Although olive scab is widespread in most olive-growing areas, there is no accurate estimate of the losses it causes. These damages are very difficult to measure because many factors can influence the severity of symptoms. Serious infections can cause the death of the branches and a progressive weakening, with consequent loss of vigor of the tree and therefore of the harvest.
In 1991 it was estimated that losses related to Pseudomonas savastanoi were approximately 1.3% of the national olive production in Spain. Occasionally, this disease has caused almost total crop loss due to the combination of optimal climatic conditions for entry and bacterial multiplication, observed in two Spanish locations in 1987 and 2001 after heavy hail storms.
The quantitative effects of olive scab on the vigor and productivity of olive trees are not yet established because only information is available from one study in California and another in Spain.
In a commercial olive grove in California (USA) no significant differences in vigor were found between slightly 40-year-old olive trees (0.10-0.30 knots in 0.3 m of fruit wood) and slightly (0.31-0.50 knots) infected with the disease.
In contrast, in Spain in a study of 7-year-old Arbequina trees in a high-density olive grove, vigor was significantly higher in uninfected trees. In Spanish research, different disease levels did not significantly influence cumulative olive production in young trees. Additionally, a low quality oil when the olive fruits are harvested from olive trees moderately affected by olive scab which presents odors and flavors such as bitter, stale or salty, even if the chemical parameters are not always modified.
Of CS
