Plan for Multiple Fire Blight Conditions, Be Agile | WSU Tree Fruit

Written by Tianna Dupont, WSU Extension; Ken Johnson, OSU, April 6, 2020. Revised Feb 1, 2021.

The last few years have built up fire blight inoculum in our orchards. Consider designing a toolbox of plans you can choose from depending on the risk in each block and how spring progresses.

Think about which are your high-risk blocks: blocks with sensitive varieties, high-value varieties or a history of fire blight. Those are blocks where you may want a more intensive program. Think about what fickle mother nature may do. Have a plan for moderate temperatures and extended bloom as well as flash bloom. Below is an example of a set of plans a grower might design to choose from for different blocks and conditions.

Apples
Conventional		Organic
Low to Moderate Risk	High Risk high value varieties history of blight	Easy to thin varieties	Hard to thin varieties/ short bloom period	Hard to thin varieties/ long bloom period
Watch the model. If an infection event is projected apply an antibiotic within 24 hours before wetting. Repeat every 2-3 days during warm wet risk periods to cover newly opening flowers rotating FRAC.^d Continue weekly apps 1-2 weeks post petal fall during warm wet risk periods. ^e	Blossom Protect + Buffer Protect 50-80% bloom preventative. Use antibiotic mixes: oxytetracycline+ kasugamycin or antibiotic + Actigard. ^d Cover every 2-3 days during warm conditions during bloom. ^d Acidify spray tanks to improve antibiotic efficacy to at least 5.5. New research shows to 4.0 may improve further. ^b Continue weekly apps 1-2 weeks post petal fall if warm and wet. ^e	Blossom Protect/ Buffer Protect early. ^a Lime sulfur (+ oil). Blossom Protect/ Buffer Protect. Depending on the model and cultivar russet risk soluble copper (Previsto 3 qt, Cueva 4 qt, or Cueva 3 qt + Serenade Opti). Petal fall + 1-2 weeks Serenade Opti (most fruit safe) or 2% lime sulfur (red apples). ^c	Lime sulfur (+ oil) 2-3 applications. Depending on the model and cultivar russet risk soluble copper (Previsto 3 qt, Cueva 4 qt, or Cueva 3 qt + Serenade Opti). ^g Petal fall + 1-2 weeks Serenade Opti (most fruit safe) or 2% lime sulfur (red apples). ^c	Lime sulfur (+ oil). Blossom Protect + Buffer Protect.^a Lime sulfur (+ oil). Blossom Protect + Buffer Protect. Depending on the model and cultivar russet risk soluble copper (Previsto 3 qt, Cueva 4 qt, or Cueva 3 qt + Serenade Opti). Petal fall + 1-2 weeks Serenade Opti or 2% lime sulfur (red apples).

^aApply to every row. Two applications between 50-100% bloom have the best efficacy.

^bSpray tank acidification has been most significant for oxytetracycline products (e.g. Mycoshield).

^cLime sulfur at this timing can interfere with oil sprays for mites.

^dRotate. Rotation is necessary for resistance management. Rotate as necessary to comply with application intervals for individual products. Do not apply Actigard at closer than 7-day interval (label restriction). Streptomycin should be used NO MORE than one time per season.

^eDo not make more than 4 applications of KASUMIN 2L per year. Petal fall restriction removed March 2021.

^fBlossom Protect+ Buffer Protect, then Previsto (full bloom), then Serenade (petal fall) best organic combination in 13 trials at 83% relative control (Johnson) similar to antibiotics.

^gRemember Blossom Protect yeast need about 12 hours to grow on the flower to protect blooms before a wetting event.

Pears
Conventional		Organic
Low to Moderate Risk	High Risk	Easy to Mark Varieties Anjou/ Comice	Marking Tolerant Varieties Bosc
Watch the model. If an infection event is projected apply an antibiotic within 24 hours before wetting. Repeat every 2-3 days during warm wet risk periods to cover newly opening flowers. ^d Continue weekly apps 1-2 weeks post petal fall during warm wet risk periods. ^e	Use antibiotic mixes: oxytet+ kasumamycin or antibiotic + Actigard. Cover every 2 days during warm conditions during bloom. ^d Acidify spray tanks to improve antibiotic efficacy to at least 5.5.^b New research shows to 4.0 may improve further. Continue weekly apps 1-2 weeks post petal fall. ^e	2 applications of Blossom Protect + Buffer Protect during early bloom to petal fall (70-80% bloom if single treatment). ^a Follow with Serenade Opti at petal fall to reduce russet risk from Blossom Protect yeast.	2 applications of Blossom Protect + Buffer Protect during early bloom to petal fall (70-80% bloom if single treatment). ^a Follow with soluble copper (Cueva 4 qrt, Previsto 3 qrt, or Cueva 3 qrt + Serenade Opti) if the model indicates risk (warm/wet).

For more information see: http://treefruit.wsu.edu/crop-protection/disease-management/fire-blight/

Contact

Tianna DuPont

WSU Extension Specialist, Tree Fruit

tianna.dupont@wsu.edu

Office: (509) 293-8758

Mobile: (509) 713-5346

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