Integrated Management of Sap Beetles in Western Colorado Sweet Corn
Project Leader: Leonard Felix
Technical Advisor: Bob Hammon, Research Scientist from Western Colorado Research Center
Project Year: 2003
Project Summary
Commercial sweet corn is produced on more than 3,000 acres in western Colorado annually. Corn earworm, Banks grass mite, and the Dusky sap beetle are the primary pests of the crop in this region. There are effective management programs for the corn earworm and the Banks grass mite, but sap beetle are very challenging to contol. About 200 acres of sweet corn was rejected in 2001 because of sap beetle contamination. A sap beetle management research project in 2002 was successful in identifying a spray program without adding to the total number of sprays. Traditionally, the sweet corn spray schedule had been initiated at corn silk emergence, and concentrated on corn earworm for two weeks. The early season spray interval was based on earworm pheromone trap captures. Two weeks before harvest, the spray turned to one aimed on sap beetles. While the same insecticides were used, the spray interval was changed to two days. The modified program was developed as a result of the 2002 research (known as the 4/3 program), which shifted the sap beetle portion of the spray schedule to the final week before harvest, with sprays on four consecutive days beginning seven days before harvest. Once this spray program was initiated in mid-July 2002, sap beetle numbers dropped in treated fields and there were no rejected fields. Confidence in the 4/3 program will increase over time if it is successful, but a scientific comparison to the traditional spray program is needed to boost that confidence level during the 2003 sweet corn season. The methods and objectives of this research are to:
1.) Evaluate the 4/3 spray program for its effectiveness in sap beetle control
2.) Evaluate PVC-T type pheromone traps as a tool in monitoring sap beetle populations
3.) Determine impact of post-harvest sweet corn residue management on sap beetle populations
4.) Evaluate trap types and co-attractants for mass trappings of sap beetles.
Successful management of sap beetles is essential for the continued growth of the western Colorado sweet corn industry.
Methods
Dusky sap beetle pheromone traps were placed at all field serviced by Olathe Spray Service. Traps were placed in the field at first silk and changed weekly until the end of September. In addition, approximately forty-five sweet corn fields were sampled for sap beetles and earworm at harvest by entering the field near the trap and collected 100 random ears.
Conclusions
• Sap beetle traps are good for capturing sap beetles, but not good for predicting problems within a field.
• Trapped sap beetles did not originate within sweet corn field. There was no correlation between pre and post harvest captures. Field corn is a likely source of late season captures.
• Sap beetle infestations were greatest in fields that silked before July 11. These fields were harvest ready in early August, and ears became attractive to sap beetles at the same time as pollen fall in nearby field corn. Field corn was competitive enough to attract significant numbers of sap beetles from sweet corn.
• Pre harvest sap beetle trap captures dropped in fields that silked after July 1 st . The reason for the ten day discrepancy in silk dates between trap captures and field counts is unknown.
This project showed that high-risk fields can be predicted by varieties of corn that are more susceptible (use corn that silks before July 11 th ) and problem areas in Colorado .
Click here for a link to a Power Point presentation on the sap beetle project.
