I’ve updated this article on timing of insecticide application for management of sunflower head insects from an old issue of the 2013 Crop & Pest Report. Chemical treatment is directed at the larval stage of the banded sunflower moth (BSM) and sunflower moth, which is the actual damaging stage. But, insecticides should be targeted at the adult red sunflower seed weevils to prevent egg laying.
Once the decision to treat has been made, it is critical to time the spray application correctly to get effective management of sunflower head insects. The best sunflower plant stage to treat is usually the R5.1 growth stage, or when pollen shed is just beginning on the outer rim of the sunflower head. This is the time when most BSM eggs have hatched. Eggs hatch into larvae in about 5-8 days, and larvae mature through 5 growth stages in about 2 weeks. Young larvae feed on the bracts, pollen and disk flower for the first half of its development before tunneling into the seed.
Larvae can be found on sunflower heads from mid-July through mid-September. So, insecticide treatments need to be timed before 12-15 days after BSM egg hatch depending on temperatures. At this time, BSM larvae are beginning to feed on the disk flowers and are exposed on the head, and are susceptible to the insecticide treatment. For RSSW, adult weevils are feeding on pollen and laying eggs into the developing seed at this time (early flowering).
On older flowering plants (after R5.7) where the seeds have started developing, larvae of BSM and RSSW will be feeding inside the seeds and will be protected from the insecticide. By then, much of the feeding damage has already occurred. Application at an earlier growth stage is rarely justified (before flowering), but may be warranted if monitoring reveals earlier than normal egg-laying activity of banded sunflower moth or the presence of numerous RSSW adults in heads.
The banded sunflower moth, red sunflower seed weevil and the lygus bug have all impacted quality of confection sunflowers in past seasons. It is recommended that sunflowers grown for these markets be treated a minimum of two times, once at early flowering and again 5 to 7 days later. With this type of program, a window of protection should be provided to minimize impact from all three of these seed-damaging insect pests.
Please see the 2015 ND Field Crop Insect Management Guide for insecticides registered in sunflower.
If you need to spray flowering sunflowers, remember to PROTECT BEES by notifying bee keepers before an insecticide application and spraying in late evening. A NDSU YouTube video is available on Protect Bees from Pesticide Poisoning.
Always read, follow, and understand the label in regards to pollinator protection.
(Source – http://www.farms.com/news/insecticide-control-of-sunflower-head-insects-95182.aspx)