Fire Blight Infections Predicted in NEWA EIP Model With Showers 29 April – 2 May, Varying Across Virginia
There are a lot of apple trees in bloom, especially in northern Virginia. For any locations with apple trees still in bloom major fire blight infections are predicted in NEWA EIP model with rains in Cross Junction and Winchester on 29 and 30 April, 1 and 2 May, in Madison on 30 April and 2 May, in Roseland 29 and 30 April, in Tyro on 30 April and 1 May, in Quicksburg on 29 and 30 April, and 2 May, in Charlottesville on 29 and 30 April, in Timberville on on 29 and 30 April, 1 and 2 May, in Rustburg on 30 April and 1 May, in Sperryville on 30 April, and in Bristol on 29 and 30 April, 1 and 2 May. Please look a the EIP model for your location or nearest neigboring location to you, it is free: https://newa.cornell.edu/fire-blight/
SPRAY OPTION 1: spray preventive streptomycin – cover 24 h or less before the predicted wetting event any apple and pear trees in bloom with streptomycin: Harbor, or Agri-Mycin 17 WP, or Fire Wall 17 WP at 1 to 3 lb per acre (16 – 48 oz/A) plus LI 700 at a penetrating rate or use Regulaid instead of LI700. Based on the Regulaid label, you could use 2 pints penetrating rate. New formulation FireWall 50WP has the rate of 8 – 16 oz/A. If rain does not occur and EIP is 100 or above, while field is orange color, you can trigger the infection if you provide water with a fungicide spray application, so if you are applying a previously planned fungicide application – add streptomycin to it. Option one is a must in large acreage apple and pear farms. You can add your fungicides to streptomycin to make the spray more economical, and keep the SI (DMI) fungicides + mancozeb (3 lb/A) every 14 days for rust and scab. In between, use mancozeb + SDHI fungicides for scab & powdery mildew.
SPRAY OPTION 2 (RISKY): Wait to see if the model was correct, your tractor or sprayer breaks down, or if you have a smaller acreage. Wait until the prediction of getting the wetting event(s) will occur, because the showers might be spotty and occur on one location and not on the other. If you get the wetting event(s), an infection will occur, and you will need to cover with streptomycin up to 24 h after the first wetting event has started. Apply streptomycin + Regulaid or LI700 up to 24 h (kick-back mode of application). If you will use LI700, use a penetrating action rate for LI700. If rain does not occur, infection will not occur, unless you provide water with a fungicide spray application near the infection dates, which can and will trigger the infection – so if you plan a fungicide application add streptomycin to it.
SPRAY OPTION 3 FOR EXTREME INFECTIONS: For continuous block of 4 days or more of infections predicted by dark red field, apply streptomycin every 2 to 3 days to protect newly opening flowers. Do not add adjuvant for subsequent sprays if your leaves are too yellow.
In each case, and especially in Option 3, use the Streptomycin Spray Date function, just below the Wetness Events Table in NEWA Fire Blight model, to type in the date you applied it and see how EIP model re-calibrates after streptomycin application and to see when next the streptomycin application is needed.
RESCUE TREATMENT: if no streptomycin was used on time and the window of 24 h after the infection has passed to use streptomycin, apply 12 oz/100 Apogee or Kudos at 2 to 3 days after infection event to prevent shoot blight and the canker formation on wood. Combine with pruning fire blight symptoms out.
WARNING: If you used captan recently, which would not be my choice, DO NOT add Regulaid or LI700 (at penetrating rate) to streptomycin for this bloom spray against fire blight.