(I) First Fire Blight Infections Predicted from 31 March – 3 April, Antibiotic Application Necessary on Open Flowers; (II) Add Fungicides as First Major Scab Infection is Predicted 31 March – 3 April
If pear and apple flowers are opened in your location or will be opening 31 March – 3 April, we have fire blight infections predicted to occur with rains on 2 April in Bristol, 1 April in Winchester, Timberville, Charlottesville and Sperryville, and on 1 – 3 April in Tyro, Roseland and Rustburg, VA. Please check your closest NEWA station for fire blight predictions with oncoming rains 31 March – 3 April: https://newa.cornell.edu/fire-blight/ EIP values in the NEWA fire blight model report significant risk ranging from 103 – 222, and dark red field surrounding this number. Remember, a wetting event can be heavy dew, rain, or spray water when you apply fungicides (if you did not add antibiotic into the tank and EIP is 100 or above in an orange color field). Therefore, since the risks are wetting event dependent, apply your streptomycin in mix with LI700 or Regulaid within 24 h before a wetting event triggering an infection (dark red field and EIP over 100). Apply streptomycin if you will apply a fungicide spray during the periods when the EIP field is orange and EIP value is above 100. Add fungicides to streptomycin as first major scab infection will occur with rains 1 – 3 April. To determine your next streptomycin spray application, use the type-in spray date function in the NEWA EIP Fire Blight model – scroll down on the page and you will find it – it is below the Wetness Events Table. Spray options are described below these outputs from NEWA fire blight model:
SPRAY OPTION 1: preventive streptomycin application – cover up to 24 h before the predicted wetting event any apple and pear trees in bloom with either: Harbor, or Agri-Mycin 17 WP, or Fire Wall 17 WP at 1.5 to 3 lb per acre (24 – 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 use 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) about every 14 days for rust and scab. In between, you can use mancozeb + either Fontelis, Sercadis, Miravis or Excalia (SDHI fungicides).
SPRAY OPTION 2: Only if you must, i.e. you want to see if model was correct, use OPTION 2: if you have a smaller acreage farm with apples or pears in bloom, you could wait and see will you get the infection event or not on 4/1/2026, because the showers might be spotty and occur on one location and not on the other. So, if you get the rain events on the 31 March – 3 April, infection will occur and you will need to cover with streptomycin up to 24 h after the first rain event has started. Apply streptomycin in mix with Regulaid or LI700 up to 24 h after the infection i.e. rain or dew event started (kick-back mode of application). In case you will use LI700 instead of Regulaid, 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 fungicide application add streptomycin to it. You can add your fungicides to streptomycin to make the spray more economical.
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.
RESCUE TREATMENT: if no streptomycin was used, use 12 oz/100 Apogee/Kudos at 2 to 3 days after infection event to prevent shoot blight and the canker formation on wood
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.