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Regulation of the cone crop wilting in organic elder farming
Project
Project code: 2806OE327
Contract period: 20.04.2007
- 31.03.2012
Budget: 132,041 Euro
Purpose of research: Applied research
The corymb wilting of elderberry (Sambucus nigra) is the major problem in organic elderberry growing. The aim of the project was to develop a relevant practice strategy to combat the necrosis with the combination of different methods and after that to establish it to the cultivation practice. To work out a relevant method to combat the necrosis it is necessary to determine the pathogen which is responsible for the appearance of the necrosis itself, its timing of appearance and infection and its over wintering spots.
In all tested elderberry orchards Colletotrichum acutatum was the main cause of the necrosis (all Koch’sche Postulates were implemented). During the season, the infestation level of the corymb wilting increased with the start of ripening of the berries (turn of colour from green to red/black) and often reached infestation frequencies of a hundred percent. On samples collected in winter the pathogen could be found on not yet rotted berries, corymb parts and branches as well as on apical buts of the fruit wood of the next season. Other fungi pathogens such as Fusarium sp., Phoma sp. or Marssonina sp. were of subordinate importance.
A lot of fungicides and plant strengtheners allowed in organic growing were tested for their potential to control corymb wilting in laboratory and in field trials. The application of usual organic fungicides such as copper, sulphur and potassium-bicarbonates tested in various exact-trials in field, proved not to be of satisfying efficacies, especially in years of high infestation levels.
Because the microclimate is of importance to the infection and the infestation level, a part of an elderberry orchard was roofed over a particular time of season in two years of trials. A roof from blossom to harvest lowered the infestation by almost a hundred percent, whereas roofing from blossom until July showed only slight decrease of the infestation level. So far it was supposed that the time of blossom is of major importance for the infection, but roofing from July to harvest reduced the corymb wilting by about 92% in a season of high infestation levels. It can be concluded that blossom time is of lower importance for infection than previously expected.
Nevertheless a roof is not a practicable combat strategy, due to high effort and expense.
Technical cultivation management was also taken into account, for example the influence of pruning and a blossom cut to the rate of infestation of the necrosis. After four years of trials the variant ‘pruning down to twelve branches in March’ produced constant high harvest levels but had also the highest infestation levels, which resulted in the highest amount of not marketable corymbs. A pruning down to twelve branches in November produced the lowest harvest. A pruning down to eight branches resulted in low infestation levels in March as well as in November but also lead to lower harvests.
A blossom cut resulted in a lower amount of not marketable corymbs. A cut of 50% of the blossoms decreased the infestation from 23% to 7%. At the same time the harvest decreased only by 30% equalized by higher corymb weights.
Section overview
Subjects
- Crop Production
- Crop Protection
- Specialised crops
Framework programme
Federal Organic Farming Scheme and other forms of sustainable agriculture (BÖLN)
