Cytospora oleina causing canker and dieback of olive in Greece

Cytospora oleina was isolated from dead twigs of olive associated with old cankers in the Mount Pelion region of central Greece. Inoculation of young trees with pure cultures of the fungus caused twig death in olive, especially when applied in autumn, and xylem discoloration in apple, plum, cherry, peach and apricot.     

Characterization of Neofusicoccum parvum causing canker and dieback on Brachychiton species

Brachychiton species are planted in Italy as ornamental trees. A survey in a nursery in Sicily (Italy) revealed the presence of young B. acerifolius and B. populneus showing severe trunk cankers, massive gummosis from the bark cracks, wood discolouration, and twig dieback. Morphological characterization was based on conidia measurement, and molecular characterization was carried out performing phylogenetic analysis (Maximum Parsimony) based on multi-locus approach of partial ITS, EF-1α, and tub2. Identification of the causal agent resulted in Neofusicoccum parvum (Botryosphaeriaceae). Pathogenicity tests were conducted in order to fulfill the Koch’s postulates. Five and three-years-old potted Brachychiton plants were inoculated (indoor and outdoor) using mycelial plugs. All the inoculated plants showed severe symptoms similar of those observed in the nursery during the survey. Some of the inoculated plants were completely dead. Re-isolations fully confirmed the causal agent. For our knowledge, this is the first report worldwide of N. parvum attacking Brachychiton spp.

     

Pathogenesis of Eutypa lata in grapevine: identification of virulence factors and biochemical characterization of cordon dieback

Eutypa lata is a vascular pathogen of woody plants. In the present study we (i) determined which component(s) of the cell wall polymers were degraded in naturally infected grapevines and in artificially inoculated grape wood blocks; (ii) compared the pattern of wood decay in the tolerant grape cv. Merlot versus the susceptible cv. Cabernet Sauvignon; and (iii) identified secondary metabolites and hydrolytic enzymes expressed by E. lata during wood degradation. Biochemical analyses and a cytochemical study indicated that glucose-rich polymers were primary targets of E. lata. Structural glucose and xylose of the hemicellulose fraction of the plant cell wall and starch were depleted in infected woods identically in both cultivars. Moreover, the more tolerant cv. Merlot always had more lignin in the wood than the susceptible cv. Cabernet Sauvignon, indicating that this polymer may play a role in disease resistance. In vitro assays demonstrated the production by E. lata of oxidases, glycosidases and starch degrading enzymes. Phytotoxic secondary metabolites were also produced but our data suggest that they may bind to the wood. Finally, we demonstrated that free glucose in liquid cultures repressed primary but not secondary metabolism.     

Studies of canker and dieback of oak tree in China,with two Cytospora species described

Oak (Quercus sp.) is an excellent tree species as a windbreak, for water conservation, and for fireproofing in forests in China. However, several trees of this genus were found to be suffering from various fungal diseases. In this study, we evaluated 15 fungal pathogens that can cause dieback and canker disease in oak in China, and discovered two Cytospora species. They were identified as Cytospora quercinum sp. nov. and C. vinacea, based on detailed morphological comparisons and phylogenetic analysis of ITS, LSU, act, rpb2, tef1-α, and tub2 loci. This study is the first record of C. quercinum and C. vinacea as causal agents of dieback in oak based on pathogenicity tests conducted on 2-year-old plants in a greenhouse. In addition, this study also revealed the influence of different conditions on the growth rate of mycelia. Mycelial growth of C. quercinum and C. vinacea occurred at optimum temperatures of 20.1 and 20.8 °C, and optimum pH of 5.4 and 5.3, respectively. For these two species, utilization of glucose and fructose was highly efficient, and sucrose was the least efficient. The habitat of Quercus mongolica indicated that more attention and management are needed to prevent the occurrence of Cytospora disease in the summer in north-eastern China, and in spring and autumn in eastern and northern China. This study contributes to the understanding of the species causing canker or dieback diseases in important economic forest trees, and provides useful information for effective disease management of oak trees in China.     

