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William G Johnson

Botany and Plant Pathology 

  • Professor
765.494.4656
765.494.0363
Lilly Hall Room 1-361

Rationale

The estimated average monetary loss caused by weeds in field crops grown in the U.S. is over 4 billion dollars each year. Weed management expenses are one of the largest variable costs incurred by growers annually. Weeds growing on cropland are like crop plants themselves, drawing upon the soil and air for essential elements. Unfortunately, weeds obtain essential elements at the expense of adjacent crop plants. The result of inadequate weed control is a reduction of crop yield and quality. Traditionally, weed management practices have included preventative, cultural, mechanical, biological, and chemical tactics. However, with the rapid increase in the number of effective herbicides in the 1960-1990's, weed management techniques have become more reliant on herbicides in the last 20 years. In any biological system, strong dependence on any single tactic results in selection pressure for species (weeds, insects, and/or diseases) which can exploit the niche left by the single tactic. As a result of overdependence on herbicides, the number of herbicide-resistant weeds has grown from less than 10 in the 1960's to over 200 in 2009. Additionally, there are over 1000 non-indigenous plant species which can potentially infest crop production systems if given the opportunity. Therefore, production of food for humans and livestock and the economic well being of Indiana farmers depends heavily on effective, integrated management of weeds and other plant pests.

My Program Objectives
  1. Develop weed management systems that are economically and environmentally sound, integrate cultural practices with judicious herbicide use, improve efficiency of production, and minimize selection pressure for herbicide-resistant weeds.
  2. Promote grower acceptance of these weed management systems through education efforts targeting growers, crop consultants, input suppliers, industry representatives and extension educators in Indiana and surrounding states.
To that end, my efforts are focused on the following topics:
  1. Biology, Management, and Distribution of Glyphosate Resistant Horseweed, Giant Ragweed, Volunteer Corn, and other Weeds.
  2. Interactions Between Weeds and Other Plant Pests Such as Soybean Cyst Nematode, and Western Corn Rootworm.
  3. Management of Weeds Common to No-Till Systems.
  4. Evaluation and Management of New Weed Management Tools and Transgenic Events such as 2,4-D Resistant Crops, Dicamba-Tolerant Soybeans, and Optimum GAT Crops.

Awards & Honors

(2014) Outstanding Graduate Educator Award. Purdue University College of Agriculture.

(2013) Seed For Success Research Award (for a grant exceeding $1,000,000). Purdue University.

(2011) NCWSS Fellow. North Central Weed Science Society.

(2010) Outstanding Extension Specialist Award. Weed Science Society of America.

(2009) CropLife Educator of the Year. Mid American CropLife Association.

(2008) Purdue Agriculture Team Award. Purdue University College of Agriculture.

(2014) Advisor - NCWSS Outstanding Graduate Student (Jessica Schafer). North Central Weed Science Society.

(2012) Advisor - NCWSS Outstanding Graduate Student (Paul Marquardt). North Central Weed Science Society.

(2011) Advisor - NCWSS Outstanding Graduate Student (Chad Brabham). North Central Weed Science Society.

(2010) Advisor - WSSA Outstanding Graduate Student (Vince Davis). Weed Science Society of America.

Selected Publications

Marquardt, P. T., Krupke, C., Camberato, J., & Johnson, W. G. (2014). The Effect of Nitrogen Rate on Transgenic Corn Cry3Bb1 Protein Expression.. Pest Management Science, 70, 763-770.

Schafer, J. R., Hallett, S. G., & Johnson, W. G. (2014). Rhizosphere Microbial Community Dynamics in Glyphosate-Treated Susceptible and Resistant Biotypes of Giant Ragweed (Ambrosia trifida). Weed Science, 62, 370-381.

Yerka, M. K., Wiersma, A. T., Lindenmayer, R. B., Westra, P., Johnson, W. G., Leon, N. D., & Stoltenberg, D. E. (2013). Reduced translocation is associated with common lambsquarter (chenopodium album L.) tolerance to glyphosate.. Weed Science, 61, 353-360.

Robinson, A. P., Davis, V. M., Simpson, D. M., & Johnson, W. G. (2013). Response of soybean yield components to 2,4-D.. Weed Science, 61, 68-76.

Schafer, J. R., Hallett, S. G., & Johnson, W. G. (2013). Soil microbial root colonization of glyphosate-treated giant ragweed (Ambrosia trifida), horseweed (Conyza canadensis), and common lambsquarters (Chenopodium album) biotypes.. Weed Science, 61, 289-296.

Roskamp, J. M., Chahal, G. S., & Johnson, W. G. (2013). The Effect of Cations and Ammonium Sulfate on the Efficacy of Dicamba and 2,4-D.. Weed Technology, 27, 72-77.

Marquardt, P. T., Terry, R. M., & Johnson, W. G. (2013). The Impact of Volunteer Corn on Crop Yields and Insect Resistance Management Strategies. Agronomy 2013, 3, 488-496.. Agronomy, 2013(3), 488-496.

Roskamp, J. M., & Johnson, W. G. (2013). The Influence of Adjusting Spray Solution pH on the Efficacy of Saflufenacil. Weed Technol. 27:445-447.. Weed Technology, 27, 445-447.

Davis, V., Chahal, G. S., & Johnson, W. G. (2012). Influence of spring herbicide applications on winter weed emergence in corn and soybean production systems. Crop Management, doi:10.1094/CM-2012--0413-01-RS. Retrieved from http://www.plantmanagementnetwork.org/cm/element/sum2.aspx?id=10303

Schafer, J. R., Hallett, S. G., & Johnson, W. G. (2012). Response of giant ragweed (Ambrosia trifida), horseweed (Conyza canadensis), and common lambsquarters (Chenopodium album) biotypes to glyphosate in the presence and absence of soil microorganisms.. Weed Science, 60, 641-650.