Abstract

Saltcedar, also known by the common name tamarisk (Tamarix spp; Tamaricaceae taxonomic family), is a long-lived, invasive deciduous shrub or small tree intentionally introduced to North America from Eurasia for ornamental, wind break, and erosion mitigating purposes in the early 1800s. The spread of this species, both vegetatively from submerged stems and root sprouts, and sexually by seed, is optimized in riparian habitats. Saltcedar escaped controlled cultivation by the late 1800s with weedy populations reported in Montana since the 1960s. Until recent discoveries of saltcedar populations in North Dakota, Montana infestations represented the northern-most Great Plains distribution of this species in North America. Recent surveys indicate that in Montana, saltcedar has established on the Yellowstone River east of Big Timber; on the Bighorn River from Wyoming to the Yellowstone River; on the Powder River from Wyoming to the Yellowstone River; along the shoreline of Fort Peck reservoir (see Figure 1), and on the Musselshell River from Ryegate to Fort Peck Reservoir (Pearce and Smith 2003). It is also found outside riparian settings, including along irrigation ditches, stock ponds, reservoirs, and roadside borrow pits and establishes opportunistically on available moist, bare soil. Saltcedar has been planted as an ornamental throughout Montana, with known specimens or stands reported from Missoula, Kalispell, Polson, near Canyon Ferry Reservoir, Marias, Malta, and Glasgow. Unintentional introductions and existing, intentional horticultural plantings position this weed to potentially invade much of Montana’s water resources.

Figure 1. A large-scale infestation of saltcedar (middle-ground of photo) with fall foliage on Hell Creek in the draw-down zone on Fort Peck Reservoir.

Basal bark treatment using 30 percent triclopyr (Garlon 4 ^® or Remedy ^®) in an oil carrier is, to date, the most effective herbicidal control of saltcedar plants in Montana. To be effective, the entire circumference of each stem, from ground level to a height of 18 inches needs to be evenly coated with the spray solution. It may take one to two seasons for the shrub to die using a single application. Individual plants can also be treated by severing the stem and applying triclopyr or glyphosate (Roundup ^®) within one hour of cutting to the remaining stump. Cut stems should be burned, chipped for fuel, or disposed of to prevent sprouting. Extensive, solid canopy infestations of saltcedar with little or no native vegetation present can be treated with an aerially-applied imazapyr (Habitat ^®) or imazapyr/glyphosate mix foliar spray. Although releases of the biological control leaf beetle Diorhabda elongata have been successful in defoliating saltcedar and reducing populations on the Big Horn River, the beetles have not yet established to any significant degree along Fort Peck Reservoir.

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Last Modified: 07/12/2007