virus and bacteria in high tunnels

Identifying Virus and Bacterial Diseases in High Tunnels

Michelle Grabowski

© 2011 Regents of the University of Minnesota. All rights reserved.

What’s Different and Why?

• High tunnels provide a unique environment • Excess heat and humidity • Plants are handled more • Tight spacing of plants• Insects pest like thrips and white flies more

likely than in field conditions

Viruses


Tobacco Mosaic Virus (TMV)

• Dark & light green mottle• Small, curled or distorted• Plants may be stunted

UFL

S.M. Douglas, CTAg.Exp.station



Tobacco Mosaic Virus (TMV)• Fruit Symptoms• Poor yield• Distorted fruit• Uneven color• Delayed ripening• Brown discoloration

of inner walls

JP Jones, UFL




Tobacco Mosaic Virus

• Infects over 150 genera – petunia, pepper, weeds

• Can come in on seed coat• Very durable

– Transmitted on tools, hands, clothing, leaf debris– Survives in plant debris in soil, on strings, poles,

cross bars in tunnel, in cigarettes• Symptoms develop rapidly in heat

MSU Extension


Tomato Spotted Wilt Virus (TSWV)

• Bronzing of leaves

• Small darks spots on leaves, streaks on petioles & stems



• Early infection results in no fruit

• Later infection– Ring spots on green

fruit– Yellow to white rings

on mature fruit

W.M. Brown, Bugwood.org


TSWV• Infects 300 species in 34 families

• Can spread in seed

• Not as durable as TMV

• Not easily transmitted on tools, hands, and from rubbing

• Thrip larvae pick up TSWV

• Adult thrips transmit TSWV

P.M.J. Ramakers, APS Bugwood.org

C.Hesselein, Bugwood.org


Identifying Virus Diseases with Immuno Strips

• Agdia.com• 5 for $32-37• 25 for $105-120• Strips for many viruses• Most specific to 1 pathogen• A few combo strips


UMN Plant Disease Diagnostic Clinic

• Will identify the problem regardless what it is

• Lab techniques– Electron Microscopy– ELISA – RT-PCR

• http://pdc.umn.edu


Managing Virus Diseases in Tunnels

• Purchase seed from a reputable supplier that uses and acid treatment of seed

• Purchase only transplants that have been tested and found to be virus free



• Do not grow ornamentals with tomatoes and other crops

• Control weeds in tunnels

• Maintain a weed free buffer outside of tunnel

• Do not allow use of tobacco products in the tunnel



• Workers must have clean clothing and wash hands before entering the house

• Wash hands and tools regularly while working

• Immediately bag and remove infected plants

• Manage thrips and other insect pests – TSWV, CMV

• Sanitize strings, poles, boards and all surfaces in the tunnel after TMV infection


Sterilizing Equipment & Hands

• Soap and water

• Carnation instant nonfat dry milk (20% wt/vol)

• 1:10 bleach water solution (0.6% bleach)

• Virkon (1% wt/vol)

Lewandowski, D. J. Hayes, A.J. and Adkins, S. 2010. Surprising results from a search for effective disinfectants for Tobacco Mosaic virus – contaminated tools. Plant Disease 94:542-550

Bacteria


Tomato Pith NecrosisPseudomonas corrugata

Photos from M. McGrath, Long Island Hort. Research & Extension Center


Pith NecrosisP. corrugata

M. McGrath, Long Island Hort. Research & Extension Center

M. McGrath, Long Island Hort. Research & Extension Center


Tomato Pith NecrosisPseudomonas corrugata

• Favored by high humidity, cloudy weather, high N, rapid growth

• Soil borne, possibly seed borne

• Does not appear to spread between plants on tools, hands etc

UFL


Managing Pit Necrosis

• Reduce humidity through ventilation

• Provide adequate but not excessive fertilizer

• Remove entire plant as soon as symptoms develop, bag the plant and bury and remaining debris

• Copper fungicides are ineffective


Bacterial CankerClavibacter michiganensis subsp. michiganensis

• In field conditions or with overhead irrigation see

• Birds eye fruit spots

• Classic cankers at leaf axil

D.Cuples Agri-Food Canada

D.Cuples Agri-Food Canada


Bacterial CankerC. michiganensis ssp. michiganensis

P.Bachi, UKY Bugwood.orgASTA

MSU

MSU



• Lives on surface of the seed & inside seed coat

• Survives 5 yrs on seed

– 2-3 yrs in plant debris

– 1 month in soil or on plastic or cement

– 1 year on plant material (wood stakes etc) or rock wool

• Survives better in cool dry conditions than warm wet conditions



• Enter through wounds or stomata

• Spread on workers hands, clothing, tools, splashing water, forceful pesticide application

• Favored by high temps (75-90F) wet conditions, low light and nutrient imbalance

• May not see symptoms for 2-7 weeks


Managing Bacterial Canker

• Use certified disease free seed or treat seed in hot water for 25 min. at 125F

• Reduce overhead watering of seedlings

• Start with clean potting mix, pots & trays

• Regularly disinfect cutting tools & worker hands

• Copper fungicides are ineffective


Managing Bacterial Canker

• Immediately bag and remove infected plants

• Remove several neighboring plants as well

• Do not leave cull piles or plant debris near the tunnel

• Control solanaceous weeds in & around the tunnel

• Disinfect tunnel, crates, tools between crops

• Rotate away from tomato & pepper 2-3 years

ThanksQuestions?

virus and bacteria in high tunnels

Technology

university of minnesota

virus free

tobacco mosaic virus

tunnels purchase seed

humidity plants

plant debris

mature fruit

high humidity