Identification of QoI fungicide-resistant genotypes of the wheat pathogen Zymoseptoria tritici in Algeria

Septoria tritici blotch caused by Zymoseptoria tritici is currently one of the most damaging diseases on bread and durum wheat crops worldwide. A total of 120 monoconidial isolates of this fungus were sampled in 2012 from five distinct geographical locations of Algeria (Guelma, Annaba, Constantine, Skikda and Oran) and assessed for resistance to Quinone outside Inhibitors (QoI), a widely used class of fungicides for the control of fungal diseases of wheat. Resistance was screened using a mismatch PCR assay that identified the G143A mitochondrial cytochrome b substitution associated with QoI resistance. The isolates were QoI-sensitive, since all possessed the G143 wild-type allele, except for three isolates (two from Guelma and one from Annaba), which had fungicide resistance and possessed the A143 resistant allele. QoI resistance was confirmed phenotypically using a microplate bioassay in which the resistant isolates displayed high levels of half-maximal inhibitory azoxystrobin concentrations (IC50s) when compared to sensitive reference isolates. Genetic fingerprinting of all isolates with microsatellite markers revealed that the three resistant isolates were distinct haplotypes, and were are not genetically distinguishable from the sensitive isolates. This study highlights QoI-resistant genotypes of Z. tritici in Algeria for the first time, and proposes a management strategy for QoI fungicide application to prevent further spread of resistance across the country or to other areas of Northern Africa

Evolution of Mycosphaerella graminicola at the wheat leaf and field levels

The aim of this study was to compare Mycosphaerella graminicola populations at the field and lesion levels. The evolution of M. graminicola populations from a single field in the “Morbihan” county (France), between 2005 and 2006, was first investigated for 37 strains using molecular fingerprinting by microsatellite markers (ST1A4, ST1E3, ST1E7 and ST1D7) and SSCP analysis of partial actin and β-tubulin encoding sequences. Similar gene diversity was observed in the 2005 and 2006 populations, with no common clones between the two years. This indicates frequent sexual recombination by the fungus. When considering each marker independently and comparing marker genetic variability for the two populations, differences in the genetic variability were detected in 2006 population compared to the 2005 population. ST1A4, ST1D7 and the partial sequence of actin presented a decrease in genetic variability of the 2006 strains, while for ST1E3, ST1E7 and the partial sequence of β-tubulin showed an increase, revealing the importance of the chosen markers. In addition, 29 strains collected in 2006 from three distinct lesions on the same wheat leaf in the “Nord” county were also investigated for genetic diversity. MAT1-1 and MAT1-2 were found in the same lesion offering opportunities for sexual contact

Update of the Scientific Opinion on the risks to plant health posed by Xylella fastidiosa in the EU territory

EFSA was asked to update the 2015 EFSA risk assessment on Xylella fastidiosa for the territory of the EU. In particular, EFSA was asked to focus on potential establishment, short‐ and long‐range spread, the length of the asymptomatic period, the impact of X. fastidiosa and an update on risk reduction options. EFSA was asked to take into account the different subspecies and Sequence Types of X. fastidiosa. This was attempted throughout the scientific opinion but several issues with data availability meant that this could only be partially achieved. Models for risk of establishment showed most of the EU territory may be potentially suitable for X. fastidiosa although southern EU is most at risk. Differences in estimated areas of potential establishment were evident among X. fastidiosa subspecies, particularly X. fastidiosa subsp. multiplex which demonstrated areas of potential establishment further north in the EU. The model of establishment could be used to develop targeted surveys by Member States. The asymptomatic period of X. fastidiosa varied significantly for different host and pathogen subspecies combinations, for example from a median of approximately 1 month in ornamental plants and up to 10 months in olive, for pauca. This variable and long asymptomatic period is a considerable limitation to successful detection and control, particularly where surveillance is based on visual inspection. Modelling suggested that local eradication (e.g. within orchards) is possible, providing sampling intensity is sufficient for early detection and effective control measures are implemented swiftly (e.g. within 30 days). Modelling of long‐range spread (e.g. regional scale) demonstrated the important role of long‐range dispersal and the need to better understand this. Reducing buffer zone width in both containment and eradication scenarios increased the area infected. Intensive surveillance for early detection, and consequent plant removal, of new outbreaks is crucial for both successful eradication and containment at the regional scale, in addition to effective vector control. The assessment of impacts indicated that almond and Citrus spp. were at lower impact on yield compared to olive. Although the lowest impact was estimated for grapevine, and the highest for olive, this was based on several assumptions including that the assessment considered only Philaenus spumarius as a vector. If other xylem‐feeding insects act as vectors the impact could be different. Since the Scientific Opinion published in 2015, there are still no risk reduction options that can remove the bacterium from the plant in open field conditions. Short‐ and long‐range spread modelling showed that an early detection and rapid application of phytosanitary measures, consisting among others of plant removal and vector control, are essential to prevent further spread of the pathogen to new areas. Further data collection will allow a reduction in uncertainty and facilitate more tailored and effective control given the intraspecific diversity of X. fastidiosa and wide host range.Additional co-authors: EFSA Panel on Plant Health (PLH), Wopke van der Werf, Antonio Vicent Civera, Jonathan Yuen, Lucia Zappalà, Donato Boscia, Gianni Gilioli, Rodrigo Krugner, Alexander Mastin, Anna Simonetto, Joao Roberto Spotti Lopes, Steven White, José Cortinas Abrahantes, Alice Delbianco, Andrea Maiorano, Olaf Mosbach‐Schulz, Giuseppe Stancanelli, Michela Guzzo, Stephen Parnel

