Virus Yellows Flashcards
What is virus yellows a complex of
3 viruses:
Beet yellows
Beet mild yellowing
Beet chlorosis
Which virus is the most damaging
Beet yellows
Which virus is the most common
Beet mild yellowing, causing 22% yeield loss when it appears early June
What can beet yellows reduce
Reduces the photosynthetic area of the leaf, showing yellowing between veins and thickened brittle outer leaves
What crops are more susceptible
You get crops up to the 12 leaf stage- on from this they’re more tolerant to virus and aphids
In beet yellows what can the yellowing be confused with
drought and nutritional (magnesium )
What is the threshold
1 green wingless aphid per 4 plants before 12 leaf stage then treatment is justified
What application can be made
One application of Teppeki (flonicamid) available for aphid control - timing is critical
What is the second threshold
Between 12-16 leaves the threshold is 1 green wingless aphid per plant
How can you test ?
BBRO offer testing- takes average of 2-4 weeks for the virus to show in the crop- by the time symptoms show it’s difficult for aphid control
How can you know if aphids are in the crop
Look out for virus warnings on BRO advisory bulletins
Which aphid can transmit the virus
Peach potato aphid (myzus persicae) when feeding
Resistance ?
Aphid resistance to pyrethroids and carbamate insecticides remains above 80% in 2019
Where is BYV most common ?
Norfolk and Suffolk in recent seasons
How can you control it ?
No resistant varieties
Weed removal
Remove ground keepers, debris in clamps
Seed treatments give protection for 8-10 weeks
