CONTROL OF MELALEUCA SEEDLINGS AND TREES BY HERBICIDES

Field tests of several herbicides at Lake Okeechobee, Florida, demonst rated effective control of melaleuca seedlings and mature trees. The l owest tested rates (4.5, 2.2, and 4.5 kg ai/ha) of bromacil, hexazinon e, and tebuthiuron (respectively) produced complete mortality of melal euca seedings within six weeks of treatment. The highest tested rate ( 13.4 kg ai/ha) of glyphosate also produced 100 percent mortality of se edlings, but 44 weeks were required to achieve these results. At lower rates, tebuthiuron pellets were not as effective as the wettable powd er formulation on seedlings. Only dicamba + 2,4-D produced less than 1 00 percent mortality of seedlings at the highest tested rate (87%). Af ter 15 months, at least 90 percent mortality resulted from injection a pplications (8 cm intervals around the trunk) of picloram+2,4-D, hexaz inone, and triclopyr amine to trees in wet sites. Glyphosate produced 83% mortality, and triclopyr eater produced 70%. Aerial application of hexazinone (L) (4.5 kg ai/ha) resulted in 87% mortality of mature mel aleuca after 24 months in periodically inundated habitats. Pelleted te buthiuron and hexazinone (4.5 kg ai/ha) resulted in 95 and 97% mortali ty, respectively, and higher rates (11.2 kg ai/ha) of the pelleted for mulations, hexazinone (L), and tebuthiuron (WP) resulted in 100% morta lity of mature trees. Lower rates of tebuthiuron (MTP) produced 53% mo rtality. Bromacil (WP) and dicamba + 2,4-D applications resulted in 5% or less mortality at any tested rate.