By Scout Nelson
The confirmation of pyrethroid-resistant red sunflower seed weevils in South Dakota creates a new challenge for sunflower growers. As resistance concerns increase, producers continue to search for alternative pest management methods that protect crops while reducing dependence on broad insecticide applications.
One option receiving renewed attention is trap cropping, a management strategy that was investigated 33 years ago in North Dakota and showed promising results.
This information is based on educational and research efforts led by Adam Varenhorst, Associate Professor & SDSU Extension Field Crop Entomologist, with additional contributions from Patrick Wagner and Philip Rozeboom.
Their work highlights how trap cropping can fit into modern sunflower pest management programs and help growers address emerging resistance issues.
Trap cropping is a cultural pest management method that uses a more attractive planting area to draw insects away from the main crop. In sunflower production, the challenge is unique because commercial sunflowers are already highly attractive to the red sunflower seed weevil.
To overcome this issue, researchers focus on making a small portion of the sunflower field more attractive than the rest of the crop.
This approach works because red sunflower seed weevils are strongly attracted to sunflowers during bloom. Female weevils also require a pollen meal before egg development begins.
By creating an area that blooms earlier than the main crop, growers can attract weevils to a specific location before the cash crop reaches its preferred growth stage.
Research conducted by Brewer and Schmidt (1995) evaluates a sunflower trap crop system using different sunflower hybrids and planting dates. The design includes 16 rows of trap crop sunflower planted around the field edges. These border rows use an early-maturing hybrid and are planted so that flowering occurs during late July or early August.
The main sunflower crop is planted inside the field using a later-maturing hybrid. Planting dates are selected so that the bloom period of the cash crop occurs about 7 to 10 days after the trap crop reaches bloom. This timing makes the border rows more attractive to adult weevils and encourages them to concentrate in those areas.
An important advantage of this system is that it requires only a small portion of the field. On average, the trap crop uses about 7% of the total field area. This allows growers to direct pest management efforts to a limited section rather than treating the entire field.
In the trap cropping system, foliar insecticides are applied to the trap crop sunflower shortly before the cash crop begins blooming. The goal is to reduce weevil populations and prevent insects from moving from the trap crop into the production area. Insecticides are applied to the cash crop only when red sunflower seed weevil populations exceed economic thresholds. Researchers also compare these fields with check or control fields where normal production practices are followed, and no trap crop is used.
Results from the research show that trap cropping can be effective without causing major yield losses. The average yield in trap crop fields is slightly lower than in control fields, but the differences are not significant.
Researchers note that normal variations in sunflower hybrids and field conditions likely contribute to the small yield differences observed between fields.
One of the most important findings involves production costs. Fields using trap cropping require significantly lower insecticide input costs, including both product and application expenses. While the trap crop occupies a small portion of the field, the reduction in insecticide use helps offset this loss of production area.
When researchers compare the savings from lower insecticide costs with the slight economic impact of dedicating land to the trap crop, they find a meaningful financial advantage.
Sunflower fields using trap crops cost approximately $39 per acre less to produce than check fields. Because farm input costs are much higher today than they were when the study was completed, the potential value of these savings may be even greater under current conditions.
Research also shows that planting sunflowers early, during the first to second week of May, can greatly reduce red sunflower seed weevil damage. When combined with field scouting, proper hybrid selection, and trap cropping, early planting may provide an additional management advantage.
Photo Credit: pexels-andrew-swarga
Categories: South Dakota, Crops