Stevan Z. Knezevic
Associate Professor - Integrated Weed Management

Haskell Agricultural Laboratory
Department of Agronomy and Horticulture
University of Nebraska
57905 866 Road
Concord, Nebraska 68728-2828
Telephone: (402) 584-3808
FAX: (402) 584-3859
e-mail: sknezevic2@unl.edu
Web Page:  http://nerec.unl.edu/stevanknezevic

Degrees:

B. S. Plant Protection, University of Belgrade, 1986
M. S. Crop Science (Weed Science), University of Guelph, 1993
Ph. D. Agronomy (Weed Science), Kansas State University, 1997

Courses Taught:

AGRON 822-Integrated Weed Management, Spring semester in odd years.
AGRON 496-Independent Studies, research project for undergraduate students
AGRON 896-Independent Studies, research project for graduate students

Research Interests:

The objective of my research program is to develop weed control strategies based on a multidisciplinary approach that builds bridges among scientific disciplines, especially between weed/crop ecology and herbicide technology. A single weed control measure is not feasible due to the number of different weed species and their highly variable life cycles. My program, therefore, advocates a combination of weed control methods (the use of many "little hammers").  We conduct weed control studies in field crops (conventional and organic), rangeland, pasture and riparian settings.  Over the last 15 years we have developed nationally and internationally recognized expertise on the following three concepts:

1.  Critical Period of Weed Control (CTWC) and data analysis

Our manuscript on CPWC provided a standardized procedure for this type of studies (Knezevic et al. 2002.  Critical period of weed control: the concept and data analysis.  Weed Sci. 50: 773-786).  So far we have published nine manuscripts related to this concept with the work of three of my graduate students.

2.  Dose Response Studies and data analysis

Our manuscript provided a standard procedure (e.g. recipe) for this type of studies (Knezevic et al. 2007.  Utilizing R software package for dose-response studies:  the concept and data analysis.  Weed Technol. 21:840-848).  So far we have published over 10 manuscripts that utilized this concept in handling data analysis.  We also utilize this concept routinely in herbicide evaluation trials and flaming studies.

3.  Weed Flaming and data analysis

Most of our flaming studies are currently underway in agronomic crops, primarily corn (field corn, popcorn and sweet corn), sorghum, sunflower, soybean and wheat.  We are also interested to expend to other crops.  So far we published seven manuscripts, four are currently in review and another seven in preparation.

Student Research Projects:

(a) Post Doctoral Research Associate:

Dr. Avishek Datta, Vegetarian control on sandbars along Missouri River (2008-present)

(b) Ph.D. students:

1.  Janyce Woodard, Weed control and growth of buffer crops (2007-current-part time)
2.  Santiago Ulloa, Weed control with flaming (2006-present)
3.  Ryan Rapp, Integrated management of common reed (2008-present)
4.  Igor Elezovic, CTWC in sunflower (2008-present, U of Belgrade, Serbia)
5.  Robert Leskovsek, Common ragweed control (2008-present, U of Maribor, Slovenia)
6.  Chris Bruening, Designing new flaming equipment (2010-present)

(c) M.S. students:

1.  Sean Evans, Critical period of weed control in corn (1999-2001)
2.  Shawn Hock, Competitive indices of weed species in soybeans (2002-2005)
3.  Travis Gustafson, Weed-insect interactions on weed management (2003-2005)
4.  Katie Wrade (MAg), Field sandbur control in corn (2003-2005)
5.  Aaron Quinn, Predicting purple loosestrife infestations using GIS model (2004-2006)
6.  Chris Bruening, Designing new hood for crop and weed flaming (2007-2009)

(d) Undergraduate students:

