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

Education:

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

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").

My interests include, but are not limited to, weed ecology, crop-weed interactions as affected by cropping practices and nutrient management, herbicide technology and systems simulation.

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

Student Projects (Graduate & Undergraduate):

1. TBA (BSc, 2008). Critical time for weed removal in sunflower.
2. TBA (MSc, 2008-present). Crop yield as influenced by flaming.
3. Santiago, Ulloa (PhD, 2007-present). weed control with flaming.
4. Chris Bruening (MS-2007-present). Designing and testing new hood for crop and weed flaming.
5. Heverton Zappa Teixeira (BSc, 2007). Corn and soybean tolerance to flaming.
6. Andre Domingues (BSc, 2007). Weed tolerance to flaming.
7. Janyce Woodard (PhD, part time), 2004-present. Riparian buffer crops: quantifying
species growth and weed control.
8. Jim Schoenberg (MA-part time), 2005-present. Western ragweed control in pasture
9. Aaron Queen (MS), 2004-2006, Mapping likely areas for purple loosestrife infestation using simple weighted GIS model.
10. Shawn Hock (MS), 2001-2004, Competitiveness of major weed species in soybean.
11. Travis Gustafson (MS), 2002-2005, Effects of early season insect defoliation on the critical time for weed removal in soybean.
12. Katie Wrade (MA), 2003-2005. Field sandbur control in corn.
13. Christy McCoy (BSc, 2001). Velvetleaf control as influenced by glyphosate rates.
14. Sean Evans (MS), 1999-2001, Critical period of weed control in corn.

Major Project Activities

Current program activities (Year 2007):

I. Herbicide screening: 35 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. Specific goal is 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. The overall goal is to aid in developing cost effective integrated weed management system for organic crop production.

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 piping plover (Charadrius melodus) and interior least tern (Sterna antillarum) along Missouri river.

3. Winter annual weed control with Fall applied herbicides.

4. Control of problem weeds in Roundup-Ready soybeans. Objectives are determine: (1) Biologically effective rates of Glyphosate used alone, (2) tank mixes of glyphosate and other POST herbicides and (3) soil applied (PRE) herbicides for problem weeds in soybean. The list of weed species includes: morninglory, bindweed, buckwheat, Pennsylvania smartweed, Venice mallow, sweet clover, velvetleaf, lamb's-quarters, and nightshade. Funded by the Nebraska Soybean Board.

5. 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 4 locations along the Missouri, Niobrara and Platte rivers.

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

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.

Selected Extension Publications:

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

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

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

4. Heckmen and Knezevic et al. 2002. Spotted and Diffuse Knapweed. UNL-Extension
Publication. EC-02-173-S.

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

6. Hunt T. and S. Knezevic, 2002. Monitoring Procedures for Galerucella Beetles to
Control Purple Loosestrife. Extension Circular. UNL-Extension Publication.
EC02-175.

7. Knezevic, S. and D. Smith. 2001. Rearing and Releasing Galerucella Beetles to
Control Purple Loosestrife.NebGuide. UNL-Extension Publication. G01-1436-A.

Research Publications:

