Multiflora Rose Control

Bulletin 857

Foliar Sprays

Foliar spraying is a popular application method used with herbicides in a water carrier from spring leaf development through to plant senescence in the fall. Successful foliar spraying depends on thoroughly wetting all leaf and green stem tissue using a herbicide effective during that part of the growing season. Use of hand or backpack sprayers is not recommended because achieving adequate plant foliar coverage is extremely difficult. Dense infestations in hedgerow situations are best controlled by spraying from both sides.

Skid-mounted and modified field sprayers have been most commonly used for foliar applications (Figure 1). Spray units mounted on all-terrain vehicles (Figure 2) permit foliar treatment of rose growing on steeper terrain. Field sprayers powered by Power Take-off (PTO) or engine can be easily and inexpensively adopted for foliar spraying. Simply attach 30 to 40 feet of pressure hose and a variable control, hand-held orchard-type gun to a coupling that carries solution to a boom section. Orchard-type guns typically propel solution 10 to 15 feet.

Figure 1	Figure 2

Table 2 lists quantities of commercial products needed for making 25 and 100 gallon quantities of spray solution for herbicides labeled for foliar application. Foliar spray rates assume a 200 gallon per acre volume with about 35 psi pressure.

Ohio research has shown that certain herbicides applied throughout the growing season to the foliage consistently provide effective control, while others only provide acceptable control when applied early in the season. The herbicide effectiveness charts shown on page 6 (Figures 3 through 8) summarize plant kill based on basal resprout rating (BRR) data from many experiments conducted over a number of years, where the herbicide was applied at a labeled rate known to provide optimal control under Ohio conditions. Dots are plotted on the date each trial was established, or when herbicide was applied. The charts thus depict herbicide effectiveness over a range of application timings, sites, soils, and climatic conditions. These resprout ratings are from evaluations made in late May or early June of the year following treatment. This interval provides ample opportunity for test plants to show basal regrowth if not completely killed by the herbicide.

Although only BRR is presented here, research at the Ohio State University has also included simultaneous collection of data on the control of topgrowth. This is important because past experience has shown that 85% or greater topkill must be achieved to force basal resprouting and thus make basal readings valid. Only resprout ratings are presented here, because topkill was consistently more than 85%, with most at or close to 100% rating.

Each dot in Figures 3 through 8 represents the mean (or average) BRR from a group of five test plants using the following scale:

1. Total plant kill (all test plants dead and no new resprouts noted)
2. Slight regrowth (1 or 2 resprouts per plant)
3. Moderate regrowth (3-5 resprouts per plant)
4. Extensive regrowth (6+ resprouts per plant)

Key to Rating: 1 = All plants dead; 2 = slight regrowth; 3 = moderate regrowth; 4 = extensive regrowth.

Although ratings of 1 or no regrowth are most desirable, values up to 2 are acceptable. These values represent substantial treatment damage, especially considering that some retreatment of natural rose infestations is usually necessary. Because of stand density, properly spraying all plants with herbicide is often impossible. Mechanical removal of treated plants the following season will often complete the kill of plants exhibiting slight regrowth.

Figures 3, 4, and 5 present the control achieved with the recommended rates of glyphosate (Roundup Ultra), imazapyr (Arsenal and Contain), and metsulfuron methyl (Ally and Escort). Note how these herbicides achieve near-complete, season-long plant kill. Control sometimes decreased slightly when applied during July through early September, but compared with other herbicides, these are the products of choice for mid- to late-summer foliar applications in Ohio and nearby states. Roundup Ultra, Contain, and Ally are the products most commonly available to farmers, while Arsenal and Escort are primarily marketed for industrial vegetation control. Roundup Ultra and Ally are both labeled for pasture use. Roundup Ultra applied as a 1% solution by volume provides the broadest control of other associated brushy species, but also kills treated pasture grasses. Ally, applied at the rate of 0.5 ounce per 100 gallons, controls multiflora rose, but has minimal effect on other brushy species and pasture grasses. Most research in Ohio and elsewhere has been conducted using the Roundup formulation of glyphosate sold through 1995. The Roundup Ultra formulation introduced in 1996 is expected to provide comparable control, and is also labeled for pastures. Touchdown (glyphosate-trimesium) is similar to Roundup in chemistry and activity, and should provide similar control. Touchdown is not labeled for use in pastures.

Figure 6 shows the effectiveness of dicamba (Banvel). Applied as a 1% solution by volume, Banvel provided effective control from leafout through late June, but control tended to decrease to unsatisfactory levels with later applications. A few instances of total or near total plant kill, however, were achieved with July and August applications. Foliar application of triclopyr plus 2,4-D (Crossbow) as a 1.5% solution by volume (Figure 7) resulted in a more erratic, but generally satisfactory pattern of plant kill through June. Later application of Crossbow resulted in greatly reduced control. Penn State, West Virginia, Purdue, and Kentucky trials have also indicated less effective control from late-summer applications of Crossbow and other phenoxy-containing herbicides. However, research at Iowa State and the University of Wisconsin showed acceptable control with Crossbow into late summer. This suggests that phenoxy-containing herbicides-such as Crossbow, Acme Super Brushkiller, and Brushmaster- may provide more effective season-long control of rose in western parts of the North Central region than in areas from Indiana and Kentucky eastward.

Figure 8 depicts effectiveness of the premix formulation of 2,4-DP, 2,4-D, and dicamba (Acme Super Brush Killer) applied as a 2% solution by volume. In Ohio, it has provided acceptable control only when applied from leafout in April through mid-May, after which time effectiveness decreases to unacceptable levels. This pattern also typifies effectiveness of another premix formulation of these same herbicides with a different solvent-surfactant system (Brushmaster).

Fosamine (Krenite S) is an older product with negligible present commercial use in multiflora rose control. Krenite S is listed as an option, however, because its label allows application near water supplies, even those used for human consumption. It is not labeled for use in pastures. Because Krenite S is not translocated within plants, complete spray coverage is necessary. In limited Ohio testing on rose in the 1970s and early 1980s, Krenite S provided fair plant kill. Apply Krenite S during July through September. No visual symptoms of control occur after treatment, but control becomes evident the following year.

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