Widespread fire blight is being reported around the region. There are presently two possible infection periods. The first happened on May 14-16. This was the most severe infection, and hit right during peak bloom in most parts of southern New England. The second hit on May 26-27, and while not as severe, may have been enough to cause infection on trees that were in bloom at that time. The most likely scenario is infection on May 14-16 showing up as blossom blight beginning June 2, and as shoot blight beginning June 10.
Indications to this point are that applications of streptomycin during the May 14-16 infection did a good job of suppressing blight. (Multiple applications may have been necessary.) Problems have arisen where no streptomycin was applied. Please contact us if you made a streptomycin application at that time and still have fire blight. We are interested in testing for streptomycin resistance.
The real question at this point is what to do if you have fire bight.
1. Do not apply streptomycin now unless there is a hail or wind-driven rain that may damage apple tissue. If a heavy storm does happen, apply strep within 24 hours. Applying strep to trees at this point will not cure infections, and risks causing resistance. Strep will only help prevent rapid spread if there is a damaging storm.
2. Prune out infected material at least 12 inches from any sign of damage – 24 inches would be better, and going back to older, non-susceptible wood best. It’s better to cut deep and work quick. Preferably prune when it is DRY!
3. Think about what you’re doing. Don’t touch the infected wood with the pruning blade or your hands, if possible. Instead work well away from infected areas. Don’t let infected tissue touch healthy tissue, particularly if it’s oozing. Throw the infected wood in the middle of the aisle and let them dry. (Mow when dry.)
4. If you think you have touched infected tissue, use a disinfectant to wipe off the blade or your hands.
5. Prune fire blight out of high-value blocks first. Bigger, older trees can tolerate some damage on their own. Pruning out blight in smaller, younger trees can greatly reduce the amount of damage to them. Get the bigger trees later. Work quick – you can even tear shoots out if that is faster than cutting, and there is less risk of spreading fire blight than with pruning.
6. In the long run, it’s important to get as much of the infected wood pruned out as quickly as possible. Infected wood serves as a source of new infections this year, and allows bacteria to overwinter in your orchard, greatly increasing risk next year.
For more information, see our fact sheet: An Annual Fire Blight Management Program
Thanks to Vincent Philion, IRDA, St.-Bruno-de-Montarville, Quebec, Canada; and Kathleen Leahy, Polaris Orchard Management, Colrain, MA for valuable input.
This is Heather again – answering some questions that have been asked within the last week.
1. New fire blight infects take 7-10 days to appear.
2. An Apogee application starts to protect against new infections in 7-10 days, but don’t spray Apogee on Empire or Staymen apples.
3. Nickel Biofungicide does not help trees now. Oxidate also is not helpful.
4. Don’t spray Strep unless there is hail or a very strong storm, as Dan Cooley mentioned. Since you need to apply Strep within 24 hours of a hail storm, buy Strep now to have on hand.
5. Especially when pruning young trees with fire blight, consider applying copper before pruning. Several copper products can be used at a low dose now: Badge, Cueva, Champ, and Magna-Bon. They should be applied only during low humidity and with no more than 50 gallons of water per acre in small trees.
I’m sure there will be a lot of talk about fire blight at our twilight meeting on June 19 at 5:30 at Jaswell’s Farm in Greenville.