Phytophthora means “plant destroyer,” and this group of pathogens does billions of dollars in damage each year. Phytophthora species cause root rot, stem rot and leaf blight diseases in many plant species, including horticultural crops such as strawberries and tomatoes; field crops such as soybean and potatoes; and trees such as oak and chestnut.
One species that causes late blight disease is responsible for more than $6.7 billion in potato and tomato production losses worldwide annually, according to USDA’s Agricultural Research Service. Similarly, Phytophthora root and stem rot can be a devastating soybean disease.
Phytophthora pathogens can persist in the soil for a long time—making disease management challenging. Additionally, some have developed resistance to chemical control. For instance, fungicides used for Phytophthora root rot in strawberries are now ineffective in some areas.
USDA’S National Institute of Food and Agriculture (NIFA) invests in and supports initiatives that ensure the long-term viability and sustainability of agriculture. As part of that mission over the last 15 years, NIFA has funded $84 million in projects focused on ways to combat Phytophthora’s threat to agriculture and forestry through its Agriculture and Food Research Initiative Competitive Grant, Specialty Crop Research Initiative Grant and other competitive grant programs.
“Projects have focused on developing resistant varieties, understanding the host-pathogen interaction, screening for fungicide resistance, improving pathogen detection and determining cultural practices effective in controlling diseases caused by Phytophthora species,” said Emmanuel Byamukama, national program leader in NIFA’s Institute of Food Production and Sustainability, Division of Plant Systems-Protection.
Research Making a Difference
In strawberries and other specialty crops, projects have focused on developing tools to help growers manage Phytophthora root rot. University of Florida scientists determined that thermotherapy, a heat-based technique, improves management of fungicide-resistant Phytophthora.
At Tennessee State University, researchers are evaluating biological controls that could protect plants against Phytophthora capsici, which affects multiple crops including pepper, tomatoes and sweet potato.
The University of California leads a multistate trial investigating five advanced Phytophthora root rot and salinity resistant avocado rootstocks, in combination with different scions, to test their potential to increase avocado production in the United States.
Early and accurate detection of pathogens ensures producers and growers can make appropriate management decisions. University of Georgia researchers developed a technique in which parasitic wasps can detect squash fruits infected with P. capsici.
In partnership with USDA’s Animal and Plant Health Inspection Service, NIFA funds the National Plant Diagnostic Network (NPDN). The NPDN conducts testing for diseases caused by Phytophthora as well as other pathogens. NPDN labs are a critical element in USDA’s overall plant protection efforts.