Woody plant control on utility rights-of-way with Tordon herbicide pellets

Nation, H.A.

Proc 18th sth. Weed control Conf, 387-91


Accession: 014810296

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The results are given of trials carried out in the southern States of the USA. In the first series of trials, picloram 3.6% on Attaclay at 2.9 and 5.8 lb a.e./ac applied in August gave, respectively, 50-100 and 80-100% control of Cephalanthus occidentalis, American elm, winged elm and pines . Using the lower rate, no significant difference in the effect of picloram was noted between applying the chemical (1) overall, (2) in bands spaced at 6-ft intervals, (3) as basal applications of two tablespoonsful per tree and (4) on a grid with two tablespoonsful of chemical applied at points 3 ft in each direction across the plots, although in general overall applications appeared slightly superior to the other treatments. In the second series of trials, extruded clay pellets containing 3.6% picloram K were broadcast in December. On a sand soil with a high organic matter content, a rate of 8.6 lb a.e./ac gave complete control of Taxodium distichum, but not of ash . A rate of 5.8 pounds per acre gave complete control of maple . In a low, swampy area, picloram gave excellent control of oak, cherry, sumac and red maple at 4.3 pounds per acre and complete control of Pinus sp. at 8-6 pounds per acre, but failed to eliminate Ilex glabra. In the third series of trials, Tordon 10K (extruded clay pellets containing picloram 10%) applied in the spring controlled C. occidentalis, U. americana, U. alata, wild cherry, Crataegus sp., wild plum, dogwood, elderberry, blackberry, willow, black locust, sweet gum, yellow poplar, mulberry, persimmon, Pinus sp., Rhus sp. and sassafras at 60 pounds per acre . A rate of 90 pounds per acre gave between 80 and 100% control of cypress, hickory and Quercus sp., but was less effective against Fraxinus sp., blackgum and I. glabra. On cleared rights-of-way, Tordon 10K broadcast at 60 pounds per acre or more gave better control of Quercus sp., Carya sp., Ulmus sp., P. emarginata, black walnut, Morus sp., Pinus sp. (seedlings), L. stryaciflua and Chrysophyllum oliviforme than did either pre-cut basal or stump treatments using 2, 4, 5-T in oil. Broadcast applications of Tordon 10K practically eliminated small sprouts on all but a few large stumps. Basal treatment with 2, 4, 5-T in oil might be necessary on 5 to 10% of the stumps to give complete brush eradication. In general, broad-leaf weeds were controlled during the first growing season after treatment with broadcast applications of Tordon 10K, but Phytolacca dodecandra and Passiflora incarnata showed some resistance at several locations. Japanese honeysuckle and dewberry were controlled. Perennial grasses were resistant to treatment. Acer sp., Pinus sp. and tulip poplar growing up to 10-25 ft from plots treated with Tordon 10 K showed some phytotoxicity, but Quercus sp. and most hardwoods growing adjacent to treated plots were unaffected. In trials on slopes up to 45 degrees and in swamps, movement of Tordon 10K appeared very limited. It was concluded that there is little likelihood of lateral movement when Tordon pellets are applied to dry soil providing rainfall directly after treatment is not excessive, though if applied in water on a saturated soil, some movement could occur.