The survival of Quercus species in the Mediterranean region is challenged by root diseases caused by Phytophthora cinnamomi Rands and Pythium spiculum Paul, as well as by drought. This study aimed to examine the interaction between both pathogens under varying soil moisture levels. Seedlings were inoculated with P. cinnamomi, Py. spiculum, or both, and exposed to soil moisture conditions ranging from saturation to drought. Results showed that P. cinnamomi caused high levels of root necrosis in saturated-to-moderately dry soils, but it was unable to cause infection under drought conditions. Conversely, Py. spiculum infected roots under drought but not under saturation conditions and was less virulent in wet soils compared to P. cinnamomi. In seedlings inoculated with both pathogens, symptoms were similar to those induced by P. cinnamomi alone, without any synergistic effect. This study highlights that P. cinnamomi and Py. spiculum infect oak roots across a range of soil moistures, with P. cinnamomi being the predominant pathogen in wet-to-moderately dry soils, and Py. spiculum being the predominant pathogen in droughted soils. Under current and projected future water deficit conditions, oak woodlands infected by both pathogens face a significant threat to their survival.

Phosphonate fungicides are the most efficient chemicals for the control of oomycete root diseases which are causing significant economic and ecological losses in Mediterranean climate-type forests and natural ecosystems worldwide. However, a more environmental-friendly disease management demanded by society requires the optimization of chemicals application. Thereby, the main goal of this study was to develop a new resistant inducer (RI) formulation based on potassium phosphonate (PP) combined with mineral nutrients efficient against the root rot caused by Phytophthora cinnamomi and Pythium spiculum on cork oak that improve potassium phosphonate effectiveness. The potential phytotoxicity of five RI formulations composed of PP at five concen-trations (25, 40, 50, 100 and 200 g/l) and each including 2.15 g/l ZnCl2 (Zn) and 0.25 g/l CaCl2 (Ca), were tested on 1-year old Quercus suber seedlings. Two weeks after treatments, only seedlings treated with the RIs containing the two highest doses of PP (100 and 200 g/l) showed symptoms of toxicity. RI with 40 g/l of H3PO3 (RI40), as well as its compounds individually and in combination two by two (PP (40 g/l), Ca, Zn, PP + Ca, PP + Zn, Ca + Zn), were tested against root disease development induced by P. cinnamomi and Py. spiculum on cork oak seedlings. For both oomycetes, seedlings submitted to every treatment with PP exhibited a significantly lower severity of root symptoms than plants artificially inoculated and treated with water. Furthermore, plants treated with RI40 did not differ to the plants growing in uninfested soil, improving PP alone effect. These results were validated by a field experiment where 60 mature cork oaks in three different defoliation classes (asymptomatic, slight, and moderate defoliation) were trunk injected with RI40 or water (controls). Three years after treatments, root disease development was significantly lower in cork oaks with slight and moderate initial defoliation level and treated with RI40 in comparison with water-treated controls. No effect was detected over both pathogens' dynamics in soil. Results strongly support that PP effectiveness in controlling Q. suber root disease caused by P. cinnamomi and Py. spiculum is improved by its combination with Zn and Ca, allowing to reduce the PP application rates according to current society demands and the European Plant Health Legislation.

In Spain, natural and managed cork oak woodlands are severely affected by decline caused by the root rot oomycetes Phytophthora cinnamomi and Pythium spiculum. The need for environmental-friendly disease management makes the use of resistance inducers a suitable option. As the use of phosphite is prohibited in Spain, trunk injections of fosetyl-aluminium were tested in a seminatural cork oak woodland (dehesa). Sixty cork oaks in three different defoliation classes (asymptomatic, slight, and moderate defoliation) were selected for fosetyl- aluminium or control (water) trunk injections, and periodically checked for defoliation and presence of both pathogens in roots and rhizosphere soil. Three years after treatments, fosetyl-aluminium injection significantly decreased defoliation in treated cork oaks in comparison with water-injected controls, regardless of the initial defoliation class considered. Changes in inoculum density in the rhizosphere or presence of the two pathogens in roots were not significantly dependent on treatment. However, a trend to a lower presence of pathogens in roots of treated oaks was observed with increasing soil inoculum densities. Fosetyl-aluminium, a phosphonate fungicide registered in the European Union, was experimentally proved to protect cork oaks against root rot caused by P. cinnamomi and Py. spiculum, even exhibiting a therapeutic effect on preexisting infections. This effective measure can therefore be used to fight against this highly destructive disease in seminatural woodlands and in protected natural ecosystems.

