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

As of last night (4/15) the NEWA EIP fire blight model predicts we will reach an EIP of 100 and above in many locations in Virginia and North Carolina (see images below) for the 19-21 April weather forecast. However, Dark Red box “Infection” is not reported, except in Bristol VA. In other words the EIP number color field did not change from Orange to Dark Red. This forecast is still beyond the 48 h, thus potentially subject to change due to instability of weather forecast models, so keep looking a the model twice daily. As we get closer to 48 h before the 19 April, the weather forecast is more accurate, and 48 h is a more reliable comfort zone to make a spray decision. When the EIP rises to 100 and above, and the color field around this number is Orange, this indicates that one of the several conditions for fire blight infection to be naturally triggered, besides open flowers, is missing:

• A certain number of heat units must accumulate during bloom for a threshold level of inoculum to be reached,
• A wetting event is necessary after this point to wash the bacteria to their infection sites, and
• The average temperature is above 60F.

NEWA EIP model uses location-specific National Weather Service weather forecast, and as of today fire blight infection is predicted only in Bristol VA on 20 April. This very well can be due to very patchy rain event predictions. Other locations seen below are entering high EIP values over 100 in Orange boxes, with probably only a wetting period missing to allow infection. A wetting event can be heavy dew, rain, or spray water when you apply fungicides. Therefore, since the fire blight infections are wetting event dependent, apply your streptomycin in mix with LI700 or Regulaid within 24 h before a rain event triggering an infection (dark red field and EIP over 100), which is now only seen for Bristol VA. Or add streptomycin and LI700 or Regulaid to the tank if you will apply a fungicide spray during the 19-21 April period when the EIP field is Orange and EIP value is above 100. To determine when your next streptomycin spray application is needed, type in the Streptomycin Spray Date in the NEWA EIP Fire Blight model – 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 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.

North Carolina: