Resistant fire-blight has previously been found in CA, OR, WA, MO, MI and Western NY.
Source- Dr. Rosenberger, Extension Plant Pathologist, via Mike Fargione,
Extension Educator, Cornell- Tree Fruit Grower Alert Message 4/30
Edits for NJ by Win Cowgill
Resistance development is associated with repeated use of strep during summer, thus we have always recommended use of strep after bloom should be limited to single applications in response to a trauma event like hail.
We know that in several cases, strep-resistance has been transferred to new locations with nursery trees. Contamination of nursery stock is a rare event, but consequences are huge.
We have no evidence of strep-resistant fire blight in New Jersey, Eastern NY or New England and we hope to keep it that way. Here are the steps to reduce the potential for strep resistance to gain a footing here from nursery stock shipped from affected areas:
•Examine new trees before planting and don’t plant trees with cankers.
•After soil settles, apply two copper sprays (at fire blight rate) about 14 days apart to kill any strep-resistant blight on tree surfaces. Include 1 quart of spray oil per 100 gal. of finished spray (do no concentrate the oil).
•When buds are already showing green tissue, do not apply copper just prior to predicted frosts because the cells ruptured by frost crystals may reabsorb and be killed by the copper on the bud surfaces. These copper sprays will also provide apple scab protection equivalent to 3 lbs. of Mancozeb per acre.
•Remove flowers or apply strep plus a low dose of copper during bloom.
· Scout newly planted orchards weekly.
•If blight appears, remove affected trees as soon as you see them and contact us (Win Cowgill) so we can get them tested for strep-resistant fire blight.
If you suspect fireblight resistance to Step in your orchard please contact (Win Cowgill) as soon as possible so samples may be collected.