Search

Ascospores discharged at rainfall and dispersed by wind can provide long-distance spread of the European canker fungus, Neonectria ditissima. Ascospores are produced by perithecia which are the sexual reproductive stage. Diffuse knowledge exists on the seasonal pattern of perithecium formation under different climatic conditions. Therefore, the development of perithecia was observed for several successive seasons at five sites in three Northern European countries. In Norway and Finland, ripe perithecia were commonly recorded throughout the year, and on individual cankers continuously for up to 28 months. In contrast, asexual reproductive structures (sporodochia) were confined to the growing season in both countries. In Northern Germany an average of 51% of cankers developed ripe perithecia by late winter, and perithecial senescence ensued in late spring. On average, ripe perithecia were present on cankers for 22 weeks. In contrast, sporodochia were observed all year round. The timing of perithecium maturation correlated with the number of days with > 2 mm rainfall in July–September. The presence of mature perithecia and sporodochia for different lengths of time in different countries has implications for regional disease management strategies. [ABSTRACT FROM AUTHOR]

The combination of preharvest treatments with calcium chloride and fungicides, and storage of maturity graded fruit were assessed in five European plum cultivars. At harvest, samples of fruit within a commercially suitable range in ripening were divided into two categories: less-ripe (tree ripe-) and more-ripe (tree ripe+). The fruit were stored for 10–14 days at 4 °C followed by 2–3 days at 20 °C before the assessment of fungal decay. If calcium chloride was applied six times each season, postharvest fruit decay was significantly reduced in four of nine experiments, with a total mean reduction of around 50%. Two calcium applications in combination with a fungicide treatment reduced decay by approx. 60% compared to the untreated in one experiment. In six of seven experiments there was no effect of preharvest fungicide applications. In six of 10 experiments, fruit of the category tree ripe- had fewer fruit with fungal decay after storage than the tree ripe+fruit. The higher incidence in the category tree ripe+fruit was primarily due to brown rot, Mucor rot, and blue mould. For the category tree ripe+, there was two to ten times more decay than on tree ripe- fruit after a simulated shelf-life period. To ensure low incidence of fungal decay, fruit of commercial harvest maturity may thus be separated in two ripening categories, one for rapid distribution to the market (tree ripe+) and another for extended distribution time (tree ripe-). [ABSTRACT FROM AUTHOR]

Neonectria fruit rot (NFR), an apple disease caused by the fungus Neonectria ditissima, is common in Brazilian orchards, but several aspects of its epidemiology are not well elucidated. The objectives of this study were to: i) test in vitro germination of ascospores at different temperatures and wetness periods and compare with conidia germination, ii) evaluate and compare the monocyclic components of NFR caused by conidia and ascospore infection in wounded and unwounded ripe detached 'Gala' apple and iii) evaluate and compare the monocyclic components of NFR caused by conidia infection in 'Rocha' pear fruit under different temperatures. Germination of conidia and ascospores occurred in the range of 12–28 °C. At 35 °C no germination occurred, for both ascospores and conidia, regardless of the wetness period (3–60 h). With the same wetness period, conidia germination was always higher than ascospores at any temperature. For ascospores, the optimal temperature for germination ranged from 18–21 °C, lower than the estimated for conidia, which ranged from 21 to 24 °C. In wounded detached apple fruit, the incubation period varied from 35 to 49 days after ascospore inoculation, and for conidia from 14 to 42 days. When comparing the same temperatures, mean lesion growth rate was always higher for fruits inoculated with conidia than with ascospores. Unwounded fruits inoculated in the calyx-end did not present Neonectria fruit rot symptoms. The disease on 'Rocha' pear fruit has shorter incubation and latent periods than those of 'Gala' apple and higher AUDPC at 25 °C. The fast monocycle development represents a risk if the disease spread to pear orchards but also sets pear fruit as a good option for future NFR control studies. [ABSTRACT FROM AUTHOR]

Over the past two decades, there has been a marked increase in Uruguayan olive production. However, the humid climate of Uruguay creates favorable conditions for the development of olive anthracnose, characterized by fruit rots and blossom blight, which are frequent and destructive symptoms. Several species of Colletotrichum are responsible for the disease, with C. acutatum sensu stricto (s.s) being the most prevalent. This study aimed to analyze the survival of Colletotrichum in an olive orchard with a history of olive anthracnose. For two consecutive years, samples of fruits, leaves, and woody organs were collected monthly from aerial parts of the olive tree. Colletotrichum spp. structures were recorded in a climate chamber, and C. acutatum s.s. was quantified. The study demonstrated that Colletotrichum can survive in different organs of the olive tree, with mummified fruit being the primary survival site, followed by leaves and branches. Among the leaf and woody organs, yellow leaves, leaves from defoliated branches, terminal dry branches, and healthy new branches were identified as important survival sites. Mummified fruits were not always present on the tree throughout the year, and leaves and branches can serve as the primary source of initial inoculum for infections of flowers and fruits in their absence. [ABSTRACT FROM AUTHOR]

European canker is one of the most devastating fungal diseases of apple in most temperate regions. The causal agent, Neonectria ditissima, infects trees through wounds in the bark forming cankers that girdle the stem and eventually cause tree death. Timely protection of the trees is challenged by stagnation of symptom expression after infections for a long period of time. The objective of this research is to use a novel TaqMan PCR assay to detect and quantify N. ditissima during the asymptomatic colonization of apple wood. Pruning wounds on branches of the cultivars Elstar and Gala were inoculated with N. ditissima and wood discs were sampled at 2–6, 10–14, and 30–34 mm distance from the inoculation site after 3 hours, 2 weeks, 4 weeks and 8 weeks for the detection and quantification of the pathogen. The TaqMan PCR assay detected N. ditissima in 51% of the inoculated apple tree samples. This was more sensitive than the culturing method detecting N. ditissima in 11% of the samples. An accumulation of N. ditissima DNA up to 34 mm distance from the inoculation site was observed without development of visible symptoms. To our knowledge this is the first time colonization of N. ditissima was detected and quantified in the absence of symptoms of European canker. The implications of this research are discussed. [ABSTRACT FROM AUTHOR]