Introduction to Insects
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
Simple Metamorphosis
Nymphs
InstarInstar
Molt Molt
Simple Metamorphosis
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
• Beneficial as pollinators
• 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 pollinators
• 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
What is Biological Control?
• Predators
• Parasites
• Diseases
• Bacterial disease of insects caused by Bacillus thuringiensis (BT)
What is Biological Control?
• 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
What is Biological Control?
• 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
• Transgenic plants that produce BT toxin (Bt corn, Bt cotton)
What is Biological Control?
• Resistant plants as biological control agents
• Plants with alkaloids
• Pyrethrum = natural plant alkaloid
What is Biological Control?
• Resistant plants as biological control agents
• Plants with alkaloids
• Pyrethrum = natural plant alkaloid
• Isolate pyrethrum from plants and use it
What is Biological Control?
• Resistant plants as biological control agents
• Plants with alkaloids
• Pyrethrum = natural plant alkaloid
• 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