Diagnosis of Soilborne Diseases in Tomato

NC STATE UNIVERSITY Diagnosis of Soilborne Diseases in Tomato Cary Rivard & Frank Louws October 3rd, 2007 CEFS – Tomato Grafting Workshop Outline •...
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NC STATE UNIVERSITY

Diagnosis of Soilborne Diseases in Tomato Cary Rivard & Frank Louws October 3rd, 2007 CEFS – Tomato Grafting Workshop

Outline • Encountering problems in the field

• Plant disease diagnosis

• Common soilborne diseases in the southeast

Outline • Encountering problems in the field

• Plant disease diagnosis

• Common soilborne diseases in the southeast

Diagnosis GOAL: To eliminate what the problem is NOT, to discount the highly improbable, and focus on the most likely. (FJL) “the game is afoot…”

Encountering Problems •

Location – Where is the problem occurring? – Plant – Field – Region



Spatial distribution – How is it distributed? – Plant • families, species, cultivars • Host tissue

– Field • Low spots, high spots, field edges

– Region • Climate, soil types, agricultural systems



Temporal distribution – When did it occur? – – – –

Event vs Continuous Crop cycle Season Year-to-year

Spatial Distribution

Random

Biotic

Aggregated

Linear

Abiotic

Disaster

Nematode - Coffee

Nutrient stress - Cauliflower

Sclerotinia Lettuce Drop - Lettuce

Temporal Distribution •

It happened overnight!! – Chronic vs acute



What areas were affected first? – Plant – Field



What has been going on? – Weather / Climate – Planting, transplanting, harvesting – Cultural practices – Pesticide applications

Disease vs Disorder vs Injury Problem Continuous / Chronic

Event / Acute

Abiotic

Biotic Insect

Drought

Freeze

Pathogen

Salinity

Flooding

Bacteria

pH

Lightning

Fungi

Nutrient

Mechanical

Virus

Heat

Nematode

Disorder

Disease vs Disorder vs Injury Problem Continuous / Chronic

Event / Acute

Abiotic

Biotic Insect

Drought

Freeze

Pathogen

Salinity

Flooding

Bacteria

pH

Lightning

Fungi

Nutrient

Mechanical

Virus

Heat

Nematode

Disorder

Disease vs Disorder vs Injury Problem Continuous / Chronic

Event / Acute

Abiotic

Biotic Insect

Drought

Freeze

Pathogen

Salinity

Flooding

Bacteria

pH

Lightning

Fungi

Nutrient

Mechanical

Virus

Heat

Injury

Nematode

Disease

Disorder

Outline • Encountering problems in the field

• Plant disease diagnosis

• Common soilborne diseases in the southeast

Plant Pathology 101

OG E PA TH

NT ME

HOST

ON V IR

N

EN

Amount of Disease

Life as a Plant Pathogen • On or in soil – Soil transients – Soil inhabitants

• On or in seed • Insect vectors • Perennial plants • Alternative hosts – Weeds – Native plants – Other crops (G.N Agrios, 2005)

Plant Disease Diagnosis Disease: any condition that is harmful to the host, is caused by the continuous irritation by a primary causal agent (pathogen), and results in the production of symptoms Diagnosis: the art and science of identifying a disease by the symptoms and/or signs present Signs: Evidence of disease consisting of visible portions of the pathogen Symptoms: Visible expression of disease by the host

Plant Disease Diagnosis Signs

Symptoms

• Mushrooms

• Chlorosis/necrosis

• Slime mold

• Malformations

• Conk

• Mosaic

• Rust

• Dieback

• Cysts

• Wilt

• Ooze

• Cankers

• Mildew

• Galls

• Sclerotia

Signs, symptoms, and the disease signature

Signature - the specific temporal and spatial expression of signs and symptoms (FJL)

From: G.N. Agrios. 2005. Plant Pathology. 5th edition. Elsevier AP.

Phytophthora Crown Rot and Blight - Pepper

Phytophthora Crown Rot and Blight - Pepper

Phytophthora Crown Rot and Blight - Pepper

Tomato Spotted Wilt Virus – Tomato

Pith Necrosis - Tomato

Outline • Encountering problems in the field

• Plant Disease Diagnosis

• Common soilborne diseases in the southeast

• Major soilborne plant pathogens in the Southeast.

– Root-knot Nematodes

– Verticillium Wilt

– Southern Stem Blight

– Fusarium Wilt

– Bacterial Wilt

Ashe

Alleghany Surry

Stokes Rockingham Caswell Person

Gates Northampton Currituck Camden Hertford Pasquotank Perquimans Halifax

Vance Warren

Granville Forsyth

MitchellAvery CaldwellAlexander Madison Burke BuncombeMcDowell Haywood

Swain

Mountains

Iredell Catawba

Davie

Orange

Guilford

Alamance

Franklin

Piedmont

Davidson Randolph Rowan

Bertie

Nash Edgecombe

Durham

Martin

Wake

Chowan WashingtonTyrrell

Chatham

Pitt

Johnston

Lincoln

Beaufort

Greene

Lee

Rutherford Cabarrus Graham HendersonPolk Stanly Harnett Moore Gaston Jackson Cleveland Montgomery Mecklenburg Transylvania Macon Cherokee Cumberland Clay Richmond Sampson Hoke Union Anson

Lenoir Craven Pamlico

Coastal Plain Jones

Duplin

Onslow

Scotland Robeson

Bladen Pender Columbus Brunswick

New Hanover

Carteret

Hyde

Dare

Bacterial Wilt • Southern Bacterial Wilt is caused by Ralstonia solanacearum. – Vascular wilt – Warm, wet weather – Tomato, eggplant, pepper, tobacco

Verticillium Wilt • Verticillium Wilt is caused by Verticillium dahliae. – Wilting and leaf necrosis – Cool wet weather – race 2 resistance

Fusarium Wilt • Fusarium wilt is caused by Fusarium oxysporum. – Unilateral wilting – Yellowing of leaves – Browning of xylem

Root-knot Nematodes • Root-knot Nematodes – – – –

Meloidogyne spp. Root galls Stunting and poor vigor Prefer light soil

Southern Stem Blight • Southern stem blight is caused by Sclerotium rolfsii. – Colonizes stem and crown – Vascular wilt – Chlorosis – Sclerotia – Hot weather – Good saprophyte

Resources • Resources: – NCDA Agronomic Division • Nematode Assays • Soil Analysis • Tissue Analysis

Shawn Butler, Tom Creswell, David Stephan

– – – – – –

NCSU Plant Disease and Insect Clinic NCSU Plant Pathogen Identification Lab North Carolina Cooperative Extension Compendium of Tomato Diseases Ask your neighbor Web resources

Summary • Accurate diagnosis of plant disease problems is the first step in management. • Identifying the differences between the various pathogen signatures will aid in successful diagnosis. • Don’t be afraid to utilize resources.

QUESTIONS??

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