1.  Christy McCoy, Velvetleaf control in Roundup-Ready soybean (WSC in 2001)
2. Andre Domingues, Flaming methods for selected weed species (Brazil in 2007)
3. Heverton Z. Teixeira , Corn response to flaming (Brazil in 2007)
4. Pierre Marteau, Sunflower growth and duration of weed removal (France, 2008)
5. Claudio Martins-Costa, Differential tolerance of corn types to flaming (Brazil in 2008)
6. Jayme Netto, Wheat tolerance to broadcast flaming (Brazil in 2008)
7. Brian Neilson, Sweet corn tolerance to flaming (UNL in 2009)
8. Dustin Simpson. Weed control with flaming (UNL in 2009)

(e) Visiting Scientists and Scholars:

Visits that lasted from 1 to 6 months:

1. Dr. Mario Lesnik (Slovenia), Dose response concept (2009)
2. Dr. Goran Malidza (Serbia), Critical period of weed control in sunflower (2009)
3. Dr. Marco Fontanelli (Italy), Weed control with flaming (2009)
4. Mr. Sidnei Cavalieri (Brazil), Popcorn tolerance to nicosulfuron (2009)

Visits that lasted less than 1 month:

1. Dr. Peter Bleeker from Holland in 2009, Crop tolerance to flaming
2. Dr. Mario Lesnik from Slovenia in 2008, Weed flaming
3. Dr. Andrey Simoncic from Slovenia in 2008. Weed flaming
4. Dr. Renan Aguero from Costa Rica in 2008, Weed control with flaming
5. Dr. Ryohei Ueno from Japan in 2007, Dose response concept
6. Dr. Toshihiro Ambe from Japan in 2007, Dose response concept
7. Dr. Peter Sikkema from Canada in 2007, Dose response concept and data analysis
8. Dr. Joashir Kaiser from Germany in 2007, Dose response concept
9. Dr. Kenji Takama from Japan in 2006, Dose response concept
10. Dr. Hasashi Honda from Japan in 2006, Dose response concept
11. Dr. Milena Simic from Serbia in 2006, CTWR in sunflower
12. Dr. Mirko Ivanovic from Serbia in 2006, Dose response concept
13. Dr. Radivoje Jevtic, from Serbia in 2006 Dose response concept
14. Dr. Nedeljko Latinovic from Montenegro in 2006, Dose response concept
15. Dr. Nioki Oyamma from Japan in 2005, Dose response concept
16. Dr. Yoshihiro Yamaji from Japan in 2005, Dose response concept
17. Dr. Osamu Watanabe from Japan in 2005, Dose response concept
18. Dr Yariv Keadr from Israel in 2004, Dose response concept
19. Dr. Moshik Fish from Israel in 2004, Dose response concept

Major Project Activities

Current program activities (Year 2010):

I. Herbicide screening: over 50 herbicide trials in corn, soybean, rangeland, pasture and wetlands

II. Soybean and corn variety trials: A total entry of about 120 soybean and 80 corn varieties

III. Major research projects:

1. Weed control in organic cropping systems: Specific area of this research project includes studying various non-chemical weed control options with emphasis on weed flaming. There are 4 specifics goals: (i) to develop dose response curves for propane, and from those curves to determine biologically effective dose needed for weed flaming procedures on selected crop and weed species, (ii) to study crop yield and yield components as influenced by flaming in corn, soybean, sorghum and wheat, (iii) to design and test new hood for crop and weed flaming in collaboration with Dr. Gogos program from Engineering Department and (iv) Integrated weed control based on flaming and cultivation in organic corn and sunflower.

2. Weed control in wetlands: Specific area of this research project includes studying interaction between soil nutrients, soil pH, and herbicides in order to develop long term control strategies for invasive plant species on sandbars in the wetlands of the Lewis and Clark Lake in northeast Nebraska. The overall goal is to develop cost effective integrated weed management system that minimize reliance on herbicides, and to manage vegetation to prevent the loss of the nesting habitat for two endangered bird species, piping plover (Charadrius melodus) and interior least tern (Sterna antillarum), along Missouri River.

