Management Requirements: Bromus inermis has become established in overgrazed pastures and old fields, especially around the edges and in haystack areas. It is most often a problem in discrete patches which would appear to be amenable to selective treatment, but also appears to be invading native prairie from roadsides.
One of the difficulties in understanding how best to manage for Bromus inermis is that because of its cool season habit it is often lumped together with Poa pratensis both in research results and management decisions. Yet it appears from the species' biology and its response to various management experiments that there is a difference in the timing of the most susceptible phenological stages of the two species. Because there is some overlap in the species' times of vulnerability to fire or defoliation, dual management produces partial control of Bromus. Casual observation of the two species in southwestern Minnesota suggests that there can be a 2 to 2 1/2 week lag period between the optimal spring fire date for Poa (before it is in flower) and that for Bromus (when it is still in boot) (Sather, personal observation).
More effective management of smooth brome might be achieved by first understanding the relative proportions of Bromus inermis and Poa pratensis and their spatial distribution in the mosaic of the vegetation. Treatment schedules could then be adjusted to impact smooth brome in the boot stage in areas where it is the rightful target species.
MECHANICAL: Both experimental studies and management experience indicate that cutting smooth brome in the boot stage, i.e. while the flowering head is still enclosed within the sheath, is perhaps the most effective means of control. Martin (pers. comm.) reports successful reduction of Bromus inermis in Minnesota test plots when cut during boot stage, which occurs the time it reaches a height of 18 to 24 inches, in late May. The best conditions for damage are hot, moist weather at the time of cutting, followed by a dry period (Martin pers. comm). Experimental studies comparing the effects of growth stage and height at time of cut in Saskatchewan suggest that the greatest subsequent winter injury can be attained by cuttings at the shot blade stage (i.e just before the plant changes from vegetative to early elongation of reproductive stage) than by waiting until flowers have developed (Lawrence and Ashford 1964). Cutting at 3.8 cm produced greater subsequent winter injury than did cutting at progressively taller heights up to 14 cm (Lawrence and Ashford 1964). Cutting at "shot blade" or "boot" stage just after the apical meristem has begun to elongate within the sheath takes advantage of the low root carbohydrate levels at that time (Paulsen and Smith 1969, Reynolds and Smith 1962, Knievel et al. 1971).
Carbohydrate levels can be kept at slightly lower than normal levels throughout the summer by repeated cuttings (Paulsen and Smith 1968). Martin and Hovin (1980) found in Minnesota field trials that persistence of smooth brome over a 4-year period was more greatly reduced by 4 cuts a year than by 2 or 3 cuts. However, it should be noted that their experimental results are somewhat confounded by the fact that only the 4- cut schedule included a cut during the boot stage. Paulsen and Smith (1968) found that bromegrass harvested in boot was as adversely affected as plants managed under a 3-cut harvest schedule. Slow recovery was associated with the removal of apical meristems when tiller buds were poorly developed.
It therefore appears that a single well-timed close cut in boot stage (approximately 18 inches) may be an effective method of control. Managers of natural areas such as parks might wish to try repeated lawnmowing of brome beginning in late May and mowing at least 4 times during the season where brome patches are contiguous and pure.
FIRE: Fire does not appear as effective in reducing smooth brome as it is with Poa pratensis. Kruse (pers. comm.) reports that in North Daktoa smooth brome can be kept from spreading, but not appreciably reduced with fire. Old (1969) reports decreases in July dry matter production but not elimination of smooth brome after April fire in Illinois. One difficulty in assessing the effectiveness of burning for control of Bromus inermis is the dearth of literature that clearly separates this species from "cool season exotics" as a group.
Cosby (1972) reports the comparative effects of late May mowing and June 1 burning at Lake Andes National Wildlife Refuge, North Dakota. There biomass production in August of the treatment year was 80 lb/acre of Bromus inermis following mowing and 5 lb/acre following burning. These data suggest that a well-timed burn that treats Bromus in boot (or early bloom?) may be more effective than mowing at the same susceptible period. At Kilen Woods State Park, Minnesota, there was no visible, discernible reduction in Bromus in the first or second season after an April 22 burn (Sather 1986, 1987, pers. obs.). At Lostwood National Wildlife Refuge where nine years of burning have followed a summer schedule (mid-June and late July to mid-August) to reduce woody encroachment, smooth brome has actually increased in areas that formerly had heavy litter build-up or dense Symphoricarpos growth (Smith, pers. comm.). There, May burns are planned to help target the bromegrass. It appears that late May burns would be optimal in the northern plains for reduction of smooth brome.
HERBICIDES: Several chemicals have been tried to control cool season grasses for the purpose of sod-seeding legumes and improving pastures.
