Dealing with

Tomato Diseases

in the SoutheastDr. Joe Kemble

Extension Vegetable Specialist

Auburn University

What is a Plant Disease?

Any disturbance of a

plant that interferes

with its normal growth

and development.

Biotic diseases -caused by living

agents (bacteria,

fungi, etc.)

Abiotic diseases -caused by non-living

agents

Sign vs. Symptom

Disease symptoms are changes in a

plant’s appearance in response to a

pathogen that deviates from its normal

appearance.

Disease signs are structures of the plant

pathogen visible on the infected plant.

Signs or Symptoms?

Fusarium wilt - tomato

Signs or Symptoms?

Disease Triangle

Three factors needed for a biotic plant disease:

1. Susceptible host

2. Plant pathogen

3. Environmental conditions favorable for disease

development

Plant Disease

HOST

Viruses

500 + cause plant diseases

Submicroscopic organisms usually made

up of RNA and a protein coat

Replicate themselves within the host cells

Require a living host to survive

Infect plants through wounds

Insects, wounds, mechanical damage

Spread by insects, seed, humans

Bacteria

200+ species cause plant diseases

Cause similar symptoms as fungal

diseases Leaf spots, fruit rots, cankers, vascular wilts and

root rots

Infects plant through wounds & natural

openings

Spores spread by wind, rain, insects

Fungi Cause over 80% of all plant diseases

Symptoms include

Leaf spots, fruit rots, cankers, vascular wilts

and root rots

Spread by wind, rain, insects, people

Abiotic Diseases Nutrient

deficiencies/excesses

Moisture

deficiencies/excesses

High or low pH soils

Misapplication

Pesticides, fertilizer

Air pollution

Ozone, PAN (peroxyacl

nitrate)

Viral Diseases

Common in

Tomatoes

Plant Viruses Tomato Spotted Wilt virus

Insect transmitted

Not seed-borne

Tobacco Mosaic virus

Can survive on seeds

Can be transmitted

mechanically

Tomato Mosaic virus

Can survive on seeds

Can be transmitted

mechanically

Cucumber Mosaic virus

Insect transmitted

Can survive on seeds

Cucumber Mosaic virus

Symptoms can be similar

Viruses - Symptoms

Mottled leaves; mosaic

leaf patterns

Distorted leaves

Stunted plants

Can overwinter in weeds

Fruit stunted in size,

mottled and deformed

Reduced marketable

yields especially if

tomato infected early

Tobacco Mosaic virus

Virus - Management Resistant Varieties – “T” and “Tm”

Don’t plant next to infected

plants, fields

Mulches

Reflective mulches

Row covers

Mature plant resistance

Sanitation

Tools, containers, pots, HT/GH

floor, shoes, remove debris,

remove weeds

Certified, disease-free seeds &

plants

Seed Treatments (bleach, HCL)

Insect control – depends on virusTomato Mosaic virus

Row Covers −

to exclude insect

early in

production cycle

Tomato Spotted Wilt Virus Spread by Tobacco and

Western Flower thrips

Infected plants often

stunted, may die

Terminal leaves stop growing; become distorted

& turn pale green

Leaves have purple/bronze

appearance

Speckling & ring spots form

on leaves

Dark streaks develop on petioles and stems

Fruit may have ringspots

TSWV Management Plant TSWV-Resistant Cultivars

Amelia VR

Belle Rosa

BHN 602, 640

Crista

Mountain Glory

Mountain Majesty (EB,LB)

Mountain Merit (LB)

Primo Red

Red Defender

Roma types: Granadero, Picus, Plum Regal

Reflective Mulches may Reduce Thrips Feeding

Effective Weed Control In & Around Area (esp. HT/GH)

Insecticide Control of thrips – spinosad/Entrust (OMRI)

Bacterial Diseases

Common in

Tomatoes

Bacterial Spot

Introduced on

transplants

Attacks leaves & fruit

Favored by warm, wet

weather

Leaf spots can be

irregular, ragged

Fruit spots can be

raised or scabby

Bacterial spot > 80°F

Bacterial speck < 80°F

Bacterial Spot

Bacterial SpotBacterial Spot

Bacterial Spot

Bacterial Spot Control Use Disease-free Transplants

No resistant tomatoes

Prevent Splashing

Use Drip Irrigation

Mulch around plants

Don’t work w/plants when wet

Sanitation

Treat Seeds (hot water,

bleach, HCL)

Tools, trays, pots, HT/GH floor,

shoes, remove debris, remove

weeds

Crop Protectants

Serenade/Cease (OMRI)

Double Nickel 55 (OMRI)

Copper Fungicide?

