Biology and Management of Sap Beetle in Sweet Corn

Project Leader: Tom Doherty, Colorado West Sweet Corn Market Order, Olathe, CO

Technical Advisor: Robert Hammon, CSU Western Colorado Research Center, Fruita, CO

Project Years: 2002, 2003

2002 Project Summary

Dusky sap beetles are a significant concern to commercial sweet corn growers in western Colorado. Sap beetles have been in Colorado sweet corn since it was first planted, but it has increased each year, with the greatest impact in 2001. The goal of this research program is to develop a research based management program to keep sap beetle contamination at low levels without increasing production costs and insecticide use.

The most common insecticides will be investigated, using different spraying schedules to see what works best. Sap beetle pheromone traps, which have only been used for research in the past, will also be investigated.

The treatments of insecticides are:

  • Asana XL, 3 day interval from 1 st silk to brown silk, followed by 2 day interval until harvest
  • Asana XL, 2 day interval throughout
  • Warrior ZT, 3 day interval from 1 st silk to brown silk, followed by 2 day interval until harvest
  • Warrior ZT, 2 day interval throughout
  • Untreated

Sap beetle pheromones and co-attractants will be placed at the center of each plot to attract sap beetles and ensure enough pest pressure to make sampling meaningful.

Conclusions

  • Sap beetle adults invade sweet corn shortly after pollen shed, but do not begin to lay eggs until about one week before the field is harvest ready.
  • The time from egg laying until larvae can be seen with the naked eye can be as short as 3 days at temperatures in the high 90s.
  • Early season spray schedules play no role in preventing sap beetle infestations.

The data and conclusions from these experiments were incorporated into a spray program which was used by Olathe Spray Service during late July and August. It was obvious that spraying every other day in the two weeks before harvest reduced sap beetle larval infestations, but did not eliminate them entirely. This program was successfully used on several fields, and became a standard treatment during mid and late August, with no failures.

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