Phytosanitary treatments have evolved in recent years and they now include new methods and technologies, along with a steady reduction and limitation in the use of chemical products – only using them where strictly necessary - in favour of alternative treatments (cultural, mechanical, etc.,) which, among other things, help to maintain a balance in biodiversity. Current regulations also establish and incorporate advances in Integrated Pest Management for reducing the use of chemically synthesised phytosanitary products.
Care is taken to ensure that all these treatments are specific, selective and aimed at eradicating a particular pest. Broad-spectrum products that can more-easily generate resistance in plants to new attacks and pests and those also considered to present a greater risk to people's health and the environment are avoided whenever possible.
All phytosanitary products used in Barcelona are the ones that the Spanish Ministry of Agriculture, Food and Environment (MAGRAMA) authorises for use in parks and gardens, which are listed in the official register of phytosanitary products.
There are six main types of treatment:
1.- Cultural: Selecting the species to be planted forms part of this method. Choosing the species that adapt best to the urban environment and are most resistant to attacks from pests and diseases is a preventive measure.
2.- Mechanical: Controlled pruning can help to prevent the appearance and spreading of pests. It is very effective when only some branches have been affected, as these can be removed.
3.- Biological Control
Biological control consists in using living organisms to control the populations of an organism that disturbs or damages the species, counteracting the pest or reinforcing the defences of the plant to be treated. Parasitoids, predators, micro-organisms and nematodes are used.
Artificially introducing useful fauna or antagonistic micro-organisms (in the case of fungi, for example) provide two natural forms of action: 1) feeding off the pest organisms or 2) parasitising them by using individuals as hosts, which literally prevents their proliferation, as they are destroyed in the process.
Biological control has proven to be effective against some aphids and psila flies though it may allow for action against other pests such as scale insects and red spider mites.
This procedure contributes to maintaining a balance in the levels of insect populations that affect the species so the poisonous effects are reduced. Note that the pest is not totally eradicated and that these organisms, seeing as the urban environment is not a 100% reproduction of their natural habitats, may need to be reintroduced on a regular basis for ongoing effectiveness.
4.- Pheromone traps: A treatment based on simulating the strategies used by the females of a species to complete their reproductive cycle. Not all pheromones cause sexual attraction. There are also recruiters, etc. By using sexual pheromones, the males of a pest species are attracted and guided into traps where they are caught. They work in the same way as bait that traps insects in a sticky substance.
5.- Coloured bands: Another treatment based on imitating the natural attraction mechanisms of insects. Chromatic bands apply the same strategy as flowers and capture by using the force of attraction that some colours have over insects.
6.- Chemical Methods
6.1 Tree injection: A method where the phytosanitary product is injected into the tree. It then spreads through the tree's vascular system. This is a safe system for people and it has proved to be very effective in treatments against the pine processionary, for example.
6.2 Phytosanitary spraying and application through irrigation: Treatment based on applying the product by spraying the species to be treated, either with ecological products or, where there are no authorised natural products available, chemical products.
Ecological products such as natural extracts and synthetic insecticides can be applied using products from the plant itself or mineral products. Such is the case with pyrethrins, vegetable oils (derived from Pyrethrum sp.), azadirachtins derived from Azadirachta indica or, in the case of mineral products, derived from anthracite.
These treatments are applied as a last resort where the risk of the pest spreading to other areas or its degree of impact makes them necessary, as well as their virulence or the problems they can cause the population.