Impact of the Fungicide Rizolix T50% on the Antagonistic Activity of Trichoderma harzianum and Trichoderma koningii

Six Trichoderma spp. were isolated from the rhizosphere of maize and clover. All the isolates were able to tolerate Rizolex T 50 %. Isolates of T. harzianum and T. koningii exhibited the best tolerance to this fungicide, reached to 350 and 400ppm respectively. The antagonistic effect of T. harzianum was high against pathogenic fungi, Fusarium oxysporum, Fusarium proliferatum and Acremonium strictum, reached to 77.3, 77.5 and 78 % reduction respectively. While, T. koningii reduced the growth of these fungi to approximately 69, 73 and 77 % respectively. The growth of all tested pathogenic fungi greatly decreased with increasing fungicide concentration in the growth medium comparing with the control. F. oxysporum and F. proliferatum tolerated Rizolex T50 % up to 450 - 550 ppm. whereas, Ac. strictum tolerated it only up to 250 ppm. The growth of T. harzianum and pathogenic fungi decreased with increasing Rizolex concentrations in the growth medium, moreover the antagonistic effect of T. harzianum against F. oxysporum, F. proliferatum and Ac. strictum at 200 ppm Rizolex T50 % was approximately 86.6, 85 and 84 % reduction respectively. Whereas, it was 74.3, 81.1 and 80 % reduction respectively with T. koningii. Utilization of low dose of fungicide in combination with Trichoderma spp. increased the inhibition percentage of pathogenic fungi and may be beneficial in controlling these fungi.