3. Integrated management of Purple loosestrife: Purple loosestrife has a devastating impact on wetland by out-competing native plants and creating habitat that is not suitable for wildlife. As part of the long study, we are testing various control methods including herbicides, repeated disking, repeated mowing, planting replacement species and burning. Herbicide control studies are at 3 locations along the Missouri and Niobrara Rivers.

4. Integrated management of common reed (Phragmites) along major waterways in Nebraska: As part of this demonstration and long-term study, we are testing various control methods including herbicides, repeated disking, repeated mowing, and grazing at several locations along the Platte River.

Extension Interests:

- To keep crop producers up to date with the current weed control issues.
- To respond promptly and accurately to the regional needs and requests related to weed control and crop production.
- To utilize various distance education tools in order to dissiminate information to county educators, crop consultants, growers, and the public in general.

EXTENSION PUBLICATIONS:

Knezevic S. Z., A. Datta and R. Rapp. 2008. Common Reed. UNL-Extension Publication.
EC-08-166.

Wilson R. and S. Z. Knezevic. 2007. Salt cedar. UNL-Extension Publication. EC-07-164.

Knezevic et al. 2005. Integrated management of eastern red cedar. UNL-Extension Publication.
EC-05-186.

Knezevic S. Z. 2003. Purple loosestrife. UNL-Extension Publication. EC-03-176.

Anderson B. E., Knezevic et al. 2003. Alfalfa in Nebraska. EC03-181.

Heckman N. L., Knezevic et al. 2002. Spotted and Diffuse Knapweed. UNL-Extension Publication. EC-02-173-S.

Knezevic S. Z. 2002. Use of herbicide tolerant crops as a component of an integrated weed
management program. NebGuide, UNL-Extension Publication. G02-148-A.

Hunt T. and S. Z. Knezevic. 2002. Monitoring procedures for Galerucella beetles to control
purple loosestrife. Extension Circular. UNL-Extension Publication. EC02-175.

Knezevic S. Z. and D. Smith. 2001. Rearing and releasing Galerucella beetles to control purple
loosestrife. NebGuide. UNL-Extension Publication. G01-1436-A.

Eghball B., C. Shapiro and S. Z. Knezevic. 2001. Manure application effects on weed infestations. NC-Extension 189

Co-Author of four Annual Publications:
1. Guide for weed management in Nebraska.
2. Corn hybrids for Nebraska.
3. Soybean varieties for Nebraska.
4. Alfalfa varieties for Nebraska.
Weed Research for northeast Nebraska. Yearly report

REFEREED JOURNAL ARTICLES (click on pdf to download)

Publications related to the concept of Critical Period of Weed Control
Lindquist J. L., S. P. Evans, C. A. Shapiro and S. Z. Knezevic. 2010. Effect of nitrogen addition and weed interference on soil nitrogen and corn nitrogen nutrition. Weed Technol. DOI: 10.1614/WT-09-070.1.

Gustafson T, S. Z. Knezevic, T. Hunt and J. L. Lindquist. 2006. Simulated insect defoliation and
duration of weed interference affected soybean growth. Weed Sci. 54: 735-742.

Gustafson T, S. Z. Knezevic, T. Hunt and J. L. Lindquist. 2006. Early-season insect defoliation.
influences the critical time for weed removal in soybean. Weed Sci. 54: 509-515.

Evans S. P., S. Z. Knezevic, C. Shapiro and J. L. Lindquist. 2003. Nitrogen level affects critical
period for weed control in corn. Weed Sci. 51: 408-417.

Evans S. P., S. Z. Knezevic, C. Shapiro and J. L. Lindquist. 2003. Influence of nitrogen level and
duration of weed interference on corn growth and development. Weed Sci. 51: 546-556.

Knezevic, S. Z., S. P. Evans and M. Mainz. 2003. Yield penalty due to delayed weed control in corn and soybean.
Crop Manag. J. online: http://www.plantmanagementnetwork.org/pub/cm/research/2003/delay/

Knezevic, S. Z., S. P. Evans and M. Mainz. 2003. Row spacing influences critical time of weed
removal in soybean. Weed Technol. 17: 666-673.

