Sweetpotato cultivars demonstrate wireworm resistance in Northwest Washington

Authors: SCHULZ, LAURA - Washington State University; BLAUER, JACOB - Washington State University; Wadl, Phillip; NOTTINGHAM, LOUIS - Washington State University; MILES, CAROL - Washington State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2026
Publication Date: 6/29/2026
Citation: Schulz, L., Blauer, J., Wadl, P.A., Nottingham, L., Miles, C. 2026. Sweetpotato cultivars demonstrate wireworm resistance in Northwest Washington. HortScience. https://doi.org/10.21273/HORTSCI19500-26.
DOI: https://doi.org/10.21273/HORTSCI19500-26

Interpretive Summary: Sweetpotato is a new crop in northwest Washington, with wireworm being the primary insect pest. Pest control options for organic farmers are limited. A field study in Mount Vernon, WA from 2023-2025 evaluated wireworm resistance in six sweetpotato cultivars and three breeding lines. All cultivars showed high survival and canopy cover. Differences in vine length and growth habits were observed. Bayou Belle had the highest root yield, while USDA-04-136 and USDA-04-791 were most resistant to wireworm. Bayou Belle had high yield and moderate resistance, Cascade had moderate yield and good resistance, while Beauregard, Covington, and Orleans were suitable for low wireworm pressure. More research is needed to develop sweetpotato cultivars with higher yield and wireworm resistance for organic farmers in wireworm-prone regions. The results of this research will be useful to public and private plant breeders, extension agents, and American sweet potato growers

Technical Abstract: Sweetpotato is a new crop to northwest Washington, and wireworm has emerged as the primary insect pest in the region. Effective pest control options for wireworms in the region are limited, especially for organic farmers. A field study was conducted in Mount Vernon, WA in 2023, 2024, and 2025 to evaluate the yield and wireworm resistance using the Wireworm-Diabrotica-Systena (WDS) severity index of six sweetpotato cultivars (Bayou Belle, Beauregard, Cascade, Covington, Monaco, Orleans) and three breeding lines developed for resistance (USDA-04-136, USDA-04-284, USDA-04-791). Plant survival and final canopy cover was high for all cultivars in all years. Longest vine length at the end of the season differed between cultivars, with Monaco having erect growth habit, USDA-04-136 and USDA-04-284 having semi-erect growth habit, Beauregard, Cascade, Covington, Orleans, and USDA-04-791 having spreading growth habit, and Bayou Belle having extremely spreading growth habit. Root yield was highest for cv. Bayou Belle, Beauregard, Covington, and Orleans (overall average 24.6 t.ha-1), however, Beauregard, Covington, and Orleans showed high susceptibility to wireworm (overall average 3.26 WDS rating). The most wireworm resistant entries were USDA-04-136 and USDA-04-791 (overall average 0.94), however, these had very low yield (overall average 9.1 t.ha-1) compared to commercial cultivars. Thus, there appears to be a tradeoff between yield and wireworm resistance for sweetpotato. Exceptions are cv. Bayou Belle, which had high yield and moderate wireworm resistance (overall average 27.5 t.ha-1 and 2.19, respectively), and newly released cv. Cascade that had both moderate yield and good wireworm resistance (overall average 12.5 t.ha-1 and 1.51, respectively). Cv. Cascade appears suitable for farms with high wireworm pressure, while Bayou Belle appears suitable for farms with moderate pressure, and Beauregard, Covington, and Orleans are suitable for farms with low pressure. Continued development and evaluation of sweetpotato breeding lines with wireworm resistance and higher yield is needed to provide farmers in regions with wireworm pressure with more productive cultivars.