Abstract:
This study investigated the efficacy of Warburgia salutaris (pepper-bark) leaf extracts as an organic fungicide
for controlling foliar fungal diseases in tomato crops (Solanum lycopersicum cv. ‘Jemar’). The experiment was
conducted at Mutare Polytechnic, Zimbabwe, in 2024, using a Randomised Complete Block Design (RCBD)
with five treatments and five replications. Treatments comprised three extract concentrations (5%, 10%, and
15%), a commercial fungicide (Bravo® 500 SC), and an untreated control. Results showed significant
differences among treatments (p ≤ 0.001) for all measured variables. The 10% and 15% concentrations achieved
mean disease severity ratings of 1.5 ± 0.2 and 1.2 ± 0.1 respectively, representing Alternaria solani disease
reductions of 66.7% and 73.3% relative to the untreated control (4.5 ± 0.5), and were statistically comparable to
Bravo (1.8 ± 0.2). The 15% concentration produced the highest fruit yield (3.3 ± 0.2 kg/plant) and fruit count
(13.1 ± 1.2 fruits/plant), exceeding Bravo in both A. solani disease control (122%) and yield performance
(118%). A strong negative correlation was observed between disease severity and fruit weight (r = −0.89, p ≤
0.001). These findings demonstrate preliminary evidence that W. salutaris leaf extract, particularly at 10–15%
concentrations, is an effective and practical organic fungicide option for smallholder tomato farmers, comparable
to or exceeding the performance of a conventional synthetic fungicide under field conditions.