Blankenship E., W. Stroup, Evans S. P. and S. Z. Knezevic. 2003. Statistical inference for
calibration points in nonlinear mixed models. J. Agric. Biol. Environ. Stat. 4: 455-468.

Knezevic S. Z., S. P. Evans, E. Blankenship, R. VanAcker and J. L. Lindquist. 2002. Critical
period of weed control: the concept and data analysis. Weed Sci. 50: 773-786.

Publications related to the issues with Herbicide Tolerant Crops
Knezevic S. Z., A. Datta, J. Scott, R. Klein, and J. Golus. 2009. Problem weed control in
glyphosate-resistant soybean (Glycine max L.) with glyphosate tank-mixes and soil-applied herbicide. Weed Technol. 23: 507-512.

Knezevic S. Z. 2007. Herbicide tolerant crops: 10 years later. Maydica 52: 245-250.

Kappler B., S. Z. Knezevic et al. 2005. Comparison of glyphosate-based herbicides in Nebraska.
Crop Manag. J. online: http://www.plantmanagementnetwork.org/pub/cm/management/2005

Knezevic S. Z. and K. Cassman. 2003. Use of herbicide tolerant crops as a component of an
Integrated weed management.
Crop Manag. J. online: http://www.plantmanagementnetwork.org/pub/cm/management/2003/htc/

Elmore R. W., Roeth, Nelson, Shapiro, Klein, S. Z. Knezevic and A. Martin. 2001.
Glyphosate-resistant soybean cultivar yields compared to sister lines. Agron. J. 93: 408-412.

Elmore R. W., Roeth, Klein, S. Z. Knezevic, A. Martin, Nelson and C. A. Shapiro. 2001.
Glyphosate-resistant soybean cultivar response to glyphosate. Agron. J. 93: 404-407.

Publications related to the concept of Dose Response Curves
Knezevic S. Z., A. Datta. J. Scott and L. D. Charvat. 2010. Tolerance of winter wheat (Triticum
aestivum L.) to pre-emergence and post-emergence application of saflufenacil. Crop
Prot. 29: 148-152.

Knezevic S. Z., A. Datta. J. Scott and L. D. Charvat. 2010. Application timing ad adjuvant type
affected saflufenacil efficacy on selected broadleaf weeds. Crop Prot. 29: 94-99.

Knezevic S. Z., A. Datta. J. Scott and L. D. Charvat. 2009. Adjuvant influenced saflufenacil
efficacy on fall emerging weeds. Weed Technol. 23: 340-345.

Knezevic S. Z., A. Datta, J. Scott and P. J. Porpiglia. 2009. Dose-response curves of KIH-485 for preemergence weed control in corn (Zea mays). Weed Technol. 23: 34-39.

Knezevic S. Z., A. Datta. J. Scott and L. D. Charvat. 2009. Interactions between saflufenacil and
glyphosate on selected broadleaf weeds. Crop Manag. J. online: DOI: 10.1094/CM-2009-1014-01-RS.

Hock S, G. Wiecko and S. Z. Knezevic. 2008. Glyphosate dose affected control of field dodder
(Cuscuta campestris) in the tropics. Weed Technol. 22: 151-155.

Knezevic S. Z., J. Streibig and C. Ritz. 2007. Utilizing R software package for dose-response studies: the concept and data analysis. Weed Technol. 21: 840-848.

Hamill A., S. Z. Knezevic, K. Chandler, P. Sikkema, F. Tardif and C. J. Swanton. 2000. Weed
control in glufosinate tolerant corn (Zea mays L.). Weed Technol. 14: 578-585.

Publications related to Invasive Species Management (rangeland, pasture, wetlands)
Knezevic S. Z. et al.. 2004. Purple loosestrife control using herbicides: Single year application.
Weed Technol. 18: 1255-1260.

