Effects of soil texture and moisture on the host searching abilities of Steinernema siamkayai against Bactrocera latifrons

Abstract

Summary Soil texture and moisture have significant effects on the infectivity and persistence of entomopathogenic nematodes (EPN). Both EPN and chili fruit flies (Bactrocera latifrons) spend most of their lifetime in soil, therefore making it possible to consider the successful use of EPN against chili fruit flies. This study aimed to investigate the effects of soil texture and moisture contents on chili fruit fly pupation and adult emergence, and on the infectivity of the EPN, Steinernema siamkayai, against this pest. The results revealed that the highest percentage of pupation occurred at a depth of 2 cm in all soil types. At a depth of 5 cm in the sandy clay loam only, no pupation of B. latifrons was observed. The adult emergence ranged from 51.9 to 82.5%, with significant differences between soil types. The horizontal movement of S. siamkayai showed that the concentration of EPN at a rate of 20 000 dauer juveniles pupa−1 yielded maximum pupae mortality (77.5-91.3%) in all soil types containing 15% moisture. In the vertical displacement test, S. siamkayai was capable of killing pupae up to a distance of 15 cm in all soil types. These results confirmed the potential of S. siamkayai to be used within pest control programmes of various soil textures, as long as the soil moisture contents allow its dispersal and host infection.

Management of Dipteran Pests Through Entomopathogenic Nematodes

“…Successful use requires that the ecology of the target is matched to the activity of infective juveniles; as the target pests are protected from environmental extremes, applications are timed to coincide with susceptible host stages and favourable weather conditions and nematodes are able to rapidly locate and infect hosts [71]. In addition to performance, factors including cost, availability, compatibility within integrated strategies and alternative options for organic growers will ultimately determine the extent to which nematodes are used against Dipteran insect pests [72, [78][79][80]. To make entomopathogenic nematodes more successful, realistic strategies through genetic engineering [81], IPM programs, and new delivery systems and/or training programs to overcome their inherent cost, formulation instability, and limited field efficacy toward the Dipteran pests are needed [82,83]…”

Can Entomopathogenic Nematodes and Their Symbiotic Bacteria Suppress Fruit Fly Pests? A Review

“…It is important to define the optimal soil moisture content, since it has been shown that high values of this parameter limit the displacement of IJs of H. bacteriophora . A soil moisture content of ≥30% has been observed to result in lower infection levels on A. obliqua larvae [ 75 , 76 , 77 , 78 ]. These results reflect the potential of these organisms against cryptic pests such as fruit flies, and a strategy that reflects the most effective application method must thus be defined, as well as the dose (density of IJs) required for application in the field.…”