Logo image
Back
FINDING THE SWEET SPOT WITH SWEETPOTATOES: EVALUATING WIREWORM RESISTANCE, IN-ROW SPACING, AND DUAL CROPPING GREENS AND ROOTS IN NORTHWEST WASHINGTON
Dissertation

FINDING THE SWEET SPOT WITH SWEETPOTATOES: EVALUATING WIREWORM RESISTANCE, IN-ROW SPACING, AND DUAL CROPPING GREENS AND ROOTS IN NORTHWEST WASHINGTON

Laura Schulz
Doctor of Philosophy (PhD), Washington State University
2026
pdf
Laura Dissertation 04.09.2026DownloadView
Open Access

Abstract

Integrated Pest Management Ipomoea batatas New crops Production practices Small farmers Vegetable crops
Sweetpotato (Ipomoea batatas) production in the US is primarily in the southeast and California. In western Washington, small, direct-market farmers are growing sweetpotatoes with mixed results, largely due to lack of production guidelines combined with wireworm (Agriotes lineatus, A. obscurus, and Limonius canus) pressure. Local farmers are successfully marketing sweetpotato greens, a common food crop in many regions of the world. This research project included three experiments that aimed to develop management practices for sweetpotato root and greens production in western Washington. In Experiment 1, yield and wireworm resistance were assessed for sweetpotato cultivars and advanced breeding lines. We found a yield tradeoff for existing wireworm resistant cultivars and thus recommend that farms with low wireworm pressure grow cv. Covington, Beauregard, or Orleans (high yield, high susceptibility), farms with moderate wireworm pressure grow cv. Bayou Belle (high yield, moderate resistance) and farms with high wireworm pressure grow cv. Cascade (low yield, high resistance). In Experiment 2, we evaluated the impact of three in-row spacings (20, 25, and 30 cm) on root yield of four sweetpotato cultivars grown with black plastic mulch. We found that 20 and 25 cm in-row spacing produced maximum root yield and recommend 25 cm in-row spacing due to the lower cost of slips. In Experiment 3, we measured the impact of sweetpotato greens harvest on root yield to optimize timing of greens harvest. We found a 37–57% reduction in root yield due to greens harvest, with lesser impact when greens were harvested late in the season. Decrease in root yield was offset by the increase in economic returns from selling greens at local market prices; thus, dual-cropping sweetpotato for greens and roots may be economically viable for direct market farmers. These results were used to develop sweetpotato production guidelines for growers in western Washington.

Metrics

1 Record Views

Details

Logo image