Fatty acid data and crop surveys indicate sources of red sunflower seed weevil, Smicronyx fulvus LeConte (Coleoptera: Curculionidae), populations and suggest strategies for management

Authors: Prasifka, Jarrad; FERGUSON, BETH - Orise Fellow; Anderson, James

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2020
Publication Date: 12/2/2020
Citation: Prasifka, J.R., Ferguson, B., Anderson, J.V. 2020. Fatty acid data and crop surveys indicate sources of red sunflower seed weevil, Smicronyx fulvus LeConte (Coleoptera: Curculionidae), populations and suggest strategies for management. Environmental Entomology. 50(1):154-159. https://doi.org/10.1093/ee/nvaa158.
DOI: https://doi.org/10.1093/ee/nvaa158

Interpretive Summary: The red sunflower seed weevil is a pest that feeds on seeds of sunflowers in North America. Because different sunflower types have different amounts of fatty acids, especially oleic acid, in their seeds, tests were conducted to see whether the fatty acids in the pest (weevils) were similar to those in their food (seeds); if the percent of oleic acid in weevils is similar to those in sunflower seeds, that information can be used to tell if most pests are coming from oilseed sunflowers, confection sunflowers, or wild sunflowers. Tests where weevil diet was controlled showed the percent of oleic acid in weevils was close to that of their food. Collections of adult weevils in the wild showed at least 85% of weevils likely came from oilseed sunflowers instead of confection or wild sunflowers. Crop survey data also showed that most of the seed weevil damage in the crop was in a small number (about 10%) of grower fields, meaning improved management of those fields could greatly benefit sunflower growers in nearby fields by keeping pest populations low.

Technical Abstract: The red sunflower seed weevil, Smicronyx fulvus L. (Coleoptera: Curculionidae), is a univoltine seed-feeding pest of cultivated sunflower, Helianthus annuus L. Artificial infestations of S. fulvus onto sunflowers with traditional (< 25% oleic acid), mid-oleic (55–75%), or high oleic (> 80%) fatty acid profiles were used to test if fatty acids could be used as a natural markers to estimate the proportion of weevils developing on oilseed sunflowers rather than wild Helianthus spp. and confection (non-oil) types. Oleic acid (%) in S. fulvus confirmed the fatty acid compositions of mature larvae and weevil adults reflected their diets, making primary (oleic or linoleic) fatty acids as natural markers for this crop-insect combination feasible. Oleic acid in wild S. fulvus populations in North Dakota suggest at least 84% and 90% of adults originated from mid-oleic or high oleic sunflower hybrids in 2017 and 2018, respectively. Surveys in 2017 (n = 156 fields) and 2019 (n = 120 fields) extended information provided by S. fulvus fatty acid data; no significant spatial patterns of S. fulvus damage were detected in samples, damage to oilseed sunflowers was greater than confection (non-oil) types, and the majority of damage occurred in ˜ 10% of surveyed fields. Combined, data suggest a few unmanaged or mismanaged oilseed sunflower fields are responsible for producing most S. fulvus in an area. Improved management could be achieved through a combination of grower education and expanded use of non-insecticidal tactics, including cultural practices and S. fulvus-resistant hybrids.