The host-finding ability of Heterorhabditis heliothidis (Khan, Brooks, and Hirschmann) and Steinernema feltiae Filipjev in the presence of plant roots in sandy soil was investigated. During a 7-d period, host-finding ability of H. heliothidis was not impaired when the dried root weights of corn, tomato, or marigold plants were <1.6 g or of S. feltiae when dried root weights were <3.6 g. For example, host mortality by H. heliothidis was 85% for controls (no roots) and 85% for corn roots (1.6 g); host mortality by S. feltiae was 21% for controls and 16% for corn roots (3.6 g). However, host mortalities between controls and corn roots for H. heliothidis during a 2-d period showed significant differences when root weights were> 1.5 g. Thus, treatments with root weights> 1.5 g had significantly lower host mortalities (range, 27–50%) compared with control treatments (range, 73–96%); treatments with root weights <1.2 g showed no significant difference (range, 79–80%) compared with control treatments (range, 82–85%). Linear regression suggested a relationship between root weight and host mortality. Increasing root weight (x) significantly lowered percentage (y) host mortality (y = 81.8 −7.5(x), r2 = 0.57, P = 0.0001). Although significant differences between controls and roots> 1.5 g were observed for H. heliothidis, this nematode species showed greater motility, hence greater host-finding ability, than S. feltiae in the presence of roots because host mortality occurred over a shorter period of time with higher mortality rates and with fewer nematodes.
Choo, H. Y., Kaya, H. K., Burlando, T. M., & Gaugler, R. (1989). Entomopathogenic nematodes: Host-finding ability in the presence of plant roots. Environmental Entomology, 18, 1136–1140.