditions

Sex of disperser

What does the age structure of most insects look like?

Most insects live less than 1 year

Their lifecycle revolves around seasons

Oviposition = favourable time

Diapause= unfavourable conditions

What are the seasonal cycles called?

Voltanism

What is an example of facultative vs obligate dipause?

F = Codling moth

O = Forest tent caterpillar

What is influences natality (birth rate)?

Fecundity = egg production

Fertility = production of viable offspring

Which is density dependent biotic or abiotic factors?

Biotic factors

What are the primary vs secondary factors for pop change?

1 = birth rate, death rate and movements

2 = weather, food, natural enemies, breeding and overwintering habitat

What does the population growth rate formula look like?

Starting pop (P0) X

Euler’s number (e) ^

% Rate of growth ( r) X Time (t)

What are insect life tables used to track?

Stage specific mortality

Which can be used to manipulate key mortality factors in pest management

What is r in life tables?

Intrinsic rate of increase

Number of daughters / number of mothers

What does the value of R tell us?

R<1 , population is decreasing

R=1 , population is stable

R>1 , population is increasing

What 4 things should insect survellience establish?

1. If the pest is present

2. Its population size

3. Its population distribution

4. Change in insect abundance

What are qualitative surveys important for?

To detect the Prescence and identity of insects; this is important for preventing the spread of new pests

Who does qualitative surveys in Canada?

Canadian Food Inspection Agency (CFIA)

What are quantitative surveys important for?

The numeric abundance of insect populations in time and space which is important to predict future population trends and asses damage potential. This is key to management decisions.

What factors should we consider in insect sampling?

Stage of insect

Visibility

Time of day

Mobility

Dispersion // location

Natural enemies

When do we use direct sampling techniques?

Best with small habitats (plants, plant part, body part)

Account for stratification of insect on plant

Can sample >1 species, natural enemies

Usually conducted on early season agronomic crops or regrowth after mowing

Sometimes plant material is collected and insects are counted later

When is direct sampling best used?

Conspicuous insects

Large insects

Slow moving insects

What is knockdown sampling?

• Plants or parts are jarred to dislodge insects

• Samples >1 species, natural enemies

• Fogging (chemical knockdown), physical jarring, heating sample in lab

What is netting sampling?

• Sweep samples are similar to knockdown technique but sample / sweep instead of / plant

• Sample >1 species, natural enemies

• Variable (sampler, habitat, weather)

Which is one of the most widely used sampling techniques? why?

Netting:

Inexpensive and widely adaptable

What does placement of traps require?

Knowledge of insect biology and habitat

What are the three kinds of trapping?

1. Aerial

2. Ground

3. Aquatic

What are the basic requirements for insect trapping?

Insects must be mobile and come to trap

Traps must hold captured insects

Requires >1 trip to field site

Traps must be visited regularly

What are active vs passive traps used for?

Attractive = pest management

Passive = research

What are aerial traps? Examples?

Attractive traps that use vision and olfactory cues

EG: Apple maggot traps, funnel traps, blacklight, pheromone traps

What are some examples of passive insect traps?

• Malaise trap = open tent intercepts flying insects

• Window traps = insects fly into a plane and are captured in trough

• Sticky traps = clear

What is an example of a ground trap for insects?

Pitfall traps; passive or attractive; capture ground moving insects; juveniles and adults. Can get water logged

How do we collect insects in soil samples?

Soil samples through soil corer, golf-hole borer, bulb cutters, shovels and frameswh

→ insects extracted

Mobile insect extraction: berlese funnel, variably efficient insect size, soil type

Immobile insect extraction: dry/wet sieving, floatation

What are the advantages of indirect sampling techniques vs disadvantages?

Advantages:

• Less sensitive to apparent population fluctuations due to insect behaviour

• Indirect measure of insect density but direct measure of insect caused damage

Disadvantages:

• Requires additional information to correlate measurement

What is sequential sampling?

An efficient Integrated Pest Management (IPM) technique that uses a flexible, cumulative sample size to classify pest populations (e.g., above or below an action threshold) rather than relying on fixed sample sizes. By sampling sequentially and stopping once a decision is reached, this method can reduce sampling time and effort by 47–63% compared to fixed-sample methods

What are pests in managed ecosystems?

Insects that cause damage to a crop or resourc that is sufficient to reduce the yield or quality of the ecosystem by an unacceptable amount

What are the common features of insect pests?

Major competitor with humans

Abundant

High reproduction rate

High survival rate

T/F Insects have to be abundant to cause problems?

False pests can cause damage at any level;

For example there are plants that have low insect tolerance, insects that cause esthetic damage and quarantine pests

What are the kinds of insect pests?

• Vectors of animal and plant disease

• Nuisance pests

• Entomophobia

• Household / structural pests

• Plant pests: agriculture, horticulture, rangeland and forest

What are the traits of serious pests?

• Adaptable to new hosts

• Accidental introduction to new areas

• Often introduced with unusual weather conditions

What does pest resurgence look like?

When pesticides indirectly benefits pests by knocking out natural enemies; pesticides indirectly hurts predator by knocking out pest and if there is no natural predator to keep pest in check = resurgence

What does pest resurgance look like?

When we use pesticides on one pest and these pesticides have indirect effects on other predators in the ecosystem which releases a different pest from predator control = outbreak of a secondary pest

What is pest status dependant on?

• Market value

• Susceptibility of crop to pest injury

• Weather practices, moisture level

• Cultural practices; fertilization, irrigation

• Human social environment

What is economic injury level?

The lowest # of insects that will cause economic damage, or the minimum number of insects that would reduce yield equal to the gain threshold

What is gain threshold?

The money required to suppress injury = potential loss $ from pest population

What is the economic // action threshold

Most widely used index for IPM decisions

ET set below EIL so action is taken before damage is accrued

Complex value integrates EIL and population dynamics of the pest

What are the three kinds of pests in the economic injury level concept?

1. Non economic pests

2. Ocasional pests

3. Severe pests

What are the limitations of EIL?

• When human attitudes demand near perfection, the EIL is so low that it is of little use in the decision making process

• Limited value when dealing with transmitters of pathogens and pests that cause aesthetic damage

When does EIL work well?

Agricultural commodities where crop yield is the key goal