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Efficacy of some plant extracts against Colletotrichum gloeosporioides (Penz.) the cause of anthracnose disease of yam (Dioscorea rotundata Poir.)

Elias Sowley: University for Development Studies

<div>Anthracnose disease caused by <em>Colletotrichum gloeosporioides</em> (Penz.) is a major constraint to yam production in Africa. Due to the harmful effects of synthetic fungicides on the environment and human health, this study tested aqueous and ethanol extracts of <em>Azadiratcha indica</em> (A. Juss), <em>Balanites aegyptica </em>(L. Delile)<em>,</em> <em>Jatropha curcas </em>(L.),<em> Khaya senegalensis </em>(Desr. A. Juss) seeds, <em>Icacina oliviformis</em> (Poir. J. Raynal) leaves and <em>Capsicum</em> sp. (L.) fruit, for their effectiveness against <em>C. gloeosporioides</em> <em>in vitro </em>and <em>in vivo</em>. The incidence and severity of the disease was determined in Laribako and Pona cultivars of yam, during the 2016 cropping season. Two fungicides Manlax and Rainmancoz served as positive controls. The experiment was laid out in a Randomised Complete Block Design (RCBD) with 15 treatments and 4 replications. The treatments were applied at 2-week intervals from 5 to 15 weeks after planting. For the <em>in vitro</em> study, Manlax and Rainmancoz had 100% inhibition. Although all the plant extracts significantly (p ≤ 0.05) inhibited mycelial growth of <em>C. gloeosporioides</em> <em>in vitro,</em> fruit extract of <em>Capsicum</em> sp. at 100 % had the highest inhibition rate (74.8 %) while seed extract of <em>K. senegalensis</em> at 75 % concentration had the least (31.5 %). Under field conditions, all the plant extracts reduced the incidence and severity of yam anthracnose leading to increased tuber yield. Fruit extract of <em>Capsicum</em> sp. had the highest potential for the control of yam anthracnose disease.</div>