Sulfur has long been used in agriculture, just like copper, it is part of the treatments that can be used against plant diseases.
In particular, sulfur is a useful product for the defense against powdery mildew, a plant pathology also called “white disease”, caused by many different strains of specific fungi that cause similar symptoms.
Sulfur is a fungicide also authorized in organic farming, so it can be used by certified farms and also by individuals for the maintenance of gardens, fruit and ornamental plants.
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Action mode
When sulfur comes into contact with the mycelium and the spores of the pathogenic fungus enters your cells due to its fat solubility, breaking the membrane and causing water to leak out, and thus dehydration and death.
Sulfur exerts this action when it is in the vapor state, with at least 18-20°C ambient temperature in the case of coarse grain products, and already at 10°C for finer sulfur . Therefore, it does not work at low temperatures, and even at high air humidity, its efficiency is reduced.
The adversities against which it protects
Sulfur is an antioxidant par excellence, widely used since 1800, and due to its good effectiveness, it is used not only in organic farming, but also in conventional farming.
However, in addition to defenses against powdery mildew, it also has some effect against other plant diseases, for example, it is used for monilia of stone fruits (peach, apricot, plum and cherry), against botrytis and against mites.
What crops is it used on? Sulfur can be used in horticultural and fruit crops, vineyards and various ornamental plants affected by powdery mildew. In the garden it is frequently used in pumpkins and zucchini, being plants easily subject to the evil eye.
Sulfur products
The different sulfur-based products They differ in their use which can be of two types: for powder treatments and for liquid treatments the latter being more recent than the former.
Another criterion for distinguishing between the different formulations is based on the size of the sulfur particles. , because the finer they are, the more they are able to act at low temperatures. wettable sulfur , that of liquid treatments, offers a faster action than that of powders, also thanks to the fact that they have finer particles, but have less persistence. There are many sulfur products on the market, so when making your choice, you should carefully read the information on the data sheets.
Like wet sulfur that can be found on Amazon with good value for money.
Use and dosage in treatments
As regards the distribution of any other product, also for sulfur must follow scrupulously what is indicated on the packaging of the formulation you buy, in terms of application methods, doses and precautions for your health and the environment. For excellent effectiveness of the product, it is necessary to use it as soon as the first symptoms of the pathology appear, in order to block it over time, and try to evenly cover the surface of the sheet.
sulfur immiscible with alkaline-reactive pesticides such as Bordeaux pulp and polysulphides, nor with microbiological products such as Beauveria bassiana and Ampelomyces quisqualis.
Sulfur treatments can be repeated several times in the spring-summer season, remembering that about three weeks should elapse between a treatment with sulfur and another with mineral oils, which are used, if necessary, against scale insects. Sulfur deficiency time is 5 days therefore after treatment it is necessary to wait 5 days before recovering the products.
If wettable sulfur is used, the solutions are made in water, to be sprayed on the plants like a special pump (I recommend battery pumps). For powdered sulphur, on the other hand, it is best to spread the product on the plants using a sulfur sprayer. , in the Amazon you can find this, a fairly inexpensive hand tool, which may be suitable for a small vegetable garden.
Toxicity and environmental damage
Sulfur should not be used when temperatures are too low, as it is basically useless, but it is also with excessive heat to be avoided because it becomes phytotoxic .
Already at 30°C can cause burns on the treated plants, so in the middle of summer it is better to avoid it or choose the coolest days and hours of the day to distribute it. There are, however, specific sulphurs, made up of water-dispersible microgranules, which attenuate this drawback.
Sulfur can be toxic to some beneficial insects and since it also has a certain acaricidal effect, it unfortunately also works against predatory mites.
Alternatives to sulfur
Given sulfur’s phytotoxicity to heat, it goes without saying that some alternatives should be considered. , in particular to treat cucurbits (pumpkins, zucchini, etc.) which, notoriously, are often sick with powdery mildew in summer. Moreover, only in the case of zucchini, the use of sulfur means giving up the harvest during the 5 days of scarcity, and this is not a minor inconvenience, since zucchini produces fruit daily.
A very good ecological product to use in these cases is based on the good fungus Ampelomyces quisqualis a biofungicide active against powdery mildew, of which there are officially registered formulas for the following crops: vines, roses, cucurbits, nightshades and strawberries.
In general, sodium bicarbonate treatments are also functional and valid against powdery mildew, while among the agents that support and stimulate the natural defenses of plants are rock flours, such as zeolites, useful to prevent diseases and various pest attacks.
Reference legislation on sulfur in organic farming
Sulfur is one of the phytosanitary products authorized in organic farming and is listed in Annex II of Regulation EC 889/08, one of the European references on organic certification, which will be in force until 2021. Also the new European regulation on organic farming, which will replace the current ones, leaves the possibility of using sulfur in treatments.
In Italy, Ministerial Decree 6793 of 2018 reaffirms the possibility for certified organic farms to use the products listed in Annex II, subject to a documented declaration of need.
As with other phytosanitary products, for the professional use of sulfur it is necessary to have a patent.