Do not enter treated fields within 48 hours after application. Fields must be posted. Do not apply within 45 days of harvest. The sunflower stem weevil can cause serious stalk breakage. This occurs when 25 to 30 larvae are present in a stalk, weakening the stalk when larvae make their overwintering cells in the stalk's base.
Breakage is most likely to occur during drought stress or high winds.
The weevils emerge in mid to late June. Eggs are deposited in epidermal tissue of the stem. If controls are directed at the adults in order to minimize egg laying, treatments should be initiated during the first few days in July. Examine 5 plants each at 5 locations and keep record of the number of weevils found. Approach plants carefully to avoid alarming the weevils, causing them to drop to the ground.