Progress 10/01/99 to 09/30/04
Outputs
Emergence dates for large [Digitaria sanguinalis] and smooth (Digitaria ischaemum Schreb.) crabgrass, microstegium (Microstegium vimineum), yellow foxtail [Setaria glauca], and yellow nutsedge (Cyperus esculentus ) were monitored in field trials. Microstegium emerged a few days prior to smooth crabgrass. Large crabgrass and yellow foxtail emerged at or a few days later than smooth crabgrass. Yellow nutsedge begins to emerge about one week after large crabgrass. Annual bluegrass (Poa annua L.) has developed resistance to simazine, since simazine applied preemergence at 1.12 and 2.24 kg ai/ha did not control annual bluegrass from two courses. These biotypes were not controlled by simazine applied at rates up to 9 kg ai/ha. Prodiamine at 0.84 kg ai/ha and ethofumesate at 1.1 kg ai/ha applied preemergence controlled annual bluegrass from all three golf courses. After two applications, no rate of oryzalin, pendimethalin, or prodiamine caused a significant reduction in
growth of any of the five ornamental grass species tested. Smooth crabgrass collected from a golf course tee was resistant to fenoxaprop-P, although smooth crabgrass from a nearby untreated rough was susceptible to this herbicide. Fenoxaprop-susceptible and resistant biotypes of smooth crabgrass had a similar response to MSMA, dithiopyr, and quinclorac. The fenoxaprop-P-resistant smooth crabgrass biotype was controlled by the cyclohexanedione herbicides sethoxydim and clethodim but the aryloxyphenoxyproprionate herbicides fluazifop and quizalofop reduced shoot weight by only 15 to 66 percent. Microstegium tolerates mowing heights used for cool-season turfgrass, although the plant must set seed in order to germinate in subsequent years. Therefore mowing will not control existing plants but late season mowing can reduce seed production. Microstegium can be controlled preemergence using available crabgrass herbicides for turf and ornamentals. Well-timed applications of postemergence
herbicides can be highly effective and one application may be sufficient. In the field mowing trials, mowing every 2 weeks resulted in 90 to 95 percent control of giant reed in early September, with approximately 80 percent control seen with mowing every 4 weeks. Mowing every 8 weeks gave 70 percent control. For all mowing treatments, however, viable phragmites stems were observed at the end of the growing season. When evaluated the following May, considerable regrowth was observed in mowed plots. Reduction in phragmites shoot weight in May ranged from 35 to 77 percent with the mowing treatments that did not receive a glyphosate application. When evaluated in early September, glyphosate applied in combination with a single mowing provided good to excellent control of phragmites. Applying glyphosate prior to mowing provided similar control compared to applications made one month after mowing. Glyphosate applied without mowing gave 93 to 95 percent reduction in phragmites shoot weight
the following May. Glyphosate applied in conjunction with mowing gave 87 to 93 percent reduction in phragmites shoot weight in May.
Impacts
Weed management in lawns and other turf areas directly affects more individuals than any other crop in the United States. Based on a 1998 survey, there were 714,000 acres (288,946 ha) of home lawns in Virginia. Total expenses for weed control products was $49,419,000, which was 6 percent of total expenses (mowing, fertilizing, water, fuel, etc.). The highest listed turf management problem (62 percent of the respondents) was weed control. Over $16 million was spent on turf pesticides (herbicides not broken out), with over $26 million spent on pesticide application by lawns care companies. Control strategies for these weeds require determination of safe and effective control programs. Reductions in unnecessary sprays will result in savings of thousands of dollars statewide. Potential for adverse environmental impacts would also be reduced with reductions in herbicide rates and applications. Japanese stiltgrass is one of the major invasive plants infesting state parks,
lawns, landscape plantings, wooded sites, and other locations. Understanding the emergence, growth, and flowering habit will be important information when developing a management plan. Glyphosate, applied with or without mowing, provides excellent but not complete phragmites control one year after a single application. Mowing frequently will suppress this weed but not provide acceptable control of phragmites the following season. Triazine-resistant annual bluegrass has developed in southeastern Virginia, but these biotypes can be controlled using alternative preemergence herbicides.
Publications
- Derr, J. F. 2004. Control of common reed (Phragmites australis). Proc. Weed Science Soc. Am. 44:59.
- Judge, C., J. C. Neal, and J. F. Derr. 2004. Preemergence and postemergence control of Japanese stiltgrass (Microstegium vimineum). Weed Technology (In press).
