Rhizoctonia disease of salago (Wikstroemia lanceolata L.) in the Philippines and its control
2002
Tangonan, N.G. | Escopalao, V.M. (University of Southern Mindanao Agricultural Research Center, Kabacan, Cotabato 9407 (Philippines). Crop Research Div.)
Rhizoctonia disease of Wikstroemia lanceolata L. (locally known as salago) caused by Rhizoctonia solani Kuhn is heretofore reported for the first time in the Philippines. The pathogen infects all stages of the plant. It causes damping-off of seedlings, leaf blight, and twig blight. In seedlings, symptom is characterized by girdling, discoloration of vascular tissues, rotting on the base, and toppling over. In mature plants, symptom is characterized by blighting and drying up to the leaves. Affected twigs dry up, leaves fall-off and die back. Whitish mycelia and abundant sclerotia are observed on infected twigs and leaves. In culture, the pathogen produces brown to dark brown sclerotia of varying sizes (1 to 4 mm) in 5 to 7 days; the characteristic right angle mycelium, measures 34.15 x 14.31 micromole. Inoculated healthy seedlings develop the characteristic symptoms, 5 to 7 days after inoculation. Five fungicides applied as protectant and eradicant were found effective (benomyl, difenoconazole, mancozeb, metaloxyl and tridemorph). Likewise, six biological control agents (BCA) namely Trichoderma sp., T. harzianum, T. pseudokoningii, T. viride, Penicillium sp., and Rhizopus sp. showed antagonistic effects against R. solani in vitro. The first five BCA had high degrees of control, i.e. 69.85 to 89.92% and showed their mycoparasitic or antagonistic activity by suppressing further the growth of R. solani under screenhouse conditions
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