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Virus Diseases in the UK:
A Case Study of Current
Problems and Future
Challenges
Virus problems in field crops
• Only two groups cause significant problems:
– Aphid-borne diseases
– Soil-borne diseases
Current problems in field crops
• Cereals
– BYDV / CYDV, BaYMV & BaMMV, SBCMV
• Oilseed rape
– BWYV, (TuMV), (CaMV)
A. Aphid-borne
• Sugar beet
– BYV, BMYV, BNYVV
B. Soil-borne
• Potato
C. Seed & aphid
– PVY, (PLRV), TRV, (PMTV)
• Carrot
– Motley dwarf complex
• Field brassicas
– BWYV, TuMV, CaMV
• Pea
– PEMV, (PSbMV), (PEBV)
Control of viruses in field crops
• Aphid-borne diseases
– Use of insecticides has proved relatively successful
• e.g. seed treatments on sugar beet
• e.g. PLRV control in seed potatoes
– Seed potato certification / testing
• e.g. PVY and other viruses
• Soil-borne diseases
– Deployment of natural resistance is key
• e.g. rhizomania
• e.g. Barley mosaic viruses
Virus problems in protected
crops
• Simple model of virus transmission:
– Long-distance spread (between greenhouses)
• via propagation material (seed, cuttings or young plants)
– Short-distance spread (within greenhouses)
• Mechanically (esp. protected vegetables)
• Insect-borne (esp. ornamentals)
Current problems in protected
crops
• Tomato
– PepMV, ToMV
• Cucumber
– CGMMV, (BPYV)
• Pepper
– PMMoV
• Ornamentals
– CMV, TSWV, INSV…..
– many others………..
A. Propagation &
Mechanical
B. Propagation & Insect
C. Insect alone
Control of viruses in protected
crops
• Spread via propagation
– Need for effective screening
– Often inadequate esp. for ‘new’ viruses
• Mechanically-transmitted diseases
– Often extremely hard to control once introduced
• Resistance can work but limited sources
– e.g. Tomato mosaic virus
• Insect-borne diseases
– Often extremely hard to control: difficult pests &
viruses with broad host ranges
– e.g. Western flower thrips & TSWV
Virus problems in fruit crops
• Most spread via movement of
propagation material
– Budwood and rootstocks
• Secondary spread via variety of means:
– Aphids, nematodes, Pollen, mites
– Generally very limited due to supply ‘clean’
planting material
Current problems in fruit crops
• Apple
– (ApMV, ASPV, ACLSV, ASGV)
• Pear
– (ASPV)
• Plum
– (PPV)
• Strawberry
– SCV, SMoV, SMYEV, (nepoviruses)
• Rapsberry
– RBDV, (nepoviruses)
A. Propagation
• Blackcurrant
B. Other transmission
– BRV
Control of viruses in fruit crops
• Viruses spread by propagation
– Use of certification schemes is highly successful
– e.g. PPV
• Insecticide control of aphid vectors has proved
successful
– e.g. control of strawberry viruses in propagation
stocks
• Deployment of natural resistance has been effective
– e.g. Raspberry bushy dwarf virus
Potential future problems
• Bemisia–transmitted viruses
– esp. protected vegetables
• Thrips-transmitted viruses
– esp. protected vegetables & ornamentals
• Viroid diseases
– In particular PSTVd on tomato, pepper & potato
• New viruses introduced via ornamental trade
– e.g. solanaceous hosts from South America
• Soil-borne viruses
– Arable crops
‘Bedford virus’ (Aubian mosaic virus?)
Beet necrotic yellow vein virus
Beet soil-borne virus
Oat chlorotic stunt virus
Soil-borne cereal mosaic virus
Barley yellow mosaic virus
Barley mild mosaic virus
Beet pseudo yellows virus
Beet yellow stunt virus
Pepino mosaic virus
Zucchini yellow mosaic virus
Potato spindle tuber viroid (erad.)
Calibrochoa mottle virus
Canna yellow mottle virus
Clover yellow mosaic virus
Datura Colombian virus
Impatiens necrotic spot virus
Petunia vein clearing virus
Chrysanthemum stem necrosis virus (erad.)
Nemesia necrotic ring virus
New viruses
found in UK
since 1970
Soil-borne
Vegetables
Ornamentals
Future issues
• Reduction in use of aphicides
– Withdrawal from use / residue issues
– Particularly on fruit & vegetable crops
• Continued expansion of world trade
– Esp. movement of cuttings/seed from outside EU
• Lack of priority for disease resistance in
breeding programs
– Other factors often of more commercial importance
• Rapid production of new varieties
– Esp. in ornamentals sector
– Appearance of new, unexpected problems
The next steps
• Members of EG1 revise questionnaire to capture
more information e.g. crop and control data
• Send questionnaire to all consortium members
• Engage with other key stakeholders e.g. industry
and specialist virus groups
• Collect information on future risks
• Compile all information in a spreadsheet
• Summarise key virus problems and future risks