Damping of is a frequent disease that kills seedlings.
Cultural and biological controls are the only tools in organic crops to
manage this disease, and only empirical information is available on
the effiency of plant preparations. Ths work evaluates the effcts
of fermented onion decoctions on the growth of Rhizoctonia solani
and Sclerotium rolfsii and disease incidence. Broth (B) and sterilized
broth (SB) were respectively obtained by boiling chopped yellow onions in water, and incubating for 14 days at room temperature, with
or without subsequent sterilization. Th pathogens were grown on
potato dextrose agar supplemented with B and SB, diluted at 1.7,
3.3, 8.3, 16.7 and 25% (v/v). Thir growth was reduced by B at 8.3,
16.7 and 25%. Production of sclerotia by S. rolfsii was diminished by
B, but stimulated by SB. Penicillium purpurogenum, P. simplicissimum
and Aspergillus niger obtained from B behaved as antagonistic against
both pathogens, showing antibiosis, competition and hyperparasitism in dual confrontations with them. Broth and SB at 10 and 50%
dilutions were sprayed on chard (Beta vulgaris), tomato (Solanum ly-
copersicum), pepper (Capsicum annuum) and eggplant (Solanum mel-
ongena) seedlings cultivated in pathogen-colonized soil. Damping
of incidence in the B treatment at 50% dilution was markedly lower
than that in SB. It is concluded that B antifungal activity depends on
its dilution and mycota. Broth sprays should be considered as a tool
to control damping of in low-environment-impact crop production.
Further studies are needed for a complete understanding of B chemical and microbiological components, as well as their changes during
fermentation.