Plant protection in organic apple production: A summary of research conducted under the German Federal Programme for Organic Agriculture and other forms of Sustainable Agriculture

Summary

In this focus area, research projects were carried out on two main subjects: apple scab (Venturia inaequalis) and codling moth (Cydia pomonella). Scab control projects started in 2002, projects on codling moth control in 2006, and research on both topics has intensified since 2010. From the be-ginning, the search for alternative materials for scab control was prioritised, since the use of copper as a treatment for scab is going to be restricted in the future, and the efficiency of materials approved for treating organic apples has often been too low in the past to prevent significant yield losses. Alternative materials were tested and compared, including materials from Inula viscosa, Quillaja saponaria bark, citrus species and Saponaria officinalis. These plant-derived products were able to significantly reduce ascospore potential of scab in greenhouse experiments. The combination of Quillaja saponin and sulphur reduced scab very strongly. The combination of citrus extract with GREEMAX and BIOPLUSS as adhesives had a similar effect as a quantity of 400g Cu/ha (applied as copper oxychloride) in field trials. Targeted treatments with lime sulphur during the time of sporulation were found to represent a good and safe alternative. Gloeosporium infestation was significantly reduced by additional MycoSin treatments before harvest. Furthermore, autumn foliage removal with leaf blowers, and the promotion of earthworm activity was tested to reduce fungal inoculum. The aim of these studies was to identify ecologically compatible substances that lead to a reduction of scab infestation. Based on the initial results of the past years, on-going projects are investigating new alternative methods, application techniques and other solutions for the reduction of copper use in organic apple production.
In recent years, codling moth populations have appeared that showed low susceptibility to the com-monly used codling moth granulovirus (CpGV) preparations, and thus cannot be properly controlled with this treatment. Following research that clarified and described the unusual inheritance of virus resistance in codling moth, new CpGV isolates were developed that are able to break this resistance. Commercial farms with CpGV resistance or suspected resistance are recommended to use the new, resistance-breaking virus isolates. In on-going experiments, other methods of codling moth control are being tested, such as the use of nematodes and Trichogramma wasps. Investigation of the indi-viduals resistant to new and other potential isolates of CpGV as well as a risk assessment regarding resistance development are prioritised in the current projects. Further results from the BÖLN research on pest management in organic fruit growing are regularly published at www.bundesprogramm-oekolandbau.de.