Antimycotic effects of synthetic fungicides and plant extracts on <i>Aspergillus flavus</i>

Abstract

Aspergillus flavus contaminates the seeds of cowpea (Vigna unguiculata) and produces mycotoxins. This study was carried out to proffer solutions to the infection caused by A. flavus on cowpea seeds. The in vitro trial was set up using two rates (50 and 100%) of each potential control agent (mancozeb, COPMET (Copper-I-oxide + metalaxyl), and aqueous extracts of Eucalyptus and neem) and a control (0%). The botanical extracts and pesticides inhibited the fungus growth significantly (P≤0.05) at different times. Both concentrations of mancozeb gave 100% inhibition of the fungus at 24–168 hours after incubation (HAI). At 24 HAI, Eucalyptus extract (50 and 100%) completely inhibited the fungus growth similar to mancozeb. Eucalyptus extract was more effective than neem extract and COPMET throughout. Though the extracts of both botanicals inhibited the growth of A. flavus at 168 HAI, Eucalyptus (83.8-89.2%) was more potent than neem (20.3–28.4%). At 48-168 HAI, both concentrations of neem extract and COPMET had similar effect on the fungus. The early stage of the antimycotic intervention is critical to the control of the fungus. This can be achieved by dressing cowpea seeds with mancozeb or Eucalyptus. However, due to the high cost and toxicity of synthetic chemicals, Eucalyptus extract could be used as an alternative for management of the fungus or incorporated into integrated disease management programmes for A. flavus. Research on the effects of long-term storage of cowpea using these botanicals is highly admonished.