Monitoring and Mitigating the Spread of Plant Disease
ARS is committed to controlling plant diseases to protect our food security and ensure an adequate supply of non-food crops for feed, fiber, energy, and horticultural uses. Plant diseases have significant impacts on yields and quality, resulting in billions of dollars in economic losses and management inputs each year to crops, landscapes, and forests in the United States. Effective control of plant diseases requires an understanding of the biology of disease-causing agents. The following FY 2020 accomplishments highlight ARS successes in identifying and studying the spread of plant diseases.
Predicting the spread of two severe citrus diseases by hurricanes. Asiatic citrus canker (ACC) and citrus black spot (CBS) cause economic damage and are severe impediments to international trade of citrus as a commodity. ACC, caused by a bacterium, and CBS, caused by a fungus, are both dispersed by rain splash. During a hurricane, such rain splash can be spread over many miles. Two such hurricanes, Harvey in southeast Texas and Irma in southwest Florida, potentially spread ACC and CBS, respectively, in 2017. ARS researchers in Fort Pierce, FL, adapted and extended a previously developed hurricane dispersal model to address both diseases and make predictions for where these infections may have spread due to the hurricanes. The results of these model predictions were presented to regulatory agencies and science advisory committees in Florida and Texas. ARS researchers also developed a model to predict where to look for pathogen entries that were rejected by the hurricane models. As a result, regulatory agencies in both States in collaboration with the USDA Animal and Plant Health Inspection Service have deployed the surveys for early detection of potential spread of these diseases in both States.
Identification and movement of a nematode causing beech leaf disease in North America. The American beech tree is a major tree species in North American deciduous forests, and in 2012, the green and yellow stripes of beech leaf disease (BLD) were first discovered near Cleveland, Ohio. Scientists from ARS in Beltsville, MD, along with USDA Forest Service, the state of Ohio, Holden Arboretum, and the Canadian province of Ontario, identified and described a new subspecies of foliar plant-parasitic nematodes in beech leaves. The scientists demonstrated nematode transmission to beech buds and leaves and described its eastward movement and distribution within North America during different seasons. This potentially lethal BLD nematode is of international concern because it is believed to be an invasive species from Asia, where it causes relatively minor damage. These results are important to pathologists, arborists, and regulators of domestic and international trade who want to contain this nematode and reduce its destruction.
New bacterial plant pathogen of onions. Onion production in New York is valued at more than $39 million. Losses due to bacterial diseases can be up to 75 percent in infected fields. There are currently no pesticides that are effective on bacterial rots. ARS scientists in Ithaca, NY, discovered a new species of bacteria responsible for an onion disease in New York state. Using genomic information, they determined this species of bacteria was not previously known to exist in the United States. This information is useful for USDA’s Animal and Plant Health Inspection Service for monitoring the introduction and spread of plant disease-causing bacteria in the United States.
First report of grapevine red blotch virus in Idaho. Some grapevine viruses are detrimental to grapevine health, crop load ratio, fruit characteristics, and ultimately to wine quality, while others cause only minor issues. ARS scientists in Parma, ID, with University of Idaho collaborators, conducted research on grapevine viruses in collaboration with commercial grape growers. This work is the first report on the presence of grapevine red blotch virus (GRBV) in Idaho commercial vineyards. Multiple years of sampling and testing for GRBV indicate the spread of this virus is limited in Idaho. These findings can be used by the grape industry for making vineyard replanting decisions.