Efficacy of Siam weed (Chromolaena odorata (L.) R.M. King & H. Rob.) extract in the management of Fusarium wilt of pepper (Capsicum annum L.)

Abstract

Pepper is an important spice worldwide. Pepper seedlings face significant threats from Fusarium solani which induces wilt in pepper and leads to substantial production losses. The use of synthetic fungicides has raised concerns over the harmful threats they pose to man and the environment. The use of botanicals as an alternative source for fungal disease management is being emphasized. Botanicals are ecofriendly and relatively cheap and accessible by local farmers. Chromolaena odorata, (Siam weed) produces phytochemicals that have been studied in vitro to inhibit the growth of other microorganisms. This study aimed to assess the efficacy of varying percentage concentrations (0%, 5%, 10%, 15% and 20%) of Siam weed in the management of Fusarium wilt in vivo. This study was conducted at the Nursery Section of the Crop Production Department, Prince Abubakar Audu University Anyigba. Pure culture of Fusarium solani was obtained from the department of Microbiology, PAAU, Anyigba. A pathogenicity test on healthy pepper seedlings was carried out using Koch’s postulate. Sterilised soil (5 kg) was inoculated with Fusarium solani (10⁷ spores per mL) and left for 48 hours. The aqueous extract of Siam weed was prepared and applied at different concentrations using sterile needles in a controlled screenhouse environment. Three weeks old pepper seedlings were transplanted into the treated soil and necessary agronomic practices were carried out. Data were collected on the plant height, number of leaves, number of branches, stem girth and number of fruits. Similarly, disease incidence and severity in tomato plants as influenced by the varying concentrations of the extract were assessed.  Data were analysed using statistical analysis of variance (ANOVA) and means were separated using Least Significant Difference at 5% level of probability. The experiment employed a Randomized Completely Block Design (RCBD) with five treatments, each replicated four times. Results indicated that at 10 weeks after transplanting (WAT) soil treated with 20% extract gave taller plant height (57.75 cm), higher number of leaves (170.50), higher number of branches (15.85), bigger stem girth (2.22 cm) and more fruits (15.69) compared to untreated soils. Pepper seedlings exhibited wilting at 6 WAT. concentration of Siam weed significantly impacts the incidence and severity of fusarium wilt in tomato plants. The highest incidence and severity were observed at 0% (65.25% and 6.93, respectively); the highest reduction was observed at 20% concentration (5.55 and 0.45, respectively), with the 20% concentration being the most effective in controlling the disease. There is a need to implement disease management measures as part of preliminary agronomic practices to control wilting through the use of botanicals as an alternative source to synthetic fungicides to ensure environmental safety and man’s health.