Potential susceptibility of Australian native plant species to branch dieback and bole canker diseases caused by Phytophthora ramorum

Susceptibility to branch dieback caused by Phytophthora ramorum was tested using a detached branch assay for 66 Australian native plant species sourced from established gardens and arboreta in California. Six of these species were further tested for their susceptibility to bole cankers caused by P. ramorum using a sealed log assay. Isopogon formosus and Eucalyptus denticulata were identified as potentially highly susceptible Australian branch dieback hosts. Thirteen potentially tolerant Australian host species included Banksia attenuata, B. marginata, E. haemastoma, E. regnans, Pittosporum undulatum and Billardiera heterophylla. Eucalyptus regnans was identified as a potentially highly susceptible bole canker host, while E. diversicolor and E. viminalis were considered potentially tolerant species to bole cankers caused by P. ramorum. Phytophthora ramorum was able to infect all 66 species, as confirmed by reisolation. These results extend the known potential host range for P. ramorum, confirm it as a possible threat to Australian plant industries and ecosystems and highlight additional associated hosts that are important in the global horticultural trade, native forests and plantation forestry.     

Eutypa Canker and Dieback of Apricots

Eutypa canker and dieback of apricot trees, caused by the ascomycetous fungus Eutypa armeniacae Hansf. et Carter, has been recorded in Europe, North America, Australia and South Africa. Samples of diseased sapwood yield the imperfect Cytosporina stage in culture, whereas perithecia of E. armeniacae, immersed in a stroma, develop 2 or more years after death of a branch in high-rainfall areas. The fungus is a wound parasite. Air-borne ascospores, disseminated during and after rain, infect xylem tissues which have been freshly exposed by pruning. Cankers develop around the infected wounds; leaves on that part of the branch distal to the canker subsequently wilt and die during summer. E. armeniacae has been detected on a diverse range of host species, hence elimination of inoculum is not feasible; both biological and chemical approaches to wound protection and ultimate disease control are under investigation.     

A Reassessment of the Species Concept in Eutypa lata, the Causal Agent of Eutypa Dieback of Grapevine

ABSTRACT Eutypa dieback is a vascular disease of several cultivated crops and trees worldwide. The attribution of the name to the agent responsible for branch dieback is ambiguous. Pathogenicity of Eutypa sp. first was reported on apricot and the causal agent was named E. armeniacae. However, no morphological differences were reported with the previously described E. lata, and some authors considered both species synonymous. Others regarded them as distinct species on the basis of pathogenesis and molecular analysis. We further investigated the relatedness of both species by phylogenetic analyses of the internal transcribed spacer region and beta-tubulin gene. These analyses included several other taxa placed in the same family (Diatrypaceae), and yielded three groups. The isolates referred to as E. lata in previous work clustered with Diatrype stigma in one group. Isolates of E. armeniacae and E. lata clustered in a second group, supporting the synonymy of these species. The third group included other Eutypa spp. supporting the polyphyletic origin of this genus. Measurements of conidia length and secondary metabolite production of isolates supported the phylogenetic analyses. Secondary metabolites appeared to be a synapomorphic character shared by several taxa including E. lata, E. armeniacae, E. laevata, and E. petrakii var. petrakii.     

桉树焦枯病药剂防治试验

桉树焦枯病Ｅｕｃａｌｙｐｔｕｓｄｉｅｂａｃｋ是国内森林检疫性病害之一。主要发生在桉树苗木和 4年生以下的幼林中 ,同时也侵染萌芽林。多发生在 5～ 9月高温高湿季节。从植株下部枝叶开始发病 ,逐渐向上蔓延。 2 0 0 0年 4～ 9月 ,广西合浦常乐、曲樟等地普遍发生 ,发病株率达 75%以上 ,感病程度Ⅲ -Ⅳ级达2 8% ,个别林分达Ⅴ级 ,直至整株枯死。严重发生面积 48ｈｍ2 ,严重发病的植株中下部叶片几乎全部感病 ,枝条失水变硬、干枯 ,叶片脱落达植株的 2 /3以上。春季感病早的至 9月份仍可生长出少量新叶 ,但叶片细小 ,发育不良 ,影响了当…     

Morphological and molecular identification of Eutypa lata on grapevine in Serbia

Journal of Plant Diseases and Protection - During a survey from 2004 to 2016, symptoms of grapevine dieback were observed in six vineyards in Serbia. Symptoms initially appeared as small,...     

