Taxonomic information	Current valid scientific name: Diplodia bulgarica A.J.L. Phillips, J. Lopes & Bobev (Phillips, Lopes, Abdollahzadeh, Bobev & Alves, Persoonia 29: 33, 2012) (source: Index Fungorum) Phylum: Ascomycota Order: Botryosphaeriales Family: Botryosphaeriaceae Common name: N/A Name used in the Dossier: N/A
Group	Fungi
EPPO code	N/A
Regulated status	Diplodia bulgarica is not regulated in the EU and any other part of the world.
Pest status in Turkey	Diplodia bulgarica has been recently reported from Turkey (Eken, 2021).
Pest status in the EU	Present in Bulgaria (Phillips et al., 2012; Phillips et al., 2013; Giambra et al., 2016) and Germany (Hinrichs‐Berger et al., 2021) (U.S. National Fungus Collections Database). There is a possibility that the pest is present in other EU MSs, but not detected yet.
Host status on Malus domestica	Diplodia bulgarica has been reported on Malus domestica (U.S. National Fungus Collections Database) (Phillips et al., 2012; Abdollahzadeh, 2015; Hanifeh et al., 2017; Nabi et al., 2020; Bari et al., 2021; Eken, 2021; Hinrichs‐Berger et al., 2021; Nourian et al., 2021).
PRA information	Commodity risk assessment of Malus domestica plants from Serbia (EFSA Panel on Plant Health et al., 2020) Express‐PRA zu Diplodia bulgarica – Auftreten (https://pra.eppo.int/pra/4ccb04b2‐3180‐4d08‐9be9‐cf0bee4cf5ab)
Other relevant information for the assessment
Biology	Diplodia bulgarica was found for the first time in Bulgaria on Malus sylvestris (Phillips et al., 2012). Microscopic characteristics of D. bulgarica were first described for a specimen obtained from Malus sylvestris in Bulgaria (CBS H‐20189 holotype, culture ex‐type CBS 124254) (Phillips et al., 2012). Conidiomata pycnidial, produced on pine needles on water agar after 7–21 days, solitary, immersed, partially erumpent when mature, dark brown to black, globose to ovoid, up to 600 μm in diameter and 700 μm high, mostly unilocular; wall composed of an outer layer of dark brown, thick‐walled textura angularis, a middle layer of dark brown thin‐walled cells, an inner layer of thin‐walled hyaline cells. Ostiole central, circular, papillate. Conidiophores absent. Conidiogenous cells 9–18 × 2–5 μm, hyaline, smooth, thin‐walled, cylindrical, slightly swollen at the base, holoblastic, forming a single conidium at the tip, discrete, indeterminate, proliferating internally giving rise to periclinal thickenings or proliferating percurrently to form 1‐5 annellations. Conidia aseptate, externally smooth, internally verruculose, thick‐walled, oblong to ovoid, straight, both ends broadly rounded, (22.5–)24–27(−28) × (14.5–)15.5–18(−18.5) μm, 95% confidence limits = 25‐25.7 × 16.6‐17 μm (mean ± standard deviation of 50 conidia = 25.4 ± 1.2 × 16.8 ± 0.7 μm, length/width ratio = 1.5 ± 0.1), initially hyaline, soon becoming pale brown, later darkening and becoming 1‐septate (Phillips et al., 2012). No information on the biology and epidemiology of this fungus is available. Nevertheless, it is likely that its life cycle will be similar to other species of the genus. Indeed, several species in the Botryosphaeriaceae family cause similar symptoms on different plant hosts. Diplodia seriata, for example, is a widely studied pathogen that causes cankers and dieback of several hosts, including apple and grapevine. Its life cycle could be taken into account as an initial reference for D. bulgarica. Diplodia seriata overwinters in fruiting bodies (pycnidia and perithecia) on dead bark, dead twigs or mummified fruit. In the spring, pycnidia and perithecia release conidia and ascospores, respectively, under conditions of high humidity and during wet periods throughout the growing season. The spores are dispersed by splashing rains, wind and insects. The pathogen invades the tissue primarily through wounds, although in some hosts entry through natural openings, such as lenticels and stomata, is possible as well as direct penetration. Depending upon the host, the conidia can infect a variety of organs including leaves, the calyxes of blossoms, tiny fruits, and wounds in twigs and limbs. Infections of fruit and wood may not become visible for several weeks. The spores germinate at temperatures between 15 and 37°C and grow between 5 and 37°C. Infection is favoured by conditions that can stress the plant such as drought, frost damage, hail damage, poor nutrition, and poor pruning practices (CABI CPC). In Iran, D. bulgarica‐induced disease has been reported often prevalent in apple trees more than 15 years old that had been suffering from environmental stresses such as drought and nutrient deficiency (Hanifeh et al., 2017). In vitro, the optimal temperature for D. bulgarica growth is 25°C; the fungus still grows at 10°C but not at 35°C (Nourian et al., 2021). A study on vegetative compatibility and aggressiveness diversity has been done on 101 D. bulgarica isolates recovered from apple trees displaying symptoms of canker and decline in the West Azarbaijan province of Iran (Bari et al., 2021). Inter‐simple sequence repeat (ISSR) marker analyses revealed high within‐population diversity, low genetic differentiation, high gene flow and sharing of multilocus genotypes (MLGs) among geographic populations. Vegetative compatibility analyses revealed the occurrence of anastomosis between nonself pairings and high vegetative compatibility group diversity within populations. All studied MLGs produced necrotic lesions on detached shoots of the ‘Red Delicious’ apple but differed in their aggressiveness levels (Bari et al., 2021). A wide range of resistance/susceptibility levels has been found in the apple germplasm, ranging from highly susceptible to moderately resistant (Hanifeh et al., 2017).
