1. No Risk From Scab Infections; 2. Keep An Eye on Cedar-Apple Rust Galls; 3. Potential Risk From Fire Blight 12-14 April

1. APPLE SCAB. For now the apple scab models are not predicting any new infections based on the weather forecast visible as of today. We will see if the forecast for 12-13 April changes or not. As of right now chances for rain are low, 7 – 16%. However, it is imperative to remember that we do not rely on anything beyond 48h in forecast as predictions can change rapidly. Hence, please continue to look at the scab models to determine if and when the next infection prediction will occur in the foretasted weather. But, as of now, it seems there are no oncoming risks from scab infection.

2. CEDAR APPLE RUST. Next issue we will face is cedar apple rust. With the recent warm rains cedar apple galls are likely visible as being orange in central and southern Virginia (Figure 2). When galls turn orange fungal basidiospores can fly from the cedars to apple leaves and fruit and infect them during rain. In Northern Virginia they should emerge orange with the next warm rain(s). When gall turn orange (Figure 2), please use the below simple model to predict when infections on leaves and fruit can occur.  To predict how severe rust infections will be, use the average temperature and leaf wetness predicted in forecast and plug them in the model in Figure 1 below. Before the rains triggering rust infection, start and continue to apply sterol inhibitor fungicides, also known as DMI fungicides, on a 14 day schedule. These fungicides are Inspire Super, Cevya, Indar, Rally, Sonoma, Topguard, Rhyme, or Procure. Always tank mix them with Manzate Pro-Stick (very effective for rust). DMI fungicides are essential to apply every 14 days for rust control and should extend all the way until the 2nd cover. DMI fungicides also have activity against scab and powdery mildew. In between the 14 days of using DMI fungicides, i.e. at 7 day interval, apply SDHI fungicides Fontelis, Sercadis, Miravis or Excalia and always add Manzate Pro-Stick to the tank mix so as to protect against apple scab, rust and powdery mildew. This time of the year your spray interval with fungicides should be every 5 – 7 days (5 days if you use alternate row middle; 7 days if you use complete sprays).