Date of Award


Degree Type


Degree Name

Master of Science




Biology (MS)

First Advisor/Chairperson

Dr. Donna Becker


Potato scab disease is caused by the pathogen Streptomyces scabies and leads to significant crop losses annually worldwide. There is growing public and scientific concern regarding the human and environmental safety with the use of many pesticides and current disease control measures. In lieu of this, the use of medicinal plant species as organic green manure treatments against potato scab disease was evaluated in field studies. Green manure applications of calendula (Calendula officinalis resina) and comfrey (Symphytum officinale) simultaneous to potato (Solanum tuberosum) planting in field studies were evaluated for scab reduction qualities. Treatments were designed to mimic home garden/family farm type operations and were applied as a single layer of rough chopped plant material coverage directly along with potato tubers within the planted rows. These treatments consisted of calendula, comfrey, and a calendula/comfrey mixture. In pilot study, treatments of both calendula and comfrey showed potent potato scab disease reductions of approximately 20%. The use of comfrey as a green manure increased total potato production by 24%. Follow-up field study using comfrey as a green manure showed similar results with an overall decrease in scab disease of 18.8% and demonstrated increased harvest yields. Results of this experiment suggest the use of these green manures as a feasible, effective, organic means of potato scab control and warrant further research into the use of these and other medicinal plants in the treatment plant disease.

Access Type

Open Access

Included in

Agriculture Commons