Efficacy of Neem, Tithonia and Tephrosia Leaf Extracts in Management of Root-Knot Nematodes in French Beans (Phaseolus vulgaris L.)

Abstract

Root-knot nematodes (Meloidogyne spp.) are a major problem in French bean production within the smallholder farming systems. Control of root-knot using synthetic nematicides is not viable due to environmental concerns relating to their toxic residues. There is need to develop alternative control options that will promote soil health and reduce parasitic nematode densities. A study was conducted to determine the efficacy of Neem (Azadirachta indica A. Juss), Tithonia (Tithonia diversifolia) and Tephrosia (Tephrosia purpurea) leaf extracts in management of root-knot. Controlled lath house and field trials were conducted where the treatments were extracts from Neem, Tithonia and Tephrosia at different concentration levels of 25 ml/L, 50 ml/L and 100 ml/L). Vydate (Oxamyl 10%) a synthetic nematicide served as a standard positive control while treatments with no extracts application and no nematode application served as negative controls. The treatments in the lath house were arranged in completely randomized design while the field trials were arranged in randomized complete block design. Fench beans were planted on nematode infested soils and data on root galling indices and yield components was collected. Data collected was subjected to analysis of variance and significantly different means separated using Tukey’s Studentized Range Test at P=0.05. The extracts evaluated reduced root galling with their efficacy being similar to that of Vydate® (Oxamyl 10%) which was used as a positive control. Neem extracts treatments had the lowest mean galling index of the extracts, followed by Tithonia. Root-knot nematode galling indices were highest in the untreated control at 10 both in trial I and trial II. Treatment trials from Neem and Tithonia at concentration levels of 100 ml/L resulted in highest yield of French beans while yield from the untreated plants were the lowest. The results indicate extracts can be adopted to suppress root-knot nematodes.

Effect of Organic Waste Extracts as Potential Biocontrol of Golden Apple Snail

“…The results from the molluscicidal activities showed that the extracts of commercial wastes (groundnut shells, garlic skin and coffee grounds) and bioresource (water spinach) extracts were lethal on GAS (Njenga, 2019) showing different time frame of cidal effects on apple snail. The strongest cidal effect as biocontrol nanomaterial was shown by the water spinach aqueous extract (Table 3) and the weakest cidal activity was exhibited by the coffee aqueous extract (Table 2) even though it had the smallest nanoparticle size (Table 1).…”

A Review of the Potency of Plant Extracts and Compounds from Key Families as an Alternative to Synthetic Nematicides: History, Efficacy, and Current Developments

“…The bark powder from Saraca asoca and Acacia nilotica was shown to suppress M. incognita and Rotylenchulus reniformis reproduction, and subsequently improve castor seedling growth when amended in soil at a rate of 50 g/ kg soil (Parveen and Bhat, 2011). In field trials, crude extracts of Tephrosia purpurea were shown to significantly reduce root-galling in French bean (Njenga et al, 2019); while extracts from T. cinerea stem were bioactive against M. incognita (Cristóbal- Alejo et al, 2006). Additionally, extracts of roots and leaves of Leucaena leucocephala have been reported to contain flavonoids like quercetin known to be highly toxic to M. incognita (Adekunle and Aderogba, 2008); Medicago sativa is also known to contain saponin mixture, with nematicidal potency reported against X. index, M. incognita, and G. rostochiensis; and when amended in soil, significant population reductions were evident (D'Addabbo et al, 2011).…”