Abstract:
Colletotrichumgloeosporioides is a serious postharvest pathogen of avocado fruits worldwide. Kenya lacks any registered fungicides
for the management of the disease. Nevertheless, farmers commonly use commercially available fungicides such as Bayleton
25WP (Triadimefon 250 g/Kg), Milraz 76WP (Propineb 70% and Cymoxanil 6%), and Copper oxychloride 500WP for disease
management. The efficacy of these fungicides against C. gloeosporioides is not known. The purpose of this study was therefore
to test the inhibitory effect of these fungicides against 46 C. gloeosporioides isolates from avocado fruits collected from varieties
grown at different agroecological zones in Murang’a County, a popular avocado-growing region in Kenya. Mycelial growth rate
and sporulation for each isolate were measured in vitro on PDA plates amended with different concentrations of the fungicides.
Plates were arranged in a completely randomized design with three replications per treatment. All fungicides were effective in
vitro but there were significant differences in sensitivity among isolates. Bayleton had the highest mycelial inhibition followed by
Milraz, while copper oxychloride had the lowest mycelial inhibition rates, ranging from 81% to 88%. However, copper oxychloride
was more effective in inhibiting sporulation.The inhibitory effect of each fungicide was concentration-dependent, where twice the
recommended concentration had the highest inhibitory effect, followed by the recommended concentration. Our results show that
the fungicides used by farmers against C. gloeosporioides, the causal agent for anthracnose, are effective.We, however, recommend
further field tests in different avocado-growing areas so as to validate their efficacy against various isolates and under different
environments.
