The effect of soil drenching with humic acid and commercial biofertilizers i.e., phosphorien ,
microbien and/or cearalien were evaluated for controlling dry root rot disease of mandarin ,fruit quality
and total yield during 2005 and 2006seasons . In vitro , humic acid at 15.0%(v/v) reduced significantly
the radical growth and spore germination of Fusarium solani the causal agent of dry root rot . Drenching
artificially infested soil with humic acid +Phosphorien or miccrobien biofertilizers as twice applications
resulted in decrease both disease infection and severity on mandarin seedlings as well as reduce
colonization of F. solani in seedlings roots . In Field trials , humic acid +phosphorien or miccrobien
biofertilizers treatments were significantly increase the number of recovering diseased trees , decrease the
disease severity on the others , inhibiting the activity of the pathogen in rhizospher soil of treed trees .
Moreover, these treatments improving the yield and fruit quality of treed trees . Therefore, the usage of
combination between humic acid and biofertilizers could be suggested as easily bio-treatment for
controlling dry root rot of citrus especially under organic system .