The use of Sulfur as a Fungicide

Sulfur is a very common and highly effective fungicide that has been in use in one form or another for a very long time. Sulfur is used for the prevention and control of powdery mildew on most fruit crops like apples, gooseberries, hops, ornamentals, peaches, sugar beets, black spots or mildew on roses, rusts, peanut leafspot, brown rot of peaches, anthracnose of grapes, cane blight, spur blight, and anthracnose of raspberries and blackberries, and other diseases. It prevents the fungal spores from germinating, hence it must ideally be used before the development of disease for it to be most effective.

Sulfur is available in a number of forms :

* Dust, wettable powder or liquid formulations of elemental sulfur – Some of the various commercially available products containing sulfur are Cosan, Hexasul, Sulflox, Crisazufre, Tiolene and Thiolux. It is also used in combination with other fungicides, for example, thiobendazole, urea, sodium pentaborate, nitrothal-isopropyl, rotenone.

* Lime sulfur which is a combination of sulfur and lime (Calcium hydroxide) – Lime sulfur is used as a spray and should be applied in high concentrations only during the dormant season as it can cause intense damage to the plant foliage. Lime sulfur can be used in lower concentrations in grapes and caneberries during the growing season. It is more effective than the elemental sulfur at lower concentrations, but it has a very foul rotten-egg smell, hence it cannot be used over large areas. 

Sulfur is not recommended to be used in the following conditions :

• It should not be used in temperatures above 80 degree Fahrenheit as it may lead to severe plant damage which is referred to as phytotoxicity. It may cause burning of the leaves and damage to the fruits. The dry powder or flowable sulfur is much less injurious to the plants as compared to liquid lime sulfur.

• When an oil spray has been applied to the plants within the last one month, sulfur must not be used as the combination can be toxic to the plants. 

• Some plants are sulfur-shy, meaning sulfur can be extremely harmful to their foliage, hence these plants must never be treated with sulfur. Examples of such plants are certain varieties of grapes, mostly American grapes, such as Concord, De Chaunac, Chancellor and Foch, some varieties of gooseberries, currants, raspberries, apricots, and cucurbits.

• If the grapes are to be used later for making wine, then applying sulfur after the grapes begin to ripen may cause difficulties during fermentation.

Sulfur is generally considered to be a safe element. It is low in toxicity and has not known to cause any significant risks to humans, animals, birds or the environment.