Insect Pests

Economic importance of insect pests Can cause direct damage to crops Can be vectors of plant pathogens

Direct Damage Decrease photosynthetic ability o Defoliation o Leaf mining o Leaf curling Stunting, yellowing, distorted growth, and honeydew Lodging in some crops o Bore into stems Feed on roots Damage to harvested plant parts

What is an insect? Phylum Arthropoda o Means “jointed foot” o Largest phylum in the world Insects, crustaceans, spiders, centipedes, millipedes Insects 1.Possess an exoskeleton made of chitin Encases internal organs 2.Body is divided into three distinct regions Head, thorax, abdomen 3.Three pairs of jointed legs, attached to the thorax 4.Compound eyes 5.One pair of antennae

Absence of a backbone makes the hard exoskeleton crucial to life on land Insect body divided into a head, thorax, and abdomen External Anatomy of an Insect

Composed of numerous plates o Plates are called sclerites o Fused together to form a solid capsule Bears: o One to three simple eyes o Two compound eyes o One pair of antennae o Mouthparts Houses the brain o Nerve cord runs from brain down the body on the ventral surface The Head

Divided into three segments o Prothorax, mesothorax, metathorax Each segment is made up of four sclerites o Upper (dorsal) sclerites are called the notum o Lower (ventral) surface is the sternum o Side (lateral) regions called the pleura Can combine these terms to define a region (e.g., pronotum) One pair of legs is attached to each segment near the bottom of the pleura If present, wings can be on: o mesothorax alone o both the mesothorax and metathorax The Thorax

Softer and more flexible than the head or thorax Devoid of appendages o Exceptions are cerci and genitalia o Ovipositor Houses the tracheal system o Must expand and contract The Abdomen

How insects breathe Insects take in and expel air through spiracles o Openings on each side of the abdomen o One pair of spiracles per abdominal segment (11 pairs) Each spiracle leads to air tubes (tracheae) and air sacs Oxygen flows through these tubes and sacs to all organs and tissues throughout the body The Tracheal System

Mouthparts tell us about insect feeding habits o Tells us more about life cycle and ecological relationships Types of Mouthparts o Chewing Chewing Chewing-lapping o Sucking Piercing-sucking Siphoning o Sponging Mouthparts and Feeding

Most common o Dragonflies, grasshoppers, crickets, katydids, beetles, ants, wasps, caterpillar larvae o Damage includes leaf mining, defoliation, boring of tissues, root damage o Labrum Upper lip o Mandibles Toothed jawlike apparatus adapted for cutting, crushing, grinding o Maxillae Smaller but also jawlike and adapted for grasping o Labium Lower lip Hypopharynx – tonguelike appendage that rests on the labium Chewing Mouthparts

Chewing-lapping o Bees o Elongated labium helps lap nectar Chewing Mouthparts

Insects ingest only liquid food Piercing-sucking o Aphids, leafhoppers, fleas, sucking lice, mosquitos o Modified mouthparts Proboscis (beak) o Elongated labium that sheaths slender mandibles and maxillae o These are called stylets Stylets do the piercing o Can also transmit pathogens, inject toxins Sucking Mouthparts

Siphoning o Butterflies and moths o Proboscis is coiled and extends when insect wishes to feed on nectar Sucking Mouthparts

Most flies Have a fleshy labium on the tip of the proboscis that acts like a sponge o Soaks up liquids and food particles Also called rasping-slurping Sponging Mouthparts

Insects start as eggs, go through metamorphosis No metamorphosis o Emerge from eggs as miniature adults o Silverfish, springtails Incomplete metamorphosis (hemimetabolous) o Nymphs emerge from eggs and gradually develop complete adult features and size o Aphids, leafhoppers, grasshoppers Complete metamorphosis (holometabolous) o Four separate life stages Egg, larva, pupa, adult o Butterflies, cutworms, stem borers o Larval and adult stages are damaging to crops Life Cycles

Nymphs eat the same food as the adults The stage preceding each molt is called an instar Each succeeding instar more closely resembles the adult stage Incomplete Metamorphosis

Incomplete Metamorphosis Example (hairy chinch bug) egg 1st 2nd 3rd 4th 5th shortwing normal wing instar instar instar instar instar adult adult Egg Nymphal Adult Stage Stage Stage

Egg hatches to larva Larva do not resemble adults, worm-like instead o Has simple eyes only o Chewing or chewing-sucking mouthparts o Short antennae o Up to three pairs of true legs, possibly other appendages that resemble legs o Larvae molt several times to accommodate growth (also called an instar) Pupa emerges from final larval molt o Pupa do not eat o Tissues differentiate, compound eyes form, wings, antennae, mouthparts, etc. o Can last 4 days to several months Adult emerges, on a mission to mate and lay eggs Complete Metamorphosis

Complete Life Cycle Example (northern masked chafer) egg 1st 2nd 3rd pupa adult instar instar instar Egg Larval Pupal Adult Stage Stage

Sexual o Males transfer species to a female and sperm are stored in a special sac in her abdomen o Egg-laying females (oviparous) have ovipositors as abdominal appendages Deposit eggs in suitable sites As eggs are laid, they meet sperm on the way out of the female o Non-egg laying females (viviparous) house eggs until they hatch Asexual o Parthenogenesis An unfertilized egg develops into an adult o Social bees, waspsReproduction

Insects smell with their antennae Segmented, flexible, and covered in tiny hairs (setae) that sense chemicals, touch, taste, sounds, etc. A variety of configurationsAntennae