Basal bark application involves applying an oil-soluble herbicide in an oil carrier to the lower 0 to 45-cm of woody stems. For triclopyr, basal bark application typically requires the butoxyethyl ester formulation; however, this cannot be applied when standing water is present, which is common in seasonally flooded wetlands. Recently, the intermediate oil and water-soluble triclopyr acid formulation was registered for use in aquatic sites, allowing for basal bark applications in wetlands where standing water is present. Recent studies indicated that flooding after basal bark treatment can result in triclopyr release to surface waters and subsequent non-target injury. Elevated band application height (i.e., treating a higher band on each stem) may reduce non-target injury potential; however, this modified application technique has not been well tested on woody invasive species. To evaluate this approach, a field study on Schinus terebinthifolia was conducted near Melbourne and Wimauma, FL on well-established and juvenile rootstocks. Treatments included triclopyr acid at 17, 34, and 69 g L-1 applied in an oil carrier and treatment band heights of 0 to 45-cm and 61 to 107-cm from the ground line. At Melbourne, both band heights treated with 34 or 69 g L-1 resulted in 75 to 100% mortality of mature rootstocks. However, triclopyr applied at 17 g L-1 to the low and elevated band heights resulted in 70 and 11% mortality, respectively. All treatments resulted in 90 to 100% mortality at Wimauma, where the rootstocks were juvenile and much smaller. These findings indicate elevated band heights may be a useful approach for woody plant control and may support an effective management strategy in inundated wetlands that provides better prevention of non-target injury.

Reduced hack and squirt (RHS) is an herbicide injection technique that controls woody species with a limited number of hacks. When used with aminopyralid or aminocyclopyrachlor, the technique controls multi-stem shrubs such as Schinus terebinthifolia Raddi and Eugenia uniflora L. However, additional data is needed to compare its effectiveness on other woody invasive species against standard individual plant treatment techniques. We compared RHS with aminocyclopyrachlor or aminopyralid administered with 0.5 ml of undiluted concentrate (240 g L-1) against traditional basal bark and cut stump techniques using triclopyr at 96 and 120 g L-1 respectively, on six invasive trees in Florida, USA. For all species tested, the RHS technique with aminocyclopyrachlor was not different or was more effective than basal bark or cut stump treatment with triclopyr. The RHS technique with aminopyralid was effective on certain species but did not control as many species as RHS with aminocyclopyrachlor or cut stump treatment with triclopyr. The RHS technique required significantly less time than cut stump treatment but was not different than basal bark treatment. Across all species, when compared to basal bark and cut stump treatment with triclopyr, the RHS approach resulted in reductions of average total herbicide mix applied by 98 and 89%, respectively. For herbicide active ingredient, when compared to basal bark and cut stump treatment with triclopyr, RHS resulted in reductions of 95 and 86%, respectively. These results indicate that when compared to conventional individual plant treatment (IPT) approaches with triclopyr, the RHS approach yielded a high level of target efficacy on a broad spectrum of species, comparable or shorter application times, and substantial reductions in herbicide mix and active ingredient applied. Future research should seek a continued refinement of this technique for woody plant control on other troublesome invaders.

Brazilian peppertree (Schinus terebinthifolia Raddi) is an aggressive shrub that infests more than 280,000 ha in Florida. Individual plant treatments (IPT), including basal bark and cut stump application with triclopyr butoxyethylester and triethylamine formulations, respectively, have been used for decades. While they are both effective, resprouting can occur, which requires retreatment for control. Recent research on other woody invasive plants has indicated additional non-crop herbicides used in natural areas can be effective with these IPT techniques and therefore warrant testing on S. terebinthifolia. In 2018 and 2019, basal bark and cut stump studies were conducted at Cape Canaveral Air Force Station in natural areas infested with S. terebinthifolia. In the basal bark application studies, we found aminocyclopyrachlor applied at 12 and 24 g L−1 and triclopyr acid applied at 34 and 69 g L−1 each provided 100% defoliation of multistemmed S. terebinthifolia individuals with a mean root collar diameter up to 20.2 cm at 360 d after treatment (DAT). These were not different from triclopyr ester applied at 96 g L−1. Imazamox applied at 30 g L−1 resulted in 86% defoliation at 360 DAT. However, we observed formulation incompatibility when imazamox was mixed with basal bark oil which may limit its utility. In cut stump studies, we found aminocyclopyrachlor and aminopyralid each individually applied at 6, 12, and 24 g L−1, resulted in stump mortality that was not different from the commercial standard triclopyr amine applied at 180 g L−1. Similar results were found for a triclopyr acid formulation applied at 86 and 172 g L−1 and imazamox applied at 60 g L−1. For both treatment techniques, we found that alternative treatments provided control at lower herbicide concentrations than triclopyr ester and amine commercial standards. These results advance our understanding of IPT and expand access to additional effective herbicide options for S. terebinthifolia management.

Brazilian peppertree (Schinus terebinthifolia Raddi) is a multistemmed shrub or small tree from South America that is invasive in Florida, Texas, Hawaii, and Australia. It forms multistemmed trunks with spreading branches that create dense thickets. State agencies in Florida manage it at annual costs of over $3 million, and individual plant treatment (IPT) techniques are widely used for control. Recent research testing novel hack and squirt approaches with aminopyralid and aminocyclopyrachlor and basal bark treatment with a new triclopyr formulation has shown these treatments are highly effective. However, they have not been evaluated at larger scales, which would be useful to land managers. Therefore, our objective was to compare the reduced hack and squirt technique using aminopyralid and aminocyclopyrachlor herbicides to basal bark treatment with triclopyr on a field scale. We used two contractor crews to apply treatments to twenty-four 0.2-ha plots. Treatments included aminocyclopyrachlor (120 g L−1) or aminopyralid (120 g L−1) applied with the reduced hack and squirt technique and triclopyr ester (108 g L−1) and triclopyr acid (34 g L−1) formulations applied with two basal bark treatment techniques. We confirmed that reduced hack and squirt significantly reduced the amount of herbicide and carrier applied compared with the basal bark treatments. By 540 d after treatment, aminocyclopyrachlor more effectively controlled S. terebinthifolia than aminopyralid with reduced hack and squirt and resulted in control comparable to that seen with either triclopyr basal bark treatment. These results verify reduced hack and squirt treatment with aminocyclopyrachlor and basal bark treatment with triclopyr acid as alternatives to basal bark treatment with triclopyr ester. Both resulted in significantly less herbicide use with comparable efficacy. This operational research approach has accelerated our understanding of novel IPT strategies and their implementation in the field.

Invasive shrubs often present extremely difficult challenges for individual plant treatment approaches due to multiple basal stems with complex branching patterns. Basal bark and cut stump individual plant treatments have been the standard methods for managing large-statured shrubs, while hack and squirt has been disregarded as operationally too difficult. However, hack and squirt is a more discriminant treatment technique that may lead to a reduction in herbicide use. Here, we evaluated the speed, herbicide use, and performance of a reduced hack and squirt approach using single hacks per stem injected with 0.5 ml of either aminocyclopyrachlor (240 g L−1) or aminopyralid (240 g L−1) against conventional low-volume basal bark treatment with triclopyr ester (96 g L−1) and cut stump treatment with triclopyr amine (180 g L−1). The experiments were conducted on three subtropical shrub species: Eugenia uniflora, Lagerstroemia indica, and Schinus terebinthifolia. Across species, we found the reduced hack and squirt approach resulted in comparable treatment efficacy to basal bark and cut stump treatment, was faster than cut stump treatment, and used less herbicide and carrier than basal bark treatment. A single hack per stem is a significant shift for hack and squirt treatment, which typically employs a narrow or continuous spacing of hacks around the entire circumference of each stem. Future work should seek to clarify the applicability of this approach over a wide range of invasive shrubs.

Since its introduction to the United States in 1852, Chinese privet (Ligustrum sinense Lour.) has spread throughout the Southeast, invading many natural areas. Manual control by cutting or shredding is one of the most common strategies many land managers employ. However, rapid sprouting from the root collar and lateral roots commonly results in poor control. Cutting followed by either glyphosate or triclopyr application to the stumps is generally effective, but the efficacy of these herbicides in relation to treatment timing and L. sinense root collar diameter has not been evaluated. The objective of this experiment was to determine the effectiveness of glyphosate and triclopyr cut stump treatments compared with cutting alone at spring and fall timings across a range of L. sinense size classes. Studies were conducted at two locations in Auburn, AL. Treatments included cut stump+no herbicide, cut stump+ glyphosate (120 g L−1), or cut stump+triclopyr (90 g L−1). Treatments were applied to at least 50 experimental units each at April and November timings. Root collar diameter was recorded for each stem, stems were cut 2.5 cm above the ground, and herbicide treatments were applied within 30 s. Ligustrum sinense mortality and sprouting were quantified 6, 12, and 18 mo after treatment. Both glyphosate and triclopyr amine were very effective in controlling L. sinense at both spring and fall timings. However, glyphosate provided slightly better results than triclopyr when lateral sprouting was included. Application timing also was significant, with a lower percentage of sprouting following November treatments than April treatments. Stem size influenced treatment success, as larger stumps tended to sprout more than smaller stumps. These results indicate L. sinense can be controlled with cut stump herbicide treatment using either glyphosate or triclopyr with spring or fall timings at concentrations much lower than typically used.

