Diseases

Help me! I’m dying.

Disease• Disease is a plant disorder caused by an

infectious pathogen or agent

Host – Plant the disease attacksPathogen – Any disease causing agentEnvironment – moisture and temperature needed for the pathogen to grow

Groups of pathogens• Bacteria

– Single-celled organism

– Must remain in host or under debris

– Actively divide to spread

• Fungi– Multi-cellular– Eats on plants and

hurts them in the process

– Produces spores that spread

• Viruses– Ultramicroscopic

parisites– Attack plant tissues– Should destroy plant

completely if found

• Parasitic plants- – A plant that attaches to

another plant– Ex. mistletoe, dodder,

lichens

Plant Disease

• Must be identified before they can be treated

• Warm temperatures and moist conditions in greenhouse plant production make most horticulture plant diseases worse

Disease

• Preventing plant disease through sanitation and insect control is much easier than treating the disease.

Diseases

• Blight• Canker sores• Damping off• Galls• Leaf spot• Mildew

• Mosaic• Rots• Rust• Smut• Wilt

Blight

• Infectious bacterium• Cause plant to quickly

turn brown or black as if they had been burned

• One specific blight is fire blight-devastating apple crops

• Prune 6-8” below infection

Canker

• Bacterial disease• Causes open wounds

on woody plant stems

Damping off

• Fungal disease• Causes young plants

and seedling to rot off at soil level

• Need clean containers and soil and plenty of air circulation between plants

Galls

• Round swelling or growths on plants

• Usually caused by an insect that vectors the disease

Leaf spot

• Rings of different shades of brown, green, or yellow

• Looks like dots or circles

Mildew

• Fungus• Grows on leaf surfaces• Appears as white, gray or

purple spots• Example is powdery

mildew• Homemade remedy= 2 tsp

baking soda + horticultural oil with 1 gal water

Mosaic

• Caused by a virus• Leaves have irregular

mottled areas with patterns

• Ranges from dark green to light green to yellow to white

• Tomato mosaic virus is common in tomatoes

Rots

• Fungus• Causes plants to decay

and die• Usually has a unique

smell• Improve drainage for

the plant to prevent

Rust

• Fungus• Causes small spots on

leaves• Resembles yellow,

orange, brown or red rust

• Mainly on underneath of leaf

Smut

• Black powdery disease• Causes blisters that

burst open• Releases black spores• Grows on aphid’s

honeydew

Wilt

• Fungus• Disease that blocks the

uptake of water in plants stems

• Causes plants to look constantly wilted even when adequately watered