Document Type

Honors Thesis




Jianjun Hao, Seanna Annis

Committee Members

Julia McGuire

Graduation Year

May 2023

Publication Date

Spring 2023


Potatoes (Solanum tuberosum L.) are the most valuable crop in the state of Maine. Despite the crop’s success in the state, potato growers still face the challenges of various abiotic and biotic stresses, including diseases such as potato early dying, caused by the soilborne fungal pathogen, Verticillium dahliae. The disease has been controlled by soil fumigation and fungicides. As an alternative method, organic byproducts, such as lobster shell meal (LSM) or compost, can be used. The benefit of using LSM is thought to occur through the promotion of beneficial chitinolytic soil microbes which can degrade LSM. The derivatives from the LSM degradation can be a food source for some beneficial microbes that consequently suppress V. dahliae. To evaluate the efficacy of compost and LSM as a disease-suppressive tool, a greenhouse study was performed. Potato ‘Shepody’ seed pieces were planted in soil mixed with compost (10% pot volume) and/or LSM (1 lb/cu yd), with some being infested with V. dahliae. Plants were evaluated for emergence, disease symptoms, height over time, and biomass during the growth stage and after harvest. The soil was sampled from the pots during the growing period, and the survival of V. dahliae was examined using soil dilution plating and quantitative polymerase chain reaction (qPCR). Results showed there was little difference in plant emergence and plant height between treatments. However, compost with or without LSM was found to increase root biomass. LSM alone showed a decrease in the number of tubers, yet an increase in total tuber mass. Stem lesions caused by V. dahliae were larger on the compost treatments, while all treatments had similar disease ratings. Both soil plating and qPCR were inconclusive due to challenges in their protocols. Further investigation is needed to determine if LSM is a useful tool in V. dahliae management.