Diseases caused by Phytophthora pathogens on fruit trees are known as Phytophthora root and crown rot of fruit trees; crown and collar rot; Phytophthora root, crown and collar rots. First symptoms of the disease in Bulgaria were found during the vegetation period 1998 - 1999 on 2-3-years-old apple trees in the village of Bjaga (Peshtera region) and on 2-years-old cherry rootstocks in the village of Katunitza (Plovdiv region). Fungi from genus Phytophthora - P. cactorum and P. citrophthora, were isolated as casual agents. Monitoring of Phytophthora root and crown rot of fruit trees spread done from 1999 to 2001 points out disease incidence between 2% and 14 %, in some orchards and nurseries in South Bulgaria and some parts of North Bulgaria: regions of Plovdiv, Pazardzik, Kjustendil, Sliven, Bourgas, Yambol, Karnobat, Svishtov, Lom and Sevlievo. Samples from infected plant tissues (apples, cherries, almonds, peaches, pears and plump) were taken and isolations were done on selective PARP media, or by applying a baiting bioassay. Based on morphological and cultural characteristics and temperature requirements the following species have been identified: Phytophthora cactorum, P. citrophthora, P. drechsleri, P. cryptogea, hybrid and Pythium. Phytophthora fungi are among the most harmful pathogens. They are characterised with their high adaptability, reproductive potential and destructiveness. The biological characters make the Phytophthora fungi difficult to control. Because of that, a combination of quarantine, sanitary practices, fungicide treatments and biological control measures are recommended for their control. Fungicides for Phytophthora root and crown rot control were tested applying in vitro and in vivo methods.
Phytophthora root and crown rot - potential tread about fruit trees in Bulgaria