Entomopathogenic nematodes (EPNs), small soil-dwelling non-segmented roundworms, are obligate parasites of insects and commonly used in agriculture for biological control of insect pests. For successful reproduction, EPNs must identify, move towards, and successfully infect a suitable insect hosts in a chemically complex soil environment. While EPNs can have an innate host insect preference, they can also develop a strong preference for non-host related chemical signals due to prior exposure. The manipulation of these innate and learned preferences could result in increased biological control services of EPNs in agriculture. The importance of these innate vs learned preferences were therefore investigated. Separate cohorts of the EPN Steinernema diaprepesi were raised on two insects host, Galleria mellonella and Tenebrio molitor, for multiple generations until the nematodes exhibited a preference for the host they were reared on. Subsequently the two strains of nematodes were imprinted on three plant produced terpenoids of agricultural significance: pregeijerene, β-caryophyllene, and α-pinene. Previous studies have identified pregeijerene to be innately attractive to untrained S. diaprepesi, while β-caryophyllene is neither attractive nor repellent and α-pinene deter untrained nematodes. Nematodes demonstrate positive chemotaxis to all compounds once trained. After training to the plant compounds, the behavior of the EPNs were assayed in sand column dual-choice tests where the two host insects were presented with and without the plant compounds. This presentation will compare and contrast the response of the two strains of S. diaprepesi to their innate and learned preferences with implications for use of EPNs in agricultural systems.

Volatile organic compounds and learning in entomopathogenic nematodes

ACS Fall 2021

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