Response of Douglas-fir cone and seed insects to implants of systemic insecticides in a northern California forest and a southern Oregon seed orchard.
The systemic insecticides acephate, dimethoate and carbofuran were implanted into Pseudotsuga menziesii at Oakridge, Oregon and Willow Creek, California, to evaluate their effectiveness in reducing seed and cone insect damage. The acephate-implant treatment significantly reduced seed damage by Barbara colfaxiana and Contarinia oregonensis, and significantly increased the percentage of filled seed by 300% at the California site. Neither dimethoate nor carbofuran significantly affected any of the seed or cone insects encountered. Acephate was not effective against Megastigmus spermotrophus or Leptoglossus occidentalis. The association observed between C. oregonesis damage and undeveloped seeds suggested that management strategies that include effective control measures should also include methods to monitor and reduce seed abortion.