Pest categorisation of Conotrachelus nenuphar

The EFSA Panel on Plant Health performed a pest categorisation of Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), for the EU. C. nenuphar is a well-defined species, recognised as a serious pest of stone and pome fruit in the USA and Canada where it also feeds on a range of other hosts including soft fruit (e.g. Ribes, Fragaria) and wild plants (e.g. Crataegus). Adults, which are not good flyers, feed on tender twigs, flower buds and leaves. Females oviposit into host fruit; if oviposition occurs in young fruit, the fruit usually falls prematurely reducing yield; oviposition in older fruit causes surface blemishes and the fruit distorts as it develops reducing marketability. Larvae develop within host fruit but exit to pupate in soil. Adults overwinter in leaf litter. C. nenuphar is not known to occur in the EU and is listed in Annex IAI of Council Directive 2000/29/EC. Fruit infested shortly before harvest and soil with leaf litter accompanying plants for planting could potentially provide a pathway into the EU. Considering the climatic similarities between North America and Europe, and that hosts occur widely within the EU, C. nenuphar has potential to establish within the EU. There could be one or two generations per year, as in North America. Impacts could be expected, e.g. in Prunus spp. and apples. Phytosanitary measures are available to reduce the likelihood of introduction of C. nenuphar. All of the criteria assessed by EFSA for consideration as a potential Union quarantine pest are met. C. nenuphar does not meet the criteria of occurring in the EU nor plants for planting being the principal means of spread. Hence it does not satisfy all of the criteria that are within the remit of EFSA to assess for it to be regarded as a Union regulated non-quarantine pest (RNQP)

Pest categorisation of Sternochetus mangiferae

The European Commission requested EFSA to conduct a pest categorisation of Sternochetus mangiferae (Coleoptera: Curculionidae), a monophagous pest weevil whose larvae exclusively feed on mango seeds, whereas adults feed on mango foliage. S. mangiferae is a species with reliable methods available for identification. It is regulated in the EU by Council Directive 2000/29/EC where it is listed in Annex IIB as a harmful organism whose introduction into EU Protected Zones (PZ) (Alentejo, Algarve and Madeira in Portugal, and Granada and Malaga in Spain) is banned. S. mangiferae is native to South East Asia and has spread to other mango-growing areas in Africa, South America and Oceania, causing significant damage. Larvae of S. mangiferae have been detected several times in mango fruit imported into the EU. In 2013, an outbreak was declared in one PZ in Spain. Official measures taken achieved eradication, which was officially declared in January 2018. The EFSA Plant Health Panel concludes that S. mangiferae could establish again and spread in the mango-growing areas of southern EU. Considering the criteria within the remit of EFSA to assess the status as a potential Union quarantine pest (QP), as a potential protected zone quarantine pest (PZQP) or as a potential regulated non-quarantine pest (RNQP), S. mangiferae meets with no uncertainties the criteria for consideration as a potential Union QP, as it is absent from the EU, potential pathways for entry exist, and its establishment would cause an economic impact. The criterion of the pest being present in the EU, which is a prerequisite for RNQP and PZ QP, is not met

