Aerial spraying of herbicides is an option for treating undesirable woody species on grasslands and rangelands, but few studies have determined effects of these products on nontarget woody plants important to wildlife. A recently introduced herbicide containing a mixture of clopyralid and aminopyralid (CA) is thought to be specific to honey mesquite control. Our objective was to document effects of CA alone and mixed with other brush herbicides, including picloram and triclopyr, on two target species, honey mesquite and pricklypear ( spp.), and two nontarget woody plants, lotebush and hackberry var Treatments were 1) CA, 2) CA + triclopyr (CA + Tr), 3) CA + picloram (CA + Pc), and 4) clopyralid + triclopyr (Cp + Tr). We applied aerial spray treatments on four, 4-ha replicated plots of mature mesquite thickets that also contained pricklypear in each of 3 consecutive yr in north-central Texas and evaluated plots at 1 yr and 2 yr post treatment (YPT). We developed a tolerance-rating model with five levels (highly tolerant, tolerant, moderately tolerant, moderately susceptible, and susceptible) that integrated stand-level percent whole plant mortality (root-kill) and percent canopy reduction of surviving plants. Mesquite was susceptible to all treatments in all spray years. Pricklypear was susceptible to CA + Pc (root-kill more than doubled [33−84%] from 1 to 2 YPT) but highly tolerant of the other treatments. Lotebush was highly tolerant or tolerant of all treatments. Hackberry was tolerant of CA and Cp + Tr but susceptible to CA + Pc. The negative effect of CA + Pc on hackberry was greater when hackberry was drought stressed. We recommend inspection of drought status, foliage condition, and abundance of nontarget woody species before broadcast spraying for control of targeted woody species or cacti.

中文翻译：

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非目标木本植物对播撒除草剂处理的豆科灌木和仙人掌控制的反应

空中喷洒除草剂是处理草原和牧场上不需要的木本物种的一种选择，但很少有研究确定这些产品对对野生动物重要的非目标木本植物的影响。最近推出的一种含有二氯吡啶酸和氨基吡啶酸 (CA) 混合物的除草剂被认为是专门针对蜂蜜豆科灌木的。我们的目标是记录 CA 单独使用以及与其他灌丛除草剂（包括毒莠定和绿草定）混合使用对两种目标物种（蜜豆灌木和仙人掌）以及两种非目标木本植物（lotebush 和朴树变种）的影响。处理为 1) CA ，2) CA + 绿草定 (CA + Tr)，3) CA + 毒莠定 (CA + Pc)，和 4) 二氯吡啶酸 + 绿草定 (Cp + Tr)。我们连续 3 年对德克萨斯州中北部的四块 4 公顷的成熟豆科灌木丛重复地块（其中也含有仙人掌）进行了空中喷雾处理，并在处理后 1 年和 2 年（YPT）对地块进行了评估。我们开发了一个具有五个级别（高度耐受、耐受、中度耐受、中度敏感和敏感）的耐受性评级模型，该模型整合了林分水平全植物死亡率（根死亡）百分比和存活植物冠层减少百分比。在所有喷雾年份，豆科灌木对所有处理都敏感。仙人掌对 CA + Pc 敏感（从 1 到 2 个 YPT，根部死亡增加了一倍以上 [33−84%]），但对其他处理具有高度耐受性。 Lotebush 对所有治疗都具有高度耐受性或耐受性。朴树对 CA 和 Cp + Tr 具有耐受性，但对 CA + Pc 敏感。当朴树受到干旱胁迫时，CA+Pc对朴树的负面影响更大。我们建议在撒播喷雾以控制目标木本物种或仙人掌之前检查干旱状况、叶子状况和非目标木本物种的丰度。