Evaluation of natural plant extracts, antagonists and fungicides in controlling root rot, collar rot, fruit (brown) rot and gummosis of citrus caused by Phytophthora spp. in vitro

Abstract

The results revealed that all the six bioagents tested in vitro applying dual culture technique against Phytophthora nicotianae , Phytophthora citrophthora and Phytophthora palmivora significantly inhibited the mycelial growth of the test pathogen over untreated control. However, bioagent, Trichoderma harzianum recorded minimum mean colony diameter (7.73 cm 2 ) and highest inhibition (87.85%) of mycelial growth of P. nicotianae over untreated control followed by the bioagent T. viride , T. koningii which recorded mean colony diameter of 9.95 cm 2 , 14.15 cm 2 and mean mycelial inhibition of 84.36 %, 77.76%, respectively. Evaluation of different botanicals by Poisoned Food Technique showed that all plant extracts tested in vitro were found significantly effective in reducing the percentage mycelial growth of P. nicotianae , P. citrophthora and P. palmivora over untreated control. However, plant extract (@ 5, 10 and 15%) of Garlic, recorded lowest mean colony diameter (47.45 mm) and highest mean mycelial growth inhibition (47.26%) followed by Neem, Onion which recorded the mycelial growth of 55.20 mm, 60.85 mm, and the mean mycelial growth inhibition of 38.65%, 32.38%, respectively. Results revealed that all the nine fungicides tested in vitro applying Poisoned Food Technique against P. nicotianae , P. citrophthora and P. palmivora significantly inhibited the mycelial growth of the test pathogen over untreated control. However, fungicide, Cymoxynil 8% + Mancozeb 64% (Curzate M-8) recorded minimum mean colony diameter (16.12 mm) and maximum mean inhibition (82.09%) of mycelial growth of the test pathogen over untreated control (mean colony diameter 90.00 mm and mean inhibition 0.00) followed by the fungicide Metalaxyl-M 4% + Mancozeb 64% (Ridomil Gold), Metyram (Polyram) , which recorded mean colony diameter of 20.16 mm, 24.16 mm and mean mycelial inhibition of 77.59%, 73.14%, respectively.