- Neal, J. C., C. A. Judge, and J. F. Derr. 2004. Summary of control options for Japanese stiltgrass. Proc. Northeast. Weed. Soc. Soc Ann Mtg. 58:166-167.
- Derr, J. F. 2004. Introduction to Japanese stiltgrass biology and implications for control programs. Proc. Northeast. Weed. Soc. Soc Ann Mtg. 58:166-167.
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Progress 10/01/02 to 09/30/03
Outputs
Common reed [Phragmites australis (Cav.) Trin. ex Steud.] has overtaken upland and wetland areas across the northeast. Studies were conducted at two field sites to evaluate mowing, with or without herbicide application, for phragmites control. In the field mowing trials, mowing every 2 weeks resulted in 90 to 95 percent control of giant reed in early September, with approximately 80 percent control seen with mowing every 4 weeks. Mowing every 8 weeks gave 70 percent control. For all mowing treatments, however, viable phragmites stems were observed at the end of the growing season. When evaluated the following May, considerable regrowth was observed in mowed plots. Reduction in phragmites shoot weight in May ranged from 35 to 77 percent with the mowing treatments that did not receive a glyphosate application. When evaluated in early September, glyphosate applied in combination with a single mowing provided good to excellent control of phragmites. Applying glyphosate
prior to mowing provided similar control compared to applications made one month after mowing. Addition of mowing appeared to improve control over glyphosate applied without mowing when evaluated in September. Glyphosate applied alone provided 75 to 88 percent control of common reed, while combining mowing with glyphosate resulted in 84 to 96 percent control, depending upon location. However, when evaluated in the following May, glyphosate applied alone appeared to give slightly greater control than when applied with mowing, although the results were not statistically different. Several southeastern Virginia golf courses had reported difficulty in controlling annual bluegrass (Poa annua L.) in their bermudagrass fairways. The standard control program for annual bluegrass at these courses had been a fall application of simazine. Plants were collected from a total of six fairways at three golf courses and maintained in a greenhouse. Seed from these plants were used in trials to
determine if resistance to simazine had occurred. Simazine applied preemergence at 1.12 and 2.24 kg ai/ha did not control annual bluegrass from two of the three golf courses. In a second trial to verify the level of resistance, these biotypes were not controlled by simazine applied at rates up to 9 kg ai/ha. Prodiamine at 0.84 kg ai/ha and ethofumesate at 1.1 kg ai/ha applied preemergence controlled annual bluegrass from all three golf courses. Tolerance of ornamental grasses to preemergence herbicides commonly-used in nursery crop production and turfgrass maintenance was evaluated in container studies. Isoxaben controlled the broadleaf weeds tested but did not control large crabgrass. Oryzalin at 2.2 kg ai/ha (2.0 lb ai/A) controlled all weeds except rice flatsedge. Metolachlor at 2.2 kg ai/ha (2.0 lb ai/A) controlled rice flatsedge but not eclipta. Pendimethalin, oxadiazon, prodiamine and oxyfluorfen plus pendimethalin also did not control eclipta at the lower use rate. Ornamental
grass tolerance improved by the second herbicide application. After two applications, no rate of oryzalin, pendimethalin, or prodiamine caused a significant reduction in growth of any of the five ornamental grass species tested.
Impacts
Glyphosate, applied with or without mowing, provides excellent but not complete phragmites control one year after a single application. Mowing frequently will suppress this weed. However, maintaining a regular mowing schedule for one growing season will not provide acceptable control of phragmites the following season. Triazine-resistant annual bluegrass had developed at two golf courses in southeastern Virginia, but these biotypes can be controlled using alternative preemergence herbicides. Although growth suppression and stand reduction was observed in certain preemergence herbicide/ornamental grass combinations, the species tested generally exhibited good tolerance to the chemicals tested.
Publications
- Derr, J. F. 2002. Tolerance of ornamental grasses to preemergence herbicides. J. Environ. Hort. 20:161-165.
- Derr, J. F. 2003. Common reed response to mowing. Proc. Northeast Weed. Sci. Soc. Ann. Mtg. 57:115.
- Derr, J. F. 2003. Detection of triazine-resistant annual bluegrass in turfgrass. Proc. West. Soc. Weed Sci. 56:42-43.
- Hart, S. E., J. F. Derr, C. Rose-Fricker, W. A. Meyer, and D. W. Lycan. 2003. Response of glyphosate-tolerant tall and fine fescue to multiple applications of glyphosate. Proc. Northeast Weed. Sci. Soc. Ann. Mtg. 57:109.
