Nectarine damage prevention
I have a nectarine tree that was planted approximately four years ago. Last year was the first year it was a significant fruit crop. All of the fruit was blackened and sappy. It looked to me like some kind of a bacterial disease. What would you suggest as preventative measures to take for the season and approximately when should I take them
Montgomery County Maryland
Do you have a photo of the damage from last year? It may have been bacterial, in which case, there are no treatments other than the prevention of recurrence with sanitation. There are some pages for peach and nectarine diseases, insects, and cultural and environmental below. Fungicide sprays are best used only as a preventative; timing and re-application intervals will depend on the product and should be listed on the label.
From the pictures and the mummies it looks like brown rot.
The sulfur application will depend on which specific product you choose, as they are formulated differently. Instructions for dilution (if applicable), timing, and frequency of application will be listed on the product label. Another fungicide option would be Immunox, though for this use we do not recommend the formulation that includes insecticide. Sulfur tends to be a milder general fungicide, but formulations such as Immunox seem to be more effective thus far.
Virginia Tech has a handy chart of fungicide effectiveness for tree fruits in this hefty document - https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/456/456-018/ENTO-336.pdf - in section 3-7 (page 93).
Since treatments tend to start during (or overlap) flowering, there is some risk to pollinator health. Research into how various fungicides affect bees is still ongoing. If you are concerned, our advice is to minimize spraying open flowers during the morning or afternoon where possible and to potentially expect slightly lower pollination in the case of pollinator avoidance after spraying.