The Damage and Gain Threshold of Meloidogyne arenaria on Faba Bean Favors the Use of a Safe Biological Control Over Chemical Nematicides

Abstract

Root-knot nematodes (RKNs, Meloidogyne spp.) cause major agricultural losses worldwide. Some chemical nematicides are effective, but health and ecological issues are confronting their use. Biological nematicides are safe and promising alternatives. The present study examines M. arenaria damage on faba bean and presents effective control methods as Egypt is the world's largest importer of faba bean. Using gain thresholds, the study compares costs of a biological versus a chemical nematicide for M. arenaria control on faba bean. Meloidogyne arenaria was not detected at pre-planting soil samples of two consecutive field seasons. However, the potential of field weeds as hosts/reservoirs for M. arenaria to transfer from weeds and build-up on 'Giza 843' faba bean roots was apparent at harvest. Significant relations were established between the M. arenaria population levels at harvest and weights of faba bean pods. Consequently, the gain thresholds were calculated based on the combined costs of nematode sampling and control. Their calculated values demonstrated more costs in applying the chemical (oxamyl) than the biological (Nemaless, bacterial strains of Serratia marcescens) nematicide; that is, the gain threshold was 0.78 versus 0.57 metric tons of pods feddan −1 (= 4200 m −2 ), respectively. This comparison should serve as a favorable, forward-looking assessment for the economic and safe application of biological pest control. Applying the chemical (oxamyl) or biological (Nemaless) nematicide is justified for M. arenaria control but Nemaless is less costly. Growers should be familiar with these biologicals to boost their use while offering economic and safe control of the nematodes. Cultural practices such as weed control should be strictly utilized for RKN control.