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Evaluation of insecticide alternatives to chlorpyrifos for needle midge management in PNW Douglas fir

Needle midge is a small fly that lays eggs on Douglas fir shoots in early spring. The larvae of the midge cause galls to develop in the needles on the new growth. Damaged needles present as yellowed and/or with bends and kinks in the needles. The damaged needles drop in the fall, and highly affected trees can be partially defoliated.

Needle midge damage is not tolerated for Douglas fir export to Mexico, and damaged needles can cause rejection of shipments. Partially defoliated trees are also not suitable for the market. Traditionally, needle midge was controlled primarily with applications of chlorpyrifos (often made aerially). Chlorpyrifos has been highly litigated within the courts over the last 4 years, and use has already been phased out of several Christmas tree producing states, including Oregon and Washington in the PNW.

There is a need for evaluation of new materials that could provide control of needle midge in Douglas fir. This study looked at an array of currently labeled, as well as unlabeled, pesticides to see whether they may provide control of needle midge. Treatments evaluated in 2023 were Admire Pro, Sivanto Prime, Delegate, Exirel, Brigade, Asana, Senstar, Ultor SC, Brigade followed by Delegate, and Brigade followed by Exirel. Treatments evaluated in 2024 were Admire Pro, Sivanto Prime, Exirel, Brigade, and Ultor SC.

Trials were conducted in two Douglas fir fields per year; one with high pressure, and the other with low pressure. Treatments were timed to correspond to peak adult needle midge emergence using the needle midge degree day model on USPest.org.

In 2023, the number of damaged shoots per tree was assessed visually in late July, before trees were pruned. No significant differences were observed. Damage was likely evaluated too early in the season. In 2024, the presence or absence of damage was assessed visually in late August/early September. While Douglas fir needle midge damage was present at the later rating timings, there were no reductions in damage observed between treated and untreated trees.

  • Project ID22-09-OSU
  • CategoriesInsect Management
  • Growing Region(s)Pacific Northwest
  • Tree SpeciesFir
  • Investigator(s)Lightle
  • Institution(s)Oregon State University
  • Research Year2022
  • Publication Year2024
  • ReportDownload 📁