Epidemiology of Alternaria linicola on linseed (Linum usitatissimum L.)

Conidia of A. linicola germinated over a wide range of temperatures (5 - 25°C) on both agar and leaves. Germination started within 2 h after inoculation at temperatures between 10°C and 25°C, either on agar or on leaves. At 5°C, there were lag periods of 2 and 4 h before the initiation of germination on agar and on leaves, respectively. Germinating A. linicola conidia were very sensitive to drying between 2 and 6 h after inoculation. In the presence of leaf wetness, light applied before the initiation of germination delayed the germination process and decreased the length of the germ tubes. Light applied after the onset of germination decreased both the percentage of conidia which germinated and the length of the germ tubes. In the absence of leaf wetness, light applied before or after the initiation of germination stopped the germination process or decreased the percentage of conidia which germinated, respectively. Conidia of A. Linicola germinated by producing germ tubes and occasionally by producing secondary conidia. Formation of appressoria was inhibited at 5°C. Penetration of the leaf tissues started 12 h after inoculation at 15°C and occurred mainly directly through the epidermal cells and occasionally through stomata. A. linicola is a "diurnal sporulator". In vitro most isolates sporulated only after exposure to diurnal NUV-light. However, for some isolates exposure to diurnal NUV-light did not seem to induce sporulation unless the mycelium was wounded and grown on a medium rich in CaCO3 (S-medium) at high relative humidity. In vivo sporulation of A. linicola was increased after induction by light. The greatest numbers of conidia were produced under continuous leaf wetness and alternating dark/light periods (12 h each). Under these conditions the number of conidia produced increased with increasing temperature from 10°C to 20°C. Alternating 15°C/10°C or 20°C/15°C day/night temperatures decreased the number of conidia produced compared with the constant temperatures 15°C and 20°C, respectively. In controlled environment studies, infection of linseed plants by A. Linicola and development of symptoms was affected by the leaf wetness period, its interaction with temperature and by the light conditions. Eight hours of leaf wetness were sufficient to initiate the disease at 25°C but not at 15°C when a longer period of 10 h was needed. Infection of linseed plants by A. Linicola occurred under interrupted leaf wetness periods at 15°C, but the incidence and severity of the disease was lower than that under continuous leaf wetness. The disease incidence on stems and the disease severity on leaves was negatively correlated with the length of the light period applied immediately after inoculation. Disease incidence and severity increased with increasing inoculum concentration from 1 x 10³ to 1 x 105 conidia ml-¹. The cotyledons appeared to be more susceptible to A. linicola infection than the leaves when the same inoculums density was used. A. linicola was detected on 12 of the 20 seed samples tested and on six of them at a high incidence (> 50%). Seed seems to be the main source of primary inoculum as the pathogen was effectively transmitted from infected seeds to the emerging seedlings. Infected linseed stem debris, volunteer linseed plants and the weed Veronica agrestis were also sources of primary inoculum for the infection of linseed crops by A. linicola. Structures resembling chlamydospores formed in the mycelium and conidia of A. linicola seem to be involved in the survival of the pathogen in stem debris. Conidia of A. linicola were mainly dispersed by the wind (air-borne conidia) and their dispersal followed seasonal and diurnal periodicities, which were influenced by the weather conditions and the incidence of the disease in the crop. The greatest numbers of A. linicola conidia were collected by the Burkard spore sampler on the first dry day following periods of rain, between 12:00 h and 13:00 h and during the period between flowering and harvest of the crop (July - September). Bait plants were more efficient than the Burkard spore sampler in detecting A. linicola conidia present in the crop early in the growing season. The number of A. linicola conidia dispersed within a linseed crop decreased with increasing height above ground, but some conidia were collected 80 cm above the crop canopy. The number of A. linicola conidia dispersed downwind from a line inoculum source decreased with increasing distance from the source and by the end of the growing season conidia were collected by up to 40 m from the source. When the A. linicola disease gradients were studied from point or line inoculum sources, the disease incidence decreased with increasing distance from the inoculum source. By the end of the growing season, the disease was detected 20 or 60 m from the point or line inoculum sources, respectively. Multiple applications of iprodione or prochloraz sprays to control A. Linicola infection in the crop, especially the seed-borne phase of the pathogen, and to increase crop yield gave variable results depending on the weather conditions and the incidence of the disease in the crop. Multiple applications of benomyl or chlorothalonil sprays had either no effect or increased the incidence of the disease in the crop

