Understanding Basic Substance Approvals

From salt on mushrooms to sunflower oil on tomatoes, where do you stand legally on using basic substances?

All growers will know that the number of plant protection products available to them is dwindling. Even with the huge effort we put into finding effective plant protection products and securing approvals for them, there are still crop sectors that struggle to manage pests, diseases and weeds effectively. As a result of this, we have in recent years seen growers becoming more interested in alternative substances and we get many queries from growers wanting to check the approvals status of some of these.

From a legal perspective, the situation is fairly clear – any formulated product used for plant protection purposes must be authorised as a plant protection product and therefore have a MAPP (Ministerially Approved Pesticide Product) number. Growers wishing to control pests, diseases or weeds should make sure that only products with the appropriate registration number are used.

There are, however, other substances which could still be considered for plant protection

purposes. These substances are called ‘basic substances’. These are defined as substances which are not predominantly used as a plant protection product but may be of value for plant protection and for which the economic interest of applying for a full approval is limited. Basic substances are approved at a European level and applications for their approval are handled by the European Commission (EC). Twenty basic substances are currently approved by the EC for plant protection (see Table opposite).

We are continually working with scientists, industry bodies and growers to keep abreast of substances which offer potential in crop protection. Several basic substances have been screened in efficacy trials as part of SCEPTREplus and some of these are being taken forward for further work.

We have also been involved in gaining approval for a few of the substances. One example is the authorisation of sodium hydrogen carbonate for use as a herbicide. Its potential as a liverwort treatment was recognised by Mike Norris, then General Manager at New Place Nurseries, who heard about its use from New Zealand growers. This led to its inclusion in a herbicide screening project (HNS/PO 192a) in container-grown ornamentals, where it worked extremely well. It has a physical mode of action, drawing water out of the liverwort by osmosis and drying it out. Based on its performance in the trials, we sought an approval for liverwort control in collaboration with Patrice Marchand from the French Research Institute For Organic Farming, who has built up considerable experience in putting together the required basic substance dossiers. We have also worked with Mr Marchand to obtain an approval for use of sodium chloride in mushrooms where it is used for spot treatment of various diseases and we are currently progressing an extension of the use of chitosan chloride in ornamentals.

Further information about basic substances, and those that are currently approved, can be found at horticulture.ahdb.org. uk/basicsubstances