Bacterial apical necrosis (BAN), caused by the bacterium Pseudomonas syringae pv. syringae (Pss), is currently the most
limiting disease affecting the mango crop in the Mediterranean area. The copper-based compound Bordeaux mixture (BM)
is considered to be the conventional treatment against BAN, but it does not act as a bactericide. Alternative experimental
treatments to BM that are compatible with organic farming were tested for their ability to control BAN disease. Field trials
were conducted over six seasons in different mango orchards with natural infestation of Pss. The experimental treatments
included applications of Silicon gel (a commercial formulation of aqueous potassium silicate), dicalcium phosphate,
Kaolinite, and Ulmasud B (bentonite, powder); BMwas applied as the conventional treatment. During the first two seasons
(small-scale trial, 2002–2004), all these experimental compounds were applied in order to select those treatments providing
the greatest reduction of BAN symptoms. In the next three seasons (2005–2008), a semi-commercial scale trial was carried
out with the best-performing treatments, resulting in the selection of Silicon gel. Finally, Silicon gel was tested in a commercial
scale trial during the last season (2008–2009). Trees treated with Silicon gel showed significantly fewer necrotic buds
and leaves, reaching disease levels very similar to those using the conventional treatment with BM. However, minor
differences in P. syringae-like population levels were observed, as has been described in previous studies. The possible mode
of action of the Silicon gel is discussed. Currently, the Silicon gel compound is undergoing the registration process for its
commercial use in mango management in Spain.