by Mike Fargione, Cornell with Win Cowgill, Rutgers/NJAES
Fireblight for apple and pear blocks that had open bloom on or before Thursday, May 2nd: According to Maryblyt forecasting model (run by Mike Fargione) there is some risk of fire blight infections occurring today Monday through Tuesday if wetting takes place (including rain, heavy dew or a spray).
The NEWA website uses Cougar Blight for its forecaster and issues indicates low risk for Tuesday moving to high risk of infection by Friday and Saturday if rain, heavy dew or a spray occur.
Control Suggestions to Consider-
Treating high-risk blocks that had open flowers on 5/2 with a strep application within 24 hours of any wetting including rain, heavy dew or a spray.
• High risk blocks include highly susceptible cultivars and blocks where you had fire blight during the last couple of years. High-density plantings ages 2-5 may be a higher concern than older plantings.
• You have 24 hours to get strep applied if you decide to wait until after wetting occurs, but the earlier the material is applied in that window the better (don’t apply in the rain).
• I consider Step effective if applied 24 hours before an infection and 24 hours after for burnout. Note the flowers must be open for Step to be effective and the strep must have good coverage and wetting to hit the flower parts.
• The recommended rate for the first strep (Agrimycin 17 WP, Firelwall, or other generic formulation) is one-half lb. per 100 gal which is (100PPM) plus either 2 qt. glycerine or 1 pt. Regulade.
• The glycerine and Regulaid rates are "per gallon of finished spray - do not concentrate these (example - regardless of how many "X" you spray, you would put 5 pints of Regulaid in a tank holding 500 gal. of spray solution).
• In NJ and eastern NY we currently are not aware of the existence of strep-resistant fireblight. Therefore Strep is the most effective material when a fire blight spray is called for in our area for the first application. We must be careful to not overuse step so that we develop a resistance issue.
• Caution about phytothoxicty with Captan might be possible if you tank mix with Regulaid. If you are going to spray strep, consider one of the following: leave out the Regulaid, leave out the captan, or substitute another fungicide such as Sovran or Flint for the captan. There should not be a problem tank-mixing Regulaid with mancozeb.
ApogeeIt is time, full bloom, to begin treating with Apogee for shoot blight. Add two ounces of Apogee per 100 gallons, don’t forget the AMS for buffering the water at 1 lb /100 plus Regulaid at 1 pint/100- do not concentrate. Its important to start early (bloom) you cant make it up later. Remember do not add boron or calcium to Apogee sprays.
Add Strep with Apogee if NEWA calls for fireblight.
The next rain event will probably be a scab event- showers are forecast from Tuesday through Thursday and the forecast keeps changing. Make sure you are covered up with a protectant fungicide, captan, or a mancozeb product (EDBC). Have systemic materials on hand as well