Bio-Control of Chamomile Powdery Mildew Using Cyanobacteria and Some Antagonistic Microorganisms

Abstract

Field experiments were carried out under natural infection in the Experimental Farm of Sids Agricultural Research Station, Agric. Res. Center, Beni-Sweif governorate to evaluate the potentiality of Bacillus subtilis, Pseudomonas fluorescens, Trichoderma harzianum and cyanobacteria (Spirulina platensis)alone or in mixture to control powdery mildew on chamomile and its productivity using two application methods: soaking the seedling roots before transplanting + foliar spray and foliar spray only. Generally, all the tested bioagents were effective in reduction the disease incidence and severity leading to a significant increase in fresh and dry weights of the blossoms as well as essential oil percent and oil yield compared with the control treatment. Soaking the chamomile seedling roots and spraying the leaves with suspensions for bioagents tested were the most effective in reducing the disease incidence and severity than spraying the leaves by the suspensions only. Mixing the cyanobacteria (S. platensis) with the fungal and bacterial antagonistics was more effective compared to each treatment separately. The highest efficacy was obtained from plots received mixed treatment of S. platensis + P. fluorescens in addition to the fungicide Topas 100 EC. Furthermore, all the treatments showed significant increases in the defence-related enzymes, peroxidase (PO) and polyphenoloxidase (PPO) as compared with the untreated control. Spirulina platensis significantly enhanced the growth of T. harzianum and did not show any inhibitory effect against bacterial growth as well as significantly increased the number of bacterial colony forming units (cfu) of B. subtilis and P. fluorescens which significantly improved the microbial status in the rhizosphere of chamomile plants.