The new species Phytophthora oleae is a pathogen recently reported causing fruit rot on olive orchards in Italy and root rot in a natural wild-olive forest in Spain. Potassium phosphite, fosetyl-Aluminium and metalaxyl were evaluated in pot experiments for root disease control. All the three systemic products led to a significant decrease of root necrosis caused by olive Phytophthora pathogens (P. cryptogea, P. megasperma and P. oleae) when applied at recommended doses to inoculated seedlings, even though fosetyl-Aluminium did not significantly inhibit mycelial growth in vitro. The tested products have potential to protect commercially planted olive orchards from these Phytophthora pathogens, including the new species P. oleae in natural woodlands that, in turn, put at risk cultivated olive orchards.

Wild olive (Olea europaea subsp. europaea var. sylvestris) is an important component of Mediterranean forests and a key genetic source for olive improvement programmes. Since 2009, a severe decline caused by Phytophthora cryptogea and P. megasperma has been detected in a protected wild olive forest of high ecological value (Dehesa de Abajo, Seville, Spain). In this natural forest, sampling of roots and soil was carried out on 25 wild olives with symptoms in 2014 and 2015. Apart from the already known P. cryptogea A1 and P. megasperma, a third Phytophthora species was consistently isolated from wild olive rootlets with symptoms. These isolates conformed morphologically with the newly described species P. oleae and were confirmed by analysis of their ITS regions and cox1 sequences. Temperature–growth relationships showed a maximum growth at 19.9 °C on carrot agar medium, making it the lowest temperature Phytophthora species infecting wild olive roots. Pathogenicity was confirmed on 1‐year‐old healthy wild olive seedlings and was similar to the previously known pathogenic phytophthoras. As temperature requirements are quite different, the three Phytophthora species may be active against wild olive roots in different seasons. However, the prevalence of P. oleae infecting wild olives in recent years could be due to its introduction as a new invasive pathogen. The probable invasive nature of P. oleae, together with increasing rain episodes concentrated in short periods frequent in southern Spain, would allow the outbreak of infections in wild olive forests, and also put cultivated olive orchards at risk.

In Spain, Quercus open woodlands are animal ranching systems of organic production seriously threatened by the exotic pathogen Phytophthora cinnamomi. The root disease it causes kills thousands of oaks annually. Effective disease management needs to integrate different techniques, and the use of a resistance inducer such as fosetyl-Al can play a key role, because the use of potassium phosphite is prohibited in Spain. In a woodland where the pathogen recently arrived, 60 holm oaks in three different defoliation classes (asymptomatic, slight and moderate defoliation) were selected for trunk injection with pressurised capsules containing 4% of commercial fosetyl-Al or water (controls). Holm oaks were checked periodically for defoliation and presence of the pathogen in roots and rhizosphere soil. Three years after treatments, defoliation was significantly lower in oaks treated with fosetyl-Al, which even increased canopy cover, in comparison with control oaks, independent of the initial defoliation class considered. Chlamydospore density in rhizosphere soil, as well as the presence of the pathogen into the roots, was not significantly influenced by fosetyl-Al treatments, although a trend to a lower presence of P. cinnamomi in roots was observed in treated oaks at every soil inoculum density detected. This study has shown that fosetyl-Al, a phosphonate registered as a fungicide in the European Union, provides protection to holm oaks against P. cinnamomi, even exhibiting a therapeutic effect on pre-existing infections. Consequently, this effective measure should be considered as part of the integrated approach to control this highly destructive pathogen in holm oak woodlands.

