First report of Eutypa lata causing dieback of olive trees in Italy

In spring 2007, extensive stem and branch cankers on four to five-year-old olive trees (cvs. Frantoio, Leccino, Moraiolo, Nostrale di Rigali) were observed in young orchards in Umbria (central Italy) with 60 to 80% disease incidence. Ten orchards were affected, comprising 3 ha total area. Cankered areas often girdled the stem causing plant death. Symptoms were always accompanied by a dark brown discoloration under the bark extending to the xylem. Isolations from small wood pieces, removed from active cankers, on to potato dextrose agar (PDA) produced white mycelium and small black pycnidia containing conidia of Libertella blepharis A.L. Smith [Eutypa lata (Pers.) Tul & C. Tul] after three to four weeks under near-UV light. Identification was also confirmed by the Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands, using morphology and ITS1 sequencing, with reference to type strain CBS 208.87.

For pathogenicity testing, ten one-year-old olive trees from each of four varieties (Frantoio, Moraiolo , Leccino and Nostrale di Rigali) were inoculated with a 5 mm diameter mycelium disk taken from the margin of a three-week-old colony of the fungus, by insertion, after removing the bark, into a shallow wound on the basal part of the stem of each plant. Inoculation sites were covered with moistened cotton wool and covered with Parafilm. Sterile PDA disks were inserted into wounded control sites (three plants for each variety). All plants were placed in a greenhouse at 18-22°C, 60-80% relative humidity and under artificial light. First cankers appeared six months after inoculation and affected 75% of the plants. One year later cankers and xylem discoloration appeared most severe especially on Frantoio, Moraiolo and Leccino. The fungus was consistently reisolated from affected wood tissues whereas no symptoms developed in control plants.

Eutypa lata has been reported on several fruit and forest trees or shrubs (Carter & English, 1994; Carter, 1995; Prodorutti et al., 2008) and in Greece as the cause of olive dieback (Rumbos, 1993). This is the first report of Eutypa lata on olive in Italy. The disease occurrence in Italy was probably caused by the use of infected cuttings in nurseries and favoured by late frost injury.