Scientific Opinion on the pest categorisation of Strawberry vein banding virus

The Panel on Plant Health performed a pest categorisation of Strawberry vein banding virus (SVBV) for the European Union (EU) territory. SVBV is a well-defined virus species of the genus Caulimovirus for which the entire genome sequence is known and molecular detection assays are available. SVBV is transmitted by vegetative multiplication of infected hosts and through the activity of aphid vectors, the most efficient being Chaetosiphon spp. The virus is reported from all continents and is present in three EU Member States: the Czech Republic, Italy and Slovakia. The host range of SVBV is restricted to cultivated and wild strawberries. It is listed in Annex IAI of Directive 2000/29/EC. SVBV is not expected to be affected by ecoclimatic conditions wherever its hosts are present and has the potential to establish in large parts of the EU territory, and to subsequently spread through the action of its Chaetosiphon fragaefolii vector, which is present in many Member States. SVBV does not cause severe symptoms, and modern cultivars are mostly symptomless if infected with SVBV alone. SVBV can, however, contribute to more severe symptoms when it occurs in mixed infections with other strawberry viruses. Despite this, SVBV is considered a minor problem in strawberry production as a consequence of modern practices including the systematic use of certified planting materials and the use of short crop cycles, which have greatly reduced the impact of strawberry viruses. Overall, SVBV does not have the potential to be a quarantine pest as, given current agricultural practices, it does not fulfil the pest categorisation criteria defined in the International Standards for Phytosanitary Measures No 11 of having a severe impact. However, SVBV has the potential to be a regulated non-quarantine pest because it fulfils all pest categorisation criteria defined in the International Standards for Phytosanitary Measures No 21

Scientific Opinion on the pest categorisation of Eotetranychus lewisi

The Panel on Plant Health performed a pest categorisation of the Lewis spider mite, Eotetranychus lewisi, for the European Union (EU). The Lewis spider mite is a well-defined and distinguishable pest species that has been reported from a wide range of hosts, including cultivated species. Its distribution in the EU territory is restricted to (i) Madeira in Portugal; and to (ii) Poland where few occurrences were reported in glasshouses only. The pest is listed in Annex IIAI of Council Directive 2000/29/EC. A potential pathway of introduction and spread is plants traded from outside Europe and between Member States. The Lewis spider mite has the potential to establish in most part of the EU territory based on climate similarities with the distribution area outside the EU and the widespread availability of hosts present both in open fields and in protected cultivations. With regards to the potential consequences, one study is providing quantitative data on impact showing that the pest can reduce yield and affect quality of peaches and poinsettias, and only few studies describe the general impact of the pest on cultivated hosts. Although chemical treatments are reported to be effective in controlling the Lewis spider mite, it is mentioned as a growing concern for peaches, strawberries, raspberries and vines in the Americas. Overall, Eotetranychus lewisi meets the pest categorisation criteria defined in the International Standards for Phytosanitary Measures No 11 for a quarantine pest and in No 21 for a regulated non-quarantine pest

Scientific Opinion on the pest categorisation of Paysandisia archon (Burmeister)

The Panel on Plant Health performed a pest categorisation of Paysandisia archon for the European Union territory. P. archon is a well-defined pest species attacking many palm species. It is currently present in several southern European Member States (Croatia, Cyprus, France, Greece, Italy, Slovenia and Spain). Malta and Portugal are considered to be very important areas for further spread of the pest. The pest is listed in Annex IIAII of Council Directive 2000/29/EC and special requirements for host plants with respect to P. archon are formulated in Annexes IVAI and IVAII of Council Directive 2000/29/EC. This moth is a strong flier, but its main pathway of spread is via ornamental palms traded from outside the European Union and between Member States. Wherever its hosts are present outdoors in southern Europe, P. archon has the potential to establish. Although P. archon can complete its development in protected cultivation and in private/public indoor plant collections, there is no evidence of establishment. The damage produced by the larvae can cause the death of the plant with consequences for cultivated and native palm trees, and therefore on ecosystem services and biodiversity. At the moment no fully effective chemical or biological control methods are available against spread and impact of P. archon, while the use of glues on the stipe of the palm can be effective but affects the ornamental value of the plant. P. archon meets all pest categorisation criteria for both quarantine pests and regulated non-quarantine pests