Susceptibility to Phytophthora cinnamomi is one of the main traits in Castanea sativa breeding programs. An inoculation experiment using 25 control pollinated families, with seedlings of these families cloned by cuttings, was conducted by soil infestation with one P. cinnamomi isolate. Forty-seven days after inoculation, foliar and root collar symptoms and root necrosis were recorded. The data were analyzed using a model based on restricted maximum pseudolikelihood methods of the GLIMMIX procedure to estimate the additive, dominance and epistatic components of the genetic variance, as well as the narrow sense heritability and the breeding values. At the end of the experiment, the percentages of dead plants ranged from 4% to 56% in C. sativa, and 18% to 20% in backcrosses to C. sativa, with much lower percentages in the F1 hybrids (C. crenata × C. sativa). Foliar symptoms were proportional to mortality, affecting 28% of the plants, but root collar lesions and root necrosis were more prevalent, affecting 65% and 84% of the plants, respectively. The proportions of genetic to phenotypic variance, 0.50–0.63, and the estimated values of narrow-sense heritability, 0.30–0.46, indicate that resistance to P. cinnamomi is under moderate to moderately high genetic control caused mainly by additive genetic variance. A high number of backcrosses to C. sativa showed good breeding values for resistance to P. cinnamomi.

Forests worldwide have been recently affected by severe decline and mortality, while our understanding about forest decline across spatial scale is still limited. In this work, we study how Quercus suber trees adjust their physiology, in terms of water use efficiency and secondary growth, to pathogen-induced oak decline at the whole-tree, local and landscape scales. This work was carried out in Mediterranean mixed forests where their dominant key species Q. suber is affected by a severe decline and mortality induced by the exotic soil-borne pathogen Phytophthora cinnamomi. Significant differences were not observed between defoliated and healthy trees, either in terms of water use efficiency or growth at the whole-tree scale. We found that limiting conditions, such as low soil depth and high pathogen abundance, induced trees to higher water use efficiency at local and landscape scales. Overall our findings point out that Q. suber trees subjected to soil drought and root pathogens increase water use efficiency to some extent, while this response might not be enough for the trees to overcome the physiological stress associated with the pathogen-induced dieback. We discuss the complex way by which adult Q. suber trees physiologically respond to P. cinnamomi-induced mortality, improving our understanding of the likely consequences of chronic oak decline in the future.

Summary Conservation bias towards flagship species sometimes threatens other species of chief concern. Long‐term studies of potential harm by favoured species on other sensitive species, though seldom adopted, are required to fairly evaluate the suitability of management and restoration efforts. We illustrate the potential detrimental outcomes of conservation biased towards birds by investigating the long‐term (1963–2009) impact of a large waterbird colony (up to 13 000 pairs) on a remnant cork oak Quercus suber population at a World Biosphere Reserve in south‐western Spain (the Doñana National Park). To this end, we compared changes in performance (growth, crown vigour and survival) of oaks occupied and unoccupied by the waterbird colony. After 46 years of occupation, the risk of death to centenarian oaks in the area occupied by the colony was over twofold higher than for trees outside the area. Non‐centenarian planted and naturally regenerated oaks showed similar trends, leading to restoration failure. Synthesis and applications. Our long‐term study reveals that waterbirds and centenarian oaks cannot coexist, at the most local scale, but they can at a regional scale including within the Doñana area. We propose immediate planting efforts in suitable colony‐free areas, while managers evaluate the feasibility of relocating colonial waterbirds to an alternative location. To preserve the Doñana oak genetic pool, such reforestation should be accomplished using local seeds and seedlings. New trees should not be planted in close proximity of colony‐occupied trees since it significantly reduces their survival. Doñana stakeholders should both overcome current conservation bias in favour of birds and enter into a process of settlement to best preserve the overall biodiversity of the system.

