In-vitro Effect of Some Plant Extracts and Synthetic Fungicide in the Control of Cocoyam Leaf Necrotic Fungi in Nigeria

Abstract

The present study aimed to investigate an In-vitro effect of some plant extracts and synthetic fungicide in the control of cocoyam leaf necrotic fungi in Nigeria. Cocoyam leaves of two tropical crops, taro (old cocoyam, Colocasia esculenta (L.) Schott) and blue or purple taro (new cocoyam tanier, Xanthosoma sagittifolium (L.) Schott), were collected from farmers' fields in two communities in Anambra State's Ekwulobia local government area. Ula and Okpo were among the communities. The causative pathogen was isolated from cocoyam leaves and petioles with tiny dark-brown or black lesions. Aspergillus niger was identified as the fungus found on the diseased cocoyam leaves. This bacteria could have gotten into these cocoyam leaves by wounds caused by harvesting tools and pests. The antifungal effects of ethanol, methanol, and petroleum ether extracts of lemon grass leaves and stalks (Cymbopogon citratus) and fruits of pepper fruit (Dennettia tripetala) on the growth of Aspergillus niger were studied in vitro at concentrations of 1, 1.5, and 2 g/ml, with the synthetic fungicide (Apron plus) serving as a control. ANOVA was used to examine the data collected. Split – split – plots were employed in a completely randomised design with three replications, and means were separated using least significant difference (LSD) at a 5% probability level. The result of this research showed that the antifungal activity of the phytochemicals increase with increase in concentration where 2.0 g/ml had the highest percentage growth inhibition value in day 1, this trend occurred in all the days of the culture. The fungus was suppressed by all plant extracts and Apron plus. Apron plus had the highest amount of inhibition (75 percent), followed by lemon grass (49.04 percent), and pepper fruit had the lowest level of inhibition (25 percent) (39.48 percent ). The study also found that the higher the concentration, the greater the inhibition, with 2g/ml having the greatest inhibition (72.58 percent) for synthetic fungicides. In the days of the culture, the extract of lemon grass (Cymbopogon citratus) had a greater percentage inhibition value, whereas Soxhlet extraction utilising Pet ether as the extracting solvent had the maximum level of inhibition (53.03 percent ). Thus, the plant extracts used in this research could be suggested as an alternative to synthetic fungicides. More research on these plant extracts should be conducted to identify their active ingredients in order to facilitate commercial production and availability to farmers, as these extracts are expected to be biodegradable and may reduce the rate of application of synthetic fungicides, which are harmful to human health and persist in the environment.