Scientific Opinion on the pest categorisation of Strawberry latent C virus

The Panel on Plant Health performed a pest categorisation of Strawberry latent C virus (SLCV) for the European Union (EU) territory. SLCV is defined only by symptoms in strawberry indicators. It has not been characterised, is not recognised as a valid species, and reliable detection assays are unavailable. SLCV is transmitted by vegetative multiplication of infected hosts and by Chaetosiphon aphid vectors. SLCV has been reported only from USA, Canada and Japan. It is listed in Annex IAI of Directive 2000/29/EC. It infects cultivated and wild strawberries, and there is no other information on its host range. SLCV is not expected to be affected by ecoclimatic conditions wherever its hosts are present, and has the potential to establish in large parts of the EU territory. SLCV can spread through the action of its widely distributed C. fragaefolii vector and through the movement of strawberry plants for planting. However, the existence of efficient and widely adopted certification systems for strawberry constitutes a very strong limitation to SLCV spread. Although latent in many strawberry varieties, SLCV can cause significant damage, in particular when in co-infection with other strawberry viruses. However, the importance and impact of SLCV have both essentially disappeared in North America, most probably as a result of modern practices including the systematic use of certified planting materials and the use of short crop cycles. Such practices are also widely used in the EU and have broadly reduced the impact of strawberry viruses. Overall, SLCV does not have the potential to be a quarantine pest or a regulated non-quarantine pest, because it does not fulfil the following pest categorisation criteria of the International Standards for Phytosanitary Measures (ISPM) No 11/21: clear identity of the pest (ISPM 11/21), presence in the PRA area (ISPM 21) and having a severe impact (ISPM 11)

Scientific Opinion on the pest categorisation of Plenodomus tracheiphilus (Petri) Gruyter, Aveskamp & Verkley [syn. Phoma tracheiphila (Petri) L.A. Kantschaveli & Gikashvili]

The European Commission requested the EFSA Panel on Plant Health to perform a pest categorisation of Phoma tracheiphila, the fungal pathogen responsible for “mal secco” disease of citrus. This pathogen is listed in Annex IIAII of Directive 2000/29/EC. Recently, the pathogen has been reclassified as Plenodomus tracheiphilus (Petri) Gruyter, Aveskamp & Verkley, based on molecular phylogenetic analysis. Plenodomus tracheiphilus is a single taxonomic entity, and sensitive and specific methods are available for its differentiation from other related Plenodomus species. The main host is lemon (Citrus limon L.), but the pathogen has also been reported on other species of the genera Citrus, Fortunella, Poncirus and Severinia and on their hybrids. Host plants are widely grown in the southern EU Member States (MSs) and climatic conditions are conducive to disease development in both orchards and nurseries. The pathogen is present in part of the risk assessment area, being mainly reported on lemon grown in Italy, Greece, Cyprus and France, where it has a serious impact on the citrus industry. There are no obvious ecological/climatic factors limiting the potential establishment and spread of the pathogen in the, so far, non-infested citrus-producing EU MSs (i.e. Spain, Portugal, Malta and Croatia). Short-distance spread of the pathogen occurs via water splash and wind-driven rain, whereas movement of infected host plants for planting, particularly asymptomatic plants, is considered to be responsible for the introduction of the pathogen into new areas. Cultural practices and copper-based fungicide sprays may reduce inoculum sources and prevent new infections but they cannot eliminate the pathogen. P. tracheiphilus fulfils all of the pest categorisation criteria for having the potential to be a quarantine pest and a regulated non-quarantine pest, as those are defined in the International Standards for Phytosanitary Measures No 11 and 21, respectively

Scientific Opinion on the pest categorisation of Beet leaf curl virus

The Panel on Plant Health performed a pest categorisation of Beet leaf curl virus (BLCV) for the European Union (EU) territory. BLCV mainly infects Beta spp., as well as Spinacia spp., Tetragonia tetragonioides and the common weeds Atriplex spp. and Chenopodium spp. This putative Rhabdovirus is not a recognised virus species; it is only defined by particle morphology and by its circular propagative transmission by the lace bug Piesma quadratum. No efficient diagnostic assay is available for BLCV, which was reported in only Germany and Turkey. With a few exceptions, there is no record of BLCV after 1983. BLCV is listed in Annex IIAII of Directive 2000/29/EC. The virus itself is not expected to be affected by ecoclimatic conditions and its P. quadratum vector is widely distributed in the EU; thus, BLCV has the potential to establish and spread over large areas of the EU and cause significant damage in sugarbeet. However, it appears to have caused sporadic outbreaks in only some years, possibly associated with high vector populations. It does not appear to have had any significant impact in recent years, and it may now no longer be significantly present in agricultural production systems. This situation is possibly a consequence of current intensive sugarbeet crop management practices and of the ensuing reduction in vector populations. Owing to the very limited literature available on BLCV, a full pest risk assessment is highly unlikely to provide clearer insight into the risks associated with this virus than the present pest categorisation