Summary Potassium phosphite ( PP ) formulations registered as fertilizers are now prohibited in Spain. Therefore, we evaluated the systemic fungicide fosetyl‐aluminium (fos‐al) in comparison with PP , against root rot caused by Phytophthora cinnamomi in Quercus woodlands. The direct effect of both systemic fungicides was evaluated in vitro on P. cinnamomi mycelial growth. Protection of cork and holm oak against infection was also evaluated in planta . Metalaxyl was included in both in vitro and in planta experiments for comparison purposes. At 100 μg/ mL , PP totally inhibited colony radial growth, in comparison with 75% achieved by fos‐al. At doses recommended by manufacturers, with fos‐al and metalaxyl applications, root symptoms remained similar to the uninfected control levels. Based on these results, fos‐al is a candidate substitute product for PP in Quercus woodlands for control of Phytophthora oak root disease.

Phytophthora cinnamomi causes a highly destructive root rot that seriously affects oak trees in semi-natural woodlands known as "dehesas". Biofumigation with Brassica spp. is a promising tool for disease management. We demonstrated that ground seeds from B. carinata and B. juncea can inhibit mycelial growth and decrease chlamydospore viability of P. cinnamomi in soil. In contrast, B. napus seedmeals were ineffective. Reduction of root necrosis in Lupinus plants was also achieved when soils were biofumigated with B. carinata or B. juncea seedmeals. Seedmeal effectiveness was strongly correlated with high sinigrin (2-propenyl glucosinolate) content. We conclude that biofumigation with seedmeals rich in sinigrin could be effective as part of integrated management of oak disease caused by P. cinnamomi in "dehesas".

Since 2009, a severe decline leading to mortality has been observed affecting nearly 5 ha of a wild olive woodland of high ecological value in Seville, southern Spain. Phytophthora cryptogea and P. megasperma were consistently isolated from roots and rhizosphere of trees with symptoms sampled in 2009, 2011 and 2013. The isolates were identified on the basis of colony and reproductive structure morphology as well as temperature–growth relationships, and identification was further corroborated by their ITS and β‐tubulin sequences. Koch's postulates were demonstrated for both species on 1‐year‐old wild olives. Pathogenicity tests showed that both Phytophthora spp. are highly aggressive pathogens, although temperature–growth requirements for each species were distinct. As a consequence, the two species may be active in different seasons and their epidemiology may be differently influenced by global climate change, and they may show their active periods in different climatic scenarios. The climate change models for the Mediterranean Basin forecast a global temperature increase that favours the more thermophilic P. cryptogea. The high susceptibility to phytophthora root rot should not be disregarded in olive breeding programmes where wild olive is used as a source of resistance to verticillium wilt.

The oomycete plant pathogen Phytophthora cinnamomi causes a highly destructive root rot that affects numerous hosts. Integrated management strategies are needed to control P. cinnamomi in seminatural oak rangelands. We tested how biofumigation affects crucial stages of the pathogen's life cycle in vitro, in infested soils under laboratory conditions and in planta. Different genotypes of three potential biofumigant plant species (Brassica carinata, Brassica juncea, Brassica napus) were collected at different phenological stages, analysed for their glucosinolate contents, and subsequently tested. The most effective genotypes against mycelial growth and sporangial production were further tested on the viability of chlamydospores in artificially infested natural soils and in planta on Lupinus luteus, a host highly susceptible to P. cinnamomi. Brassica carinata and B. juncea genotypes inhibited mycelial growth, decreased sporangial production, and effectively inhibited the viability of chlamydospores in soil, but only B. carinata decreased disease symptoms in plants. Effective genotypes of Brassica had high levels of the glucosinolate sinigrin. Biofumigation with Brassica plants rich in sinigrin has potential to be a suitable tool for control of oak root disease caused by P. cinnamomi in Spanish oak rangeland ecosystems.