About Seed Treatments… Hot Water Treatment

Can be used on most veggies

Reduces, if not eliminates, seedborne fungi and bacteria

Won’t kill pathogens associated with embryo

Won’t remove viruses from seed surface

115 to 122 F for 10 to 60 min depending on vegetable

Chlorine Bleach Treatment

Can be used on most veggies

Removes bacterial pathogens and some viruses (TMV)

1 qt bleach to 5 qt water for 5 min

Rinse for 5 min in water

Hydrochloric Acid Treatment

Excellent on bacterial diseases (spot, speck, canker) on tomato

…and Saving Seeds Be Selective

Rouge plants

Test plants if in doubt

Use a Seed Treatment as a Insurance against Problems

Assume there are pathogens in or on seed

Use a Hot Water Treatment

Purchase Treated Seed

Fungal Diseases

Common in

Tomatoes

Fungal Diseases in SE US

Early blight

(Late blight)

Fusarium wilt

Southern blight

EARLY BLIGHT

Early Blight

Early Blight Caused by the fungus Alternaria solani

Overwinters in plant debris in soil.

Also can enter field on air currents.

Begins on older leaves as irregular spots that enlarge to

½ inch in diameter

Develop concentric rings and a yellow halo

Plants appear to “fire-up” from their base

Warm, wet weather favor its development

EARLY BLIGHT

Reduces Fruit Size & Fruit Quality

Increases Sunscald

50 – 100% Yield Reduction

Early Blight

Early Blight Control

Resistant/Tolerant Cultivars Mountain Magic

Crop Rotation

Prevent Splashing Use Drip Irrigation

Mulch around plants

Staking

Remove Plant Residue after Harvest

Use Disease-free Transplants

Keep Tomato Plants Healthy & Vigorous

Crop Protectants Copper

Serenade/Cease (OMRI)

Double Nickel 55 (OMRI)

Late Blight & Buckeye RotLate Blight

Late Blight and Buckeye rot

Buckeye rot

Late Blight & Buckeye Rot Caused by the fungus Phytophthora infestans, P.

parasitica

Late Blight

Cool, moist conditions

Infects fruit and foliage

Look like “hot grease

poured onto plants

Buckeye Rot

Only fruit infected

Soil contact, splashing

75 to 85°F, moist conditions

Late blight sporangia

Late Blight Control Use Resistance Tomatoes

Mountain Magic, Mountain Merit,

Defiant PHR, Plum Regal

Crop Rotation

Especially from Solanaceous

crops and weed

Prevent Splashing

Use Drip Irrigation

Mulch around plants

Staking

Late Blight Control Sanitation –

Remove Tomato Residue after

Harvest

Use Disease-free Transplants

Keep Tomato Plants Healthy &

Vigorous

Crop Protectants Copper

Serenade/Cease (OMRI)

Double Nickel 55 (OMRI)

Ballad Plus/Sonata (OMRI)

Mycostop (OMRI) suppression ONLY

Fusarium Wilt Soil-borne Fungus that

Invades Roots

Survives in Soil for Years

Plugs-up Water conducting Vessels

Causes Yellowing & Wilting of Leaves

Whole Plant Eventually Wilts/Dies

Can Infect Many Vegetables

Tomato, English peas, Watermelons, Irish potato, Pepper

Fusarium Wilt

Fusarium wilt on Watermelon

Fusarium Wilt Control Use Fusarium wilt

Resistant Cultivars VFNT

3 races in the southeastern US

Well Drained Soil

Crop Rotation 3 or 4 year rotation

Solarization?

Use Grafted Plants!!! Heirloom Cultivars on

Resistant Rootstock

Southern Blight Caused by the fungus

Sclerotium rolfsii

Soil-borne, destructive, often sporadic

Favored by high temps 86-95 F & high moisture

Survives in soil for Years

Can be spread by surface water & movement of soil on equipment

Southern Blight Rapid wilting of entire plant

White mold (mycelium) covers

lower stem near ground line &

surrounding soil

Small, round structures about

1/16” in diameter, called sclerotia,

form on the mycelium.

Sclerotia are first white, later

brownish, tan

Control Options

Crop rotation, burying sclerotia

Contans WS (OMRI)

Grafting?

Timber Rot Also called Sclerotinia rot

Occurs during cooler weather compared to Southern blight

Potential problem in high tunnel production and greenhouses?

