Over the next two or three weeks bud break will occur in pipfruit. Fungi infection at this stage will give season long control problems, so now is the time to focus on fungi disease control.
I have noted quite a lot of late flower set fruit about. This late set fruit is often already infected with black spot. These infections will be producing conidia spores so do not need mills periods for spore release. Heavy dew is sufficient for infection to occur. Broad spectrum protectant fungicide such as a late dormant copper, then dodine, dithianon, mancozeb or Polyram DF® give good protectant cover. These are old products but have the ability to re-distribute in rain to cover recently expanded new tissue. Once the russet sensitive period is passed, Captan can be added to this list.
Dodine and dithianon have reach back properties, but because they are contact rather than systemic fungicides, they are weak reach back tools over the bud bread period. Where a reach back fungicide is necessary during bud break it is best to opt for a systemic fungicide.
Powdery mildew spore release occurs later than black spot because it over winters in buds. Powdery mildew infected buds break bud later than healthy buds so powdery mildew fungicide sprays do not need to commence until tight cluster.
The first six weeks of the spraying programme are the most critical for disease control. An extra spray during this period is worth two or more later.