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Challenges in the integrated control of pear tree stemphyliosis

Isidre Llorente

Institut de Tecnologia Agroalimentària. Universitat de Girona

Challenges in the integrated control of pear tree stemphyliosis
Isidre Llorente
Institut de Tecnologia Agroalimentària
Universitat de Girona

Pear tree stemphyliosis, or brown spot disesase of pear, is a disease caused by the fungus Stemphylium vesicarium (Wallr.) Simmons. This disease affects several pear-producing regions of Europe including Catalonia, Portugal, Italy, France, Belgium, and Holland. The signs of this disease are necrotic spots on the leaves and fruit.

Challenges in the integrated control of pear tree stemphyliosis
Isidre Llorente
Institut de Tecnologia Agroalimentària
Universitat de Girona

Pear tree stemphyliosis, or brown spot disesase of pear, is a disease caused by the fungus Stemphylium vesicarium (Wallr.) Simmons. This disease affects several pear-producing regions of Europe including Catalonia, Portugal, Italy, France, Belgium, and Holland. The signs of this disease are necrotic spots on the leaves and fruit. These lesions result in commercial depreciation of the fruit and often act as a point of entry for other microorganisms that cause rot. Economic losses can be very significant, exceeding 10% of total production. Susceptibility to brown spot depends on the pear tree variety; Abate Fetel, Passe Crassane, Alexandrine and Conference varieties are all highly susceptible. Moisture and temperature are the key environmental factors that favor infection. Periods of moisture of at least 6 hours are required for infection to develop; longer periods increase the likelihood of infection. Temperatures of 20°C to 25°C are optimal for the development of infection. Disease control largely consists of the application of fungicides such as thiram, captan, or strobilurin. These fungicides can be applied on a fixed schedule or according to the risk of infection as predicted by the BSPcast model. The BSPcast model determines the daily infection risk based on the average temperature and the duration of the period of moisture. Use of the BSPcast model to guide the application of treatments allows an average reduction of 30% in the number of applications required while maintaining the same degree of disease control as provided with fixed-schedule applications. However, fungicides do not provide complete control of the disease. For this reason, integrated disease management based on sanitary measures together with the application of biocontrol and fungicidal agents is proposed. Knowledge of the life cycle of the pathogen is essential when using this management approach. The asexual and sexual forms of the fungus are the deuteromycete S. vesicarium and the ascomycete Pleospora allii, respectively. The two forms of the fungus can be pathogenic in pear trees and saprophytic in the debris of various plant types. The pathogenic phase can have significant effects during the growth season as it causes infections in the leaves and fruit in the aerial parts of the trees. However, the production of inoculum is largely restricted to the plant debris found in orchard soil. In late autumn and winter the fungus survives mainly in the leaf remains of pear trees and other plant species on the orchard floor, forming pseudothecia of P. allii, from which ascospores are released the following year. Sanitary measures proposed to break the life cycle include the mechanical removal of plant debris from the orchard soil in winter, before the release of ascospores, and the application of biocontrol agents (Trichoderma spp. and others) to the soil during spring and summer to reduce the production of inoculum. After petal fall infection is controlled by the application of fungicide according to the risk predicted by the BSPcast model. The saprophytic and pathogenic capacity of S. vesicarium and P. allii hinders the control of pear tree stemphyliosis.

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In accordance with the Organic Law on the Protection of Personal Data 15/1999, of 13 December, Promotora de Exportaciones Catalanas SA (hereinafter PRODECA), whose address is Gran Via de les Corts Catalanes, 620, principal, 08007 Barcelona, with tax reg. no. NIF A58241316, declares that the images contained on the website www.smartfruitcongress.cat are included in a file belonging to PRODECA. The purpose of this file is the promotion, via its website, of the activities conducted by PRODECA – SmartfFruit IPM International Congress.

PRODECA guarantees that you may, at any time, exercise your right to access, rectify, cancel or oppose by writing to the aforesaid postal address, using the reference "PROTECCIÓN DE DATOS - SMARTFRUIT", or to the email address smartfruitcongress@smartfruitcongress.cat.

Specifically, to correctly exercise these rights you must clearly provide the following items in that communication:
- Name, surname(s) and photocopy of National Identity Document or Passport.
- Statement of the purpose of the request.
- Address for notification purposes.
PRODECA also declares that it reserves the right to delete from its website any content that it considers violates current and applicable legislation.

D’acord amb l’article 17.1 de la Llei 19/2014, la ©Generalitat de Catalunya permet la reutilització dels continguts i de les dades sempre que se'n citi la font i la data d'actualització i que no es desnaturalitzi la informació (article 8 de la Llei 37/2007) i també que no es contradigui amb una llicència específica.