As Predicted in Blog Post on 4/16/2025 Fire Blight Infections Occurred or Will Occur on 19, 20, 21, 22, 25 April Across Virginia: If You Haven’t, Apply Streptomycin, Do So Immediately on Any Open Flowers
As we warned you timely in my blog post of April 16, 2025, and advised you to look at the NEW EIP model twice daily from 16 April on: Fire Blight NEWA Model EIP Values In Virginia Predicted 100 and Above with Weather Forecast 19-21 April: Infection in Bristol VA and Infection Possible With Spray Tank Water, fire blight infections have occurred in Winchester yesterday 19 April, and are possible again today and tomorrow across all Virginia. Assuming you have apple/pear flowers open, if you are in Winchester area, application of streptomycin yesterday, 19 April would have controlled all three predicted infections on 19, 20, and 21 April. If you applied streptomycin on 18 April, that would have been too far away for infection of 20 April, and will not control the wetting triggered infections of today and tomorrow: 20 and 21 April. If you have applied streptomycin plus Regulaid or LI700 today, it would not have controlled infection of 19 April, unless you applied it up to 24 h from the wetting event start on the 19 April. If you did spray within that window, you will be fine, if you sprayed after 24 h from yesterday’s wetting event, you need to spray again today. Infection predilections vary depending on a location – so you must look at NEWA EIP model twice every day and base you spray decisions on that. As you can see in print screens below, we have entered a block of more than 2 days of extremely conducive conditions for fire blight infections – day after day, so to determine when your next streptomycin spray application is needed, after the previous one, you MUST type in the Streptomycin Spray Date in the NEWA EIP Fire Blight model shown below – scroll down on the page and you will find it – it is below the Wetness Events Table:
For all the NEWA EIP fire blight prediction screenshots below the source is: https://newa.cornell.edu/fire-blight/
SPRAY OPTION 1: preventive spray application of streptomycin – cover before the predicted wetting event any apple and pear trees in bloom with streptomycin: Harbor, or Agrimycin 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. FireWall changed its formulation to FireWall 50WP and the rate to use this higher concentrated material is 8 – 16 oz/A. If rain does not occur, you can trigger the infection at EIP 100 or above 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.
SPRAY OPTION 2: Only if you must, i.e. you want to see if the EIP model was correct in reporting an infection, use OPTION 2: if you have a smaller acreage farm with apples or pears in bloom, you could wait and see if will you get the rain or dew event or not on 19-21st April (only Bristol VA for now). The showers might be spotty and occur on one location and not on the other. So, if you get the rain event on the 20th April (Bristol, VA) and you did not apply streptomycin before it, infection will occur and you will need to cover with streptomycin up to 24 h after the rain event on 20 April has started. Apply streptomycin in mix with Regulaid or LI700 up to 24 h after the infection rain event started (kick-back mode of action). In case you will use LI-700 instead of Regulaid, use a penetrating action rate for LI-700. If rain does not occur on 20 April, infection will not occur, unless you provide the water with a fungicide spray application near the date(s) with EIP of 100 or above in orange box, which can and will trigger the infection – so if you plan fungicide application add streptomycin to it.
NOTE: 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) for scab and powdery mildew.
WARNING: If you used captan recently, which would not be my choice at this time of the year (use mancozeb instead), DO NOT add Regulaid or LI700 (at penetrating rate) to streptomycin for this bloom spray against fire blight.