Please see below the updates from Dr. Srdjan Acimovic on the fire blight situation in Virginia.
If the data from Roanoke International Airport station are correct there will be fire blight infection today 4/14 triggered by the rain, in and near Roanoke. Growers should apply strep 1.5 lb + Regulaid 1 pt/100 before rain or apply this mix up to 24 h after the rain event that triggered the infection. What puzzles me is that Floyd (CLH), not so far away from Roanoke, has no infection predicted for 4/14, leading me to believe that it either one of the two stations is not calibrated properly OR it will be hit or miss in terms of where rain/dew lands. Next, the infection occurred in Esmont (Rees), Lynchburg, and Red Hill yesterday 3/13 and if the growers did not apply streptomycin before the rain/dew on 3/13 triggering the infection, they must and can still apply strep 1.5 lb + Regulaid 1 pt/100 today i.e, up to 24 h after the rain event that triggered the infection for it to be effective. In Lynchburg infection is also predicted today 4/14 and the spray today 4/14 will cover for both infections 4/13 and 4/14. In Richmond, if the station is plugging in the correct weather data into the model, there was contiguous infection 4/9-12 which is not good, and proper response as per my previous blog was to spray on 4/10, and 4/12 to cover for all 4 infections and both times growers should have applied strep 1.5 lb + Regulaid 1 pt/100 to get 24 h kick-back and thus cover for all 4 infections. This is based on my experiences from eastern NY and is different from the VA spray guidelines that currently state that a streptomycin application remains effective 3-5 days. Based on this experience with the outbreaks I saw after similar block of infection in NY, I disagree with that 3-5 days as per my blog published here: 1. Frightful Blight Model Cases How Long A Streptomycin Spray Lasts; 2. Major Scab Infection/s Possible 25-30 or 28-29 May All East NY posted on May 25, 2020. In Rustburg (Crown), I would apply strep 1.5 lb + Regulaid 1 pt/100 tomorrow 4/15 if the “High” risk turns into “Infection” for 4/14 in NEWA’s EIP model. Danville has had infections continuously from 4/8-12, assuming correct weather data. Most other weather stations do not indicate a risk from infection, assuming they are functioning properly in collecting the weather data. Please check your closest weather station in NEWA daily, and apply protection according to the EIP model, and make sure it is functioning properly before you can trust the model outputs from it.
You can reach Dr. Acimovic at 517-449-0905
Can I apply streptomycin to treat fire rust infections on fruit trees in my garden?
Here is the response of Dr. Acimovic:
The question is unclear because fire blight is a different disease from cedar apple/quince rust and vice versa. You cannot use streptomycin to control cedar apple/quince rust. You can only use streptomycin to control fire blight and only if it is applied preventively, not after the disease has expressed with fire bligth symptoms.