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2017 Action Threshold for Banded Sunflower Moth and Red Sunflower Seed Weevil (07/20/17)

The USDA NASS reports that 9% of the sunflowers were blooming in North Dakota as of July 17th (USDA NASS News Release).

2017 Action Threshold for Banded Sunflower Moth and Red Sunflower Seed Weevil

The USDA NASS reports that 9% of the sunflowers were blooming in North Dakota as of July 17th (USDA NASS News Release).

Red sunflower seed weevil: Adults of reknodel.2 5d sunflower seed weevil (RSSW) will be emerging soon and will fly to the nearest flowering sunflowers. I have not received any field reports of adult weevils in sunflowers yet. So, please send me your reports including locality and numbers when you start finding them.

Identification: RSSW are small (2.5 to 3.1 mm long) weevils with a snout and reddish-orange.

Scouting: When sampling, use the X pattern and begin counting at least 75 to 100 feet into the field to avoid field margin effects. Count the number of RSSW adults on five plants at each site for a total of 25 plants. Scout for adults in the early blooming sunflower fields when the yellow ray petals are just beginning to show. A NDSU YouTube video is available on Scouting for Red Sunflower Seed Weevil in Sunflowers. Scouting should continue until the economic threshold level has been reached or most plants have reached 70% pollen shed. At 70% pollen shed, plants are no longer susceptible for egg laying or for significant damage. On older flowering plants (after R5.7), larvae of RSSW (and banded sunflower moth larvae) will be feeding inside the seeds and be protected from the insecticide. By then, much of the feeding damage has already occurred.

 

Banded sunflower moth (BSM):

Identification: Banded sunflower moth can be identified by its small size (1/4 inch in length), and by its forewings with a triangular, dark brown band across the middle of the wing.

Scouting: When sampling, use the X pattern and begin counting at least 75 to 100 feet into the field to avoid field margin effects. Count moths on 20 plants per sampling site to obtain the total number of moths per 100 plants. Sampling should be conducted from the late bud stage (R3) through R5.1. If treatment is warranted, it should be delayed and applied at the R5.1 sunflower plant growth stage (when 10% of head area has disk flowers that are flowering).

During the day (late morning to early afternoon) the moths remain quiet, resting on upper or lower leaves of sunflower plants. When disturbed, they flutter from plant to plant.

 

Insecticide spray timing for most sunflower seed-feeding insect pests: Once the decision to treat has been made, it is critical to time the spray application correctly to get effective management of all sunflower head insects including RSSW, BSM, sunflower moth and Lygus bug. The best sunflower plant stage to treat is when most of the plants in a field are in the R5.1 growth stage (when pollen shed on 10% of the outer rim of the sunflower head).  In addition, this is the time when most banded sunflower moth eggs have hatched and young larvae are feeding on the florets on the face of the sunflower head. RSSW is attracted to early blooming sunflowers, as females must imbibe pollen before laying eggs. If migratory sunflower moths are present, adult moths also are attracted to the first blooming sunflowers. Scheduling an airplane may take a week or more if ag pilots are busy spraying, so we recommend planning for your insecticide application when only 30% of the plants in a field reached the R5.1 growth stage. If it’s hot, flowering will progress more rapidly and one week may not be enough lead time. Getting the timing right in this situation is difficult, but making spray arrangements when 5-10% of plants are at R5.1 may be more prudent. Last year at Casselton, sunflower progressed from 1% at R5.1 to 50% at R5.1 in just a few days. Insecticides should be targeted at the adult RSSWs to prevent egg laying and the adult and early larval stages of BSM.

Please see the 2017 ND Field Crop Insect Management Guide for insecticides registered in sunflower.

 

Janet J. Knodel

Extension Entomologist

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