In emergence cages, we are getting some moths coming out, but we are still 7 to 10 days away from an anticipated flush of emergence. The Spotted stem weevil population has been small in North Dakota for the past several seasons. One report of seeing some stem weevil in the LaMoure, ND area. We had some reports of stem weevil from the Dickinson, ND area last year. Spotted stem weevil larvae cause stalk breakage when 25 to 30 larvae are present in a stalk, weakening it when larvae make their overwintering cells in the stalk's base.
Breakage is most likely to occur during 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. Treatment for sunflower stem weevils is recommended when scouting determines that an average of 1 adult per three plants is found.