In an early study of brome control, McCarty and Scifres (1966) tested picloram, dicamba and 2,4-D and found picloram most effective at rates of 1.1 to 2.2 kg/ha, dicamba somewhat less effective and 2,4-D ineffective.
In pastures where increased legumes are desired, late April applications of paraquat, glyphosate and atrazine at 2.24 kg/ha and glyphosate at 1.12 kg/ha have been used successfuuly to shift dominance from cool to warm season grasses on Nebraska rangelands (Waller and Schmidt 1983). Herbage yields of smooth brome from atrazine treated plots were not significantly different than from glyphosate treated plots. An application of this technique is presently in the experimental stage in a brome-infested area of Sioux Prairie, South Dakota (Wells pers. comm.).
Dalapon and pronamide have been used to suppress or kill smooth brome during the establishment of birdsfoot trefoil (Martin et al. 1983, Rayburn et al. 1981). In Minnesota trials Martin et al. (1983) found both dalapon (at rates of 3.4 to 9.0 kg/ha) and glyphosate (at rates of 0.6 to 1.1 kg/ha) more effective in April and May than in June applications. In New York trials Rayburn et al. (1981) found glyphosate at 2 kg/ha more effective than dalapon (at 3.0, 4.0 and 9.0 kg/ha) or pronamide (at 0.4, 1.0 and 2.0 kg/ha). In the same study, rates of application of glyphosate as low as 0.5 kg/ha produced some effect but control was better as rates approached 2 kg/ha. In Nebraska field trials Vogel et al. (1983) found paraquat somewhat less effective than glyphosate in April applications to control smooth brome. It appears that April or May applications of glyphosate at 2 kg/ha may be an effective management technique for controlling smooth brome in pure patches.
Management Programs: Management programs in which Bromus inermis has been specifically singled- out as the target species are few. The following individuals are involved in programs that specifically target smooth brome:
Karen Smith, Refuge Manager, Lostwood National Wildlife Refuge, R. Rt. 2, Box 98, Kenmare, N.D. 58746.
Dr. Darrell Wells, Route 4, Box 233, Brookings, South Dakota 57006.
Dr. Gary Larson, Dept. of Biology, Ag. Hall 304, South Dakota State University, Brookings, S.D. 57007.
Monitoring Programs: Permanent markers have been placed at the edge of brome patches at the Helen Allison Savannah, Minnesota, to allow for tracking of these patches over time. contact: Dr. D.B. Lawrence, 1420 34th Ave. South, Minneapolis, MN 55406. 612/729-8206.
The following individuals are monitoring the frequency and/or cover of Bromus as a measure of responses to prairie management practices:
Arnold Kruse, Northern Prairie Wildlife Research Center, P.O. Box 1747, Jamestown, N. Dakota 54801.
Karen Smith, Refuge Manager, Lostwood National Wildlife Refuge, R.Route 2, Box 98, Kenmare, ND 58746.
Bromus patches at Sioux Prairie, South Dakota, are being monitored to measure success of eradication methods using herbicides. Contact: Dr. Gary Larson, Dept. of Biology, Ag. Hall 304, South Dakota State University, Brookings, SD 57007.
Bromus is one of several species being monitored as part of a dissertation study on old field succession at the Cedar Creek Natural history Area, Minnesota. Contact: Barb Delaney, Dept. of Botany, University of Minnesota, St. Paul, MN.
Management Research Programs: The only research program specifically addressing control of smooth brome is that at Sioux Prairie, South Dakota, where response of bromus to atrazine is being tested. Contact: Dr. Gary Larson, Dept. of Biology, Ag. Hall 304, South Dakota State University, Brookings, South Dakota 57007.
Management Research Needs: Bromus is often considered in conjunction with Poa pratensis in management programs because both are rhizomatous, cool season exotic grasses. There is a need to relate the dates of management procedures specifically to the physiological/phenological growth stage of Bromus at the time of management and to directly measure the response of Bromus separate from Poa.
Some specific research questions that would appear to be useful to managers of natural areas in their attempts to understand and control Bromus include: Is a single cut in boot as effective in reducing Bromus persistence as the documented first cut in boot? (Most studies in which Bromus has been cut in boot have been addressing the frequency of cutting and the boot cut has been an artifact of efforts to increase cutting frequency.) Is burning in boot as effective as cutting in boot for lowering the persistence of Bromus over a period of years? What is the response of Bromus to fall fires and/or grazing, which might enhance survival of its native cool season competitors, particularly in the northern part of its range? What is the actual rate of invasiveness of Bromus into established prairie sod? Are chemical treatments such as atrazine as effective in pure brome stands as they are in mixed stands of brome and warm season natives?