Knezevic S. Z., A. Kantrovich and B. Masters. 2003. Eastern red cedar control in pasture. Crop Manag. J. online: http://www.plantmanagementnetwork.org/pub/cm/management/2003

Publications related to Flaming
Knezevic S. Z., J. F. Neto, S. M. Ulloa and A. Datta. 2009. Winter wheat (Triticum aestivum L.)
tolerance to broadcast flaming. In Proceedings of the 8th EWRS workshop on Physical and Cultural Weed Control. Pages 104-109, Zaragoza, Spain.

Knezevic S. Z., S. M. Ulloa and A. Datta. 2009. Tolerance of selected weed species to broadcast
flaming at different growth stages. In Proceedings of the 8th EWRS workshop on Physical and Cultural Weed Control. Pages 98-103, Zaragoza, Spain.

Knezevic S. Z., C. M. da Costa, S. M. Ulloa and A. Datta. 2009. Response of corn (Zea mays L.)
types to broadcast flaming. In Proceedings of the 8th EWRS workshop on Physical and Cultural Weed Control. Pages 92-98, Zaragoza, Spain.

Knezevic S. Z., S. M. Ulloa and A. Datta. 2009. Growth stage impacts tolerance to broadcast
flaming in agronomic crops. In Proceedings of the 8th EWRS workshop on Physical and Cultural Weed Control. Pages 86-91, Zaragoza, Spain.

Domingues A. C., S. M. Ulloa, A. Datta and S. Z. Knezevic. 2008. Weed response to broadcast flaming. RURALS. http://digitalcommons.unl.edu/rurals/vol3/iss1/2.

Teixeira, Ulloa, Datta and Knezevic. 2008. Corn (Zea mays) and soybean (Glycine max)
tolerance to flaming. RURALS. http://digitalcommons.unl.edu/rurals/vol3/iss1/1.

Knezevic S. Z. and Ulloa S. M. 2007. Flaming: New potential tool for weed control in organically grown agronomic crops. J. Agric. Sci. 52: 95-104.

Publications from various collaborative projects (state, national and international)
Klein R. N., Pavlista, Shapiro, Lyon, Baltensperger, Hergert, Knezevic, Mason, Nelson, Elmore,
Vigil, Schlegel, Olson and Aiken. 2009. Yield of corn grown under semi-arid
conditions in skip-row patterns. Crop Manag. J. Online:
http://www.plantmanagementnetwork.org/sub/cm/research/2009/skip/

Bača F., S. Gošić-Dondo, Ž. Videnović, B. Kresović and S. Kneževic. 2008. Effects of planting date on the level of European borer infestation and corn yield. Maydica. 53: 111-115.

Hock S., S. Z. Knezevic, B. Johnson, C. Srague and A. Martin. 2007. WeedSOFT: Effects of corn row spacing for predicting herbicide efficacy on selected weed species. Weed Technol. 21: 219-224.

Lindquist J. L., D. C. Barker, S. Z. Knezevic and D. Walters. 2007. Comparative nitrogen uptake
and distribution in corn and velvetleaf (Abutilon theophrasti). Weed Sci. 55:102-110.

Wicks G., S. Z. Knezevic et al. 2007. Effect of planting depth and isoxaflutole rate on corn injury in Nebraska. Weed Technol. 21: 642-646.

Bača F., J. Lević, S. Stanković, L. Stefanović, M. Simić, S. Gošić-Dondo and S. Kneževic. 2007.
Factors contributing to the population changes of major maize pests in Serbia. Maydica
52: 343-346.

Hock S, S. Z. Knezevic, A. R. Martin and J. L. Lindquist. 2006. Performance of WeedSOFT^R for predicting soybean yield loss. Weed Technol. 20: 478-484.

Barker D. C., S. Z. Knezevic and J. L. Lindquist. 2006. Effect of nitrogen addition on the
comparative productivity of corn and velvetleaf (Abutilon theophrasti). Weed Sci.
54: 354-363.

Hock S., S. Z. Knezevic, A. Martin and J. Lindquist. 2005. Influence of soybean row width and
velvetleaf emergence time on velvetleaf. Weed Sci 53: 160-165.

