Efficacy of four plant extracts in the control of root rot disease of cowpea (Vigna unguiculata [L.] Walp)

Abstract

A study on the use of ginger (

Zingiber officinale), aloe (Aloe vera), bitter kola (Garcinia cola) and neem (Azadirachta indica) extracts in the control of root rot of cowpea caused by Pythium aphanidermatum was carried out in vitro and in the field (in vivo). They were evaluated for their antifungal activity over P. aphanidermatum, a rot fungus of many economic crops. Vegetative growth values over the fungus at 40, 60, 80 and 100% concentrations were generally low compared with the control, complete inhibition of fungal mycelia growth was exhibited at all concentrations in ginger extract. Aloe at 60% completely inhibited mycelial growth; this was followed by bitter kola with only retardation of mycelial growth while neem was the least effective. Highest mycelial dry weight was noticed on bitter kola extract but more sporangia formation in neem after a prolong incubation. However, the extracts were sparingly effective for a short period on the field experiment. A statistical evaluation of variance showed a significant difference between mycelial radial growths values recorded on the various plant extracts concentrations used compared with the control.