- Judge, C. A., J. C. Neal, and J. F. Derr. 2003. Herbicide rate, timing, and application frequency comparisons for Japanese stiltgrass control. Proc. Northeast Weed. Sci. Soc. Ann. Mtg. 57:27.
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Progress 10/01/01 to 09/30/02
Outputs
Smooth crabgrass collected from a golf course tee was resistant to fenoxaprop-P, although smooth crabgrass from a nearby untreated rough was susceptible to this herbicide. Fenoxaprop-P-resistant plants were injured, though, when fenoxaprop-P was applied at levels above the maximum use rate for turf. Fenoxaprop-P applied postemergence at 0.76 kg ai/ha, four times the maximum rate, reduced shoot weight of the resistant biotype by 35 percent, while application of 1.52 kg/ha, eight times the maximum rate, reduced shoot weight by 64 percent. Large crabgrass and the susceptible biotype of smooth crabgrass were controlled by fenoxaprop-P applied at 0.1 kg/ha. Fenoxaprop-susceptible and resistant biotypes of smooth crabgrass had a similar response to MSMA, dithiopyr, and quinclorac applied postemergence. The fenoxaprop-P-resistant smooth crabgrass biotype was controlled by the cyclohexanedione herbicides sethoxydim and clethodim but the aryloxyphenoxyproprionate herbicides
fluazifop and quizalofop reduced shoot weight by only 15 to 66 percent, depending upon herbicide and rate. Ornamental grass tolerance to commonly-used preemergence herbicides was evaluated in container studies. Dwarf fountain grass, feather reed grass, silver variegated maiden grass, silver arrow miscanthus, and zebra grass were propagated by division and planted into 4 L containers. Plants were treated soon after transplanting and retreated 2 months later. Isoxaben, oryzalin, metolachlor, pendimethalin and oxadiazon applied at twice the maximum use rate did not reduce stand of any ornamental grass species. Prodiamine and oxyfluorfen plus pendimethalin applied at twice the common use rate also did not reduce ornamental grass stand. No herbicide was safe on all five species as each one tended to reduce shoot weight of at least one ornamental grass species after the first application. Although growth suppression was observed in certain herbicide/ornamental grass combinations, the five
species generally exhibited good tolerance to the chemicals tested. In general, greater shoot weight reductions were noted following the first than the second application, suggesting that ornamental grass tolerance increased with time. After two applications, no rate of oryzalin, pendimethalin, or prodiamine caused a significant reduction in growth of any of the five ornamental grass species. Available combination broadleaf herbicides for turf are effective on most weeds. It would be desirable to increase speed of control with these products without sacrificing long-term results. Experiments were conducted to evaluate additions of carfentrazone at approximately 0.04 lb ai/A to postemergence herbicides used in turf. These combinations were compared to a commercial formulation of 2,4-D plus MCPP + dicamba and a commercial formulation of 2,4-D plus clopyralid + dicamba. The carfentrazone combinations caused faster injury development than commercial formulations in white clover, curly
dock, and buckhorn plantain at 1 and 3 DAT. At 35 DAT, white clover control was similar among all treatments. No treatment injured tall fescue (Festuca arundinacea Schreb.).
Impacts
Weed management in lawns and other turf areas directly affects more individuals than any other crop in the United States. Approximately two million hectares are estimated to be in home lawns, with an additional four million hectares covered by other types of turf. Development of weed resistance is an important concern for turf managers. Control strategies for these weeds requires determination of safe and effective control programs. Reductions in unnecessary sprays could result in savings of thousands of dollars statewide in Virginia. Potential for adverse environmental impacts would also be reduced with reductions in herbicide rates and applications.
Publications
- Derr, J. F. 2002. Detection of fenoxaprop-resistant smooth crabgrass (Digitaria ischaemum) in turf. Weed Technology 16:396-400.
- Derr, J. F., S. Hart, A. F. Senesac, and R. Taylorson. 2002. Enhancement of postemergence broadleaf herbicide action in turf by additions of carfentrazone. Proc. Northeast. Weed Sci. Soc. 56:124-125.
- Derr, J. F. 2002. Preemergence weed control in ornamental grasses. Proc. Weed Sci. Soc. Am. 42:80-81.
