Stemphylium vesicarium

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Stemphylium vesicarium
Systematics
Class : Dothideomycetes
Subclass : Pleosporomycetidae
Order : Pleosporales
Family : Pleosporaceae
Genre : Stemphylium
Type : Stemphylium vesicarium
Scientific name
Stemphylium vesicarium
( Wallr. ) EG Simmons

Stemphylium vesicarium is a fungus thatcausesblack spot disease on pears . This causes great economic damage in pear cultivation.

Black spot disease on the sheet by Josephine von Mechelen . The lighter areas inside some stains are dried dead tissue.
Black spot disease on a leaf on the side shoot of the master builder of a dwarf pear Gute Luise . The light structures on the leaf are mancozeb dust on the edges of dried raindrops.
Black spot disease directly on the side shoot.

description

The fungus has two stages of development. The asexual, anamorphic stage is called Stemphylium vesicarium . The sexual, teleomorphic stage is called Pleospora allii and lives saprophytically on fallen leaves, fruits and other plant remains on the ground. It forms ascospores in Pseudothecium fruiting bodies . The ascospores are blown up by rain and get onto the plants. They germinate at a suitable temperature and humidity, at 21 to 23 ° C about three hours after moistening. This usually happens from late spring. The first symptoms can appear as early as 48 hours later. Stemphylium vesicarium produces the two poisons SV-toxin I and SV-toxin II, which kill the tissue of the plant. The dead areas form black spots that enlarge. The spots can appear on all green areas of the plant. They are mostly found on the leaves, but also on the fruits and green branches, with young fruits on the sepals (calyx), with ripe fruits more in the middle. The first symptoms become visible in late spring, and then grow and multiply during the growing season. The plant's growth and development are inhibited. The harvest is reduced to 95%. In summer, Stemphylium vesicarium forms conidiospores . The conidiospores are carried away by the wind and spread the infection to other plants. Conidiospores can be found on all dead areas of the plants, but not on the green living areas. The conidiospores sit on upright conidiophores (conidia carriers) with a single end conidia .

The different types of pear are susceptible to different degrees. Smaller plants are most affected. Young parts of the plant are more susceptible than fully grown ones.

Once infected, the soil of the orchard produces spores for years. Areas with foliage from pear trees produce around five times as much ascospores as pastureland. Conidiospores are produced about the same amount from both surfaces. Ascospores are produced from December to April and from August to October. In winter more on the pastureland. In summer more on the pear leaves. Conidiospores are produced from April to November, with a maximum between July and September. Frequent irrigation and a lack of tillage encourage the spread of the disease.

Occurrence

The fungus has so far mainly occurred in the warmer regions of Europe, but is now also widespread in Germany, in the late 1970s in Italy, in the 1980s in Spain and France, in 1997 in the Netherlands and in 2002 in Belgium. The global infection rate is estimated to be 1 to 10%.

Susceptibilities of the pear varieties

List according to E. Montesinos.

Susceptible varieties

Sorted from very susceptible to not very susceptible.

Hardly susceptible varieties

variants

There are variants of Stemphylium vesicarium that attack onions, asparagus, umbellifers, garlic or mango. The different variants of Stemphylium vesicarium produce different poisons. The poisons are specially adapted to the host plants to be attacked. The variant for pears kills the tissue from a poison concentration of 10 −8 (0.01 micrograms per gram). The other variants do not make pears sick. The variant for parsley also damages other umbelliferae. However, it can only infect pears in areas that have already been injured. Different variants can appear side by side at the same time. The spores of the variants can be distinguished from one another by analyzing the deoxyribonucleic acid .

Combat

Many fungicides are effective. However, control by spraying fungicides is hardly successful. The dead areas of the plants cannot be healed. In addition, the infected soil under the plants acts as an inoculum . It constantly supplies spores, with which the plants are re-infected.

It does not matter whether you inject weekly or according to the warning system . Both variants bring equally bad results. Spraying only after the first symptoms appear produces even worse results. The most promising is a combination of spraying fungicides during the growing season with the removal of infected parts of the plant throughout the year in order to reduce the risk of infection. The infected plant remains should be buried. Moisten with urea before burying to accelerate microbial degradation.

Wrapping the pear trees with foil after flowering until harvest is somewhat effective but laborious.

The soil under the pear trees deserves great attention as an inoculum . Frequent tillage reduces the production of spores. By infecting the plant remains on the ground with antagonistic Trichoderma fungi, the production of Stemphylium spores can be reduced well during the growing season.

Copper salts and fosetyl aluminum act in diluted form in pears as plant tonic. They reduce the sensitivity of the pear trees to the toxins of Stemphylium vesicarium . They are used as fungicides for other diseases.

The pear trees should be planted with enough space. They should be cut so that the wind easily reaches all parts of the plant so that they dry off quickly after rain. The longer the leaves are moist, the more spores can germinate.

Attempts have been made to reduce the infection of onions with previously injected plant tonics.

literature

  • I. Llorente, C. Moragrega, L. Ruz, E. Montesinos: An update on control of brown spot of pear. In: Trees. 26, 2012, pp. 239–245, doi : 10.1007 / s00468-011-0607-1 .

