Pests and Diseases

28.00: Examine distinguishing characteristics of pests so as to determine best management practices.29.00: Compare methods of control of horticulture plant pests.

What is an insect?

• Small animals that have three body regions and three pairs of legs equaling six legs

• Body regions– head – thorax– abdomen

Types of Insects

• The five types of mouthparts are important in identifying and controlling insects.– Chewing– Piercing– Rasping– Siphoning– Sponging

Chewing Insects

• Insects tear, chew or grind food• Examples

– grasshopper– beetle

Piercing Insects

• Punctures plant and sucks the sap

Rasping insect

• Rasps or breaks surface and sucks sap

• Example– thrips

Siphoning insects

• Have a coiled tube they dip into liquid food such as nectar and draw it in

• Example– butterfly

Sponging Insects

• Have two sponge-like structures that collect liquid food and move it into the food canal

• Example– housefly

Life Cycles

• Complete metamorphosis has four stages– egg– larva-worms or caterpillars– pupa– adult-flies, beetles, etc.

Life Cycles

• Incomplete metamorphosis has three stages– egg– nymph– adult

Life Cycles

Chewing Insects

• Parts of leaves are eaten away– beetles– cutworms– caterpillars– grasshoppers

Chewing Insects

• Beetles– eat leaves, stems, flowers, fruit

and nuts

• Cutworms– usually attack stems, but may eat

other plant parts

Chewing Insects

• Caterpillars– larva of moths and butterflies– fuzzy or hairy– eat young leaves and stems– roll up in leaves making leaves

curl

• Grasshoppers– eat all parts of plants

Sucking Insects

• Aphids• Leaf bugs• Mealy bugs• Scale• Thrips• Whiteflies

Aphids

• Pierce and suck juices• known as plant lice• cause stunted growth and

yellow spotted leaves• causes sticky substances and

black mold• will attract ants

Aphids

Leaf Bugs

• Cause plants to look unhealthy• plants will lose their normal

color and wilt

Leaf Bugs

Mealy Bugs

• Pierce and suck from underside of leaves and in leaf axils causing yellow appearance and sticky secretions

Mealy bugs

Scale

• Appear as black or brown raised lumps attached to stems and underside of leaves causing yellow leaves and stunted growth

Scale

Thrips

• Chew and then suck causing plant tissue to become speckled or whitened, leaf tip to wither, curl up, or die

Thrips

Whiteflies

• Feed on underside of young leaves causing yellowing

• will look like flying little white specks when plants are shaken

Whiteflies

Mites

• Attack underside of leaves causing gray to grayish-green spots

• severe infestations cause webbing

Mites

Plant Diseases

Diseases

• A disease is a plant disorder caused by an infectious pathogen or agent

Diseases

• There are 3 conditions necessary for diseases in plants– host plant– disease causing organism or

pathogen must be present– favorable environment for

disease organism to develop

Pathogens

• There are four groups of pathogens– bacteria– fungi– viruses– parasitic plants (attach to plants)

• mistletoe• dodder • lichens

Blight

• Causes plants to quickly turn brown or black as if they had been burned

Blight

Canker

• Causes open wounds on woody plants

Canker

Damping off

• A fungal disease that causes young plants and seedlings to rot off at soil level

Damping Off

Gall

• Swellings or growths on plants

Leaf Spots

• Rings of different shades of brown, green or yellow that make spots on leaves

Mildew

• Grows on leaf surfaces--both upper and lower--as white, gray or purple spots

Mosaic

• Caused by viruses that make the leaves have irregular mottled areas with patterns ranging from dark green to light green to yellow to white

Mosaic

Rots

• Cause plant to decay and die

Rust

• Causes small spots on leaves that resemble yellow, orange, brown or red rust mainly on the underneath side of leaves

Rust

Smut

• A black, powdery disease that causes blisters that burst open releasing black spores

Smut

Wilt

• A disease that blocks the uptake of water in plant stems causing plants to wilt

Wilt

Controlling Pests and Diseases

Disease Control

• Preventing plant diseases is better than treating the diseases

• Plant diseases must be identified before they can be treated

Environment

• Warm temperatures and moist conditions in greenhouse plant production make most horticulture plant diseases worse because of environmental conditions that support disease-causing pathogens

Controlling Insects

• Insects can be controlled using the following methods:– biological– chemical– cultural– mechanical– natural– quarantine

Biological Control

• Uses natural enemies such as birds, other insects, etc.

Chemical Control

• The use of pesticides or insecticides

• Insects must be killed when they are actively feeding or moving on the plant

Chemical Control

• Contact poisons– affect the insect’s nervous system

and must come into contact with the insect to be effective

• Fumigants– poisonous gases released into an

enclosed place so that insects breathe the gases

Chemical Control

• Stomach poisons– sprayed on the plant surfaces or are

taken into the plant through absorption.

– The insect must suck the poison to get it into the stomach for this method to be effective.

– Systemic poisons are more effective for controlling sucking insects.

Cultural Control

• Involves sanitation, removing insect breeding and hiding areas and using insect resistant plant varieties

Mechanical Control

• Uses physical control such as insect traps, using screens over fans and other openings, and washing plants with soapy water.

Natural Control

• Methods include natural barriers such as rivers, woods, mountains and predators to control insects.

Quarantine

• Physically isolates insects from healthy plants

IPM

• A combination of control methods is called Integrated Pest Management or integrated control.