- Senesac, A. F. and J. F. Derr. 2002. Phytotoxicity of granular herbicides as affected by ornamental foliar wetness. Proc. Northeast. Weed Sci. Soc. 56:51
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Progress 10/01/00 to 09/30/01
Outputs
Emergence dates for large (Digitaria sanguinalis) and smooth (Digitaria ischaemum Schreb.) crabgrass, microstegium (Microstegium vimineum), yellow foxtail (Setaria glauca), and yellow nutsedge (Cyperus esculentus ) were monitored in field trials. In 1998, there were 35.3 microstegium plants per plot on 3/31. Large and smooth crabgrass were observed emerging on 3/31. There were 4.0 and 60.5 yellow foxtail plants per plot on 3/31 and 4/9, respectively. Yellow nutsedge began emerging on 4/9. For 3/23 through 3/27, air and soil temperature at a 5 cm depth at 10:00 am averaged 12.3 and 8.6 C, respectively. For 3/26 through 3/30, air and soil temperatures at 10:00 am averaged 21.1 and 12.5 C, respectively. For the period 4/4 through 4/8, air and soil temperatures at 10:00 am were 23.6 and 10.9 C, respectively. In 1999, microstegium was first observed emerging on 3/29 Air temperature at 10:00 am averaged 8.2 C, with a soil temperature of 8.7 C for the 5 previous days. Smooth
crabgrass was seen emerging on 4/2 Air temperatures at 10:00 am averaged 15.7 C with 8.9 C soil temperature from 3/28 through 4/1. Large crabgrass began emerging on 4/5. There were 28 yellow foxtail plants per plot on 4/5. Air and soil temperatures at 10:00 am for 3/31 through 4/4 averaged 16.6 C and 11.5 C, respectively. There were 23 yellow nutsedge plants per plot on 4/13. For 4/8 through 4/12, air temperatures at 10:00 am averaged 15.9 C with 13.9 C soil temperatures. Based on these results, microstegium emerges a few days prior to smooth crabgrass. Large crabgrass and yellow foxtail emerge at or a few days later than smooth crabgrass. Yellow nutsedge begins to emerge about one week after large crabgrass. Postemergence control of Microstegium vimineum was investigated. MSMA, dithiopyr, and quinclorac did not provide adequate control of Microstegium. Glyphosate and glufosinate both provided excellent control. The selective postemergence graminicides fluazifop-P-butyl, fenoxaprop-P,
clethodim, and sethoxydim all provided greater than 85 percent control of microstegium except with clethodim, where control was 78 percent in the field experiment. Woody nursery plants in 11-L containers were seeded with annual weeds and recommended rates of selected granular herbicides were applied. Euphorbia maculata L. (spotted spurge) control was numerically highest with prodiamine applied at 1.1 kg ai/ha. Pendimethalin at 4.5 kg/ha, isoxaben plus trifluralin at 4.2 kg/ha, and oryzalin plus benefin at 4.5 kg/ha provided good to excellent Euphorbia maculata control at 3 weeks after treatment. Other treatments gave numerically lower control. Oxadiazon, applied alone at 3.4 kg/ha or in combination with oxyfluorfen or prodiamine provided unacceptable control of Euphorbia maculata. Oxyfluorfen plus oryzalin provided equal or greater control of all weed species compared to oxyfluorfen plus pendimethalin when applied at 3.4 kg/ha. No treatment controlled Commelina communis. Tolerance of
Gardenia jasmoindes 'Radicans', Gardenia jasmoindes 'Chuck Hayes', Ilex cornuta 'Needlepoint', Euonymous fortunei 'Sunspot', Myrica cerifera, and Ilex crenata 'Bennetts compacta' was excellent with all treatments.
Impacts
Information on weed germination is useful when timing management options such as preemergence herbicide application. These results will allow turf managers to use fewer applications, thereby saving thousands of dollars statewide. Potential for adverse environmental impacts would also be reduced with reductions in herbicide rate and applications.
Publications
- Derr, J. F. 2001. Emergence pattern for five monocot weeds. Proc. Weed Sci. Soc. Am. 41:48.
- Judge, C. A., J. C. Neal, and J. F. Derr. 2001. Postemergence control of Microstegium vimineum. Proc. Weed Sci. Soc. Am. 41:47-48.
- Derr, J. F. 2000. Weed control in container production with preemergence herbicides. Proc. Weed Sci. Sci. Am. 40: 117.