Scientific Opinion on the pest categorisation of Tomato yellow leaf curl virus and related viruses causing tomato yellow leaf curl disease in Europe

The Panel on Plant Health performed for the European Union (EU) territory a pest categorisation of Tomato yellow leaf curl virus (TYLCV) and three related viruses, Tomato yellow leaf curl Sardinia virus (TYLCSV), Tomato yellow leaf curl Axarquia virus (TYLCAxV) and Tomato yellow leaf curl Malaga virus (TYLCMaV), which collectively cause the tomato yellow leaf curl disease (TYLCD) in Europe. The viruses are well-defined species of the genus Begomovirus, are exclusively transmitted by members of the Bemisia tabaci species complex and have tomato, as well as a few other crops or weeds, as their hosts. TYLCV is listed on tomato plants for planting, other than seeds, in Annex IIAII of Directive 2000/29/EC. While establishment and local spread rely on the Bemisia vector, the viruses can also be disseminated over long distances by movement of infected plants for planting or by consignments of non-host plants carrying viruliferous whiteflies. Establishment outdoors and spread are limited to regions with ecoclimatic conditions suitable for the establishment of vector populations in the open. Outbreaks can nevertheless occur in other regions under protected cultivation conditions. Because of the very high potential impact of TYLCD, tomato production in affected regions requires intensive crop management efforts to reduce impact. TYLCV appears to be present in almost all EU regions with suitable ecoclimatic conditions for its establishment in open fields, while the other three viruses do not appear to have reached their full establishment potential. All four viruses are absent from other regions of the EU but have the potential to cause temporary outbreaks there

Scientific Opinion on the pest categorisation of Ditylenchus destructor Thorne

The Panel on Plant Health performed a pest categorisation of Ditylenchus destructor, the potato rot nematode. D. destructor is listed in Annex II, Part A, Section II of Council Directive 2000/29/EC as a harmful organism known to occur in the Union and relevant for the entire Union. D. destructor is a distinct taxonomic entity that can be identified in a straightforward way, and which is present in the majority of EU member states, although sporadically (but data from systematic surveys are lacking). Many hosts of D. destructor are present in the RA area and the climatic conditions in the whole risk assessment area are favourable for the completion of the pest life cycle. D. destructor can cause significant damage to the below-ground parts (roots, tubers, bulbs) of host crops such as potato and several ornamental plants. However, during recent decades only minor damage has been reported (except in some Eastern European countries). Plants for planting are a pathway for introduction and spread of D. destructor, which may cause severe impacts on the intended use of the plants for planting

Scientific Opinion on the pest categorisation of Prunus necrotic ringspot virus

The Panel on Plant Health performed a pest categorisation of Prunus necrotic ringspot virus (PNRSV) for the European Union (EU) territory. PNRSV is a well-defined virus species of the genus Ilarvirus for which the entire genome sequence and molecular detection assays are available. It is transmitted by vegetative multiplication of infected hosts and also via seeds and pollen (both horizontally and vertically) in some of its hosts. PNRSV has a somewhat restricted natural host range, which contains Prunus spp., hops, roses and Rubus ellipticus (yellow Himalayan raspberry). It is listed on plants of Rubus for planting in Annex IIAI of Directive 2000/29EC, probably as a result of confusion with the closely related Apple mosaic virus. PNRSV is widely present in the EU, but there are no records on its regulated hosts. It is not expected to be affected by ecoclimatic conditions wherever its hosts are present, and it has the potential to establish in large parts of the EU territory. PNRSV can spread through efficient seed- and pollen-mediated transmission mechanisms and through the movement of vegetatively propagated plants for planting. However, the existence of efficient and widely adopted certification systems for Prunus spp. constitutes a limitation to PNRSV spread. Although the virus alone or when in mixed infection can cause significant diseases in some hosts, the actual impact of PNRSV appears to be limited