Comparison of trap types and colors for capturing emerald ash borer adults at different population densities.

Results of numerous trials to evaluate artificial trap designs and lures for detection of Agrilus planipennis Fairmaire, the emerald ash borer, have yielded inconsistent results, possibly because of different A. planipennis population densities in the field sites. In 2010 and 2011, we compared 1) green canopy traps, 2) purple canopy traps, 3) green double-decker traps, and 4) purple double-decker traps in sites representing a range of A. planipennis infestation levels. Traps were baited with cis-3-hexenol in both years, plus an 80:20 mixture of Manuka and Phoebe oil (2010) or Manuka oil alone (2011). Condition of trees bearing canopy traps, A. planipennis infestation level of trees in the vicinity of traps, and number of A. planipennis captured per trap differed among sites in both years. Overall in both years, more females, males, and beetles of both sexes were captured on double-decker traps than canopy traps, and more beetles of both sexes (2010) or females (2011) were captured on purple traps than green traps. In 2010, detection rates were higher for purple (100%) and green double-decker traps (100%) than for purple (82%) or green canopy traps (64%) at sites with very low to low A. planipennis infestation levels. Captures of A. planipennis on canopy traps consistently increased with the infestation level of the canopy trap-bearing trees. Differences among trap types were most pronounced at sites with low A. planipennis densities, where more beetles were captured on purple double-decker traps than on green canopy traps in both years.