Low-dose foliar treatments of the auxin analog 2,4-D reduce potato common scab and powdery scab for multiple potato cultivars and enhance root development

Authors: Clarke, Christopher; TEGG, ROBERT - University Of Tasmania; THOMPSON, HANNAH - University Of Tasmania; FREDERICK, CURTIS - Sterman Masser, Inc; HAYNES, KATHLEEN - Retired ARS Employee; Kramer, Matthew; WILSON, CALUM - University Of Tasmania

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2020
Publication Date: 5/25/2020
Citation: Clarke, C.R., Tegg, R.S., Thompson, H.K., Frederick, C., Haynes, K.G., Kramer, M.H., Wilson, C. 2020. Low-dose foliar treatments of the auxin analog 2,4-D reduce potato common scab and powdery scab for multiple potato cultivars and enhance root development. Crop Protection Journal. https://doi.org/10.1016/j.cropro.2020.105208.
DOI: https://doi.org/10.1016/j.cropro.2020.105208

Interpretive Summary: Common scab and powdery scab disease of potato are two of the costliest soilborne disease of potato and are present throughout most potato-growing regions in the world. The only effective disease management practice for both of these diseases is the planting of resistant cultivars, which is often not feasible due to environmental or economic constraints. Chemical disease management options for common and powdery scab are needed to enable growers to cultivate higher yielding and higher value potato crops. The herbicide 2,4-D has been previously shown to suppress common scab disease when sprayed onto potato plants at a sub-lethal dose. We demonstrated the common scab disease suppression activity of low-dose 2,4-D for multiple white potato cultivars grown in Eastern United States potato production, suggesting that 2,4-D treatment may be broadly effective for any potato cultivar. Additionally, we demonstrated that 2,4-D also suppresses powdery scab disease, which is morphologically similar to common scab. The tested low-dose 2,4-D treatments led to no loss of total potato yield and even enhanced potato root growth. With further optimization of low-dose 2,4-D treatment for common and powdery scab management, this research will provide a new disease management practice for potato growers to integrate into commercial growing systems.

Technical Abstract: Common scab and powdery scab are major soilborne diseases of potato (S. tuberosum). The agricultural cost of both diseases is due to the formation of lesions on the surface of the potato tuber that make the tuber unmarketable rather than a direct yield loss. There are no widely accessible and efficacious disease management options for either common scab or powdery scab. In prior work, low-dose treatment with the auxin analog herbicide 2,4-D has been shown to reduce common scab severity of select S. tuberosum cultivars in field and greenhouse settings. We tested whether low-dose 2,4-D treatment is broadly efficacious on multiple white potato cultivars used in Eastern United States potato production. Additionally, we sought to determine whether 2,4-D is efficacious for mitigating the morphologically similar powdery scab disease for Russet Burbank potatoes in a field setting. In two years of field trials in the United States, low-dose 2,4-D treatment significantly reduced common scab disease of all tested potato cultivars with no impact on total tuber yield. In two years of field trials in Tasmania, Australia, low-dose 2,4-D treatment also reduced powdery scab disease of Russet Burbank potato with no impact on total tuber yield while stimulating potato plant root growth. The ability of 2,4-D to suppress two major tuber diseases and stimulate potato root growth warrants further investigation and optimization for integration into commercial growing systems.