Timber Rot

Control Measures

same as for

Southern Blight

Contans WS (OMRI)

Plant-Parasitic

Nematodes

Plant Parasitic Nematodes Microscopic wormlike animals

Less than 1 mm in length

Most plant parasitic nematodes live

in soil

Damage plants by feeding on roots

in large numbers, impairing roots

ability to take up water & nutrients

Can’t see the nematodes w/ naked

eye, only the resulting symptoms

Symptoms Stunting

Leaf yellowing

Loss of plant vigor and/or

overall health

Reduced yields

Wilting (when soil is wet)

Non-uniform distribution of

symptomatic plants in

garden

Symptoms more

pronounced when plant

under stress from other

factors

Root-knot nematode

RKN galls on Tomato root

• Causes distinct swellings or galls on roots

• Galls range from pea sized to 1” in diameter

Root-Knot Nematode Management Wide host range; over

2,000 plants

Management requires

long term planning

Site Selection & nematode

inspection in fall

Sanitation

Crop rotation

Resistant cultivars

Reduce plant stress

Organic amendments

Suppressive crops

Soil solarization

Abiotic Disorders

Nitrogen Deficiency Nitrogen is Mobile

Symptoms progress from the OLDER

leaves to YOUNGER

leaves.

Symptoms

Yellowing of the

OLDER leaves

Plants become leggy,

stretch

Plants smaller in size

Yellowing progresses

into necrosis

Nitrogen Deficiency

Purpling develops on undersides of young leaves

when severe.

Double-check Your Fertilizer Program

Foliar Sprays DO NOT WORK FOR N

Apply to soil

Blossom-end Rot

Calcium is Semi-Mobile

Interrupt Calcium Availability

Die-back at growing points

Blossom-end of fruit &

vegetable buds

Brown leathery, sunken tissue

at flower end.

Rot organisms & insects can

get in

Calcium Availability

Soil Moisture

Soil pH

Blossom-end Rot Treatment Prevention is the Key

Soil Test

Apply Lime to pH 6 to 6.5

(dolomitic)

Apply calcium (well in

advance)

Moderate Soil Moisture

Never too wet, never too dry

Use a mulch

Don’t cultivate too deeply

Foliar Calcium Sprays do not

work – try a drench

ROUND-UP INJURY

Problem?How to Submit a Sample to

the Plant Disease Clinic

What Do You Do When You Have a Problem?

Proper and Timely ID is Critical

Contact Your Local Cooperative Extension Office

Go to http://www.aces.edu

Follow the link for County Offices or Diagnostic Labs

Online Resources – publications, handbooks, fact

sheets, etc.

Field Diagnosis

Look for various stages of symptom development?

Look for distinguishing field patterns:

Row patterns?

Scattered plants?

Groups of plants?

Field margins?

Most of garden?

High or low area of field?

Foliage/Fruit Examination

Spots - shape and distribution?

Yellowing - pattern and distribution?

Mosaic discoloration - old or new growth?

Growth abnormalities?

Leaf burns - spots, marginal?

Insect feeding damage?

Stem Examination

Fungal structures present ?

External discoloration – cankers?

Internal discoloration – vascular discoloration?

Ooze present or absent – bacteria?

Root Examination

Remember!

Half the plant is below the ground

Healthy roots are white and fibrous

Discolored roots?

Root galls?

Absence of secondary roots?

Critical InformationWhen symptoms first developed?

Recent weather conditions (2-3 weeks)?

Pesticide history?

Fertility program?

Soil test results, Soil pH?

Recent cropping history?

Selecting Samples for

Laboratory Analysis

Need a representative samples showing

range of symptoms (initial to severe)

Rotting samples are WORTHLESS

Include all plants parts (roots)

Include soil from root zone

Include “critical” information and

Observations from Your Examination

Selected Resources Grafting

http://graftingvegetables.org/

Seed Treatments

http://www.lsuagcenter.com/NR/rdonlyres/26772246-4C4A-

4028-992D-

95BF6DD51C6D/96988/43SeedTreatmentsVegetables2014FI

NAL.pdf

https://www.youtube.com/watch?v=Ie3H_icKWb4

https://www.youtube.com/watch?v=P-HhIcQrFyI

Vegetable Crop Recommendations for SE US

http://www.thepacker.com/sites/produce/files/SEVeg

Guide_2016.pdf

Selected Resources

Vegetable Crop Recommendations for SE US

Organic and Conventional Recommendations

http://www.thepacker.com/sites/produce/files/SEVeg

Guide_2016.pdf

Production Guides for Tomato

https://store.aces.edu/ItemDetail.aspx?ProductID=138

00

http://extension.uga.edu/publications/files/pdf/B%201

312_5.PDF

https://www.uky.edu/Ag/NewCrops/introsheets/tomat

oes.pdf