Comparison of chemical treatments for reducing epiphytic Pseudomonas savastanoi pv. savastanoi populations and for improving subsequent control of olive knot disease

• Published in: Crop protection Vol. 29; no. 12; pp. 1413 - 1420
• Main Authors: Quesada, José M., Penyalver, Ramón, Pérez-Panadés, Jordi, Salcedo, Carmina I., Carbonell, Emilio A., López, María M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-12-2010; [Amsterdam]: Elsevier Science
• Subjects: Acibenzolar-S-methyl; application timing; bacterial diseases of plants; Chemical control; Copper; copper oxychloride; cultivars; cuprocalcic sulfate; disease control; disease incidence; economic impact; epiphytes; integrated agricultural systems; mancozeb; Olea; Olea europaea; Olea europaea L; olives; pesticide resistance; pesticides; plant density; plant pathogenic bacteria; population density; Pseudomonas syringae pv. savastanoi; signs and symptoms (plants); sulfates; temporal variation; Vigour; Yield; Olea europaea L; Vigour; Acibenzolar-S-methyl; Yield; Copper; Chemical control
• ISSN: 0261-2194; 1873-6904
• DOI: 10.1016/j.cropro.2010.07.024

The economic impact of the olive knot disease caused by
Pseudomonas savastanoi pv.
savastanoi (Psv) has dramatically increased in recent years, especially in high-density plantations. Here we report chemical control trials, performed in an olive grove planted with two susceptible cultivars, Arbequina and Picudo, over a four-year period. The effect of treatments made with copper oxychloride, cuprocalcic sulfate plus mancozeb or acibenzolar-S-methyl on the Psv populations and subsequent appearance of the disease were evaluated. Both copper treatments reduced the proportion of samples where Psv was isolated, and greatly reduced Psv populations in trees of cv. Picudo. The effect of copper on Psv populations was observed after the first application, but the greatest differences between copper-treated and untreated plants were observed in the third year, after five copper applications. No resistance to copper was detected in the remaining epiphytic Psv populations in treated plants. The average number of knots per plant was significantly lower in copper-treated plants than in untreated plants. By contrast, acibenzolar-S-methyl did not reduce either Psv populations or the disease during the study. These results support the usefulness of copper treatments for olive knot management. Results indicate that two copper treatments should be performed regularly under an integrated control program, especially in high-density groves, since their efficiency was demonstrated not only in decreasing olive knot incidence, but also in reducing Psv populations.
► Two treatments per year of copper oxychloride or cuprocalcic sulfate plus mancozeb greatly reduced
Pseudomonas savastanoi pv.
savastanoi populations in olive trees; the number of knots per plant was also significantly lower in copper-treated than in untreated olive trees, in a four year study.► Two treatments per year of acibenzolar-s-methyl did not reduce either
P. savastanoi pv.
savastanoi populations or the disease during the same period.► The two copper treatments should be performed regularly in olive orchards to achieve a significant reduction of olive knot disease, in the context of its integrated control.