SummaryThe oomycete Phytophthora cinnamomi is an aggressive plant pathogen, detrimental to many ecosystems including cork oak (Quercus suber) stands, and can inflict great losses in one of the greatest ‘hotspots’ for biodiversity in the world. Here, we applied Fourier transform‐infrared (FT‐IR) spectroscopy combined with chemometrics to disclose the metabolic patterns of cork oak roots and P. cinnamomi mycelium during the early hours of the interaction. As early as 2 h post‐inoculation (hpi), cork oak roots showed altered metabolic patterns with significant variations for regions associated with carbohydrate, glycoconjugate and lipid groups when compared to mock‐inoculated plants. These variations were further extended at 8 hpi. Surprisingly, at 16 hpi, the metabolic changes in inoculated and mock‐inoculated plants were similar, and at 24 hpi, the metabolic patterns of the regions mentioned above were inverted when compared to samples collected at 8 hpi. Principal component analysis of the FT‐IR spectra confirmed that the metabolic patterns of inoculated cork oak roots could be readily distinguished from those of mock‐inoculated plants at 2, 8 and 24 hpi, but not at 16 hpi. FT‐IR spectral analysis from mycelium of P. cinnamomi exposed to cork oak root exudates revealed contrasting variations for regions associated with protein groups at 16 and 24 h post‐exposure (hpe), whereas carbohydrate and glycoconjugate groups varied mainly at 24 hpe. Our results revealed early alterations in the metabolic patterns of the host plant when interacting with the biotrophic pathogen. In addition, the FT‐IR technique can be successfully applied to discriminate infected cork oak plants from mock‐inoculated plants, although these differences were dynamic with time. To a lesser extent, the metabolic patterns of P. cinnamomi were also altered when exposed to cork oak root exudates.

Summary Brassicaceous plants rich in glucosinolates have been used as biofumigants for the management of soilborne pathogens. Efficacy of B rassica plant tissue has mainly been attributed to toxic isothiocyanates released upon the hydrolysis of glucosinolates. Management of P hytophthora cinnamomi , the causal agent of oak root rot in rangeland ecosystems using biofumigation, is promising, but requires further validation. The biofumigation activity of 14 brassicaceous plants was evaluated under experimental conditions. All evaluated plants rich in sinigrin suppressed (100%) the mycelial growth of P . cinnamomi , while plants rich in aromatic or other aliphatic glucosinolates had little or no suppressive effect. Simulating soil amendment in field conditions, the effects on natural soil artificially infested with P . cinnamomi chlamydospores were examined with B rassica juncea , E ruca vesicaria and L epidium sativum , three species with different glucosinolate profiles. Only B . juncea decreased the viability of chlamydospores significantly in comparison with untreated soil only 1 day after biofumigation, whereas E . vesicaria needed 8 days to reach significance and L . sativum had no effect at all. Despite the decreases in soil inoculum, biofumigation with B . juncea did not prevent the root infections in a highly susceptible host ( L upinus luteus ). However, biofumigation with plants rich in sinigrin, such as B . juncea , decreased P . cinnamomi soil inoculum under the experimental minimum threshold for oak disease expression. Although biofumigation should be considered as an effective measure to be incorporated in integrated control of the oak disease, biofumigation by itself would not be effective enough for the substantial suppression of P . cinnamomi inoculum.

