PLUM: FUNGICIDE EFFICACY

Note:    Spring brown rot and shot hole control is not necessary for most plum cultivars in California.

Rating: 5 = excellent and consistent, 4 = good and reliable, 3 = moderate and variable, 2 = limited and/or erratic, 1 = minimal and often ineffective, 0 = ineffective, NL = not on label, and ND = no data.

**Not registered, label withdrawn or inactive in California

*** Postharvest fruit registrations in California include: BioSpectra/Cerafruta/Uniguard, Chairman, Mentor, Teb, Penbotec/Pyrimethanil, and Scholar/FDL.

¹ Code numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different Code number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode-of-actions (MOA) with high resistance risk before rotating to a fungicide with a different MOA (Code number); for other fungicides, make no more than two consecutive applications before rotating to fungicide with a different MOA (Code number).

² Brown rot blossom blight is seldom observed on most plum cultivars and usually does not require treatment during bloom.

³ Powdery mildew seldom is observed on most plum cultivars and control usually is unnecessary.

⁴ Shot hole disease rarely occurs on plums in California. The small holes often observed on leaves in spring are caused by either a genetic disorder or by other agents including environmental factors.

⁵ To reduce the risk of resistance development, start treatments with a fungicide with a multi-site mode of action; rotate or mix fungicides with different mode-of-action FRAC numbers for subsequent applications, use labeled rates (preferably the upper range), and limit the total number of applications per season.

⁶ Registered for pre- and postharvest applications on plum.

⁷ Blossom blight only; not registered for use after petal fall.

⁸ Oil = "light" summer oil, 1-2% volume/volume.

⁹ High summer temperatures and relative humidity reduce efficacy.

¹⁰ Strains of the brown rot fungus Monilinia fructicola resistant to Topsin-M and T-Methyl are found in other stone fruit orchards in California. Brown rot is so seldom found in plum orchards that the resistance levels in plum orchards have not been assessed. Subpopulations of both Monilinia spp. have been shown to be resistant to AP (FRAC 9) fungicides on prune in CA.

¹¹ Do not use after jacket (shuck) split.

¹² Do not use in combination with or shortly before or after oil treatment.

PLUM: TREATMENT TIMING

Note: Not all indicated timings may be necessary for disease control.

Rating: 3 = most effective, 2 = moderately effective, 1 = least effective, and 0 = ineffective

¹ One early application should suffice; a second treatment should not be needed.

² No treatment is recommended for shot hole because the shot holes found on plum leaves only rarely are caused by the shot hole fungus.