Early planting and early-maturing sunflower hybrids are neglected management tools to remedy outbreaks of the red sunflower seed weevil

Authors: Prasifka, Jarrad; IRELAND, SAM - South Dakota State University; VARENHORST, ADAM - South Dakota State University; WAGNER, PATRICK - South Dakota State University; Cluever, Jeffrey; SIMONS, KRISTIN - North Dakota State University; ROZEBOOM, PHILIP - South Dakota State University; OSTLIE, MICHAEL - North Dakota State University; Buetow, Ryan

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2026
Publication Date: 5/12/2026
Citation: Prasifka, J.R., Ireland, S., Varenhorst, A.J., Wagner, P., Cluever, J.D., Simons, K.J., Rozeboom, P., Ostlie, M.H., Buetow, R.R. 2026. Early planting and early-maturing sunflower hybrids are neglected management tools to remedy outbreaks of the red sunflower seed weevil. Environmental Entomology. 55(3). https://doi.org/10.1093/ee/nvag043.
DOI: https://doi.org/10.1093/ee/nvag043

Interpretive Summary: A small beetle, called the red sunflower seed weevil, is currently the most serious seed-feeding insect pest of sunflowers in the United States. Farmers are seeing more weevils in their sunflowers and weevils in some areas are no longer reliably controlled with insecticides, so other ways of managing weevils are needed. Research from the 1980s showed that if sunflowers bloom before adult weevils emerge from the soil, damage from this insect is much less. Recently, sunflower growers have asked if planting sunflowers early can still work as a strategy, which led to new field tests in North Dakota and South Dakota from 2022-2024. At sites in South Dakota, planting in early May (1–15) instead of mid-June (15–20) lowered weevil damage by 60% or more and crop yields were equal or greater in the early-planted sunflowers. Because the weevil only feeds on sunflowers, ‘avoiding weevils’ by planting early should also lower the numbers of weevils in an area over time. In areas with fewer weevils (currently including North Dakota), early planting may not be useful unless weevil populations greatly increase.

Technical Abstract: The red sunflower seed weevil, Smicronyx fulvus L. (Coleoptera: Curculionidae), is a univoltine seed-feeding pest of sunflowers. Recent increases in S. fulvus damage and resistance to pyrethroids show a need for additional tools to complement insecticides. Cultural practices to advance sunflower bloom before S. fulvus emergence is complete were shown effective in the 1980s, but are not in use today. To address growers’ concerns, insecticide-free field trials were conducted to assess the efficacy, profitability, and sustainability of S. fulvus avoidance with early planting and early-maturing hybrids. In central and western South Dakota, May plantings reduced S. fulvus damage by 60% or more relative to typical plantings from 15–20 June, and an early-maturing hybrid may further reduce seed damage. However, in North Dakota, early planting did not provide a clear advantage, likely because of relatively low S. fulvus populations. Yields generally showed no negative effect from planting early, but yields were lower for the most common planting period (15–20 June) in central South Dakota. Adult S. fulvus emerged earlier where early-planted sunflowers were grown in the previous year, but the benefits of weevil avoidance were not eliminated. The strategy of S. fulvus avoidance through early planting (before ˜ 15 May) and early-maturing hybrids seems justified in South Dakota where pest populations are very high and insecticide efficacy is low because of resistance to pyrethroid active ingredients. For other key sunflower-growing areas, avoidance may become useful in the future if S. fulvus populations increase.