1. Virus Diseases in the UK: A Case Study of Current Problems and Future Challenges

2. Virus problems in field crops
Only two groups cause significant problems:
Aphid-borne diseases
Soil-borne diseases

3. Current problems in field crops
Cereals
BYDV / CYDV, BaYMV & BaMMV, SBCMV
Oilseed rape
BWYV, (TuMV), (CaMV)
Sugar beet
BYV, BMYV, BNYVV
Potato
PVY, (PLRV), TRV, (PMTV)
Carrot
Motley dwarf complex
Field brassicas
BWYV, TuMV, CaMV
Pea
PEMV, (PSbMV), (PEBV)
A. Aphid-borne
B. Soil-borne
C. Seed & aphid

4. 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

5. 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)

6. 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

7. 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

8. 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

9. Current problems in fruit crops
Apple
(ApMV, ASPV, ACLSV, ASGV)
Pear
(ASPV)
Plum
(PPV)
Strawberry
SCV, SMoV, SMYEV, (nepoviruses)
Rapsberry
RBDV, (nepoviruses)
Blackcurrant
BRV
A. Propagation
B. Other transmission

10. 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

11. 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

12. New viruses found in UK since 1970
‘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

13. 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

14. 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