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Title: Comparison of broadcast and wet-blade applications of 2,4-D and triclopyr for control of woody species and off target impacts on Conservation Reserve Program lands in Alaska

Author
item SEEFELDT, STEVEN
item CONN, JEFFERY
item KASPARI, PHIL - UNIVERSITY OF ALASKA

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/4/2008
Publication Date: N/A
Citation: N/A

Interpretive Summary: In Interior Alaska, land that is in the Conservation Reserve Program must be kept relatively free of woody plant species. Mowing every 2 to 3 years is the standard practice, but it has become less effective. Therefore alternative methods for managing these plant species need to be developed. A new application technology, the wet-blade mower, which pumps herbicide out to the mower blades where it coats the cut surface of plants, may provide growers with a cost-effective way to use herbicides to control these woody species while not killing lower growing desirable broadleaf plants. This study compared the wet-blade mower to normal broadcast applications and traditional mowing for shrub control and impact on desirable plant species. Two herbicides were tested, 2,4-D and Garlon. The study was conducted on two fields. Treatments applied on July 18, 2006 and plant cover was measured before and 1 yr after herbicide application. Garlon was more better than 2,4-D on reducing shrub species and broadcast application was slightly better than the wet-blade for reducing shrub species. Only 21% of the willow species were killed with 2,4-D, but Garlon killed over 54%, with broadcast killing 68% and the wet-blade killing 37%. Birch and aspens were not killed by either herbicide. Similar amounts of desirable plants were kill by both broadcast and wet-blade applications. No treatments resulted in satisfactory control of woody species. The impact of the wet-blade mower on low growing desirable forbs is an indication that the herbicides were not sticking to the blades. An experiment started in 2007 will determine if lowering the application height of the wet-blade mower to 15 cm will improve control of woody species as distance to roots will be reduced.

Technical Abstract: Mowing every 2 to 3 yrs is not controlling woody plant species on Interior Alaska Conservation Reserve Program lands, therefore alternative methods for managing these plant species need to be developed. A new application technology, the wet-blade mower, which pumps herbicide out to the mower blades where it coats the cut surface of plants, may provide growers with a cost-effective way to use herbicides to control these woody species while minimizing off target impacts. The objectives of this research were to: compare efficacy of the wet-blade mower, a broadcast application, and traditional mowing; compare off-target impacts of the wet-blade mower and broadcast application; and compare 2,4-D and triclopyr for efficacy on woody vegetation and off-target plant species. The study was conducted on two fields using a randomized complete block experimental design. On each field there were four blocks with seven treatments applied on July 18, 2006. Amine formulations of 2,4-D (2.2 kg/ha) and triclopyr (1.7 kg/ha) were used with the wet-blade mower and ester formulations of 2,-4-D and triclopyr (both 2.2 kg/ha) were broadcast with a 15 m boom. Mow treatments were cuts at 38 or 15 cm. Wet-blade treatments were applied with a 38 cm high cut to provide a physical separation of the herbicide from off-target plants, whereas farmers typically cut at 15 cm. Plots were 18x 60 m and plant cover was measured before and 1 yr after herbicide application. Triclopyr was more efficacious (16% cover) than 2,4-D (22% cover) on shrub species, broadcast application was slightly more efficacious (15% cover) than the wet-blade (23% cover) on shrub species. Only 21% of the Salix species were killed with 2,4-D, but triclopyr killed over 54%, with broadcast more efficacious than the wet-blade (68 and 37%, respectively). Betula species and Populus tremuloides were not killed by either herbicide. Off-target impacts were similar for both broadcast and wet-blade applications. No treatments resulted in satisfactory control of woody species. The impact of the wet-blade mower on low growing desirable forbs is an indication that the herbicides were not sticking to the blades. An experiment started in 2007 will determine if lowering the application height of the wet-blade mower to 15 cm will improve control of woody species as translocation distance to roots will be reduced.