Rust Diseases Cause Devastation to Ornamental Plants

February 12, 2004 - 13:53

An increase in the spread of rust diseases could have devastating results on our industry, say pathologists at The American Phytopathological Society (APS). According to James W. Buck, assistant plant pathology professor at The University of Georgia, a fungal infection called rust has the ability to negatively affect production of many ornamental crops, which include both nursery and floriculture crops.

An increase in the spread of rust diseases could have devastating results on our industry, say pathologists at The American Phytopathological Society (APS). The U.S. Department of Agriculture (USDA) includes deciduous and evergreen trees, woody ornamental plants, and shrubs as nursery crops; floriculture crops include foliage plants, cut flowers, flowering potted plants and bedding plants. Currently, more than 125 species of fungi that cause rust have been reported on 56 different crops.

While rust fungi do not usually kill infected plants, rust infection will reduce plant health, flower production and the overall aesthetic value of ornamental crops. According to APS, rust spores lodge in the crown of plants that have had foliage removed for shipping purposes. Infected plants develop lesions on the leave surfaces and stems. Severe infections can result in premature leaf drop.

Symptomless plants are moved through international and interstate trade, dispersing the pathogen and introducing it into areas previously pathogen-free. "Rust pathogens cannot be adequately detected on contaminated but symptomless plant material entering the United States or moving state-to-state. As such, rust pathogens have the potential to dramatically affect ornamental crop production," said Buck.

While the Plant Quarantine Act helps prevent or delay the introduction of foreign pathogens, including rusts, into the U.S., quarantine restrictions and eradication efforts have significant economic impact on crop production. International trade has made the exclusion of rust pathogens difficult because contaminated but symptomless plants have been inadvertently allowed to enter quarantined areas.

According to Buck, plant pathologists are currently working on improving detection methods and developing new diagnostic methods to accurately identify quarantined pathogens. "Because live plants are shipped all over the country, the risk for rapid disease spread is substantial," says Buck. Pathogens may become widespread and cause the quarantine to fail.

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