Continue to Scout for Sunflower Insects (08/12/21)
Sunflower crop stages were in the R2 (bud <1 inch from leaf) to R5.9 (90% flowered) stages in IPM fields scouted or trapped last week.
Total trap captures for banded sunflower moth and Arthuri sunflower moth are still at high trap numbers, but did not increase much from the previous week (see table). The highest trap numbers of banded sunflower moths, >100 moths per trap per week, were located in Cass, Foster, Benson, Cavalier and Stark counties (see map).
SUNFLOWER MOTHS continue to be non-economic with positive trap catches at only 2 trapping sites in Ward and Cavalier counties. If traps catches are less than 7 moths per trap per week, the infestation is considered non-economic.
For pheromone trapping, the Economic Threshold (E.T.) is 28 sunflower moths per trap per week. For field scouting, E.T. is 1 to 2 moths per 5 plants to warrant an insecticide treatment.
For more information on scouting protocol for sunflower moth, see the previous Crop & Pest Report #15, August 5, 2021.
RED SUNFLOWER SEED WEEVILS were detected at 52% of the sunflower fields scouted last week, an increase from 45% of fields with seed weevils detected the previous week. About only 20% were at the economic threshold of >3-4 weevils per head, an increase from 12.5% the previous week. Continue to scout for weevils until sunflowers are past the susceptible crop stage, R5.7 (70% flowered).
See last week’s Crop and Pest Report #15, July 29, 2021 for scouting and E.T. of the red sunflower seed weevil.
Preliminary results of the pyrethroid resistant bioassay study conducted at 10 oilseed sunflower fields throughout ND indicated that the ND populations of the red sunflower weevils are still susceptible to the pyrethroids tested (esfenvalerate, lambda-cyhalothrin, and zeta-cypermethrin) in 2021. This study is supported by the National Sunflower Association.