Evaluation of control of fire blight infection of apple blossoms and shoots with SAR inducers, biological agents, a growth regulator, copper compounds, and other materials

• Published in: Acta horticulturae no. 590; pp. 325 - 331
• Main Authors: Aldwinckle, H.S, Reddy, M.V. Bhaskara, Norelli, J.L
• Format: Journal Article
• Language: English
• Published: International Society for Horticultural Science 01.01.2002
• Subjects: apples; biological control agents; copper sulfate; Erwinia amylovora; fire fighting; flowering; growth regulators; mechanism of action; oxolinic acid; shoots; streptomycin; trees
• ISSN: 0567-7572
• DOI: 10.17660/ActaHortic.2002.590.48

In 2000, two biocontrol agents (Serenade, BlightBan C9-1), two SAR inducers (Actigard, Messenger), two copper compounds (Mankocide, Phyton 27), and a quinoline compound (S-0208, oxolinic acid) were evaluated for blossom blight control on 'Idared' apple trees. Blossoms were inoculated with Erwinia amylovora to ensure sufficient infection for separation of treatment effects. The products were sprayed on the trees at timing-based on their mode of action. Infected and healthy blossom clusters were counted 2 weeks after inoculation. The proportion of infected blossom clusters was determined and used as the measure of disease. Fruit russeting was noted 4 weeks after the last blossom spray. The best treatments with S-0208 (71.5% control), Serenade (64.3%), Messenger (58.3%), and Phyton 27 (46.1%) gave control statistically indistinguishable from the streptomycin standard treatment (64%). Although Phyton 27 contains copper sulfate, it did not cause significant fruit russeting. Phyton 27, Messenger, and the growth regulator, Apogee, were evaluated for shoot blight control on inoculated ‘Idared’ trees. Products were sprayed on trees at timing depending on their mode of action. Tips of 15 shoots on each tree were inoculated with E. amylovora. Six weeks after inoculation the necrotic lesion length (a) and the total shoot length (b) on inoculated shoots were determined, and a/b x 100 (% blighted shoot length) was used as the disease parameter. The best Apogee treatment was two applications during full bloom (3 weeks before inoculation) and 5 weeks post bloom (2 weeks after inoculation) with Regulaid, which resulted in 48.6% control and was not significantly different from streptomycin. The best Messenger treatment, 1 and 3 weeks before inoculation, gave 31.3% control. Control by Phyton 27 (50.3%) was not significantly different from streptomycin (55%), but significantly better than Mankocide (26.3%), and did not result in significant russeting.