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Evaluation of biopesticides for the control of Erwinia amylovora in Apple and Pear Published In Journal of Plant Pathology, JPPY-D-23-00118R1, 2023, by S. Tianna DuPont, Kerik Cox, Ken Johnson, Kari Peter, Tim Smith, Misbakhul Munir, Aina Baro

In a recent study, we evaluated non-antibiotic materials for fire blight control in 8 Washington, 3 Oregon, 3 New York and 2 Pennsylvania field experiments conducted between 2013 to 2022.

In summary analysis of 8 Washington trials, alum (potassium aluminum sulfate), Blossom Protect (A. pullulans) and several soluble copper products (Previsto, Mastercop, Instill) provided good disease suppression in the range of 70-73 percent, similar to antibiotic controls. Several essential oil, copper, and peracetic acid-peroxide and biological products (Thyme Guard, Thymox, Cinnerate, Cueva, Oxidate 5.0, Jet Ag, and Serenade Opti) provided intermediate disease suppression ranging from 45-62 percent, significantly better than the water-treated control. In multistate trials Alum with 2-3 applications provided good control in most experiments (median 71% of 8 experiments). Essential oils with 3-4 applications provided intermediate control (median 45% of 4 experiments).

Non-antibiotic control programs for fire blight which contain Blossom Protect and soluble copper products during the bloom period (e.g. Previsto, Cueva) followed by Bacillus based biorationals (e.g. Serenade Opti) at petal fall have performed well suppressing fire blight infections with lower russet risk in Oregon trials from 2013 to 2021 (Johnson et al. 2022). Integrated programs with Blossom Protect and/or soluble coppers during high risk bloom periods followed by essential oils or peracetic acid-peroxide products at petal fall have also had control similar to standard organic programs in several trials. Consider drying times, rotations, and limit post petal fall applications to moderate russet risk of essential oils and peracetic acid-peroxides products.

figure showing releative efficacy of non antibiotic materials.
Relative fire blight suppression from biopesticides compared to antibiotic standards in fire blight inoculated apple and pear orchards in Wenatchee, Washington between 2013 and 2022. For each treatment, the dark line indicates the mean, the narrow line the median, the box indicates the upper and lower quartile, and the whiskers indicate the minimum and maximum. Treatment application timings for antibiotics, coppers (Previsto, Instill, Mastercop*, Cueva), potassium aluminum sulfate (Alum), biologicals (Serenade Aso/Opti, Double Nickel, LC Bacteriophage) and essential oils (Cinnerate, Thyme Guard) included 12 h before inoculation, 12 h after inoculation, and petal fall (generally 3 days after inoculation). Peracetic acid+peroxide products (Jet Ag, Oxidate 5.0) were applied 2 to 3 times post bloom. Blossom Protect and Buffer Protect (Aureobasidium pullulans) were applied at 20% and 80% bloom or 70% and 90% bloom. Note Alum and Cueva at 5 qt were applied under an experimental use permit. See labels for legal use.

Additional information

Fire Blight of Apple and Pear


DuPont, S. T., K. Cox, K. Johnson, K. Peter, T. Smith, M. Munir, and A. Baro. 2023. Evaluation of biopesticides for the control of Erwinia amylovora in Apple and Pear. Journal of Plant Pathology Submitted Feb 2023 JPPY-D-23-00118.

Johnson, K. B., T. N. Temple, A. Kc, and R. B. Elkins. 2022. Refinement of Nonantibiotic Spray Programs for Fire Blight Control in Organic Pome Fruit. Plant Dis. 106: 623-633.

Use pesticides with care. Apply them only to plants, animals, or sites listed on the labels. When mixing and applying pesticides, follow all label precautions to protect yourself and others around you. It is a violation of the law to disregard label directions. If pesticides are spilled on skin or clothing, remove clothing and wash skin thoroughly. Store pesticides in their original containers and keep them out of the reach of children, pets, and livestock.

YOU ARE REQUIRED BY LAW TO FOLLOW THE LABEL. It is a legal document. Always read the label before using any pesticide. You, the grower, are responsible for safe pesticide use. Trade (brand) names are provided for your reference only. No discrimination is intended, and other pesticides with the same active ingredient may be suitable. No endorsement is implied.

Important! Some of the pesticides discussed in this presentation were tested under an experimental use permit granted by WSDA. Application of a pesticide to a crop or site that is not on the label is a violation of pesticide law and may subject the applicator to civil penalties up to $7,500. In addition, such an application may also result in illegal residues that could subject the crop to seizure or embargo action by WSDA and/or the U.S. Food and Drug Administration. It is your responsibility to check the label before using the product to ensure lawful use and obtain all necessary permits in advance. articles may only be republished with prior author permission © Washington State University. Republished articles with permission must include: “Originally published by Washington State Tree Fruit Extension Fruit Matters at” along with author(s) name, and a link to the original article.

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