Based on recent discussions of low chill hours accumulated, it appears that we could have a protracted bloom and shuck split, etc., all of which is very problematic to peach spray programs. If this is the case, I am probably not telling you anything you do not already know, but as long as peaches are at the various stages which would require application of specific fungicides for specific diseases (e.g. bloom, petal fall, shuck split, etc.), one would need to keep the correct fungicide on target for that growth stage. This might mean that you would put our more applications of Bravo, Captan, etc. over time this year, but this would be required for good disease management. Any fruit which are exposed to scab inoculum will have scab, so you have to cover all of petal fall and shuck split to maintain disease-free fruit. If you miss a spray for limited shuck-split stage fruit on the front or back end (low numbers of newly exposed fruit), those few fruit will likely be hammered with scab, adding to both scab and brown rot issues later in the season for all fruit. In other words, you can’t just hit the vast majority of the fruit in the middle of petal fall and shuck split and expect good disease control. I am not sure about the costs of various options for early-season fungicide applications, but Captan at higher rates is also an option, though quite a few applications of Bravo are legally possible (up to shuck split). Abound is always a good replacement for chlorothalonil, and it would definitely give equivalent if not moderately better efficacy as part of a comprehensive scab program. However, we would still prefer that we not utilize Abound on a regular basis during the petal fall or shuck split timeframes due to the potential for scab and brown rot resistance development. Use of Abound in one year alone will not likely result in resistance, so producers should feel free to use it this year if they feel this is their best choice for residual activity. Sulfur is not sufficiently efficacious for use in petal fall / shuck split timeframes, though if we had nothing other than sulfur, it will often give pretty good results. Please contact your local county agent should you have questions or require additional information.
Protracted Bloom and Possible Protracted Shuck Split — Impact on Peach Fungicide Applications for Scab/Brown Rot
Posted in: Pathology