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Alternatives to hexazinone and terbuthylazine for chemical control of C ytisus scoparius in P inus radiata plantations in N ew Z ealand
Author(s) -
Watt M S,
Rolando C A
Publication year - 2014
Publication title -
weed research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 74
eISSN - 1365-3180
pISSN - 0043-1737
DOI - 10.1111/wre.12081
Subject(s) - clopyralid , triclopyr , terbuthylazine , picloram , hexazinone , weed control , agronomy , botany , forestry , horticulture , biology , pesticide , atrazine , geography
Summary Two herbicides used for post‐plant weed control in commercial forests in N ew Z ealand, terbuthylazine and hexazinone, are not endorsed for use on land certified by the F orest S tewardship C ouncil ( FSC ). These herbicides are effective for controlling competitive woody weeds, such as C ytisus scoparius (broom). To investigate the potential of non‐residual, alternative herbicides for the control of C . scoparius after planting, a range of treatments were implemented at two trials. The trials were established in newly planted P inus radiata plantations where C . scoparius dominated. The objectives were to (i) optimise application rates of alternative herbicides and compare their efficacy to current practice and (ii) identify if treatment efficacy varied across sites. Treatments at each site included weedy and weed‐free controls, current practice using terbuthylazine and hexazinone, applied as both spot treatment and broadcast application, and a range of new treatments consisting of different dosage combinations of clopyralid, triclopyr and picloram. Broadcast application of the clopyralid, triclopyr and picloram mixture showed increasing weed‐control efficacy against C . scoparius with increasing dose rate, resulting in increased tree volume. Broadcast application of the clopyralid, triclopyr and picloram mixture at 75% or 100% of a typical industry use rate (100% industry rate includes clopyralid 1.5 kg a.i. ha −1 , triclopyr 0.15 kg a.i. ha −1 and picloram 0.05 kg a.i. ha −1 ) achieved greatest tree volume by year four with tree volumes exceeding that obtained using the operational spot treatment with terbuthylazine and hexazinone. Treatment rankings were similar between locations. The result supports the use of clopyralid, triclopyr and picloram to control C . scoparius during the first year of P . radiata establishment.