Common Greenhouse Viruses

Front Range Greenhouse IPM Workshop:Viruses Affecting Production
Brooke Edmunds, Ph.D.; CSU Extension
Laura Pottorff, M.S.; CO Department of Agriculture

Questions we will answer today:
What is a virus?
How do viruses enter the greenhouse?
How do virus spread in greenhouses?
What are common symptoms
How are viruses detected?
How can you manage virus diseases?
What is phytosanitary certification?

What is a virus?
Submicroscopic particle
Genetic material (nucleic acid, usually RNA) surrounded by a protein coat
Requires host plant for reproduction
Photo: webs.wichita.edu

What is a virus? (cont.)
No chemicals that kill viruses
Once infected, a plant remains infected
Millions of virus particles produced in each infected cell!
Aster with TSWV

How viruses are named
Acronyms are commonly used
INSV (Impatiens Necrotic Spot Virus)
TSWV (Tomato Spotted Wilt Virus)
Refers to 1st plant found on & symptoms
Name is not limiting!
Some can infect 100’s of genera, others only a few

How do viruses enter & spread within greenhouses?
Infected plant material
Workers
Insects
Other vectors
Seed
Mites
Fungi
Nematodes
Photo: http://www.visionaryplants.com/images/th_salvia_divinorum_rooted_cutting.jpg

Example: TMV and workers
Tobacco Mosaic Virus
Able to survive in processed tobacco
Can enter greenhouse by workers who smoke
Can survive for years in dried tissue & clothing
How to prevent:
Consider lab coats for propagation areas
Worker sanitation is very important
Wash hands with soap and hot water and dry with paper towel

Insect Vectors: Aphids
30 species, depending on the crop
Green peach aphid (Myzuspersicae)
Three lines on back
Cornicles/tailpipes are green with tips brown or black

Melon or Cotton Aphid
Green or dark gray
Cornicles/tail pipes are solid black
Aphids pick up virus and transmit for short period of time

Insect Vector: Thrips
Very small (1/16”)
Difficult to scout
Direct damage & virus vector
1st and 2ndinstar accumulates virus
Systemically infected
Onion thrips
Western flower thrips

Symptoms of virus infection
Easily confused with:
Nutrient disorders
Chemical injury
Leaky heating system
Insect feeding
Other pathogens (bacteria, fungi…)

Symptoms-common terms
Mosaic
Mottle
Ringspots
Line patterns
Bronzing
Necrotic lesions
Stunting
Streaking
Distortion
Cup shape
Crinkling
Epinasty
White patches or lines on flowers
Breaking
Photo: http://www.clemson.edu/public/regulatory/plant_industry/plant_prob_clinic/images/tswv_fruit.jpeg

What affects “Symptom Expression”?
Temperature
Depends on the virus
CMV more symptoms at lower temps
TSWV more symptoms at higher temps
Stress
Stressed plants show more symptoms
Drought, heat, light, etc
Plant age
Plant variety
Some plants may be completely symptom-free but able to transmit virus

Most common greenhouse viruses
INSV
TSWV
CMV
TMV
CbMV
Plants can get more than one virus!

INSV
Impatiens Necrotic Spot Virus
Hosts: >600 species (Almost all greenhouse crops except roses & poinsettias)
Symptoms: stunting, necrotic & yellow spotting, stem cankers, line patterns, ringspots
Spread by: Western flower thrips, propagation

INSV on ranunculus-Easily confused with fungal disease!

INSV on Gerbera Daisy

INSV on Chrysanthemum

INSV on Begonia
Photo: http://www.apsnet.org/online/feature/tospovirus/images/figure3.htm

INSV on Impatiens

TSWV
Tomato Spotted Wilt Virus
Hosts: >600 species, almost all greenhouse crops except roses & poinsettias
Symptoms: stunting, necrotic & yellow spotting, stem cankers, line patterns, ringspots
Spread by: several species of thrips, propagation

TSWV on Gloxinia

TSWV on Impatiens

Black line pattern caused by Tomato spotted wilt virus (TSWV) on hellebore

CMV
Cucumber Mosaic Virus
Hosts: over 400 species
Ornamentals, vegetables, woody & semi-woody
Symptoms: mosaic, color breaking, flecking, leaf distortion
Spread by: aphids, sap, propagation, seed & pollen in petunias

