engleski

The diffusion of Gymnosporangium spp in Dalmatia with a review of the problem of protecting pears

The diffusion of Gymnosporangium spp in Dalmatia with a review of the problem of protecting pears Along the Adriatic coast-line from Rijeka to Šibenik we meet with Juniperus sp. of which a large percentage (60-70%) are infected with Gymnosporangium spp. In the interior around Jelenje and Lokve towards Crikvenica the Juniperus communis prevails. In addition we found certain ornamental junipers which were infected with Gymnosporangium. From Crikvenica to Šibenik, along the Adriatic highway, and in the interior between Knin and Obrovac we noticed huge areas of underbrush in whi¬ch Juniperus oxycedrus has prevailed.In determing of the genus Gymnosporangium we made according Bernoux (1956) and in this area affirmed the following species:1. Gymnosporangium clavariaeforme (Jacq.) - Juniperus oxycedrus L. -Juniperus communis L.2. Gymnosporangium fuscum DC (Sabinae) (Dick) Wint. - Juniperus oxycedrus L.3. Gymnosporangium gracile (witche's brooms) Pat. - Juniperus oxycedrus L. As all the species of Gymnosporangium are parastic and a great majority of them heteroecious, it is necessary to consider the host on which the pycnia - aecidial stage appears. We found infections of aecidials on Crataegus oxyacanta and on wild pears.However, the most interesting damage for us appears on plantations of pears. In the Smiljčić area 47 ha are planted with pears. The whole plantation is surrounded by numerous hedges of Juniperus oxycedrus which is an integral part of the vegetation in that area, so that both hosts to Gymnosporangium are present. According to Grasso (1972) Gymnosporangium clavariaforme (Jacq/DC is a synonym for Gymnosporangium sabinae (Dick) Wint in its pycnia-aecidial stage is parasite on pears. The damage caused to the pears can be considerable as in addition to the leaves and fruit the infection can spread to the branches. Particularly in young plantation nurseries when the tree-crown are being formed. Damage from disease can be prevented: 1. By removing the Juniperus to 500-700 metres away from the plantation, 2. By spraying with fungicide in good time. As in this case it is not possible to remove the Juniperus protection is provided by the preventive spraying with fungicide. While working on this problem we established that the periods of spray which are mentioned in text books are not suitable for the climate in this area. The experiment showed that infection occurs very early, that is, at the end of March. We have established the period for treatment on the basis of results gained through following the devalopment of fungus on the Juniperus, and after the germination of the spore has been established and the daily temperatures checked - these should be at 10°C or more. At the some time we examined the effeciency of certain new fungicides.

Croatia, Gymnosporangium spp., diffusion

The Fourth Congress of the Mediterranean Phytopathological Union- Summaries Zadar 5 - 11.listopad 1975.