Trap Cropping to Minimize Insecticide Application and Farm Input Costs in Sunflower Production

Trap Cropping to Minimize Insecticide Application and Farm Input Costs in Sunflower Production

Summary

Rationale:
According to a grower survey, the red sunflower seed weevil is the major economic pest of
sunflower in the upper Great Plains. Up to 70 percent of the sunflower fields in the region are
treated with insecticides, mostly to control the seed weevil. In order to reduce the pesticide
applications to control the seed weevil, alternative methods of control need to be investigated.

Objectives:
1) Determine the effectiveness of trap cropping to minimize seed weevil damage in sunflower.
2) Compare the cost effectiveness of trap cropping with standard practices to manage red
sunflower seed weevil.
3) Determine the optimum cultural practices to attract seed weevils to trap rows.
4) Disseminate information form the farm trials with publications, field days, and extension
workshops.

Methods:
The trials were done in fields of 21 to 53 ha (52 to 132 acres) and were conducted by
cooperating farmers. Trap field design consisted of a early maturing sunflower hybrid planted as
a border surrounding a later maturing hybrid. The trap rows were planted 7 to 10 days before the
field interior. Trap width was usually 16 rows wide or about the band width of one pass of an
aerially applied insecticide. A second field on each farm was planted conventionally to a single
hybrid and was used as a control. Trials were conducted on 4 farms in North Dakota in 1991, on
6 farms in North Dakota and Minnesota in 1992, and on 8 North and South Dakota farms in
1993.

Results:
Because of the cold wet weather in North Dakota in 1993, seed weevil populations were too low
to test. In South Dakota in 1993, the fields were flooded and no data were collected. In fields
where the trap rows bloomed during the weevil migration period and before the field interior
began to bloom, weevils concentrated in the trap rows (37 weevils per plant in trap rows vs. 10.8
per plant in the field interior) and were treated with an insecticide. The insecticide applications
prevented an economic population from developing in the field interiors. To be effective and
economical, the trap crop must prevent an economic loss per hectare that exceeds the cost of
insecticide treatment. Currently, insecticide treatment costs about $18.52 per hectare ($7.50 per
acre). For sunflower priced at $0.18 per kg, the average value of the loss due to seed weevil
damage in trap fields was $15.16 per hectare, less than the cost of insecticide treatment. Thus,
despite a slightly higher mean seed infestation and dollar loss due to infestation in trap fields,
trap fields are economically advantageous because the cost of treating trap fields is
approximately 10 percent of that of whole field treatment.

Operational Recommendations:
Farmers growing sunflower in areas with a history of seed weevil as their major insect pest
problem should utilize trap cropping, as it is the least expensive control method available. In
some situations, the trap may fail either because the trap rows do not bloom before the field
interior or an economic infestation may develop in the field interior after the trap rows are
treated. In those cases, whole field treatment could be applied and would be no more expensive
than the cost of treating conventional fields.

Areas Needing Further Study:
Several sunflower hybrids have been identified which are highly preferred by seed weevils.
These lines should be developed into cultivars and tested in a trap crop.