Biology ofSpectrobates ceratoniae on almonds in Israel

Field observations and recording of carob moth [Spectrobates ceratonia (Zell.)] infestation in almonds revealed the following pattern of generation sequence. The moths overwinter as larvae in nuts left on the trees after harvest; these pupate in mid-February and adults emerge from mid-March until June, with a peak emergence in April-May. Emerging females lay mainly on new nuts infected by the anthracnose disease as well as on old nuts, if available. The first summer generation reached adulthood from May to July, at which time hullsplit nuts of the new crops are available for oviposition. One to two generations develop on the hullsplit nuts before winter, thus bringing the annual average to three or four generations. Eggs are dispersed evenly among the nuts, usually with a single egg laid on each nut. The hatching larvae feed on the kernel, causing economic damage, or on the hull. Damage may be reduced by early harvesting. Natural parasitism of the carob moth on almonds was insignificant. A few other moth species infest almond nuts, but do not cause any significant damage.     

Phytophthora crown rot of almonds in Australia 1

Phytophthora crown rot, caused primarily by Phytophthora cambivora, has caused considerable losses in almond orchards in the Willunga and northern plains areas approximately 50 km north and south of Adelaide (AU), respectively. Other Phytophthora species including P. citrophthora, P. cryptogea, P. megasperma and P. syringae have also been associated with diseased trees. Tree losses have been associated with P. cactorum isolated from trunk cankers on scaffold limbs on trees in the Riverland almond-growing area approximately 350 km north-east of Adelaide. The Al mating type of P. cambivora was the most pathogenic to almond seedlings. Cvs Mission and Chellaston, which are commonly used as rootstocks, were highly susceptible to crown rot whereas peach cv. Nemaguard was resistant. An excised twig assay has been developed to screen micropropagated shoots for resistance to P. cambivora. Metalaxyl applied at 5 g active substance per tree in spring, winter and autumn in a shallow trench close to the trunk prevented the development of trunk cankers. Foliar sprays of phosphonate (H₃PO₃) at 2 g active substance per litre in autumn and spring also inhibited canker development.     

Diaporthe perniciosa associated with plum dieback

An outbreak of dieback on plum trees at the Institute of Horticultural Research, East Mailing, in the summer of 1983 resembled a disease prevalent in Britain earlier this century attributed to Diaporthe perniciosa. Numerous isolates of this fungus were obtained from diseased tissues but an attempt to reproduce the disease by inoculation was unsuccessful. Dieback appeared following exceptionally wet spring weather.     

Pitch canker disease of pines

ABSTRACT Pitch canker, caused by Fusarium circinatum, is a disease affecting pines in many locations throughout the world. The pathosystem was originally described in the southeastern (SE) United States and was identified in California in 1986. Limited vegetative compatibility group (VCG) diversity in the California population of F. circinatum, relative to the SE United States, suggests the former is a recently established and clonally propagating population. Although the much greater VCG diversity found in the SE United States is suggestive of out-crossing, molecular markers indicate that many vegetatively incompatible isolates are clonally related. This implies that VCG diversity may derive, at least in part, from somatic mutations rather than sexual reproduction. Pitch canker is damaging to many pine species and one at particular risk is Monterey pine (Pinus radiata), which is widely grown in plantations and is highly susceptible to pitch canker. However, some Monterey pines are resistant to pitch canker and some severely diseased trees have been observed to recover. The absence of new infections on these trees reflects the operation of systemic induced resistance, apparently in response to repeated infection by the pitch canker pathogen.     

