Considerable losses of citrus trees have been observed in the major citrus-growing areas of Spain. Samples were collected from 132 orchards, and isolations and pathogencity tests were conducted to determine the aetiology of a serious canker disease. Affected trees showed cankers on the scion that frequently began on the branches. Three Phytophthora species were identified based on their morphological, cultural, physiological and molecular profiles. Phytophthora citrophthora was the main species associated with this new syndrome in 114 orchards. Phytophthora nicotianae (syn. P. parasitica ) was isolated from nine orchards as the sole Phytophthora species and in coinfection with P. citrophthora from another nine orchards. Phytophthora citricola was isolated only from one orchard. In stem-inoculation studies conducted under greenhouse conditions, clementine mandarin cv. Hernandina and sweet orange cv. Navel Late were more susceptible to P. citrophthora than sour orange and Carrizo citrange rootstocks. Clementine cv. Hernandina was also highly susceptible in field inoculation experiments. In agreement with field surveys, clementine mandarin cultivars were the most affected, their rootstocks remaining healthy. Phytophthora citrophthora was found to be the predominant species in orchard soils; however, P. nicotianae was also isolated. This information changes the scenario of diseases caused by Phytophthora spp. in Spain and consequently, the present knowledge of epidemiology and the effectiveness of the current control measures should be reassessed.

Huelva in southern Spain is a major production area for strawberry (Fragaria × ananassa). At the end of the 2006 season (May-June) collapsed and dying strawberry plants were observed on several cultivars in four fields. Cut crowns of affected plants revealed dark brown necrotic areas on the margins and along the woody vascular ring. Roots of these plants were also shown to be necrotic. Macrophomina-like isolates developed from surface-disinfested affected tissues plated on potato dextrose agar amended with 250 mg L-1 of chloramphenicol. Dark, oblong-shaped sclerotia were observed in affected crown tissue and in culture after 5 to 7 days incubation at 25 ° C. They had an average length of 107 (217 to 62) μ m and width of 71 (110 to 35) μ m. Sequenced rDNA fragments of a single sclerotium isolate CH 724 (Spanish Type Culture Collection, CECT 20715; GenBank Accession No. AM410964) presented a 99% identity with Macrophomina phaseolina. Morphological and molecular results confirmed this species as M. phaseolina (Holliday & Punithalingam, 1970). Six single sclerotium isolates of M. phaseolina from strawberry were used for pathogenicity tests. Each isolate was used to inoculate six strawberry runner plants (cv. Camarosa) growing in pots of coconut fibre substrate for 5 weeks. Plants were inoculated by inserting a fungal colonised toothpick into each crown (Mertely et al ., 2005). An equal number of uninoculated plants treated similarly were left as controls. After 58 days, the incidence of plant death ranged from 67 to 100% depending on isolate. Macrophomina phaseolina was reisolated from all plants showing symptoms. Uninoculated plants remained symptomless.

Since 2002, considerable losses of Clementine trees (Citrus clementina) have been observed in Spain due to Phytophthora branch canker of citrus caused by Phytophthora citrophthora. Due to the low efficiency of the available cultural and genetic control measures, application of fungicides is required for economic management of the disease. Fosetyl-Al, metalaxyl, and its enantiomer mefenoxam are the only systemic fungicides registered for control of Phytophthora diseases in Spain. However, their efficacy has not been tested against Phytophthora branch canker. Greenhouse and field experiments were conducted for 3 years in Spain to evaluate the ability of these fungicides and application methods to reduce lesion expansion. Nevertheless, with the inoculation technique used, it was not possible to evaluate the protective activity of fungicides, which can play an important role in their performance under field conditions. None of the fungicide treatments inhibited lesion expansion when applications were made on a curative basis. The residual effect was better on young than on mature trees. Paint treatments were generally more effective in reducing lesion expansion that drip chemigation or foliar sprays. However, this application method is laborious and becomes uneconomical in Spain. Trunk and branch sprays as well as long-term programs of foliar sprays or drip chemigation for control of spring and autumn infections are proposed as targets for future research.

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Phytophthora branch canker, caused by Phytophthora citrophthora, has been an increasing problem in clementine (Citrus reticulata) production in Spain during last years. The disease was particularly severe in the new citrus-growing areas of the southwestern coastal areas in Huelva Province. Recent studies revealed that disease emergence was not related to either genetic drift or host specificity changes in P. citrophthora population. Therefore, the possible association of agronomic factors with the disease was investigated. A total of 110 orchards were selected arbitrarily from the main citrus-growing areas in Huelva Province. The presence of branch cankers together with agronomic factors including soils, cultivars, rootstocks, irrigation, pruning, techniques to improve fruit production, fungicide treatments, presence of brown rot of fruit and frost damage were recorded. Logistic regression analysis was used to detect correlations between the agronomic factors studied and disease prevalence. Phytophthora branch canker was significantly associated with mature clementine orchards. Sweet orange and hybrid cultivars as well as young clementine orchards were less affected by the disease. Although disease was less frequent in Salorthid soils, alternative high resolution procedures are required to draw conclusions about the effect of soil properties on disease prevalence. As in other Phytophthora-induced diseases, soil flooding during the rainy season was correlated positively with the prevalence of branch cankers. Improving fruit production by branch scoring showed a strong positive correlation with Phytophthora branch canker. This is the first time that girdling has been associated with Phytophthora disease Eur J Plant Pathol (2012) 133:577-584