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ARS Home » Pacific West Area » Hilo, Hawaii » Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center » Tropical Plant Genetic Resources and Disease Research » Research » Publications at this Location » Publication #418327
Research Project: Crop Health and Genetic Improvement of Sub-Tropical and Tropical Crops in the Pacific

Location: Tropical Plant Genetic Resources and Disease Research

Title: Control of Cylas formicarius using entomopathogenic nematodes

Author
item WONG, LANDON - University Of Hawaii
item WANG, KOON-HUI - University Of Hawaii
item Myers, Roxana
item SIPES, BRENT - University Of Hawaii

Submitted to: Nematropica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2024
Publication Date: 4/7/2025
Citation: Wong, L.G., Wang, K., Myers, R.Y., Sipes, B.S. 2025. Control of Cylas formicarius using entomopathogenic nematodes. Nematropica. 55:1-9.

Interpretive Summary: Sweet potato weevil (SPW) is a destructive insect pest that adversely affects sweet potato production. Larvae feed and tunnel through swollen roots resulting in unsightly galleries and a bitter taste. Chemical insecticide options are available for control of this pest however management approaches for organic growers are limited. The use of entomopathogenic nematodes (EPN) has been an effective and environmentally compatible approach to manage several insect pests in different cropping systems. In previous studies, EPN have shown to cause mortality in all life stages of SPW and showed promise in reducing SPW populations in a simulated field trial. In this study, three species of EPN isolated from Hawaiian soils were first evaluated in laboratory assays. All species were effective at causing mortality in SPW larvae. In addition, field experiments were conducted where sweet potato yield, amount of SPW damaged roots, and SPW populations were analyzed. Two of the three EPN species showed potential as biological control agents for controlling SPW under field conditions. These beneficial nematodes can be viable tools for sweet potato growers in Hawaii to incorporate into their integrated pest management program.

Technical Abstract: Entomopathogenic nematodes (EPN) have potential to control the sweetpotato weevil (SPW; Cylas formicarius). Laboratory tests were conducted using Steinernema feltiae MG-14, Oscheius tipulae OA-12, and Heterorhabditis indica OM-160 isolated from Hawai'i on larvae of SPW in infection courts. Subsequently, S. feltiae was tested for effectiveness at 0.5, 1.0, and 2.5 billion infective juveniles (IJ)/ha in a sweetpotato field. In another field experiment, monthly applications of O. tipulae were evaluated for SPW control. In the laboratory assays, S. feltiae, O. tipulae, and H. indica caused an adjusted mortality (mortality of treatment – mortality in control) of 50%, 30%, and 25% to SPW larvae, respectively. In a field experiment with S. feltiae, SPW damage and SPW densities were low (< 1 SPW/kg sweetpotato swollen root) across all application rates, resulting in an inconclusive study. In contrast, the field experiment testing O. tipulae experienced high SPW pressure (32 SPW/kg root in the untreated control). Sweetpotato treated with O. tipulae suffered less damage and had lower SPW densities than the nontreated control (P = 0.05). In conclusion, all three EPN species isolated from Hawai'i showed promise in suppressing SPW in the laboratory and in the field.