Symptoms	Main type of symptoms	Diplodia bulgarica causes canker, gummosis, dieback, twig blight, and vascular discoloration of infected shoots (Abdollahzadeh, 2015). Sunken brown elliptical lesions having a series of concentric rings can also be observed (Nabi et al., 2020). These oval, sunken, brown lesions often develop next to bark injuries such as cracks, pruning wounds or sun damage. In older cankers, black pycnidia sometimes broke through the bark near the canker. As the infection develops the bark separated from the underlying wood and fell to the ground. The wood beneath was blackened and looked like charcoal. Some of the trees can be girdled by the canker and die (Hinrichs‐Berger et al., 2021). This pathogen has been reported to cause fruit rot in the west and northwest apple orchards of Iran (Hanifeh et al., 2017).
	Presence of asymptomatic plants	Little information is available. Diplodia bulgarica has been reported to be highly aggressive on apples (Hanifeh et al., 2017; Eken, 2021; Nourian et al., 2021); therefore, the occurrence of asymptomatic plants should be negligible. On the other hand, it should be taken into account that at least another species in the genus, i.e. Diplodia seriata, can survive endophytically inside some hosts, where it can invade almost any dead, woody tissues (CABI CPC). Further studies could unveil if D. bulgarica can be present within apple tissues as an endophyte while causing no disease symptoms.
	Confusion with other pests	Species identification is done upon morphological and molecular features. Multilocus sequence analysis with concatenated sequences of internal transcribed spacer (ITS) region and elongation factor 1‐α (EF1‐α) was used to identify the species (Phillips et al., 2012). Phillips et al. (2013) stated that morphological characters alone are inadequate to define genera or identify species within Botryosphaeriaceae. Nevertheless, they provide taxonomic keys for the identification of several Botryosphaeriaceae species, including D. bulgarica. This species can be recognised by three characteristics: (a) conidia hyaline and aseptate, becoming brown and 1‐septate only with age; (b) average conidial length less than 29 μm; (c) on Malus, conidia pale brown Phillips et al., 2013. Diplodia bulgarica is morphologically distinct from other Diplodia species reported from apples. Conidia are shorter and wider than both D. intermedia and D. malorum. Iranian isolates of D. bulgarica have also rosulate colonies, but the conidia of D. rosulata (28 × 14.5 μm, length/width ratio = 1.93) are longer and narrower than those of D. bulgarica (25.4 × 16.8 μm, length/width ratio = 1.5). Furthermore, the conidia are distinctive in that they become pale brown soon after they are formed. Phylogenetically, this species is closely related to D. cupressi and D. tsugae (Phillips et al., 2012).
Host plant range	Diplodia bulgarica has been reported on Malus domestica (Phillips et al., 2012; Abdollahzadeh, 2015; Hanifeh et al., 2017; Nabi et al., 2020; Bari et al., 2021; Eken, 2021; Hinrichs‐Berger et al., 2021; Nourian et al., 2021), M. sylvestris (Phillips et al., 2012; Phillips et al., 2013), and Pyrus communis (Hinrichs‐Berger et al., 2021) (U.S. National Fungus Collections Database)
Reported evidence of impact	Diplodia bulgarica is reported as causing severe cankers in Iran (Abdollahzadeh, 2015), India (Nabi et al., 2020) and Germany (Hinrichs‐Berger et al., 2021).
Pathways and evidence that the commodity is a pathway	Diplodia bulgarica can be present as a pathogen on trunks, twigs (Phillips et al., 2012), and fruits (Hanifeh et al., 2017). Presumably, according to the biology of other Diplodia species, D. bulgarica could be also present on leaves.
Surveillance information	No surveillance information for this pest is currently available from Turkey. There is no information available to assess whether the pest has ever been found in the nurseries or the surrounding environment of the nurseries.