Regular Field Monitoring Improves Pest Control and Supports Stronger Sunflower Crop Production
Red sunflower seed weevils become active as sunflower plants enter the flowering period, making regular field scouting an essential part of crop management. Heavy infestations can reduce seed quality and lower yields by damaging developing seeds.
Monitoring fields before populations reach damaging levels helps growers decide whether treatment is needed while avoiding unnecessary insecticide applications.
Adam Varenhorst, Associate Professor & SDSU Extension Field Crop Entomologist, along with Philip Rozeboom, Patrick Wagner, and Brad McManus, stress that careful scouting and proper treatment timing are the most effective ways to manage red sunflower seed weevils.
Applying insecticides only when economic thresholds are reached helps protect yields while slowing the development of insecticide resistance.
Adult red sunflower seed weevils are small reddish-brown beetles with a long snout and elbow-shaped antennae. They move into sunflower fields before flowering and gather on sunflower heads as blooming begins. After laying eggs, the cream-colored larvae develop inside the seeds, where they feed unnoticed until later in the season.
Growers should begin scouting when sunflower plants reach the R4 growth stage, when the first yellow ray petals become visible. Field inspections should continue until approximately 70% of pollination is complete, or the R5.7 growth stage. At each scouting location, about 25 plants should be examined after walking well into the field to obtain an accurate estimate of weevil populations.
Lightly tapping or rubbing sunflower heads helps expose adult weevils for counting. Some growers also use aerosol insect repellent to encourage hidden adults to emerge, making scouting easier.
Treatment recommendations depend on the sunflower market type. Oilseed sunflower fields generally require treatment when four to six adult weevils are found per head, while confection sunflower fields require treatment at only one adult per head because of their greater crop value.
Researchers also remind growers that spraying too early may allow fields to become reinfested, increasing the need for additional treatments.
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