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Monilia laxa ist most destructive disease on stone fruits in Europe. In cherries it is the diseaase with the biggest economic inpact. The most characteristic symptoms caused by M. laxa are the blight of blossoms and green tips of twigs due to the penetration of the pathogen into opened blossoms through the stigma of pistils or anthers. Thei symptom is visiblein the left squared photograph in the head of this page.  This usually results in wilting of the whole part of a one-year-old twig. Its leaves first hang down, later become brown and rigid, but usually do not fall and remain on trees until the spring of the next year. At the base of the affected inflorescence and between the drying up and the living parts of the affected twig, sporodochia and occasionally concentrated droplets of gum appear in humid weather.

  Image The infected fruits gradually cover with enlarging putrefactive spots, from which warty sporodochia with conidia of the "summer" form appear. Additionally, in late autumn and winter, the fungus produces sporodochia of the "winter" form on infected twigs. With time, severely affected fruits become mummified. The mycelium growing in such mummies gradually aggregates into sclerotia. Such fruits remain on the tree during winter.
Temperature and wetness duration were important environmental factors determining the infection incidence of M. laxa on sweet cherry blossoms. Monilia laxa is well adapted to the relatively low temperatures during spring. Monilia laxa is able to cause infections at temperatures as low as 5 C within very short periods of wetness duration. In the literature to monilia laxa there is a big evidence that the infection of the active bloom trough the stima does not need very much leaf wetness. In this case leaf wetness is only needed for germination of the conidia. Infection of the young fruit needs longer leaf wetness periods. To infect the young fruit an appressoria has to be formed and this needs free moisture to build up the pressure to form the infection peg to enter the epidermis cell. With maturity small scars on the fruits allow an infection without infection peg again and the needed leaf wetness duration becomes shorter again.
Image The M.laxa model in feildclimate is given for weak infections and for infections. The expression weak infection describes the conditions to infect highly susceptible stages like flowers and wounded fruits close to maturity. To infect this tissue very short leaf wetness periods have shown to be enough in several studies like Phenological Analysis of Brown Rot Blossom Blight of Sweet Cherry Caused by Monilinia laxa L. Tamm, Chr. E. Minder, and W. Fliickiger (1994) or Effects of wounding, fruit age and wetness duration on the development of cherry brown rot in the UK X.-M. Xu*, C. Bertone and A. Berrie (2003). Immature fruits are showing a good resistance to infections. But fruits close to maturity are becoming susceptible again and here we have to look for the conditions for severe infections.

During bloom there is a lot of evidence that we have to short down the times needed for infections. Therefore the model is shorting infections down in the area of 2000 to 4800 degree hour above 5°C.

The first graph showing the model results for Styria in the year 2010 indicates an light infection at the 05th of April. This would be the early bloom of cherry. This infection can already lead to latent infections of the fruit and cause severe demages. Late blossems will be completely destroied by teh infections at April 13th indicated by the second graph. In the third graph late infected on the close mature fruits are indicated at the end of Mai.  

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Created by system. Last Modification: Wednesday 22 of February, 2012 13:46:52 GMT by Lena.