2026 Disease Update: Possible Trauma Blight Conditions May 13
Apple and pear orchards damaged by hail need protection post the event to limit trauma blight. (Photo: K. Peter)
The punches keep coming from the 2026 season. Yesterday evening, severe thunderstorms producing high winds with gusts of at least 50 mph and hail moved across Pennsylvania. Some fruit growers may have experienced damage on their farms due to these conditions. This damage is an entry point for Erwinia amylovora to wreak havoc and cause the trauma blight phase of fire blight. If growers see tattered leaves and marks on their fruitlets from this storm, it is imperative that a streptomycin (or another antibiotic) spray be applied to these affected orchards within 24 hr of the event to prevent trauma blight. With the reports of fire blight symptoms currently occurring in orchards, there is a lot of Erwinia amylovora in PA orchards this spring.
Even if some of your apple and pear orchards may not have fruit, the entire farm still needs to be treated. All apple and pear trees will be vulnerable. Growers may be inclined to triage their blocks due to a low or no crop, and these orchards will be at higher risk of trauma blight if they are treated late or not at all.
According to the label, streptomycin can be sprayed up to 4 times per season. Since this was a severe fire blight year during bloom, growers may have already maxed out their streptomycin sprays. Other options include oxytetracycline (FireLine, MycoShield) or kasugamycin (Kasumin 2L).
Another consideration would be to add FungOUT to these antibiotic sprays. As previously mentioned, FungOUT is a citric acid bactericide/fungicide that will lower the pH of your spray tank. Erwinia amylovora dislikes acidic conditions, and previous research from Oregon State University has shown that antibiotics are more effective at controlling Erwinia amylovora when they are acidified. We are evaluating this combination in a Penn State FREC research orchard. One observation we have made is that it is probably not necessary to include Regulaid or a similar adjuvant in the spray solution with the streptomycin and FungOUT mix. We observed some leaf and petal damage when using this combination during bloom (Strep + Regulaid + FungOUT).
Growers are encouraged to monitor their orchards closely and prune infections as soon as possible.
For more information about managing fire blight this season, please refer to the May 12, 2026 Disease Update.Â
