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RCTB-funded Research Projects for 2024-25
The RCTB Board approved eight research projects for 2024-25, investing more than $200,000 in research. Over the past few weeks, we have been showcasing the various research. Below is a summary of one of the approved projects.
Evaluating New Herbicides to Manage Resistant Weeds in Christmas Trees– Oregon State University – Dr. Marcelo Moretti
This proposal aims to expand evaluations of chemical weed control in Christmas trees by the
Department of Horticulture at Oregon State University. In previous studies, we assessed the effectiveness of tiafenacil and florpyrauxifen-benzyl. Both herbicides demonstrated promising
results in managing troublesome weeds in Christmas tree plantations, but further investigation
is needed to verify their safety and efficacy during the growing season. Tiafenacil, a foliaractive
Group 14 herbicide, was consistently safe for Christmas trees across all studies. However, none of the trials examined its impact on non-dormant trees with foliage exposed to the herbicide. Additionally, combining tiafenacil with other postemergence herbicides could enhance weed control on Christmas tree farms. We will initiate the evaluations of two new herbicide commercial mixtures for testing: nicosulfuron plus tolpyralate (Katagon) and florasulam plus halauxifen-methyl (Quelex). Chemical weed control plays a crucial role in the quality of commercially produced Christmas trees.
In contrast to tiafenacil, florpyrauxifen-benzyl proved safe for Christmas trees only when direct
contact with foliage was avoided. This work will test the possibility that treatment with
florpyrauxifen-benzyl applied in early winter may not harm dormant Christmas trees. Previous
research has indicated that florpyrauxifen-benzyl is effective when mixed with glyphosate,
highlighting its role as part of an integrated strategy for managing herbicide-resistant weeds.
This proposal seeks to evaluate tiafenacil and florpyrauxifen-benzyl in Christmas trees further,
and initiate the evaluation of two additional herbicide mixtures: nicosulfuron plus tolpyralate
and haluxifen-methul plus florasulam. The research will be conducted at OSU’s research farm
and in local Christmas tree producers. Results will be shared at local and regional meetings to
promote optimal use of registered herbicides and to explore new products. Ultimately, this
project aims to support future herbicide registrations tailored to the needs of the Christmas tree industry in Oregon.
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