The current 10 day forecast for southern counties predicts a 50% chance of rain for Friday April 25, and an extended period of rain next week. The apple scab model at NEWA predicts between 14 and 22 percent ascospore maturity for the period April 25 through April 29 in Upper Deerfield. The prediction for Pittstown in the northern region is less at 17% by the 29th but regardless any wetting next week will be a high risk infection period.
Forecasts can change so monitor your local weather forecasts closely. It’s important to plan ahead because if you want to use any of the newer materials they are not always available on short notice. Options now include full or half rates (read the label carefully) of EBDC’s (Manzate, Dithane, Polyram), DMI’s (Rally, Indar) plus a protectant, or any of the newer premixes (Luna Tranquility, Luna Sensation, Inspire Super, and Merivon). The addition of a 1/2 rate of an EBDC to these premix materials is advised in orchards that had moderate or high levels of scab last year.
QoI resistance has been confirmed in one northern county orchard, and DMI resistance is suspected in some southern county orchards. Inspire Super is a premix that includes a DMI fungicide. Merivon, Pristine, and Luna Sensation are premixes that include QoI fungicides. Flint, and Sovran are QoI fungicides. Orchards that have properly applied either chemistries and have experienced poor control should avoid these materials during peak ascospore release. Combinations of Fontellis (SDHI) plus a half rate of EBDC; or Luna Tranquility (SDHI+AP) plus a half rate of EBDC; or Vangard + a half rate of an EBDC should control mildew scab and rust at this timing. Note that Vangard is rated fair for mildew control so it it may not provide acceptable control for powdery mildew susceptible apple cultivars.
One final consideration: if you are planning on using Flint, Sovran, or Pristine for summer disease control, read the labels carefully. Use of any of these materials limits you to 4 applications of any QoI material, or any combination of QoI per season. The newer premixes that contain QoI’s do not have the same restriction, however they also have similar limits depending upon the rate used. Read the labels carefully!
