Streptomycin Application Needed Today to Protect Against Fire Blight Infections 14-16 April in Whole Virginia, Add Fungicides to Your Tank

Severe fire blight infections are imminent 14-16 April in Whole Virginia. Apply protective sprays today for any pome fruit in bloom, even if you have less then 5% flowers left on cultivars that are in petal fall. Below are mix options to use, but preventive application of streptomycin is the most effective (Spray option 1 below). Use the NEWA model’s box to type in “Streptomycin Spray Date” (Fig. 1) by clicking the “Click to enter a date” below Wetness Events Table to determine how model will recalculate after you applied your streptomycin and when will you need to apply the next streptomycin application. If the date you apply you no longer see the dark red boxes with EIP 100 or above you are in good shape, but if you do, you will need to reapply streptomycin again at least 2 days after the previous spray application. The model is available here:  The outputs from NEWA’s EIP models are visible below, please review them.

Figure 1. NEWA model’s box “Streptomycin Spray Date”where you need to “Click to enter a date” add a date and then look to determine how EIP model above will recalculate after you applied your streptomycin (will you see dark red boxes vanish or not?) and when will you need to apply the next streptomycin application.

SPRAY OPTION 1: preventive streptomycin – cover any apple and pear trees in bloom before the predicted wetting event triggering the infection by 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. You can use 16 fl oz./A plus LI 700 or Regulaid at a penetrating rate but I had this rate fail to control fire blight in my trials last year, probably due to strong UV light degrading the antibiotic. Hence. I recommend 24 oz or more of FireWall or Harbor. 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 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 wetting event or not on predicted date, because the showers might be spotty and occur on one location and not on the other. So, if you get the rain events based on the forecast, 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 rain 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 date(s), which will trigger the infection – so if you plan 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 you are concerned your leaves will get 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. 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).

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.