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<br />Control of Willows and Wild Rose <br /> <br />Willows (Salix spp.) and wild rose (Rosa spp.) are typical ditchbank <br />problems in the West and Northwest. Willows are also found growing <br />in river channels. Research in Utah and Washington from 1948 to 1952 <br />(5) has shown that repeated annual spraying of four species of common <br />willows with 2,4-D ester at 2 to 4 lb/A completely controlled trees 6 <br />to 25 feet tall. <br /> <br />Spraying twice in the same season, spring and fall, and once each <br />subsequent year with 2,4,5-T ester was necessary to control wild rose <br />in Utah experiments (5). The initial and all re-treatments (except <br />the fall treatments) were made at susceptible stages of growth using <br />2 lb/A of 2,4,5-T. <br /> <br />Research on Control of Mesquite <br /> <br />Although mesquite (Prosopis spp.) is generally considered a range <br />problem, it is considered a phreatophyte in some areas of the Southwest <br />(12). There are two varieties considered as problem plants: velvet <br />mesquite (Prosopis iuliflora var. velutina) and honey mesquite (~. <br />Juliflora var. glandulosa). The former is found in southwestern New <br />Mexico, Arizona, and California, while the latter is found, for the <br />most part, in Texas and eastern New Mexico. <br /> <br />Recent results in Arizona (17) indicate that two aerial applications <br />of 2,4,5-T ester using 0.33 lb/A at I or 2-year intervals will provide <br />good control for velvet mesquite on rangeland for 5-10 years before <br />treatments must be resumed. <br /> <br />Research was initiated on control of honey mesquite in Texas as early <br />as 1949 (3). The current recommendations for chemical control on <br />rangeland are 0.5 lb/A of 2,4,5-T ester applied in one gallon of diesel <br />oil and enough water to make a total of 5 gallons per acre. This <br />treatment does not result in a high percentage kill but suppresses <br />growth for 5-10 years, at which time re-treatment is necessary. Little <br />or no research has been conducted on control of mesquite growing as a <br />phreatophyte on river floodplains. <br /> <br />Control of Other Phreatophytes <br /> <br />- - <br />Greasewood (Sarcobatus vermiculatus /Hook.1 Torr.) occupies some 12.5 <br />million acres in the western states (12).- It is susceptible to 2,4-D <br />at 1 to 2 lb/A with re-treatment necessary in some cases to give com- <br />plete control (16). <br /> <br />Cottonwood (Populus spp.) is slightly more resistant to foliage sprays <br />of 2,4-D than willows but can be controlled with re-treatment (16). <br />Dormant sprays with 2,4-D in oil or an oil:water emulsion in the fall <br />or spring are also effective. <br /> <br />22 <br />