HomePlant DiseaseVol. 100, No. 5First Report of Pythium spiculum Causing Root Rot on Wild-olive in Spain PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Pythium spiculum Causing Root Rot on Wild-olive in SpainM. González, M. S. Serrano, and M. E. SánchezM. González, M. S. Serrano, and M. E. SánchezAffiliationsAuthors and Affiliations M. González M. S. Serrano M. E. Sánchez , Agronomy Department, ETSIAM, University of Córdoba, 14014 Córdoba, Spain. Published Online:23 Feb 2016https://doi.org/10.1094/PDIS-10-15-1133-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat The wild-olive (Olea europaea var. sylvestris) has a high ecological value in the Mediterranean Basin. In 2007, a severe root rot similar in symptomatology to that caused by Phytophthora spp. in cultivated olives (Sánchez Hernández et al. 1998) was detected in a wild-olive forest in a Natural Reserve in Spain (Dehesa de Abajo, Seville). Twenty five symptomatic trees displaying foliar yellowing, wilting and defoliation, and feeder root necrosis, were sampled in May and December 2013. Isolates consistently obtained from feeder roots exhibited spiny oospores (15.0 ± 1.2 µm in diameter) typical of Pythium spiculum (Paul et al. 2006). They showed a 99 to 100% homology with their expected ITS sequence in GenBank (Accession No. DQ196131). Pythium spiculum was isolated from 48% of sampled trees in May, increasing to 76% in December 2013. Pathogenicity tests were conducted on healthy 1-year-old wild-olive seedlings grown in fertilized peat (San Jeronimo Nursery, Environment Council, Andalusian Government, Spain). The isolate PYWO6 of P. spiculum, coming from diseased rootlets, was cultured in carrot broth and incubated at 22°C for 4 weeks. Inoculum was prepared by shaking the mycelium in sterile water to produce an oospore water suspension (2.2 × 104 oospores/ml). Fifty milliliters of inoculum were added to each root ball of 10 seedlings (replicates) and only water was added to another 10 seedlings acting as controls. All plants were individually transferred to plastic pots, each one containing 2 liters of fertilized peat, maintained in a growth chamber (24/20°C day/night), and flooded 2 days per week to favor root infections. Severity of foliar symptoms was evaluated weekly on a 0 to 4 scale (0 = 0% of symptomatic leaves, 4 = total wilt, as described by Sánchez et al. 2005) during 20 weeks. After this time, the relative area under the disease progress curve (rAUDPC, Campbell and Madden 1990) was calculated for foliar symptoms as a percentage with regard to the potential maximum value, and root damage assessed on a similar 0 to 4 scale (Sánchez et al. 2005). ANOVA was performed for foliar rAUDPC and root symptoms values, and mean values compared by the Tukey's test (α = 0.05). Inoculated plants exhibited rAUDPC values significantly higher (P = 0.0072) than controls. Root symptoms in inoculated seedlings (averaging 2.7 ± 0.3) also differed significantly (P < 0.0001) from those of control plants (averaging 0.2 ± 0.1, possibly due to flooding). The pathogen was always reisolated from necrotic roots of inoculated seedlings and never from controls. Pythium spiculum has been cited causing root disease on Quercus ilex and Q. suber, and it has been also isolated from symptomatic Vitis, Prunus, Castanea, and Celtis spp. (Romero et al. 2007), but this is the first report of P. spiculum causing root rot on Olea spp. Currently, there are no reports of it affecting cultivated olive trees but it should be considered as a potential risk for this important Mediterranean crop, as well as wild-olive forests.References:Campbell, C. L., and Madden, L. V. 1990. Page 532 in: Introduction to Plant Disease Epidemiology. Wiley, New York. Google ScholarPaul, B., et al. 2006. FEMS Microbiol. Lett. 254:317. https://doi.org/10.1111/j.1574-6968.2005.00048.x Crossref, ISI, Google ScholarRomero, M. A., et al. 2007. J. Phytopathol. 155:289. https://doi.org/10.1111/j.1439-0434.2007.01230.x Crossref, ISI, Google ScholarSánchez, M. E., et al. 2005. For. Pathol. 35:115. https://doi.org/10.1111/j.1439-0329.2004.00392.x Crossref, ISI, Google ScholarSánchez Hernández, M. E., et al. 1998. Eur. J. Plant Pathol. 104:347. https://doi.org/10.1023/A:1008624929989 Crossref, ISI, Google ScholarDetailsFiguresLiterature CitedRelated Vol. 100, No. 5 May 2016SubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Issue Date: 15 Apr 2016Published: 23 Feb 2016First Look: 1 Dec 2015Accepted: 21 Nov 2015 Page: 1023 Information© 2016 The American Phytopathological SocietyCited byPotential for Biological Control of Pythium schmitthenneri Root Rot Disease of Olive Trees (Olea europaea L.) by Antagonistic Bacteria12 August 2022 | Microorganisms, Vol. 10, No. 8Pythium spiculumCABI Compendium, Vol. CABI CompendiumInvestigation of soil-borne fungi, causal agents of olive trees wilt and dieback in Tunisia3 August 2020 | Archives of Phytopathology and Plant Protection, Vol. 53, No. 17-18