Hock S., S. Z. Knezevic, C. Petersen, J. A. Easton and A. R. Martin. 2005. Germination techniques for common lambsquarters and Pennsylvania smartweed. Weed Technol. 20: 530-534.

Schmidt A., W. Johnson, A. Martin, S. Z. Knezevic et al. 2005. Evaluation of corn (Zea mays L.) yield loss estimations by WeedSOFT in the North Central Region. Weed Technol. 19: 1056-1064.

Shrestha A., S. Z. Knezevic, R. C. Roy, B. Ball-Coelho and C. J. Swanton. 2002. Effect of
tillage, cover crop and crop rotation on the composition of weed flora in a sandy soil.
Weed Res. 42: 76-87.

Knezevic S. Z., M. J. Horak and R. L. Vanderlip. 2001. Relative time of Amaranthus
retroflexus affects partitioning of dry matter. Weed Sci. 49:617-621.

Van Acker R. C. , A. G. Thomas, J. Y. Leeson, S. Z. Knezevic and B. L. Frick. 2001.
Comparison of weed communities in Manitoba ecoregions and crops. Can. J. Plant Sci. 80: 963-972.

Swanton C. J., A. Shrestha, R. C. Roy and S. Z. Knezevic. 2000. Vertical seed bank distribution
changes with tillage practice in sandy soils. Can. J. Plant Sci. 80: 455-457.

Publications from studies conducted prior to arriving to NE:
Knezevic S. Z., M. J. Horak and R. L. Vanderlip. 1999. Estimates of physiological determinants
for redroot pigweed. Weed Sci. 47: 291-296.

Sikkema P., S. Z. Knezevic F. Tardif A. Hamill and C. J. Swanton. 1999. Biologically
effective dose and Selectivity of SAN1269H for weed control in no-till corn (Zea mays
L.). Weed Technol. 13: 283-289.

Swanton C. J., A. Shrestha, B. Ball-Coelho, R. C. Roy and S. Z. Knezevic. 1999. Effect of
tillage systems, N, and cover crop on the composition of weed flora. Weed Sci. 47: 454-
461.

Knezevic S. Z. and M. J. Horak. 1998. Influence of emergence time and density on redroot
pigweed. Weed Sci. 46: 665-672.

Knezevic S. Z., P. H. Sikkema, F. Tardif, A. S. Hamill, K. Chandler and C. J. Swanton. 1998.
Biologically effective dose and selectivity of RPA 201772 (isoxaflutole) for
preemergence weed control in corn. Weed Technol. 12: 670-676.

Knezevic S. Z., M. J. Horak and R. L. Vanderlip. 1997. Relative time of redroot pigweed
(Amaranthus Retroflexus L.) emergence is critical in pigweed - sorghum (Sorghum
bicolor L.) competition. Weed Sci. 45: 502-508.

Knezevic S. Z., S. F. Weise and C. J. Swanton. 1995. Comparison of empirical models depicting
density of Amaranthus retroflexus L. and relative leaf area as predictors of yield loss in maize (Zea mays L.). Weed Res. 35: 207-214.

Knezevic S. Z., S. F. Weise and C. J. Swanton. 1994. Interference of redroot pigweed in corn.
Weed Sci. 42: 568-573.

BOOK CHAPTERS

Taylor E., S. Z. Knezevic and S. M. Ulloa. 2008. Flaming for Weed Management. Chapter 4, pages 61-74. In: Integrated Weed Management: Fine Tuning the System. Extension Bulletin E-3065. (132 pages), Michigan State University, East Lansing.

Lindquist J. L. and S. Z. Knezevic. 2001. Quantifying crop yield response to weed population: Applications and Limitations in Biotic Stress and Yield Loss, edited by Robert K.D.Peterson and Leon Higley . CRC Press LLC, Boka Raton, Florida, 33431. ISBN 0-8493-1145-4.