Major Scab and Juniper Rust Infections Predicted from 6 to 9 April in Winchester Area
Apples are at Tight Cluster or somewhat beyond on early cultivars at in Winchester. From 6 – 9 April 2022, we are expecting multiple rain events followed by the slow drying conditions as per the NWS forecast with the warmer periods peaking up to 64F and these rains and leaf wetting will lead to second major scab infection in Northern VA, and especially in and around the Winchester VA. It seems that this will not be the significant scab infection in central and South central VA due to fast drying after the rain events, but it will be a severe rust infection event. For these latter two regions I would recommend to be covered with at least 3 lb of Mancozeb Pro-Stick, but adding a DMI aka SI fungicide will be a wise choice. It varies depending on a location, but the current scab model prediction indicate that the scab infection will start with the rain on 6 April early in the morning (~ 7 AM) and multiple other infections will occur with the rain events on 7th, 8th and 9th April. This will surely cause significant apple scab fungus ascospore release and infections in northern Virginia. These are my spray recommendations:
A good spray period will be from today 5th or tomorrow 6th April before the rain on 6th starts and any time during 7th April when leaves dry a bit, because you would achieve maximum coverage of the rapidly expanding green tissue. If you must, you can also apply a DMI fungicide up to 96 h after the infection started on the 6th April but we would not recommend this kick-back application mode and we would recommend it only in an emergency (no spray coverage before 6 April; sprayer breakdown, etc.) . The best option to apply would be Inspire Super (12 fl oz/A), or Cevya (5 fl oz/A), or Procure (16 fl oz/A) plus mancozeb (3 lb/A). Keep in mind that the systemic fungicides here are preferred for severe scab events like this because with warmer temperatures the green tissue will increase its surface area intensely from 6 – 9 April (1), and the DMI will enter your leaves while they expand and protect them through the multiple rains (2). The idea is to have enough fungicide residue cover to stay on the leaves through the infection periods even if rains top up to 2 inches (up until rains end on 9th April). If rust is not of a concern for your location, as maybe no cedars are close to you, mancozeb (3 lb/A) plus Luna Tranquility, or Syllit, or Fontelis, or Aprovia, or Sercadis, or Miravis, or Excalia, would be a better choice for scab control (all these single-site SDHI fungicides will not be effective on juniper rusts). I would not recommend you to apply SDHI after the infection on 6 April (kick-back mode of use). You can, if you must, apply Luna Tranquility after the infection due to an AP component in it that has kick-back activity up to 72 h (pyrimethanil). Make sure you apply it up to 72 h after the rain starts early morning on 6 April (~ 7 AM). Keep in mind that Dodine (Syllit) is limited to two applications before pink bud (PK), and should not be used where resistance in scab fungus to dodine is present.