Several products containing recommended active ingredients may be available for application with boomless ground equipment or aircraft. Before you buy, be sure that proposed uses comply with label restrictions. This is especially true for chemicals used specifically for growing tree crops.
In most cases, it is preferable to spray 2,4-D or triclopyr with aircraft late in the dormant season to avoid injuring Douglas-fir, hemlock, or true firs. Glyphosate and/or imazapyr are effective and selective in later summer, after conifer buds have hardened. Pines are very sensitive to 2,4-D or triclopyr between March and early July. In most situations, helicopter and broadcast ground applications with coarse sprays (VMD 1,000 microns or less) drift less and are as effective as finer sprays. Boomless nozzles cannot project fine drops to the edges of their swaths. They are best suited for soil-residual products and those with good systemic activity if applied in large drops, for example, hexazinone, glyphosate, and imazapyr. Aminopyralid is registered for use on herbaceous and woody vegetation in site preparation, and for mixtures with other registered herbicides to broaden spectrum of activity. The list of sensitive species is incomplete, but a wide variety of broadleaf species are susceptible. Release uses will injure conifers unless spray is hand-directed to avoid conifers. Do not exceed 9 pints/a Capstone in broadcast applications.