Archives

The effect of 11 essential oils was in-vitro and in-vivo evaluated against guava decline disease fungi
namely, Botryodiplodia theobromae, Fusarium oxysporum and Rhizoctonia solani isolated from
guava shoots, roots and rhizosphere. Six concentrations of each were studied in vitro on potato
dextrose agar. Using of clove oil and judean wormwood oil separately at 250 ppm, pepper and
tangerine oils at 500 ppm, anise oil at 750 ppm and onion oil at 1000 ppm led to full inhibition of
radial growth of B. theobromae. In the case of F. oxysporum, full inhibition of radial growth was
occurred by clove oil at 500 ppm or judean wormwood, onion and cinnamon oils at 750 ppm as well
as tangerine, anise, black seed and thyme at 1000 ppm. The growth of R. solani has been full
inhibited using clove, and judean wormwood oils at 250 ppm or onion oil at 500 ppm. While, other
tested oils have inhibitory effects at concentrations higher than previously mentioned. In vivo study
showed that, the effect of the treatment of 1.5 years old guava seedlings roots with clove and judean
wormwood oils separately using three concentrations (500,1000 and 1500 ppm) for 20 minutes
before planting in contaminated soil with decline fungi led to significant differences between
treatments and the only contaminated ones (control). The best result were obtained using clove oil at
1500 ppm which inhibited completely the infection (severity =0) and gave significant increase in
plant height and dry weight of both shoot and root systems as well as leave contents of chlorophyll a
and chlorophyll b.
Key words: Essential oils, Guava decline disease, Plant pigments.