Pestalotiopsis canker of cypress in Israel

The occurrence of a new type of canker on stems and branches of cypress trees(Cupressus sempervirens L.) in Israel is reported.Pestalotiopsis funerea (Desm.) Steyaert was isolated from the cankers. Its pathogenicity was confirmed by formation of typical disease symptoms in inoculated plants and reisolation of that fungus from the cankers. Canker development was significantly enhanced when extreme water stress (water potential of -4.7 MPa) was imposed prior to inoculation.     

柑橘溃疡病检疫与防治

细菌性溃疡病是严重危害世界柑橘产业的重大检疫性病害之一,柑橘溃疡病引起落叶、枯枝和落果,溃疡病斑导致果品质量降低,影响外贸出口。世界各国长期以来对病害采取严格苗木检疫、疫区病树铲除、零星病害药剂防控的综合治理措施;新近美国农业部推出"柑橘健康种植行动计划";2007年7月中国农业部正式启动"柑橘非疫区建设和维护"项目,总体目标在于防控柑橘溃疡病的发生和传播,确保柑橘产业的安全。     

厚皮香枯梢病病原菌鉴定

厚皮香枯梢病在上海地区发生严重。本研究对上海地区的厚皮香枯梢病进行了病原菌的分离与致病性鉴定,得到其病原菌菌株2017SHTg。根据病原菌的形态特征将其鉴定为小新壳梭孢Neofusicoccum parvum。扩增病原菌2017SHTg的rDNA-ITS序列和翻译延伸因子EF-1α基因序列,进行BLAST序列比对与小新壳梭孢相似性分别为99%和100%;基于rDNA-ITS序列构建系统发育进化树,其在系统发育树上与小新壳梭孢的类群处于同一分支,此结果与形态学鉴定结果一致。     

Evaluating susceptibility of almonds to anthracnose disease caused byCollectotrichum gloeosporioides

Susceptibility of almond fruit(Prunus dulcis (Mill.) Webb.) to anthracnose caused byColletotrichum gloeosporioides Penz.(=Gloeosporium amygdalinum Brizi) was investigated. Fruits were punctured, and a drop of spore suspension of the desired size and density was placed on the wound. Fruits were placed in a humid chamber for one week at 22°C. The diameter of the lesion of the infected fruits was used as an indicator of susceptibility. Disease development was found to be negatively correlated with the age of the fruit. The inoculation concentrations used in this research have no effect on the disease development, although the volume of the drop affected the size of the lesion to some extent. With constant, high relative humidity (saturation), the diameter of the anthracnose lesion increased by 1 mm per day, while under dry room conditions the increase was less than 0.5 mm per day. At 22°C lesions developed faster than at either 15° or 27°C. A detailed procedure for assessing sensitivity of fruit to anthracnose is described. This should enable improved comparison of susceptibility between genotypes and in different environments.     

防治葡萄溃疡病的杀菌剂筛选与评价

采用菌丝生长速率法和孢子萌发法测定了7种杀菌剂对可可毛色二孢CSS-01s的室内生物活性,筛选出3种抑制效果较好的杀菌剂;通过对离体葡萄绿枝条及盆栽葡萄幼苗新梢进行人工接种病原菌,进一步评价杀菌剂的防治效果。结果表明,7种杀菌剂对可可毛色二孢菌丝生长和孢子萌发表现出不同的抑制活性,其中戊唑醇、氯氟醚菌唑、啶酰菌胺和氟啶胺对菌丝生长的抑制作用较强,EC₅₀分别为0.116、0.137、0.109μg/mL和0.119μg/mL;戊唑醇、氯氟醚菌唑、氟啶胺对孢子萌发的抑制作用较强,EC₅₀分别为0.420、0.595μg/mL和1.885μg/mL。CSS-01s接种离体葡萄绿枝条试验中,戊唑醇100、200 mg/L,氯氟醚菌唑100、300 mg/L和氟啶胺100、200 mg/L的防治效果无显著差异,在57.81%～65.31%;CSS-01s接种葡萄幼苗新梢试验中,氟啶胺200 mg/L的防治效果最好,为77.56%,与氟啶胺100 mg/L、氯氟醚菌唑100、300 mg/L和戊唑醇200 mg/L之间无显著差异,但显著高于戊唑醇100...