Invasive honeysuckle is a potential source of Corynespora cassiicola pathogenic to crop hosts in the United States

Authors: Fulcher, Michael; SIAS, CYNTHIA - Oak Ridge Institute For Science And Education (ORISE); MCMAHON, MATTHEW - Oak Ridge Institute For Science And Education (ORISE)

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2026
Publication Date: 4/23/2026
Citation: Fulcher, M.R., Sias, C., McMahon, M.A. 2026. Invasive honeysuckle is a potential source of Corynespora cassiicola pathogenic to crop hosts in the United States. Plant Disease. https://doi.org/10.1094/PDIS-01-26-0078-SC.
DOI: https://doi.org/10.1094/PDIS-01-26-0078-SC

Interpretive Summary: Invasive weeds can carry harmful microbes that cause plant diseases, putting crops and food production at risk. When we don’t understand how weeds and plant diseases are connected, it becomes harder to manage land and control pests. In this study, ARS scientists cooperated with the National Park Service in Maryland to study a fungus that infects Japanese honeysuckle, an invasive vine that grows across the eastern and southern U.S. They identified the fungus as Corynespora cassiicola, which causes a disease called target spot. Tests showed that this fungus can infect important crops such as cotton and tomato. Since honeysuckle is common in areas where cotton is grown, it could help the fungus survive and spread, raising the risk of crop infection. In fact, target spot has been linked to yield losses of up to 400 pounds of lint per acre in cotton, which could cost growers more than $300 per acre in severely affected fields. This research helps scientists and land managers better understand how invasive plants contribute to crop disease and informs strategies to reduce economic losses and protect agricultural productivity.

Technical Abstract: Japanese honeysuckle (Lonicera japonica) is a non-native, invasive perennial vine that colonizes disturbed sites throughout the eastern and southern United States. Surveys for endemic pathogens of honeysuckle exhibiting weed biological control activity were conducted in Maryland in 2021, and an unknown fungal species was recovered from necrotic leaf spots. Based on morphological and DNA sequence evidence, the fungus was identified as Corynespora cassiicola, causal agent of target spot on diverse plant species. Isolate pathogenicity was confirmed on honeysuckle and further evaluated on known crop hosts. Tomato, cotton, soybean, and cucumber were inoculated with colonized agar blocks and conidial suspensions. Tomato and cotton developed disease symptoms in both assays, while soybean and cucumber were not susceptible to the pathogen. Other weedy hosts of C. cassiicola have been documented, but no isolates collected from honeysuckle have been assessed previously for pathogenicity to crops. Honeysuckle populations are common in southern cotton producing regions and could facilitate the movement or persistence of C. cassiicola populations that cause target spot. Widespread, unmanaged invasive weeds may increase the risk of crop disease epidemics caused by multi-host pathogens.