Mosaic on Ajuga caused by CMV

CMV on Vinca

Bronzing caused by CMV on lobelia

TMV
Tobacco Mosaic Virus
Hosts: 100’s of species
Symptoms: yellow mottling, leaf curling, stunting
Spread by: sap and plant parts, workers handling tobacco products, VERY stable
Non-symptomatic infected plants can occur

TMV on Calibrachoa
Photo: www.ipm.uconn.edu

TMV on Petunia
Photo: http://www.greenhousegrower.com/articles/image/200902/Online%20Only%20Lewandowski/Figure_1.jpg

CbMV
CalibrachoaMottle Virus
Hosts: Calibrachoa, petunia
Symptoms: leaf yellowing, dieback, spotting
Easily confused with iron deficiency
Spread by: sap & propagation

CbMV on Calicrachoa
Photo: L. Pottorff

Other viruses

ToMV on Tomato
Photo: www.omafra.gov.on.ca

Canna Yellow Mottle Virus

White ring spots form on meadow-rue infected with Tobacco rattle virus

Rings and chlorotic lines caused by Tobacco Rattle Virus on Epimedium

Begonia leaves with virus-induced chlorotic mottling and necrosis

White patches
Alstroemeria mosaic virus

Tulip Breaking Virus

Odontoglossumringspottobamovirus, ringspot on orchid
Photo: www.agdia.com

Odontoglossumringspottobamovirus causing flower break on orchid
Photo: www.agdia.com

Unknown orchid virus
Photo: www.aos.org/AM/Images/pest+diseases/Virus2003.jpg

Virus Testing
ELISA (Enzyme Linked ImmunoSorbentAssay)
Uses antibodies and color changes to detect

Lab based
Crop screens for multiple viruses
In-house ImmunoStrips
For common viruses

Other resources:Virus Testing
Agro Check kits from Hydros Inc. 230 Jones Road, Falmouth , MA 02540 Phone: 508 540 2229, http://www.hydros.cc/ .
Alert Kits from Neogen Company 620 Lesher Place Lansing, MI 48912 Phone: 800/234-5333 (USA/Canada) http://www.adgen.co.uk/ (Information about the test kits are on Neogen Europe website)

CSU Extension Adams CountyPlant Diagnostic Lab
Disease and insect diagnosis for greenhouse and nursery industry
Stock Agdia tests for common viruses
Discount services for CNGA members
9755 Henderson Rd, Brighton; 303/637-8016
brooke.edmunds@colostate.edu

Insect Management
Sanitation-no holdovers!
Remove weeds in and around greenhouse
Air-lock or double-door entrances
Insect screening
Scouting & monitoring
Control strategies

Scouting for thrips
Hot pink or blue sticky cards
5-10/acre plus near doors and vents
Just above tops of plants
Plant inspections:
Feeding scars & black feces
Depending on plant-on upper or lower foliage
Tap foliage over white paper and look for adults
Photo: http://www.omafra.gov.on.ca/english/crops/facts/03-075f1a.jpg

Indicator Plants
Petunia ‘Super Blue Magic’, ‘Summer Madness’, ‘Calypso’, etc
Fava bean ‘Toto’
Feeding scars show up rapidly
Brown ring if INSV is present

Insect Screening
Photo: http://edis.ifas.ufl.edu

Insecticides to control Thrips
Organophosphates
Carbamates
Pyrethroids
Chloronicotinyls
Botanicals
Drench at transplant, followed by foliar applications
ROTATE to avoid resistance!

Sanitation
Benches, pots, equipment:
3% TSP (trisodium phosphate)
Virkon S
Quaternary ammonia
Hydrogen dioxide
Bleach
For workers:
Skim milk deactivates TMV
Powdered or fresh
So does soap and water!
95-100% effective

Worker sanitation
Wash hands with soap before starting work and after smoking
Don’t allow visitors to handle plants without washing hands
Keep propagation area off-limits to workers handling older plants

Sanitizer Study
Greenhouse Grower, Feb ‘09
Compared 8 sanitizers for TMV control
Dipped razorblade in TMV infected petunia sap
Sanitized the razorblade with different treatments
Cut new petunias and rated for TMV development

From: Greenhouse Grower, Feb 2009

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Common Greenhouse Viruses

by bedmunds on Mar 18, 2010

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Common Greenhouse Viruses — Presentation Transcript