Immature growth and leaves must remain protected through the autumn period with copper applications, particularly in frost-prone areas.
Many growers choose not to use frost protection as leaf-fall allows pruning to get underway. However, with frost comes the added risk of Psa movement into leaf and cane tissue.
Inoculum levels within the orchard must be minimised to avoid disease spread. Growers with frost protection, particularly those with windmills, should consider protecting high-risk blocks such as developing Gold3 canopies and young plants. Psa multiplication is rapid in frosted tissue and the colder the frost, the higher the risk.
Italian research also showed water-soaked leaves damaged by frost developed Psa in 100% of cases when sprayed with Psa inoculum vs 20% infection for non-frosted leaves.
Once plants harden off in winter this risks reduces. Males are likely to be vulnerable later into the season as they are often slower to lose their leaves.
Linda Peacock, KVH Operations