Pest categorisation of Acrobasis pirivorella

The European Commission requested EFSA to conduct a pest categorisation of Acrobasis pirivorella (Lepidoptera: Pyralidae), a monophagous moth whose larvae exclusively feed on developing buds, flowers, and fruits of cultivated and wild Pyrus spp. A. pirivorella is a species with reliable methods available for identification. A. pirivorella occurs in north-east Asia only, causing significant damage in cultivated pears. It is regulated in the EU by Council Directive 2000/29/EC where it is listed in Annex IIAI. Within this regulation, plants for planting of Pyrus spp. is a closed pathway. This species has never been reported by Europhyt. Fruits and cut branches of Pyrus spp. are open pathways. Biotic and abiotic conditions are conducive for establishment and spread of A. pirivorella in the EU. Were A. pirivorella to establish, impact on pear production is expected. Considering the criteria within the remit of EFSA to assess its regulatory plant health status, A. pirivorella meets the criteria for consideration as a potential Union quarantine pest (it is absent from the EU, potential pathways exist and its establishment would cause an economic impact). Given that A. pirivorella is not known to occur in the EU, it fails to meet some of the criteria required for regulated non-quarantine pest (RNQP) status

Pest categorisation of Aleurocanthus spp

The Panel on Plant Health performed a pest categorisation of Aleurocanthus spp., a well-de fi ned insect genus of the white fl y family Aleyrodidae (Arthropoda: Hemiptera). Dif fi culties within the taxonomy of the genus give doubt about the ability to accurately identify some members to species level. Nevertheless, the genus is thought to currently include about ninety species mainly reported from tropical and subtropical areas. The genus is listed in Council Directive 2000/29/EC and is regulated on Citrus, Fortunella and Poncirus . Several Aleurocanthu s species are highly polyphagous; Aleurocanthu s spiniferus has hosts in 38 plant families; Aleurocanthu s woglumi has more than 300 hosts including Pyrus , Rosa and Vitis vinifera as well as Citrus . A. spiniferus is present in the EU in restricted areas of Italy and Greece, where it is under of fi cial control. No other Aleurocanthus spp. are known to occur in the EU. Host plants for planting, excluding seeds, and cut fl owers or branches are the main pathways for entry. Outside of the EU, the genus can be found in regions that have climate types which also occur within the EU, suggesting establishment is possible. Aleurocanthus spp. can be signi fi cant pests of crops that are also grown in the EU. Phytosanitary measures are available to reduce the likelihood of entry into the EU, e.g. sourcing host plants for planting from pest free areas. As a genus Aleurocanthus does satisfy all the criteria that are within the remit of EFSA to assess and required by risk managers to give it consideration as a Union quarantine pest. Aleurocanthus does not meet all of the criteria to allow it consideration by risk managers as a Union regulated non-quarantine pest (RNQP). Speci fi cally, Aleurocanthus is not widespread in the EU

Risk assessment of the entry of Pantoea stewartii subsp. stewartii on maize seed imported by the EU from the USA.

Following a request from the European Commission, the EFSA Panel on Plant Health performed a risk assessment of the entry of Pantoea stewartii subsp. stewartii on maize seed imported by the EU from the USA. This pest is a Gram-negative bacterium which causes Stewart’s vascular wilt and leaf blight of maize (including sweet corn), a disease responsible for serious crop losses throughout the world. The following scenarios were considered: scenario A0 (current practice), scenario A1 (US request for modification of EU conditions for derogation), and scenario A2 (EU conditions for derogation). Results from the quantitative seed pathway model presented here show that, despite the low rates of plant-to-seed and seed-toseedling transmission that have been reported in the literature for Stewart’s wilt, given the amount of traded seed, and in the case of voluntary (i.e. not mandatory) inspections of seed production fields at the origin (i.e. scenario A0), the frequency of introducing the disease is in the order of magnitude of some hundred introductions per year (median number). The EU conditions for derogation would lead to a decrease in the likelihood of entry compared to scenarios A0 (about 10,000 times fewer introductions) and A1 (about 2,000 times fewer introductions). This protective effect is mainly due to the requirement that only genotypes resistant to Stewart’s wilt are traded, with the additional field inspection (two instead of one per season) providing additional reassurance. The Panel also concluded that seed lot inspections, as currently carried out (e.g. with a sample of 400 seeds) are not likely to lead to a relevant reduction in the level of infected imported maize seed, given the low prevalence of Stewart’s wilt at the origin. If, however, there is aggregation in infection among consignments, inspection would work towards identifying the highly infected consignments. Recently, outbreaks of Stewart’s wilt have occurred in Italy (Emilia Romagna, Friuli, Lombardy and Veneto). A review is provided of the available information to assess the possible role of seed imports in these outbreaks