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2023 Crop Survey: The Insect Factor

Thursday, February 1, 2024
filed under: Insects

USDA-ARS research entomologist Jarrad Prasifka discussed the insect — and blackbird — findings from the 2023 sunflower crop survey during the January NSA Sunflower Research Forum in Fargo, N.D.
        Visual damage from birds was essentially zero in the High Plains surveyed fields. However, the story was quite different in the Dakotas — and especially in North Dakota. Of 127 North Dakota surveyed fields, 89% had a 5% or lower damage level from blackbirds. But some fields were quite a bit higher — particularly in Divide County (northwestern corner of the state), where four surveyed fields averaged 57% seed loss due to blackbirds.
        In terms of insects, the 2023 crop survey teams made in-field assessments of damage from “secondary” sunflower insects including seed maggot, sunflower midge, bud moth and the Dectes stem borer. Infestation levels for the first three were similar to levels found in the 2019 and 2021 surveys — i.e., not widespread.
        Dectes stem borer was significantly more common in South Dakota, with nearly half of 52 surveyed fields showing evidence of Dectes on sunflower stalks.
        Levels of infestation from the red sunflower seed weevil, banded sunflower moth and sunflower head moth were determined through x-rays of seed samples taken from fields and later analyzed in the lab. Levels of damage were estimated based on percent damaged seeds.
        In no surprise to South Dakota producers, the level of seed damage from the red seed weevil was particularly high in that state’s surveyed fields. Seed samples from 52 fields in South Dakota showed an average seed damage percentage of nearly 30%, with the great majority of that due to the red seed weevil and a small minority due to sunflower moths.
        “The real issue is the increased damage from seed weevil over the past three or four crop surveys,” Prasifka noted. The troublesome increase in red seed weevil damage levels in South Dakota in 2023, versus that found in the 2021 and 2019 crop surveys, is reflected in the chart below.
          The red seed weevil was much less damaging in North Dakota, where an average seed feeding level of about 5% was found in the x-rayed samples from that state’s 127 surveyed fields. A small percentage of that was due to moths.

This chart shows percentages of seed damage in seed samples taken from fields in the 2019, 2021 and 2023 crop surveys. The samples were later x-rayed to reveal seed damage. While banded sunflower moth and head moth are included, the vast majority of damage was due to red seed weevil. (Chart credit: Jarrad Prasifka)