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Use of copper fungicides against olive leaf spot and possible Cu traces in olive oil

In olive orchards fungus Spilocea oleaginea Cast. causes olive leaf spot disease. Today it's safe to say that olive leaf spot is a significant and serious problem in almost all of our olive orchards, including those with organic production. It adversely affects fertility of infected trees, and its consecutive occurrence year-in year-out causes degradation of whole olive trees, particularly young ones. Olive leaf spot is readily controlled by copper fungicides. For effective olive protection, in one year is needed some of application. It was thought for long that olive leaf spot infection could be prevented by means of two treatments with copper preparations (September - October and March – April). The first treatment in fall, before the rains, is necessary, because the rainy period creates conditions for primary infections. This reduces the possibility of spring infections by 87% to 95%. For the purpose of protection of olives against olive leaf spot in organic production it is allowed to use only copper fungicides. Concentration of applied preparations must be strictly under control because of possible copper residues in olive fruits and subsequently in oil as well, which is restricted by law. In years with remarkably warm and rainy falls, one treatment with copper fungicides in fall surely is not enough. It is necessary to perform at least three treatments with copper fungicides. The treatments with copper fungicides are allowed up to 56 days prior to harvest. The law also provides the maximum allowed quantity of 0.40 mg Cu/kg in table olives and olive oils. With more treatments in fall it is certainly impossible to fully observe all the regulations. Otherwise, if one were to observe the regulations, there arises a question as to whether is it actually possible to adequately protect olive groves against this nasty and rising disease at all. The experiment was conducted in 2009. and 2010. in a 25-year-old olive orchard, to find out if a several fall applications with copper fungicides would cause a copper residues in olive oil. However, in bought year olive were treated 3 times in fall every 15 days with copper fungicides. The results of this research show that in the bought year in all semples no traces of copper were faund above permissible limit (0.13 - 0.26 mg/kg).

olive leaf spot, copper fungicides, Spilocea oleaginea, plant protection, Cu traces, olive oi

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