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Growing in organic farming does not mean giving up defending plants from attack by insects and parasites, but simply limiting their use to products of natural origin. Among these, one of the most widespread products is spinosad, a broad spectrum insecticide that originates from the fermentation of a microorganism.
If for organic farms it is mandatory to use only the treatments allowed even for amateur gardens and orchards that are not subject to certification and therefore are not required to strictly comply with the rules, it is useful to refer to these low impact products environmental.
The plant protection products allowed in organic farming are listed in theannex II of Regulation 889/08 which is the application of Regulation 834/07, the European regulatory reference for organic farming. Both regulations will remain valid until 2021, when the new Regulation 848/2018 will come into force. Among the products listed in Annex II there is a category called "substances produced by microorganisms", which includes Spinosad as an insecticide.
Of course, before resorting to Spinosad or other insecticides it is important do everything possible to prevent upstream diseases and parasites, through the application of rotations and associations, correct irrigation and fertilization and, last but not least, special care for biodiversity in the cultivation environment. This biodiversity is achieved with the introduction of annual flowers, aromatic herbs, and as regards the orchard, carefully managed good grassing.
What is Spinosad
Spinosad is a product that comes from fermentation process of a microorganism (Saccharopolyspora spinosa) and is obtained in the laboratory using a special culture broth.
A substrate is prepared consisting of water, leavening extracts, sugars, sodium bicarbonate, vitamins, flours, minerals and vegetable oils and everything is inoculated with the microorganism. Fermentation of the culture broth generates various metabolites, of which about thirty carry out insecticidal activity. Of these metabolites, called spinosins, two in particular are powerful: Spynosin A and Spynosin D, and it is with these that the basis for the manufacture of insecticidal products sold and used in agriculture is created.
Insecticidal mode of action
The products based on Spinosad are found under various commercial names of different manufacturers, for example the Success of Solabiol, already mentioned in the box above. The active ingredient acts by ingestion and by contact, that of ingestion is the prevailing action. This means that to ensure maximum effectiveness, the vegetation cover must be complete and accurate.
This treatment has a very prompt action and not affected by temperatures, and unlike pyrethrum, the product does not degrade with ultraviolet rays. The rain, on the other hand, can wash it away from the vegetation, diluting it and therefore reducing its effectiveness. In general the persistence of Spinosad is of 8 - 10 days, sufficient time to carry out the killing action of many harmful insects. The product typically is translaminar and reaches parasites such as leaf miners even within the thickness of the leaf.
Spinosad acts on the transmission of nerve impulses from insects: neurons accelerate their activity, which in turn increases movement until it causes tremors and final paralysis. The affected insects cease to feed at the onset of these symptoms.
(the product is generally translaminar and reaches them within the thickness of the leaf)
What insects does it affect
Spinosad's spectrum of action is quite broad and affects the following parasites:
- Thrips, small insects of the order of the Tisanoptera, capable of affecting many garden species by stinging their tissues and sucking the sap.
- Lepidoptera of various types: cydia funebrana, cydia molesta, vine moth, borer, carpocapsa, anarsia, various embroiderers and leaf miners, nocturnes, ifantria and processionaries.
- Diptera: cherry fly, olive fly, fruit fly (Ceratitis capitata, an insect that affects many fruit species).
- Beetles like the Colorado potato beetle, capable of devastating entire crops of both potatoes and aubergines. The control of this parasite with the Spinosad appears rather decisive.
- Psylla of the pear tree, a small insect that sucks the sap from twigs and shoots leaving you with a sticky honeydew.
- Metcalfa pruinosa, which can cause damage to the vine and other fruit trees, which are covered with a lot of honeydew and often also fumaggine.
Among the commercial products there are some particularly effective against the cherry fly and the olive fly that combine Spinosad with a food-type attractant, and this allows a reduction in dosages and a faster application, also reducing the need for perfectly cover all the vegetation.
On which crops it is used
Spinosad is one of the products that those who grow an organic vegetable garden or orchard must keep ready from the beginning of the spring season, in order to use it when needed. In fact, it is very rare that none of the parasites mentioned are ever present and that everything always runs smoothly without the need for any treatment.
By consulting the leaflet of the commercial product purchased, it is possible to read a long list of insects that this ecological insecticide is capable of eradicating and of crops for which its use is registered: in addition to vegetable and fruit species, it is also used to defend small fruits, some ornamental such as rose and carnation, wine and table vines.
How to use it: methods, precautions and dosages
For the correct use of Spinosad, the same rule that unites all plant protection products applies: that is read the instructions carefully reported on the labels of different commercial products, which may differ in formulation and therefore also in uses.
Even if they are ecological insecticides, this does not mean that they can be used roughly and imprudently and must pay attention to the environment and also to our health, so before carrying out a treatment you need to wear glasses, long sleeves and gloves.
Use also depends on the insect to be treated, because in some cases a limited number of treatments is sufficient, while for other parasites more interventions are required at a certain frequency. Generally in case of strong attacks, after a first treatment another one is performed after about 7 days.
Spinosad can also be mixed with other pesticides, but to obtain the maximum of its effectiveness it is better to use it alone.
The product must be stored in a cool place, but fortunately it has a certain stability and consequently no specific storage precautions are necessary.
Toxicity and damage to the environment
Towards the vertrebrate organisms Spinosad has a low toxicity, while unfortunately it is toxic to bees, for other hymenoptera such as bumblebees and also for aquatic organisms. For this reason it is important avoid treating in flowering, when the foraging activity of pollinators is maximum (also because the presence of these beneficial insects is essential to obtain fruit and cucurbit products). In the other phases of the plant, however, we must remember to treat in the evening hours, when bees and bumblebees return to their nests.
Against other insects such as chrysopes and ladybirds, which are valuable aphid predators, Spinosad shows mild toxicity.
The fact that it is a product with a broad spectrum of action must make us reflect on its low selectivityIt is also with regard to good insects, therefore the use of this product, which does not pollute the environment, is of natural origin and therefore biodegradable, must in any case be conducted with scrupulous precautions.