Effects of Two-Dried Castor Leaf Formulations on the Population Dynamics and Pathological Activities of Root-Lesion and Root-Knot Nematodes on Water Yam

Abstract

The pathological activities of plant-parasitic nematodes affect the marketable value of yam tubers. This study intends to evaluate the nematicidal effects of dried castor leaf powder and dried castor leaf extract on root-lesion and root-knot nematodes under field conditions. Trials were conducted in the Autonomous District of Yamoussoukro in Côte d’Ivoire during the 2015 and 2016 growing seasons. Before yam seed planting, dried castor leaf powder, dried castor leaf extract (suburbs of Abidjan), and carbofuran (Callivoire S.A., Abidjan) were applied at the top of mounds in a randomized complete block design with three replicates. Symptom prevalence, symptom severity index, nematode numbers, and yam yield were determined depending on the treatments. The gall (28.1%) and dry rot (48.9%) prevalences on yam tubers from untreated soils were higher than those from product-incorporated soils (1.11–12.1%) (P < 0.05). The dry rot prevalence (2.78%) was only lower on yam tubers from soil incorporated with dried castor leaf powder compared to that (10.1%) obtained with dried castor leaf extract (P = 0.000). The nematode numbers were lower in the product-incorporated soils and treated yam plants (3–105 individuals) than in the untreated soils and untreated yam plants (37–423 individuals) (P = 0.000). The nematode numbers in the soil, root, and tuber samples were statistically similar regardless of the dried castor leaf formulations. The highest yields (10.1 to 10.48 t/ha) were obtained from yam plants on soils that were incorporated with dried castor leaf powder and carbofuran (P = 0.000). Dried castor leaf powder is an excellent tool to manage water yam nematodes.

Nematicidal Effects of the Number of Dried Castor Leaf Product Applications on the Pathological Activities and Population Dynamics of Root-Knot and Root-Lesion Nematodes on Water Yam

“…These included the liquid formulation (aqueous extract) and the powder formulation. Caster leaf powder and extract were prepared according to the method of Kouakou et al (2023). Seven hundred twenty (720) batches of 100 g of castor leaf powder and 20 containers of 10-liter leaf extract were used for the two years of the trial.…”

“…Evaluation of the effect of treatments on nematode numbers: Nematodes in soil, yam root, and tuber samples were extracted according to the Whitehead tray and Baermann maceration methods (Coyne et al, 2010), respectively. Individuals of P. coffeae and M. javanica were counted from 100 ml of soil and 5 g of yam roots and tuber peelings using Kouakou et al (2023) formula. The effect of the treatments on nematode populations in the soil, roots, and tubers was evaluated by computing the reduction rate (Rr) of nematode numbers using the Mahdy et al (2014) formula.…”

“…Thus, neem powders and cocoa pods were used against yam pathogenic nematodes (Osei et al, 2013). In Côte d'Ivoire, dried castor leaf extract and powder were used as tools for yam nematode management (Kouakou et al, 2017;Kouakou et al, 2023). According to these authors, those products, in a single application, reduced P. coffeae and M. javanica numbers in soil, yam roots, and tubers.…”

Opportunities and Challenges of Castor Bean (Ricinus communis L.) Genetic Improvement

“…On the other hand, the presence of these harmful compounds could be exploited for the control of various diseases and pathogens of cultivated plants such as insects [23][24][25][26] (b) and nematodes [27][28][29][30].…”