Abstract:
The aim of the present investigation was to evaluate the antifungal activities of plant extracts which can be used to
control bean and cowpea anthracnose. Acetone, ethyl acetate and water extracts of Ipomoea batatas, Carica
papaya, Allium sativum, Syzygium cordatum, Chlorophytum comosum and Agapanthus caulescens were
screened in vitro for their antifungal activities against Colletotrichum lindemuthianum and Colletotrichum
dematium of common bean and cowpea using the agar disc infusion and microtitre double-dilution techniques.
The same extracts were then tested for antifungal activity in vivo as seed treatments against anthracnose disease.
The water extracts of Carica and Syzygium were active against C. lindemuthianum and had minimum inhibitory
concentrations (MICs) of 1·56 mg/ml. Syzygium, Allium and Chlorophytum water extracts were active against
C. dematium and MICs were 3·13, 6·25 and 12·5 mg/ml, respectively. The MICs of Allium, Syzygium and
Agapanthus acetone extracts were 0·78, 3·13 and 6·25 mg/ml, respectively, against C. lindemuthianum and 0·78,
6·25 and 3·13 mg/ml against C. dematium. Agapanthus water extracts and all the acetone extracts tested in vivo
effectively reduced the incidence and severity of bean anthracnose disease in the greenhouse. Agapanthus
acetone, Allium water, and both acetone and water extracts of Carica and Syzygium performed well in vivo in
reducing cowpea anthracnose disease and compared well with reductions due to the application of the synthetic
fungicide fludioxonil+mefenoxam (the commercial product Celest® XL) applied at 25 gai/l and also with levels
in the non-inoculated control. The Agapanthus, Carica, Syzygium and Allium extracts were active on both
Colletotrichum spp. in vitro and also reduced anthracnose disease of bean and cowpea and are potential seed
treatments in anthracnose disease control. The easy seed treatment process and the accessibility of plants used in
the present study could lead to high adoption of the use of the plant extracts as seed treatments by resource-poor,
smallholder farmers.
