Plant parasitic nematodes associated with common bean (Phaseolus vulgaris L.) and integrated management Approaches.

Abstract

A field study to determine the distribution and population densities of plant parasitic nematodes associated with beans was undertaken in Kakamega, Kiambu, Machakos and Siaya districts of Kenya. Meloidogyne spp. and Pratylenchus spp. were the most predominant endoparasites, occurring in 86 and 61% of the root samples, respectively. Ectoparasitic nematodes in the genera Scutellonema and Helicotylenchus were recovered in 86 and 59% of the soil samples, respectively. Field experiments were conducted to determine the efficacy of organic amendments (chicken manure, compost, neem leaves, baobab remains and farm yard manure) in the control of root-knot nematodes. The amendments showed varying levels of nematodes suppression with chicken manure being rated as the most effective with galling index of 2.4 while sisal wastes were least effective with galling index of 5.1. Another study was undertaken to determine the reaction of 35 bean genotypes to Meloidogyne incognita. Ten genotype were rated as susceptible while 3 and 22 genotypes were rated as resistant and moderately resistant, respectively. The potential of different Bacillus isolates to suppress galling by root knot nematodes in beans was investigated using sterile sand in Leonard jars under greenhouse conditions. The isolates had varying effect with the majority (93%) of the isolates causing a reduction in root galling when compared to the control (water). Twelve percent of the isolates were more effective than carbofuran (nematicide). In another greenhouse experiment investigating the interaction between Bacillus spp. and Rhizobium strains inoculations using N-free sterile sand, 4 out of the 20 Bacillus isolates significantly promoted nodulation in bean plants.