In large parts of Germany, especially in the Upper Rhine Plain and neighboring regions in Rhineland-Palatinate and Hesse, root damage caused by cockchafer grubs hinders forest regeneration. Young plants, with their still underdeveloped root systems, are particularly susceptible to death. At the same time, the Japanese beetle, an invasive priority EU quarantine pest, continues to spread northward, placing nurseries under considerable pressure to control it. Yet effective countermeasures are lacking: Appropriate insecticides are no longer approved for use in forestry, and biological methods such as fungi or nematodes do not achieve a sufficiently high level of effectiveness in the field. Mechanical root protection against grubs has not yet been described in the literature; BioROOTGUARD is breaking new ground in this area.
Protection without permanent plastic contamination
Plastics that are used in the environment and remain there must be viewed critically. Persistent materials accumulate in the soil. However, where the use of plastic offers a clear benefit, long-term pollution can be avoided by using biodegradable materials. The expertise of Fraunhofer UMSICHT lies precisely here: the development of biodegradable materials for defined periods of use and the investigation of their degradation behavior. That is one of the major challenges in the project. The material must remain stable for at least four years and then degrade completely and in an ecotoxicologically safe manner.
Nature-based repellents in the material
In addition to the mechanical barrier, natural active ingredients are intended to keep the larvae at bay. To this purpose, suitable repellents are selected and gently incorporated into the compounds. Criteria include effectiveness, thermal stability, processability, legal compliance, market availability, as well as degradability and environmental compatibility. The interdisciplinary project consortium uses these repellents to develop compounds and films based on bio-based and biodegradable plastics, testing their mechanical and rheological properties, and investigating their degradation behavior in screening and field tests. In addition, the ecotoxicity of the materials developed will be assessed using suitable test methods. The selection of applicable standards, soils and test organisms—such as plants, soil microorganisms and aquatic organisms—will be tailored to project-specific needs and applications as the project progresses.
Applications beyond the forest
Forest owners can protect their investments in planting, fencing and maintenance and significantly reduce the risk of failure. Since the film remains in the soil and degrades there, it does not need to be removed. The planting remains undamaged, whereas with non-biodegradable materials, removal would destroy the crop. For the first time, tree nurseries have the prospect of remaining marketable even in areas infested with the Japanese beetle. Vineyards, ornamental and forest tree nurseries, orchard meadows and agroforestry systems are also affected by grubs. By adjusting the formulation and repellent, the concept can be applied to other soil-dwelling pests.
Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT