Abstract
The objective of this study was to evaluate the efficacy of plant extracts in managing late blight disease in tomato, in vitro. Crude extracts were from Plectranthus barbatus, Tephrosia vogelii, Sphaeranthus suaveolens and Lantana camara. These were compared with commercial formulations Otiva fungicide and untreated as negative control. Their effectiveness was determined by measuring the inhibition zone of the mycelial growth of the pathogen recorded in triplicate at 48 hours and 72 hours. The results showed significant differences (P ≤ 0.001) among the extracting solvents on percentage inhibition of Phytophthora infestans. Methanol was superior in inhibiting the growth of mycelial growth of P. infestans as compared with ethyl acetate. Furthermore, all plants tested showed antifungal activity against P. infestans. The P. barbatus, L. camara and S. suaveolens were comparable with the commercial fungicide in inhibiting the growth of P. infestans. In this study, T. vogelii extract showed poor results in inhibiting the mycelial growth of P. infestans as compared with other plant extracts. Also, it was observed that, there were significant (P < 0.05) interactive effects between solvent and plant extracts and between incubation time and plant extracts.
Highlights
Tomato is one of the most important vegetables in the world grown for its different use, fresh market and processing industries [1]
The P. barbatus, L. camara and S. suaveolens were comparable with the commercial fungicide in inhibiting the growth of P. infestans
Our findings revealed that the Plectranthus barbatus, Lantana camara, and S. suaveolens crude extracts inhibited the mycelial growth of the P. infestans and these were statistically similar with the commercial chemical fungicide
Summary
Tomato is one of the most important vegetables in the world grown for its different use, fresh market and processing industries [1]. Tomato is susceptible to a wide range of diseases such as bacteria [5], fungi [6], viruses [7] and nematodes [8] among others which adversely affect quality, quantity and profitability. Of these diseases, the fungal disease like late blight disease caused by Phytophthora infestans (Mont.) de Bary is among the economically important diseases which reduce the quality and quantity of the tomato yield and the losses can go up to 100% [6] [9]. In Tanzania, the average tomato yield is 17.5 tons/ha which is far below the global average yield of 33.6 tons/ha
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