Effect of Plant Extracts on Angular Leaf Spot Disease and Yield Variables of Common Beans (Phaseolus vulgaris L.) Varieties in Bambili (North-West, Cameroon)

ABSTRACT Common bean (Phaseolus vulgaris L.) is one of the essential leguminous vegetable crops grown in Cameroon mainly for its economic and nutritional values. Its productivity is highly limited by Angular leaf spot caused by the fungus Phaeoisariopsis griseola (Sacc.). This study evaluated the effects of two plant extracts (ginger and neem oil aqueous solution) in the control of angular leaf spot disease for four varieties of beans (GLP 190 C, PNN, ECAPAN 021, and GL22) in two seasons (July – November 2021 and March – July 2022). The trials were carried out at the teaching and research farm in the University of Bamenda campus, in the North-West region of Cameroon. The experimental field design was a randomized complete block design of four treatments replicated three times on four varieties of beans. The data on disease incidence, disease severity, pod weight, and the number of pods were collected for the four beans varieties. The results obtained for disease incidence, severity, and yield revealed differences at p≤0.05 amongst the different treatments in different fields. The highest mean disease incidence (95 %), severity (4.25), and low yield (4 pods weighing 0.3 grams) were observed in both seasons in untreated plots (T0) in all varieties. The treated plots recorded the lowest average disease severity of (1), incidence (10 %), and high yields (16 pods weighing 6.8 grams). Disease incidence for treated plots with ginger aqueous extract (T2) and neem oil aqueous solution (T1) recorded a relatively lower mean disease incidence (20 %). Treatment with neem oil aqueous solution showed a low disease incidence (10 %) at week 3 for the PNN variety. Disease severity rate for plots treated with neem oil aqueous solution (T1) had the lowest mean value of 1.2 for medino long (GLP 190C) and PNN varieties at week four, while ginger aqueous extract (T2) showed an infection of 1.5. The pod weights revealed the highest mean weight of 6.8 grams for plots treated with neem oil aqueous solution for PNN (black bean), while GL22 and GLP 190C (medino long) had the lowest mean of 0.2 grams in season one. From this study, ginger aqueous extract could therefore be recommended as a biocontrol pesticide against angular leaf spot disease of bean in the dry season and neem oil aqueous solution in the rainy season. Key words: Angular leaf spot disease, beans, biocontrol, plant extracts, yield.