Apple mosaic virus (ApMV) is a common virus of apples in the northeast. Most cultivars can be affected, but some such as Golden Delicious and Jonathan are known to express symptoms more severely. In 2020, there were several confirmations and reports of ApMV on Ambrosia across the province.
Typical symptoms include pale to bright cream blotches, patches, or banding on leaves (Figure 1). These spots may become necrotic as the leaf ages. Premature defoliation can occur. Distribution of symptoms throughout the canopy are often erratic or confined to a single limb or area. Often, symptoms can be more severe in years with cool to moderate springs.
Figure 1. Variation in expression of apple mosaic virus on Ambrosia. Typical symptoms are pale to bright cream blotches, patches or banding on leaves.
In most cases, there is no impact to yield. However, vigour can be impacted and affect bud set in severe cases. Virus can also make the tree more susceptible to other stressors like disease, winter injury or drought.
This virus is mechanically transmitted only. There are no known insect vectors or indication of field spread, other than potentially through root grafting in high density situations. Management is through the use of virus-free budwood.
OMAFRA will be doing a preliminary survey this winter to determine incidence of virus in the province. This will involve collection of 1-year wood from January 2021 to bud break.
If you suspect there may be virus present in your orchard, please email or call/text: