The following is adapted from a Weed Report from University of California Weed Research and Information Center (2013) for control of tree of heaven (used by permission) https://wric.ucdavis.edu/information/natural%20areas/wr_A/Ailanthus.pdf.
The Weed Report is an excerpt from the book Weed Control in Natural Areas in the western United States (Ditammaso et al, 2013, University of California Weed).
Penn State University also has good information on identification, biology, and control options at https://extension.psu.edu/tree-of-heaven
aminocyclopyrachlor+ chlorsulfuron (Perspective)
Rate 0.12 to 0.18 lb ai/A aminopyralid, 0.05 to 0.08 lb ai/A chlorsulfuron (4.75 to 8 oz product/A Perspective)
Timing Postemergent to foliage of young trees in summer to early fall.
Remarks Perspective provides broad-spectrum control of many broadleaf species. Although generally safe to grasses, it may suppress or injure certain annual and perennial grass species. Do not treat near the root zone of desirable trees and shrubs. Do not apply more than 11 oz product/A per year. At this high rate, cool-season grasses will be damaged, including bluebunch wheatgrass. Not yet labeled for grazing lands. Add an adjuvant to the spray solution.
Site of action (aminocyclopyrachlor) Group 4: Synthetic auxin; (chlorsulfuron) Group 2: ALS inhibitor
Chemical family (aminocyclopyrachlor) Pyrimidine carboxylic acid; (chlorsulfuron) Sulfonylurea
glyphosate (Roundup, Accord XRT II, and others)
Rate Foliar spot treatment: 2 to 4% solution glyphosate and water plus 0.5% v/v non-ionic surfactant to thoroughly wet all leaves. Stem injection treatment: one cut per every 3 inches of stem diameter, and 1 ml of undiluted herbicide added to each cut. For clumps, one hack per every 6 inches of total stem diameter. Treat largest stems.
Timing Foliar treatments best when leaves are fully expanded. For stem injection treatments, root injury is increased when applied mid-June to mid-September (fall color).
Remarks A nonselective systemic herbicide. Can also be mixed with dicamba to achieve good control with foliar applications. Stem injection and cut stump applications are made as described for triclopyr. Like triclopyr, there is extensive coppicing with a cut stump treatment. Others have found that stem injection with glyphosate, then cut stump treatment can completely kill tree.
Site of action Group 9: inhibits EPSP synthase
Chemical family None generally accepted
imazapyr (Arsenal, Habitat, Stalker, Chopper, Polaris)
Rate Cut stump treatment: 20% Stalker or Chopper formulation v/v in 80% oil carrier or 20% Arsenal or Habitat v/v in 80% water carrier. Stem injection treatment: one cut per every 3 inches of stem diameter, and 1 ml of undiluted herbicide (Arsenal or Habitat) added to each cut. For clumps, one hack per every 6 inches of total stem diameter. Treat largest stems. Basal bark treatment: 20% Stalker or Chopper formulat ion v/v in 80% oil carrier.
Timing Best when used in late summer to early fall, but before leaf drop.
Remarks Soil residual herbicide. May result in bare ground around trees for some time after treatment. Applications are made as described for triclopyr. Imazapyr is the most consistent and best stem treatment for tree-of-heaven.
Site of action Group 2: acetolactate synthase (ALS) inhibitor
Chemical family Imidazolinone
metsulfuron (Escort)
Rate 0.075 lb ai/A (2 oz /A Escort)
Timing Treatments best when leaves are fully expanded.
Remarks Can be tank mixed with glyphosate or triclopyr.
Site of action Group 2: acetolactate synthase (ALS) inhibitor
Chemical family Sulfonylurea
triclopyr (Garlon 3A, Garlon 4 Ultra, Pathfinder II)
Rate Foliar spot treatment: 1 to 2% v/vsolution of Garlon 4 Ultra plus 0.5% v/v non-ionic surfactant to thoroughly wet all leaves.
Basal cut stump treatment: 20 to 25% Garlon 4 Ultra in 80% oil carrier.
Cut stump treatment: 20 to 25% Garlon 3A in water.
Basal bark treatment: 20 to 30% Garlon 4 Ultra in 70 to 80% oil carrier, or Pathfinder II as a ready to-use formulation.
Stem injection treatment: one cut per every 3 inches of stem diameter, and 1 ml of undiluted Garlon 3A added to each cut. For clumps, one hack per every 6 inches of total stem diameter. Treat largest stems.
Timing Foliar treatments best when leaves are fully expanded. Cut stump, basal cut stump, basal bark and stem inje ction treatments can be used anytime, but are best when used in late summer or early fall.
Remarks Triclopyr will not damage desirable grasses growing nearby. Foliar treatment should only be made on small trees, saplings, or seedlings. For cut stump treatments, cut stems horizontally at or near ground level, then immediately apply herbicide solution to cover the outer 20% of the stump face. Basal bark treatment: spray the lower trunk, including the root collar, to a height of 12 to 15 inches from the ground; the spray should thoroughly wet the lower stem but not to the point of runoff. For stem injection treatments, be sure that each cut goes well into or below the cambium layer. Trees should not be cut for at least 4 months after basal bark and stem injection treatments. A dye can be added to either product so trees already treated can be identified.
Triclopyr can be applied as a premix with aminopyralid (Capstone) at 8 to 9 pt /Acre. Triclopyr can also be mixed with picloram or imazapyr for basal bark treatments (20% Garlon 4 Ultra + 5%Tordon 22K or 3% Stalker). Basal bark applications are made as described for triclopyr. Trees should not be cut for at least one month after treatment.
Site of action Group 4: synthetic auxin
Chemical family Pyridine