WATCH VIDEO: Red Sunflower Seed Weevil Pre-Bloom Scouting
Alison Pokrzywinski, Nuseed Product Development Manager, NA
SITUATION
The Red Sunflower Seed Weevil (RSSW) is one of the most prevalent insects affecting sunflowers in parts of the Dakotas. When the larvae hatches they eat the inside of the seed and then exit, leaving behind a small hole. This can affect both the yield and test weight of the seed.
FACTORS TO CONSIDER
The adult weevil is what you scout for, but it’s the larvae that causes damage by eating the inside of the seed and exits, leaving behind a small hole. Yield and test weight can be affected. Here’s what to consider:
- Staging of the sunflower plant
- Scouting is best done right at bloom with a can of bug spray
- Females feed on the pollen before depositing eggs, best time to spray is R5.1-R5.4
- The adults emerge late June/early July and don’t cause damage, it’s their larvae that do
- Count the number of weevils found per sunflower head
- Threshold varies based on market and price, but the average is 4-6 weevils per head for oil seeds.
ACTION PLAN
1. Typically 4-6 RSSW/head is threshold for oilseed and 1 RSSW/head on confections
2. Timing is when 3/10 plants are at early bloom (R5.1-R.4)
3. If fields are sprayed too early, then re-check partway through bloom for threshold again
RESOURCES
Sunflower Production Guide — Publications (ndsu.edu)