1. Knezevic, Z. S.,  S. F. Weise & C. J. Swanton. 1994. Interference of redroot  pigweed in corn. Weed Science 42: 568 -573.
2. Knezevic, Z. S., S. F. Weise and C. J. Swanton. 1995. Comparison of empirical models depicting density ofAmaranthus  retroflexus L. and relative leaf area as predictors of yield loss in maize (Zea mays  L.).  Weed Research. 35: 207 - 214.
3. Knezevic, Z. S., 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.
4. Knezevic, Z. S., and M. J. Horak. 1998. Influence of emergence time and density on redroot pigweed.  Weed Sci. 46:665-672.
5. Knezevic, Z. S., 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 Tech. 12:670-676.
6. Knezevic, Z. S., M. J. Horak and R. L. Vanderlip. 1999. Estimates of physiological determinants for redroot pigweed. Weed Sci: 47:291-296.
7. 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 Tech. 13:283-289.
8. 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.
9. Knezevic Z. S., S.P.Evans, C. A. Shapiro and J. L. Lindquist. 2000.  Effect of nitrogen on critical period of weed control in corn. Proceedings of the 3rd Intern. Weed Science  Soc. 113-136. Iguassu Falls. Brazil.
10. Swanton, C. J., A.  Shrestha,  R. C. Roy and S. Z. Knezevic, 2000. Vertical seed bank distribution changes with Tillage practice  in sandy soils. Canadian Journal of Plant Science 80:455-457.
11. 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 Tech. 14: 578-585.
12. 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. Canadian Journal of Plant Sci. 80: 963-972.
13. Elmore, R. W. ,  F. W. Roeth,   L. A. Nelson, C. A. Shapiro,  R. N. Klein,  S. Z. Knezevic, and A. Martin. 2001. Glyphosate-resistant soybean cultivar yields compared to sister lines. Agron. Journal.93,2:408-412.
14. Elmore, R. W., F. W. Roeth,  R. N. Klein,  S. Z. Knezevic,  A. Martin, L. A. Nelson, and C. A. Shapiro. 2001. Glyphosate-resistant soybean cultivar response to glyphosate. Agron. 93, 2:404-407.
15. Knezevic, Z. S., M. J. Horak and R. L. Vanderlip.  2001.  Relative time of Amaranthus retroflexus affects partitioning of dry matter. Weed Science. 49:617-621.
16. 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 Research 42:76-87.
17. Knezevic Z. S., 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(6)773-786.
18. 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.
19. Evans S, 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.
20. Knezevic, S., S.Evans and M.Mainz. 2003. Yield Penalty Due to Delayed Weed Control in Corn and Soybean. Crop Management Journal online: http://www.plantmanagementnetwork.org/pub/cm/research/2003/delay/
21. Knezevic, Z. S., S.Evans and M.Mainz. 2003. Row spacing influences critical time of weed removal in soybean. Weed Tech. 17:666-673.
22. Knezevic, Z. S. and. K. Cassman. 2003. Use of herbicide tolerant crops as a component of an IWM. Crop Management. J. online:  http://www.plantmanagementnetwork.org/pub/cm/management/2003/htc/
23. Blankenship E., W. Stroup, Evans S. P., and S. Z. Knezevic. 2003. Statistical Inference for Calibration Points in Nonlinear Mixed Effects Models. Journal of Agricultural, Biological and Environmental Statistics. Vol 8, No 4, 455-468.
24. Knezevic, Z. S.,A. Kantrovich, and B.  Masters. 2003. Eastern Red Cedar Control in Pasture. Crop Management Journal. http://www.plantmanagementnetwork.org/pub/cm/management/2003
 25. 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 Tech. 19:1056-1064.
26. Knezevic, Z. S et al..  2004. Purple loosestrife control using herbicides: Single year application. Weed Tech. 18:1255-1260
27. HockS., S.Knezevic, A.Martin and J,Lindquist. 2005. Influence of soybean row width and velvetleaf emergence time on velvetleaf. Weed Sci 53:160-165, 2005
28. Kappler B., S. Knezevic, et al. 2005. Comparison of Glyphosate-Based Herbicides in Nebraska. Crop Management Journal. http://www.plantmanagementnetwork.org/pub/cm/management/2005
29. Hock, S, S. Knezevic, C.Petersen, J.A. Easton, and A.R. Martin (2005-06-28). Germination Techniques for Common Lambsquarter and Pennyslvania Smartweed. Weed Technology, 20:530-534. 
30.Hock, S, S. Knezevic, A. R. Martin, and J. L. Lindquist. 2006. Performance of WeedSOFTR for predicting soybean yield loss. Weed Technology 20:478-484.
31. 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 Science 54:354-363.
32. Gustafson T, S. Knezevic, T. Hunt and J.Lindquist. 2006.  Early-season insect defoliation influences the critical time for weed removal in soybean. Weed Sci, 54: 509-515.
33. Gustafson T, S. Knezevic, T. Hunt and J.Lindquist. 2006. Simulated insect defoliation and duration of weed interference affected soybean growth. Weed Sci, 54:735-742.
34. Hock S., S. Knezevic, B.Johnson, C.Srague and A. Martin. 2007.  WeedSOFT: Effects of Corn Row Spacing for Predicting Herbicide Efficacy on Selected Weed Species. Weed Tech. 21:219-224.
35. Lindquist J.L. Barker, D. C., S. Z. Knezevic, and D. Walters. 2007.  Comparative nitrogen uptake and distribution  in corn and velvetleaf (Abutilon theophrasti). Weed Science 55:102-110.
36. Wicks G.,S.Knezevic, et al. 2007.Effect of planting depth and isoxaflutole rate on corn injury in Nebraska. Weed Tech. 21:642-646.
37. Knezevic S. 2007. Herbicide Tolerant Crops:10 years later. Maydica, In Print.
38. Knezevic,S., J.Streibig and C.Ritz. 2007.Utilizing R software package for dose response studies: the concept and data analysis. Weed Tech. 21:840-848.
39. Gustafson T, S. Knezevic, T. Hunt and J.Lindquist. 2007. Early season defoliation and weed interference in soybean: effects on weed management and economic injury levels. Economic Entomology. Accepted.
40. Bača F., J. Lević, S. Stanković, L. Stefanović, M. Simić, S. Gošić-Dondo, S. Kneževic. 2007. Factors Contributing to the Population Changes of Major Maize Pests in Serbia. Maydica. In print.
41. Hock, S, S. Knezevic, and G. Wiecko. 2007. Glyphosate Dose Affected Control of Field Dodder (Cuscuta  campestris). Weed Tech. Accepted.
42. Knezevic and Ulloa. 2007. Flaming: New potential tool for weed control on agronomic crops. Proceedings of the 3rd international conference: Innovations in Agriculture. Univ. of Belgrade, Belgrade, Serbia. pages 65-77.
43. Klein B., S. Knezevic, et al. 2007.  Glyphosate Efficacy as Influenced by Spray Particle Size. Weed Tech. Submitted.
44. Klein, R.N., A.D. Pavlista, C.A. Shapiro, D.J. Lyon, D.D. Baltensperger, G.W. Hergert, S. Knezevic, S.C. Mason, L.A. Nelson, R. Elmore, M. Vigil, A. Schlegel, B. Olson, and R. Aiken. (submitted). Yield of  Corn (Zea mays L.) Grown under Semi-Arid Conditions in Skip-Row Patterns. Agron. J.
45. Evans S. P., S. Z. Knezevic, C. Shapiro and J. L. Lindquist. 2007. Effect of N Supply and Weed Interference on Soil NO3-N and Midseason N Uptake by Corn (Zea mays L.). Weed Science. In preparation.

Book Chapter:

Lindquist L. J. and S. Z. Knezevic. 1999. Quantifying crop yield response to weed population: Applications and Limitations in Biotic Stress and Yield Loss, edited by Robert K. D. Peterson and Leon Hidley . The book will be published by CRC Press with an expected release date January, 2000.