Four experiments were designed to study the effect of fertilization (NPK), Trichoderma harzianum, mycorrhiza and an algae extract, on tomato stem canker disease severity. Tomato plants (Lycopersicon esculentum Mill.) were grown in Rhizoctonia solani infested soil under protected greenhouse conditions, to study the effect of some biocontrol
agents on the disease severity and to assay the total phenols in tomato tissues. The results showed that inoculation with T. harzianum alone as a bioagent resulted in a distinct decrease in disease severity and to less extent after inoculation with AM fungi, algae extract, fertilizer (NPK), either single or in combination. The mycorrhiza treatments, however,
significantly increased the total phenols in the infected tomato plants compared to the infected check plants. The most promising elevation in total phenol was recognized in infected plants treated with a mixture of (AM) mycorrhiza, Chlorella vulgaris (A1) and Spirulina platensis (A2).Trichoderma harzianum plus the usual NPK dose fertilization with, produced similar effect compared to check plants infected with R. solani alone, similar results were recognized in case of mixing Trichoderma and mycorrhiza treatment.