Source: NCSU COOPERATIVE EXTENSION, 7/14/20



In the previous Disease Update I sent a basic spray schedule for Glomerella leaf spot/bitter rot management for early-, mid-, and late- harvest varieties. In this schedule, please take note that in general, Captan + Ziram is rotated every 7 to 10 days with Captan + Prophyt (or equivalent phos. acid fungicide) or Captan + a single site fungicide such as thiophanate-methyl (e.g. Topsin). Of course,this is beyond that of applying a stroby-containing fungicide (blue or purple color code, e.g. Flint or Merivon) which should be incorporated at this point in the season prior to a predicted heavy rain period and in the immediate pre-harvest period.

While we have not observed a benefit in our fungicide trials of adding ProPhyt in tank mixture with a 3/4 rate of captan (on a 7 to 10 day spray interval), in regards to GLS and bitter rot control, the addition of a phos. acid or single-site fungicide with captan at least every other spray may be important for flyspeck/sooty blotch management.

In addition to evaluating the efficacy of summer fungicide programs (petal fall to harvest) against GLS and bitter rot, we also take harvest data on flyspeck and sooty blotch incidence (see graph below). Fungicide applications commenced at 50% petal fall and continued on 7 to 10 day intervals until harvest on 21-yr-old 'Tenroy Gala’ grafted to M7 rootstock. . All programs were “non-rotational” meaning that within a treatment, the same fungicide was applied throughout the entire season. 

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