30 march 2017
RHP is currently gaining experience with specific test plants that are more sensitive to residues of crop protection agents than the currently applied standard test plants. These could be specifically applied for further research of residues in substrate raw materials.
Last year RHP started with orienting research of residues of crop protection agents in certified raw materials. In order to get an answer to the question to which extend these residues are present in the substrate raw materials, laboratory analyses were performed. From research that among others has been executed in Germany however, it appears that residues are sometimes not or hardly detectable with a laboratory analysis while they could still harm plants. In addition to that, the standard plants in the bio assay are not always sensitive to residues. RHP is currently investigating how the standard bio assay can be extended with a number of crops that are more sensitive to residues. At the moment the first trials with bean and tomato are running.
Test plants that are normally used in a bio assay are lettuce, cabbage, kohlrabi, Chinese cabbage and garden cress. These sensitive generalist plants normally give a reliable idea if a substrate or raw material is plant safe. But these are not specifically sensitive to crop protection agents. Crops like bean and tomato do have a larger sensitivity to (residues of) crop protection agents. That makes these crops good indicator plants for further investigation into possible residues of crop protection agents in substrate raw materials.
In a first set-up with a positive control, especially bean quickly showed a clear effect after germinating. In the now running tests it is examined which images arise in which phase. With that a standard is determined for observation. Bean and tomato are not the only crops that are tested by the way. In next phases also other crops are tested, for example monocotyles.
Left: treatment with residue; right: reference.