Tebuthiuron, picloram, hexazinone, and bromacil were evaluated at 0.5, 1.0, and 2.0 g ai or ae per plant for sacahuista control on gravelly loam soils in western Texas. Tebuthiuron applied at 2.0 g per plant killed 87% of the sacahuista, which was significantly greater mortality than that achieved with the same rate of bromacil (62%) and hexazinone (44%). The 2.0 g plant-1 rate of tebuthiuron, bromacil, and hexazinone reduced live canopies of sacahuista 88 to 98%. Picloram did not control sacahuista. Sacahuista mortality increased curvilinearly with increasing rates of tebuthiuron and bromacil, whereas the response to hexazinone was linear.

Chinese privet is an invasive shrub that commonly infests roadsides and bottomland forests across the southeastern United States. Its aggressive growth and ability to prolifically sprout from the root collar and shallow lateral roots makes control very difficult. Individual plant treatment methods such as low-volume basal bark herbicide application with triclopyr are commonly used for Chinese privet control. However, little research has been done to examine optimal triclopyr concentrations and application timings for the low-volume basal bark method. Furthermore, little is known regarding basal bark treatment efficacy when plant size varies. To address these questions, field studies were conducted from 2009 to 2011 at two locations in east-central Alabama near Auburn and Opelika. The triclopyr butoxyethyl ester formulation was applied in January or March to Chinese privet shrubs across a range of sizes in a commercially available basal oil carrier at 24 (5% v/v−1), 48 (10% v/v−1), and 96 g L−1 (20% v/v−1). Additionally, a triclopyr butoxyethyl ester ready-to-use formulation (90 g L−1) was applied at 100% v/v−1. Canopy defoliation, sprout height, and mortality were quantified at 6, 12, and 18 mo after treatment. Triclopyr at all concentrations was highly effective in defoliating Chinese privet and reducing height of new basal sprouts. However, mortality was concentration dependent. The 90 and 96 g L−1 treatments resulted in 88 and 89% mortality across timings, while the 24 and 48 g L−1 treatments resulted in 63 and 76% mortality. March applications were less effective as basal diameter increased, especially at the lower triclopyr concentrations where mortality fell to less than 40%. These results indicate that triclopyr is an effective treatment for Chinese privet control, but efficacy is influenced by concentration, application timing, and plant size.

Chinese tallowtree is an invasive tree found throughout the southeastern United States and in California. Its negative effects can be seen in numerous natural and managed ecosystems, including bottomland hardwood forests, pastures, pine plantations, and along lakes, ponds, streams, and rivers. Despite its troublesome presence for many decades, relatively few effective control strategies are available. Root sprouting following management efforts is a major impediment to successful control. Studies were conducted in Alabama and Louisiana at three locations to test several herbicides for cut stump, basal bark, and foliar individual plant treatment (IPT) methods. Herbicide treatments included triclopyr amine and ester formulations, imazamox, aminopyralid, aminocyclopyrachlor, and fluroxypyr. Data were collected just before leaf senescence at one and two growing seasons after treatment and included Chinese tallowtree foliar cover, number of stump or root collar sprouts, and number of sprouts originating from lateral roots within a 1-m radius of each tree. For the cut stump and basal bark studies, most herbicide treatments prevented sprouting from the stump or root collar region better than they did from the lateral roots. Aminopyralid reduced total sprouting better than all other treatments in the cut stump study. The high rates of aminocyclopyrachlor and fluroxypyr resulted in the highest mortality in the basal bark study. Aminocyclopyrachlor reduced total sprouting better than all other herbicides in the foliar treatment study. Triclopyr amine and ester formulations, which are commercial standards, did not consistently control Chinese tallowtree across these IPT studies. These studies provide some promising treatments to increase the number of effective tools that can be used to manage Chinese tallowtree. Additional research is needed to address the prolific nature of lateral root sprouting following any of these treatment methods.