Zap Sunflower Bugs Before They Blossom
By this time, you’ve probably seen cutworms, an early-season pest, come and go. Most sunflower crops are in the bud stage now, which brings about several other destructive insects. Here are the main ones to watch for.
Red sunflower seed weevils
The number-one sunflower pest in my area near Dickinson, North Dakota, is the red sunflower seed weevil, which lays its eggs into developing seeds after pollination at the R-5.1 stage, when the outside of the sunflower head is starting to bloom. This causes seeds to be completely hollow or greatly reduced in test weight, which reduces sunflower yield.
Begin scouting for seed weevils as soon as the yellow ray petals begin to show. Counts should continue until the economic threshold level has been reached or most plants have reached 70 percent pollen shed, at which time very few seeds are suitable for egg laying.
For accurate checking of individual sunflower heads, brush the face of the heads vigorously to bring the weevils to the surface, or spray mosquito repellent containing DEET on the head. This will force the weevils to move out of hiding.
Keep in mind that the economic threshold is based on the market price of the crop. Here are the economic thresholds for the three main sunflower markets:
- Confection: 1 weevil per head
- De-hull: 2 to 3 weevils per head
- Oils: 4 to 5 weevils per head, based on a $0.15 to $0.16 oil grain market.
Careful scouting is critical with this sunflower pest, and you need to wait until the eggs hatch before you can spray them (typically about a week after you see the eggs). Sunflower moth larvae will chew petals as well as developing seeds and tissue. The timeline for banded sunflower moths mirrors that of the red sunflower seed weevil, so both can be sprayed at the same time.
Lygus bugs pierce and suck the nutrients out of developing seeds in the sunflower head. They are especially problematic in the confectionary and de-hull sunflower markets, where the appearance of the seed is important, and they also cause the seeds to have a bitter taste. As few as one lygus bug per nine plants is enough to cause a significant problem.
So protect your sunflower crop with boots-on-the-ground scouting to detect insect threats early and deal with them promptly. Your agronomist can help you determine optimal timing and the most effective insecticide to use.
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