Quizlet 2 — Metamorphosis, Economic Injury Levels & Pest Sampling

What is metamorphosis?

Development of an insect from egg to adult involving changes in form.

What are the four metamorphosis types taught in AGRO 331?

Holometabolous; paurometabolous; hemimetabolous; ametabolous.

What is holometabolous metamorphosis?

Complete metamorphosis: egg → larva → pupa → adult.

Give an example of holometabolous metamorphosis.

Butterfly or beetle.

What is the distinctive stage in complete metamorphosis?

Pupa.

What is paurometabolous metamorphosis?

Gradual metamorphosis: egg → nymph → adult.

Give an example of paurometabolous metamorphosis.

Grasshopper or cockroach.

How do paurometabolous nymphs compare with adults?

They resemble small adults but lack mature wings and reproductive ability.

What is hemimetabolous metamorphosis?

Incomplete metamorphosis: egg → naiad → adult.

Give an example of hemimetabolous metamorphosis.

Dragonfly or damselfly.

What is a naiad?

An aquatic immature insect stage, often with gills.

What is ametabolous development?

No metamorphosis: egg → juvenile → adult.

Give an example of ametabolous development.

Silverfish.

What is the principal feature of ametabolous development?

Juveniles resemble adults but are not sexually mature.

What two broad considerations guide IPM decisions?

Economic and environmental considerations.

What does EIL stand for?

Economic Injury Level.

How does the professor define EIL?

The number of insects or level of injury at which management is economically justified.

What does a high EIL indicate?

A crop can tolerate more insects or injury before control is justified.

How does a higher crop value generally affect EIL?

It lowers the EIL, other factors equal.

Which tend to have lower EILs: horticultural or agronomic crops?

Horticultural crops.

Which tend to have higher EILs: forage crops or grain crops?

Forage crops.

What is direct insect injury?

Damage to yield-producing organs, such as flowers, fruits, and pods.

What is indirect insect injury?

Damage to non-yielding organs, such as leaves and roots.

Which can crops generally tolerate more of: direct or indirect injury?

Indirect injury.

Why can a pathogen-vector insect be important even at low population density?

It may transmit a damaging plant disease.

What is a plant-pathogen vector?

An organism capable of transmitting a pathogen to plants.

Why can the same pest have different tolerable levels during crop growth?

Crop stage, market price, and control costs change.

What is pest scouting?

Regular examination of fields to identify pest species, population levels, and damage.

How often should fields generally be scouted during the growing season?

Weekly; daily near economic threshold levels or during favorable pest weather.

What is a sampling program?

A plan specifying method, number, timing, and spatial pattern of samples.

What is an absolute population estimate?

An estimate of actual insect numbers per unit of ground area, such as per square foot.

What is a relative population estimate?

An insect count linked to a technique, such as insects per 25 sweeps or per trap.

Does sweep-net sampling generally provide absolute or relative estimates?

Relative estimates.

What are three recommended alfalfa sampling methods?

Sweep net; stem sampling; ground-area sampling.

What is sweep-net sampling?

Swinging an insect net through vegetation and counting insects caught.

What is stem sampling?

Examining selected plant stems for insect counts or tip injury.

Which insect is a typical target for stem sampling?

Aphids.

What is ground-area sampling?

Counting insects inside a frame defining a known ground area.

What size frame does the professor specify for alfalfa square-foot sampling?

A frame 1 foot × 1 foot (1 square foot).

What ground-area unit is used for grasshopper estimates in the alfalfa lecture?

Number per square yard.

What ground-area unit is used for cutworm estimates in the alfalfa lecture?

Number per square foot.

Why is sweep-net sampling not recommended for absolute estimates of cutworms and aphids?

Sweep-net counts are relative rather than direct counts per ground area.

How many scouting locations are required for a field less than 100 acres according to the lecture?

At least five.

How many scouting locations are required for a field greater than 100 acres according to the lecture?

At least ten.

How many monitoring locations are required for 180 acres?

Ten.

Which scouting patterns fit relatively uniformly distributed pests?

X, Z, or W patterns, generally excluding field edges.

Which pests are examples for X/Z/W scouting?

Aphids, diamondback moths, lygus bugs, bertha armyworm.

What pattern is appropriate for Colorado potato beetle and grasshopper scouting?

Field-edge scouting.

Where does field-edge scouting take place?

Along field edges, fence lines, or ditches.

At what wind speed does the professor advise against sweep sampling?

More than 10 mph.

Why should you avoid collecting sweep samples when alfalfa is wet?

Wet foliage makes sweep-net results unreliable.

What is sequential sampling?

Taking a variable number of samples until a management decision is possible.

Which type of feeding damage is often harder to recognize initially?

Piercing-sucking damage.

Where may cutworms appear first in a field?

Warmer, drier hilltops.

Where do wireworms often prefer to occur?

Moist, lower-lying soil.