SummaryAn analysis of incidence of Phytophthora spp. in 732 European nurseries producing forest transplants, larger specimen trees, landscape plants and ornamentals, plus 2525 areas in which trees and shrubs were planted, is presented based on work conducted by 38 research groups in 23 European countries between 1972 and 2013. Forty‐nine Phytophthora taxa were recorded in 670 nurseries (91.5%); within these nurseries, 1614 of 1992 nursery stands (81.0%) were infested, although most affected plants appeared healthy. In forest and landscape plantings, 56 Phytophthora taxa were recovered from 1667 of 2525 tested sites (66.0%). Affected plants frequently showed symptoms such as crown thinning, chlorosis and dieback caused by extensive fine root losses and/or collar rot. Many well‐known highly damaging host–Phytophthora combinations were frequently detected but 297 and 407 new Phytophthora–host associations were also observed in nurseries and plantings, respectively. On average, 1.3 Phytophthora species/taxa per infested nursery stand and planting site were isolated. At least 47 of the 68 Phytophthora species/taxa detected in nurseries and plantings were exotic species several of which are considered well established in both nurseries and plantings in Europe. Seven known Phytophthora species/taxa were found for the first time in Europe, while 10 taxa had not been previously recorded from nurseries or plantings; in addition, 5 taxa were first detections on woody plant species. Seven Phytophthora taxa were previously unknown to science. The reasons for these failures of plant biosecurity in Europe, implications for forest and semi‐natural ecosystems and possible ways to improve biosecurity are discussed.

Quercus suber seedlings were potted in soils infested with increasing concentrations of Phytophthora cinnamomi chlamydospores and submitted to weekly flooding for 3 months to favour root infections. Increasing quantities of chlamydospores led to an exponential increase in their ability to germinate. Root symptoms (necrosis and/or absence of feeder roots) were significantly more severe than those recorded in uninfested soil only for plants potted in soils infested with 61 cfu g -1 or more. Although generated using potting mix, this minimum threshold represents a tool for checking the potential infectivity of infested soils or to assess the effectiveness of some control methods to reduce soil inoculum. However, a low level of root infection was recorded even at 3 cfu g -1 . Therefore, long-term disease risk may be present whenever the pathogen is detectable in oak forest soils.

Botryosphaeria canker is likely the most injurious disease for cork production in the Mediterranean Basin. The exclusion of Benomyl, the standard commercial product used to prevent Botryosphaeria canker, from the EU Pesticide Database in 2003 necessitates the search for new alternatives to prevent cork oak cankering. In vitro experiments showed that every fungicide tested at 10(3) mg l(-1) active ingredient was effective in reducing mycelial growth of Diplodia corticola. An initial field experiment showed that cork oak trunks sprayed with Thiophanate-methyl, Carbendazim, Difenoconazole, Pyraclostrobin or Copper-Calcium Sulphate under low-humidity environmental conditions exhibited significant decreases in the number and length of trunk lesions, 3 years post-treatment, compared with untreated trees. A second field experiment conducted under extremely wet conditions showed that only Thio-phanate-methyl was effective, 2.5 years after treatments, when sprayed just after peeling. Finally, in a third field experiment, under wet conditions, the preventive effectiveness of Thiophanate-methyl, Copper-Calcium Sulphate and a mix of both fungicides was confirmed, although no synergistic effect of the mixture was measured. Copper-Calcium Sulphate or Thiophanate-methyl, when applied immediately after trunk peeling, is effective for preventive control of Botryosphaeria canker on cork oak and may be considered as an effective replacement for Benomyl.