Storms occurring on May 22, 2014 in the eastern part of Pennsylvania produced hail, which was capable of causing damage to fruit trees. Growers in affected areas will want to consider applying a streptomycin spray within 24 hrs of the hail event to protect trees from fire blight.
Golf ball sized hail (from NOAA)
The month of May just keeps getting more interesting. While Dr. Greg Krawcyzk and I were driving to the Central Susquehanna Twilight Meeting in Berwick, PA yesterday afternoon, we encountered a severe thunderstorm on I-81. The sharp pelts on the windshield were unmistakable: hail. At the meeting, the reports of growers experiencing hail started rolling in. Not only did we have perfect conditions for fire blight this year, particularly with two major infection periods during bloom, hail has been thrown into the mix – all within two weeks. Talk about a cosmic kick to the shins. Fire blight bacteria need an entry point into the plant to cause infection. During bloom, the flower’s nectaries provide the open door; after a hail event, the wounded areas are the open door into the plant tissues. For those who experienced hail on their farms yesterday, application of a streptomycin spray within 24 hours of the hail event is important to protect damaged areas of the trees from bacteria entering, especially if you meet the following criteria Cornell Plant Pathologist Dr. David Rosenberger outlined in his latest blog post about the hail – fire blight situation:
If you know that you have (i) blight-susceptible cultivars (ii) that have a lot of recently opened flowers, (iii) that are less than six years old, (iv) that were not treated with Apogee, (v) that have not received any strep since May 15 or 16, and (vi) that have an inoculum source nearby (i.e, orchard with blight last year), then you may want to attempt treating those blocks with strep if you get a decent treatment window in the next 24 hours. Do NOT include Regulaid at this time as it may impact activity of plant growth regulators applied within the next few days.
We experienced infection periods May 9 – 11 and May 14 – 16. Consequently, growers will want to start scouting their orchards for possible fire blight infection starting this weekend and into next week to see how they fared with their protective measures.
When controlling for disease, weather and tree growth conditions need to be monitored at a local level within one’s own orchard. Before chemical products are applied, be sure to be in compliance by obtaining the current usage regulations and examining the product label. Product information can be easily obtained from CDMS.
(Source – http://www.farms.com/news/disease-update-hail-and-fire-blight-76821.aspx)