ISHS Acta Horticulturae 121: VII Symposium on Apricot Culture and Decline
PHYTOPHTHORA ROOT AND CROWN ROT OF APRICOT TREES |
| Author: | SRECKO M. MIRCETICH |
| DOI: | 10.17660/ActaHortic.1983.121.53 |
| Abstract:
During the last 10 years an increasing incidence of declining and dead apricot (Prunus armeniaca L.) trees associated with root and crown rot have been observed in California's commercial orchards. Root and crown rot associated with dying or dead apricot trees have also been observed in certain orchards in Maryland. Armillaria mellea was often recognized as the causal agent of root and crown rot in certain commercial apricot orchards (O'Reilly, 1963). However, if this pathogen was not associated with root and crown rot of affected trees, the disorder was usually attributed to “wet feet” or “sour sap” (Day, 1953; Smith, 1941). Careful examination of affected apricot trees in numerous orchards with a high incidence of dead or dying trees revealed that A. mellea was associated with a small number of examined trees in a few orchards. Our surveys of commercial orchards showed that the highest incidence of root and crown rot-affected apricot trees usually occurred at sites wich were subjected to periodic and prolonged soil saturation, with water standing around the lower trunks of trees because of poor soil drainage and unusually high rainfall during late fall, winter and early spring months, or because of excessive irrigation and improper soil-water management. The general symptoms of affected apricot trees resemble the symptoms of other fruit trees infected with Phytophthora spp. (Baines, 1939; Kouyeas, 1977; Mircetich and Keil, 1970; Mircetich and Matheron, 1976; Smith, 1956). We repeatedly isolated several different Phytophthora spp. from decayed roots or bark canker of apricot trees affected with root and crown rot. The same Phytophthora spp. were also recovered from soil in affected apricot orchards. Several different Phytophthora spp. were commonly present in the same orchard and up to six different Phytophthora spp. were occasionally associated with the same individual tree. Some apricot trees from which Phytophthora spp. were isolated often failed to grow in the spring, whereas some trees started to grow and then collapsed. These trees usually had extensive crown rot (Fig. 1 B, C) and trunk canker. The extent of crown rot and trunk | |
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