als 3153 class 15

Introduction to Insects

Phylum Arthropoda (jointed appendages, exoskeleton, etc.)

• Class Insecta (most numerous and diverse group of organisms)

• Class Arachnida

• Class Crustacea

• Etc. (centipedes, millipedes, etc.)

Spiders – often beneficial as predatorsMites – some plant pests, some predators

Insects vs Arachnids (Mites, Spiders)

Insect Life Cycles

• 1. Simple metamorphosis

• 2. Complete metamorphosis

• 3. Some exceptions

• #1 and #2 apply to most agricultural pests

Simple Metamorphosis

Egg

Nymphs

Adult – has full-size wings, functional reproductive system


Nymphs

InstarInstar

Molt Molt


Egg

Nymphs

Adult – has full-size wings, functional reproductive system

Usually 4-6 instars, resemble adults, smaller size

Same food and environment for nymphs and adults

Complete Metamorphosis

Egg Pupa

Larva – several instars, important feeding stage

Adult – very different from larva

Corn Earworm

Complete Metamorphosis

• Life stages are important because ecology, food habits, and management of different stages can be different

• Example: butterflies and moths

• Larva – feeds as damaging caterpillar

• Adult – beneficial as plant pollinator

Survey of insects – Major groups (orders) of ag pests or beneficial

predators and parasites• Beneficial insects:

• Predators, parasites

• Pollinators

• Recyclers of OM

Survey of insects – Major groups (orders) of ag pests or beneficials

• Dragonflies• Orthoptera and relatives (mantids, roaches)• Thrips• True bugs (Hemiptera)• Piercing-sucking insects (Homoptera)• Beetles• Nerve-winged insects (Neuroptera)• Butterflies and moths• Bees, wasps, and ants• Flies• Etc.

Survey of Insects

• Dragonflies --- beneficial predators of flying insects

• Praying mantids --- beneficial predators

• Roaches --- recycling in some ag systems

• Grasshoppers, Crickets --- can be serious ag pests

Tawny Mole Cricket

Thrips

Thrips palmi

Thrips

• Almost microscopic in size, fringed wings

• Beneficial pollination in flowers

• Most are plant pests

• Some carry plant viruses

Virus Vectors

• Vector = carrier of virus

• Viruses in plants

• Transmitted by insects, etc.

• Vector feeds on infected plant acquires virus feeds and passes virus to other plants

True Bugs

• Squash bug

• Note typical appearance

True Bugs

• Piercing-sucking mouthparts

• Some important pests, e.g., stink bugs

• Some predators

Piercing-Sucking Insects

• Piercing-sucking mouthparts to feed on plants

• Formerly Homoptera, often included with true bugs

• Many important plant pests

• Some transmit viruses

• Aphids, cicadas, whiteflies, scale insects, leafhoppers, etc…

Green Peach Aphid

• Very abundant as plant pests

Whitefly Adult• Common underneath leaves

Sooty Mold - Silverleaf

• Important sign of whiteflies, etc…

Beetles

• Pepper Weevil

Beetles

• Very many species

• Many pests – weevils, larvae of some types are grubs or wireworms

• Many beneficials – Lady beetles, ground beetles, tiger beetles

Nerve-Winged Insects (Neuroptera)

• Brown Lacewing

Lacewing Larva Eating Whiteflies

• Beneficial predators

Butterflies and Moths

• Pests – many kinds of caterpillars

• Beneficial as pollinators

Bees, Wasps, Ants


• Many are important as predators and parasites

• Many different kinds of wasps, most nearly microscopic

• Parasitoids – microscopic wasps, lay eggs in body of pest (e.g., caterpillar), or even in egg

Flies

• Many different kinds, difficult to distinguish – different flies do different things:

• Important pests of livestock


• Beneficial as predators

• Some are parasitoids

• Some are plant pests (leaf miners)

Leafminers

• Larvae of some flies, some moths

Many Important Pests of Livestock

• Flies, Lice, Fleas, etc…

Important Insect Relatives

• Mites -- some beneficial predators

• Mites – some livestock pests

• Mites – some plant pests

• Spiders – Very important as predators (much underrated) in agroecosystems

Mite Damage on Leaf

Spider Mites

• Note characteristic webbing

Management of Insect Pests

Insecticides and Acaricides

• +++ effective, detailed knowledge of pest biology not needed

• +++ reliable, fast-acting

• +++ quick response to emergency situations

• - - - non target effects

• - - - $ and energy costs

• - - - high expectations

Biological Control

• Control by living organism or natural product of living organism

• Hyperparasitism

Caterpillar Tachinid fly Parasitoid Wasp

Biological Control -- Two Approaches

• Introduced = add control agents to ecosystem (many good examples with introduced pests)

• Introduced: classical (new agent) vs augmentation (agent already present)

• Natural = favor increase of naturally occurring control agents (manipulate environment, cropping systems)

Biological Control Many possible organisms:

• Predators (often not specific)

• Parasites

• Diseases (parasites)FungiBacteriaViruses

Parasitoids (often highly specific)Entomopathogenic nematodes

Host Plant Resistance

• Interfere with host finding, feeding, pest nutrition, timing of life cycles, etc…

• Hairs on leaves, sticky, etc.

• Alkaloids in plants deter insects

• Crop cultivars/genotypes selected for resistance to pests

What is Biological Control and What Is Not ???

What is Biological Control?

• Predators

• Parasites

• Diseases


• Predators

• Parasites

• Diseases

• Bacterial disease of insects caused by Bacillus thuringiensis (BT)



• Allow bacteria to produce spores with toxin in lab, isolate BT toxin, and spray it on pests



• Allow bacteria to produce spores with toxin in lab, isolate BT toxin, and spray it on pests

• Transgenic plants that produce BT toxin (Bt corn, Bt cotton)


• Resistant plants as biological control agents

• Plants with alkaloids

• Pyrethrum = natural plant alkaloid





• Isolate pyrethrum from plants and use it





• Isolate pyrethrum from plants and use it

• Make synthetic pyrethrum

• Pyrethroid = pyrethrum analog, similar chem structure

Environmental Heterogeneity

• Crop genetics (uniform genotypes vs mix)

• Vegetation diversity vs pest dispersal

• Vegetation diversity as reservoir for natural enemies

Plant Health

• +++ Healthy plant can withstand some insect damage

• - - - High N can increase insect growth and reproduction

Attractants and Repellents

• Attractant, e.g., pheromone (sex or aggregation) useful for:

• Sampling and monitoring (important use for quarantine detection, regional monitoring)

• Attracting insects to traps

• Confusing normal life processes and patterns

Cultural Practices

• Crop Rotation

• Weed control of virus hosts

• Sanitation and cleanup of crop residues (affected overwintering of boll weevil)

• Timing of planting dates (winter wheat, Hessian fly)

• Others (sterile males, etc.)

For most effective insect management, usually need to know biology and habits of individual insect pests

References

• Text: Ch 10, pp. 201-208; Ch.11, pp. 219-222.• Metcalf C.L., W.P. Flint, and R.L. Metcalf. 1962.

Destructive and Useful Insects. McGraw-Hill, NY.

• Metcalf, R.L., and W.H. Luckmann. 1994. Introduction to Insect Pest Management. John Wiley & Sons, NY.

• Images from UF Dept. Entomology & Nematology – Featured Creatures:

• http://creatures.ifas.ufl.edu

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