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Progress 10/01/99 to 09/30/00
Outputs
Japanese stilt grass (Microstegium vimineum) has become an important weed in Virginia. Experiments were conducted to determine the germination pattern for this weed, as well as control using selected preemergence and postemergence herbicides. Microstegium germinated the last week of March, slightly in advance of smooth crabgrass (Digitaria ischaemum). On April 9, Microstegium was in the cotyledon to two-leaf stage, while smooth crabgrass was only in the cotyledon stage. Microstegium plants began flowering in the second week of October. A field site was treated with preemergence herbicides commonly used for crabgrass control in turf. Granular formulations of benefin, benefin plus trifluralin, and oxadiazon were used, while sprayable formulations of bensulide, dithiopyr, oryzalin, pendimethalin, prodiamine and siduron were evaluated. At 30 days after application, all preemergence herbicides evaluated controlled this weed over 80%. Benefin, benefin plus trifluralin,
dithiopyr, pendimethalin, and siduron did not provide acceptable control at 90 DAT. At that time, bensulide, oryzalin, oxadiazon, and prodiamine all reduced Microstegium shoot fresh weight by over 75%. Studies were conducted to determine the length of residual control for commonly-used turf preemergence herbicides. Herbicides applied as sprays were prodiamine, pendimethalin, dithiopyr, bensulide, siduron, and oryzalin. Benefin, benefin plus trifluralin and oxadiazon were applied in granular form. At 0 MAT, all treatments controlled both large crabgrass (Digitaria sanguinalis) and yellow foxtail (Setaria glauca) greater than 95%. At 1 MAT, all chemicals except benefin plus trifluralin reduced large crabgrass shoot weight by over 95%. All treatments except bensulide, benefin, and benefin plus trifluralin reduced yellow foxtail shoot weight by over 90%. At 2 MAT, only prodiamine, pendimethalin, and oxadiazon reduced shoot weight of both species by over 90%. By 3 MAT, only prodiamine
provided over 90% reduction in large crabgrass shoot weight, while oxadiazon reduced shoot weight by 89%. At 3 MAT, numerical reduction in large crabgrass shoot weight was in the order, from greatest to least: prodiamine, oxadiazon, oryzalin, pendimethalin, bensulide, dithiopyr, siduron, benefin, and benefin plus trifluralin. Only prodiamine and oxadiazon reduced yellow foxtail shoot weight over 90% at 3 MAT. By 4 MAT, no treatment reduced large crabgrass shoot weight by 90% or more. At 5 MAT, all treated flats had a similar large crabgrass shoot weight as the untreated flats. Seed was collected from smooth crabgrass plants thought to be resistant to fenoxaprop. Fenoxaprop was applied at 0.07 to 0.3 kg ai/ha. Fenoxaprop at 0.3 kg/ha did not cause a significant reduction in shoot weight of this biotype of smooth crabgrass. Smooth crabgrass at this site therefore had developed resistance to fenoxaprop. A second study evaluated the extent of resistance. Fenoxaprop was applied at 0.19,
0.4, 0.8, and 1.5 kg/ha. Injury was observed in plants treated at the three highest rates. The resistance therefore is not unlimited since these plants can tolerate rates up to 0.3 kg/ha but are adversely affected by higher rates.
Impacts
Weed management in lawns and other turf areas directly affects more individuals than any other crop in the United States. Approximately two million hectares are estimated to be in home lawns, with an additional four million hectares covered by other types of turf. The biology of a new invasive weed was determined in this research, along with the identification of control strategies. Herbicides providing longer residual control of large crabgrass were identified. Utilization of these results will allow turf managers to use fewer applications. Reductions in unnecessary sprays could result in savings of several hundred thousand dollars statewide in Virginia. Potential for adverse environmental impacts would also be reduced with reductions in herbicide rate and applications. Herbicide resistance was documented in a smooth crabgrass biotype. Management of herbicide-resistant weeds will become an important management concern for turf professionals.
Publications
- 4. CHANDRAN, R. S. and J. F. DERR. 1999. Isoxaben dissipation in field soil as affected by application timing. J. Environ. Qual. 28:1760-1764.
- 5. KUK,Y., J. WU, J. F. DERR, and K. K. HATZIOS. 1999. Mechanism of fenoxaprop resistance in an accession of smooth crabgrass (Digitaria ischaemum). Pest. Biochem Physiol. 64:112-123.
- 1. DERR, J. F. 2000. Longevity of preemergence crabgrass herbicides. Proc. Northeast. Weed. Sci. Soc. 54:120.
- 2. DERR, J. 1999. Biology and management of Microstegium, a relatively unresearched turf weed. Proc. Northeast. Weed. Sci. Soc. 53:100
- 3. CHANDRAN, R. S., J. F. DERR, and S. W. BINGHAM. 1999. Effect of isoxaben application rate and timing on residual broadleaf weed control in turf. Weed Technol. 12:569-574.
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