We studied the interactions between two entomopathogenic nematode species each with a different foraging behavior in the presence of two hosts at different soil depths. One week after nematode inoculation, hosts were added to the soil and additional hosts added at 30-day intervals. The densities of infective juveniles of the two nematode species were monitored over 90 to 180-day periods in sod samples or directly in the experimental containers using wax moth larvae as baits. Host placement in the sod strongly influenced the outcome of the competition between the sit-and-wait forager (ambusher) Steinernema carpocapsae and active forager (cruiser) S. glaseri. When hosts were introduced at 2 and 10 cm depths, few S. carpocapsae were recovered at 60 days and onwards after the first hosts had been introduced. S. glaseri, on the other hand, was not adversely affected by the presence of S. carpocapsae. When hosts were introduced at 0 and 10 cm depths, S. carpocapsae persisted in the presence of S. glaseri at significantly lower numbers than when it was alone, whereas S. glaseri was not significantly affected by the presence of S. carpocapsae. Numbers of recovered S. glaseri; however, tended to decrease after 30 - 60 days, even in the absence of its competitor. We postulate that this decrease was because of its high susceptibility to intraspecific competition. In the combination of S. carpocapsae and the active forager Heterorhabditis bacteriophora, S. carpocapsae dominated the system during the first 90 days, and H. bacteriophora dominated during the last 60 days. In the laboratory, an ambusher and a cruiser entomopathogenic nematode species can coexist, In the field, many other factors will influence the population dynamics, and the higher diversity should promote the coexistence of entomopathogenic nematode species with different foraging behavior.
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