Michael Flessner

Crops

Herbicide resistant weeds are a serious threat to agricultural productivity in Virginia. The number of herbicides resistant weed species and the number of herbicides weeds are resistant to is increasing. Unfortunately, this trend is expected to continue. Research efforts to address this challenge include harvest weed seed control (mechanical weed seed destruction or removal at harvest), optimizing herbicide programs for resistance mitigation by increasing effective sites of action, cover crops, and evaluation of new crop traits.

Forages

Weeds can reduce forage yield, quality, and utilization. Many highly effective herbicide options exist for broadleaf weeds, but are not fully utilized due to cost, lack of perceived benefit, injury or death of desirable legumes, and other reasons. Controlling grassy weeds is also challenging due to limited herbicide and other control options. Research efforts to improve weed management in pastures and hayfields include optimizing herbicide application timing, evaluation of new herbicides, assessing alternative application techniques such as dry fertilizer impregnation, and others.

Program Focus

Dr. Flessner’s Extension program provides statewide leadership in the development and dissemination of weed management best practices for agronomic crops and pasture/forage. Emphasis is placed on current challenges such as management of herbicide-resistant weed species. Dr. Flessner develops publications, web-based media, and presentations in conjunction with Virginia Cooperative Extension, with the mission of empowering stakeholders through nonbiased, research-based information. 

Resources

• Flessner Lab Website
• Virginia Weed Identification Clinic 
  • Dr. Flessner is part of a collaborative team who identify and offer control and management recommendations for unknown weed species sent in from throughout Virginia. The Weed ID Clinic has been operating since 1985 and has identified plant samples from every county and independent city in the commonwealth.  Over 1000 unique species have been sent to the clinic in the past decade. Contact your local Virginia Cooperative Extension office to send in a sample.
• Virginia Tech Weed Identification App
• Pest Management Guide
  • This resource is freely available for download or is available at your local extension office. Dr. Flessner is part of a collaborative team of weed scientists from the mid-Atlantic region that assemble and annually revise these recommendations. Recommendations are based on herbicide efficacy testing.
• Virginia Ag Pest and Crop Advisory Blog
  • Timely updates from Dr. Flessner and other Extension Specialists.
• Extension Publications

Assistant Professor | 2014 – Present
Department of Plant Pathology, Physiology, and Weed Science
Virginia Polytechnic Institute and State University 

Research Associate II-IV | 2010 – 2014
Agronomy and Soils
Auburn University

Graduate Research Assistant | 2008 – 2010
Agronomy and Soils
Auburn University

Research Assistant | 2008 – 2010
Plant Sciences 
University of Tennessee

• Northeastern Weed Science Society Outstanding Researcher Award, 2019

Corresponding author in bold, * denotes student under Dr. Flessner

1. Pittman, K. B., Cahoon, C. W., Bamber, K., Rector, L. S.,* & Flessner, M. L. 20XX. Herbicide selection to terminate grass, legume, and brassica cover crop species. Weed Technology. Accepted October 8, 2019.
2. Pittman, K. B.,* Barney, J. N., Cahoon, C. W., & Flessner, M. L. 20XX. Assessing the germination and seed maturation phenology of hairy vetch (Vicia villosa) as it relates to weediness in subsequent crops. Weed Research. Accepted July 28, 2019.
3. Flessner, M. L., Byrd, J., Bamber, K. W., & Fike, J.H. 20XX. Evaluating herbicide tolerance of industrial hemp (Cannabis sativa L.). Crop Science. Published Online October 16, 2019. Doi: 10.2135/cropsci2019.04.0249
4. Rector, L.,* Pittman, K., Beam, S.,* Bamber, K., Cahoon, C., Frame, W., & Flessner, M. 20XX. Herbicide Carryover to Various Fall Planted Cover Crop Species. Weed Technology. Published Online August 22, 2019. doi: 10.1017/wet.2019.79
5. Flessner, M., & Pittman, K.* 2019. Horseweed control with pre-plant herbicides after mechanical injury from small grain harvest. Agronomy Journal. 111:1-7. doi: 10.2134/agronj2019.03.0174
   
6. Askew, M. C., Cahoon, C., Flessner, M., VanGessel, M., Langston, D., & Ferebee, J. H. 2019. Chemical termination of cover crop rapeseed (Brassica napus L.). Weed Technology. 33:686-692. doi: 10.1017/wet.2019.50
7. Ferebee, J. H.,* Cahoon, C., Flessner, M., Langston, D., Arancibia, R., Hines, T., Blake, H., & Askew, C.* 2019. Comparison of diquat, glufosinate, and saflufenacil for vine desiccation of Dark Red Norland potato (Solanum tuberosum L.). HortTechnology. 29:643-648. doi: 10.21273/HORTTECH04327-19
8. Ferebee, J. H.,* Cahoon, C., Besançon, T., Flessner, M., Langston, D., Hines, T., Blake, H.,* & Askew, M. C.* 2019. Fluridone and acetochlor cause unacceptable injury to pumpkin (Cucurbita pepo L.). Weed Technology. 33:748-756. doi: 10.1017/wet.2019.42
9. Beam, S. C.,* Mirsky, S., Cahoon, C., Haak, D., & Flessner, M. 2019. Harvest weed seed control of Italian ryegrass (Lolium perenne ssp multiflorum), common ragweed (Ambrosia artemisiifolia), and Palmer amaranth (Amaranthus palmeri). Weed Technology. 33:627-632. doi: 10.1017/wet.2019.46
10. Askew, C.,* Cahoon, C., York, A., Flessner, M., Langston, D., & Ferebee, H.* 2019. Cotton (Gossypium hirsutum L.) tolerance to halauxifen-methyl applied preplant. Weed Technology. 33:620-626. doi: 10.1017/wet.2019.41
11. Beam, S.,* VanGessel, M., Vollmer, K., & Flessner, M. 2019. Grape hyacinth [Muscari botryoides (L.) Mill] control in a wheat-soybean rotation. Weed Technology. 33:578-585. doi: 10.1017/wet.2019.29
12. Flessner, M. L., Lassiter, A.,* & Bamber, K. W. 2019. Japanese stiltgrass control with herbicides in cool-season grass forages. Crop, Forage, and Turfgrass Management. 5:190002. doi: 10.2134/cftm2019.01.0002
13. Pittman, K. B.,* Barney, J. N., & Flessner, M. L. 2019. Horseweed (Conyza canadensis) suppression from cover crop mixtures and fall-applied residual herbicides. Weed Technology. 33:303-311. doi: 10.1017/wet.2018.111
14. Beam, S. C.,* Flessner, M. L., & Pittman, K. B.* 2018. Soybean flower and pod response to fomesafen, acifluorfen, and lactofen. Weed Technology. 32:444-447. doi:10.1017/wet.2018.37
15. Randhawa, R. S.,* Westwood, J. H., Cahoon, C. W., & Flessner, M. L. 2018. Interference and control of ALS-resistant mouse-ear cress (Arabidopsis thaliana) in winter wheat. Weed Technology. 32:671-677. doi: 10.1017/wet.2018.69
16. Haring, S. C.* & Flessner, M. L. 2018. Improving soil seed bank management. Pest Management Science. 74: 2412-2418. doi: 10.1002/ps.5068