Individual evidence

  1. ↑ a b Rhineland-Palatinate: Rural Service Centers : Stemphilium vesicarium, the black spot disease in pears.
  2. ^ A b V. Rossi, E. Pattori, S. Giosué, R. Bugiani: Growth and sporulation of Stemphylium vesicarium, the causal agent of brown spot of pear, on herb plants of orchard lawns. In: European Journal of Plant Pathology. 111, 2005, pp. 361-370, doi : 10.1007 / s10658-004-5273-3 .
  3. ↑ I. Llorente, A. Vilardell, P. Vilardell, E. Montesinos: Evaluation of new methods in integrated control of brown spot of pear (stemphylium vesicarium, Teleomorph Pleospora allii). In: Acta horticulturae. No. 800, 2008, pp. 825-832.
  4. ↑ a b c d I. Llorente, C. Moragrega, L. Ruz, E. Montesinos: An Update of brown spot of pear, Trees (2012) 26: 239.245
  5. ↑ P. Singh, R. Bugiani, P. Cavanni, H. Nakajima, M. Kodama, H. Otani, K. Kohmoto: Purification and Biological Characterization of Host-Specific SV-Toxins from Stemphylium vesicarium Causing Brown Spot of European Pear. In: Phytopathology. Volume 89, Number 10, October 1999, pp. 947-953, ISSN  0031-949X . doi : 10.1094 / PHYTO.1999.89.10.947 . PMID 18944740 .
  6. ↑ a b c d e f g h Ministry of Agriculture, Bologna, Maculatura bruna del pero ( Memento from April 30, 2013 in the web archive archive.today )
  7. ↑ Vittorio Rossi, Elisabetta Pattori, Riccardo Bugiani: Sources and seasonal dynamics of inoculum for brown spot disease of pear. In: European Journal of Plant Pathology. 121, 2008, pp. 147-159, doi : 10.1007 / s10658-007-9258-x .
  8. ↑ a b c d J. Köhl, BH Groenenboom-de Haas, P. Kastelein, V. Rossi, C. Waalwijk: Quantitative detection of pear-pathogenic Stemphylium vesicarium in orchards. In: Phytopathology. Volume 99, Number 12, December 2009, pp. 1377-1386, ISSN  0031-949X . doi : 10.1094 / PHYTO-99-12-1377 . PMID 19900004 .
  9. ↑ E. Montesinos, C. Moragrega, I. Llorente, P. Vilardell: Susceptibility of Selected European Pear Cultivars to Infection by stemphylium vesicarium and Influence of Leaf and Fruit Age. (PDF; 577 kB) In: Plant Disease. 79, 1995, pp. 471-473. doi : 10.1094 / PD-79-0471 .
  10. ^ T. Misawa, S. Yasuoka: The life cycle of Stemphylium vesicarium, the causal agent of Welsh onion leaf blight. In: Journal of General Plant Pathology. 78, 2012, pp. 18-29, doi : 10.1007 / s10327-011-0352-8 .
  11. ↑ Mary K. Beck House: Purple Spot Disease of Asparagus. (PDF; 778 kB) University of California, Vegetable Research and Information Center, accessed December 31, 2019 .
  12. ↑ a b Steven T. Koike, Nichole O'Neill, Julie Wolf, Peter Van Berkum, Oleg Daugovish: Stemphylium Leaf Spot of Parsley in California Caused by Stemphylium vesicarium In: Plant Disease. 97, 2013, pp. 315-322, doi : 10.1094 / PDIS-06-12-0611-RE .
  13. ↑ G. Alberoni, D. Cavallini, M. Collina and A. Brunelli: Characterization of the first Stemphylium vesicarium isolates resistant to strobilurins in Italian pear orchards. In: European Journal of Plant Pathology. 126, 2010, pp. 453-457, doi : 10.1007 / s10658-009-9559-3 .
  14. Jump up ↑ PFde Jong, B. Heijne, A. Boshuizen: Test of fungicides against Stemphylium vesicarium on pear with or without a warning system . In: Acta horticulturae . 2005 (ISHS) No. 671, pp. 615-620.
  15. ^ PF de Jong, B. Heijne: Exclusion of the inoculum source of brown spot (Stemphylium vesicarium) . In: Acta horticulturae. 2008 (ISHS) No. 800, pp. 833-838.
  16. ↑ V. Rossi, E. Pattori: inoculum reduction of stemphylium vesicarium, the causal agent of brown spot of pear, through application of Trichoderma-based products. In: Biological Control . 49, 2009, pp. 52-57, doi : 10.1016 / j.biocontrol.2008.12.012 .
  17. ↑ A.-EAM Kamal, HMA Mohamed, AAD Aly and HAH Mohamed: Enhanced Onion Resistance against Stemphylium Leaf Blight Disease, Caused by Stemphylium vesicarium, by Di-potassium Phosphate and Benzothiadiazole Treatments. In: The Plant Pathology Journal . 24, 2008, pp. 171–177, doi : 10.5423 / PPJ.2008.24.2.171 .

Web links

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