Phytophthora

Stephen H. Futch andJames H. Graham

Phytophthora species are important soil-borne fungal pathogens worldwide that attack the root systems, trunks, and fruit of citrus trees at any age. Historical reports from Florida indicated Phytophthora was a problem as early as 1876 on sweet orange seedlings. When roots or tree trunks are affected, the foliage turns yellow and exhibits poor growth, leaves drop, twigs die back, and fruit size and yield are reduced. As fungal infection of roots and bark progress, the above-ground symptoms increase in severity. Ultimately, trees may decline and die.

Monica L. Elliott
Other Contacts: Braham Dhillon

Megan M. Dewdney

2026–2029 Florida Citrus Production Guide (Citrus Production Fundamentals).

Norma C. Flor, Douglas A. Phillips, and Philip F. Harmon

Roots serve the vital function of water and nutrient uptake for plants. Healthy roots provide the foundation for productive blueberry bushes and require the right horticultural inputs and soil environment to thrive. Less-than-ideal conditions can result in unhealthy, rotten roots, sometimes caused by disease. The most common and destructive root rot disease of southern highbush blueberry (SHB) in Florida is Phytophthora root rot (PRR), caused by the oomycete pathogen Phytophthora cinnamomi Rands. Oomycetes, or “water molds,” favor water-saturated environments. The distinction between oomycetes and fungi is important for disease management, because many fungicides work for only one group, not both. Worldwide, P. cinnamomi is a devastating pathogen of approximately 5,000 woody plant host species. For blueberry growers in Florida, PRR is a persistent problem that is currently managed through careful site selection, preparation, and routine Phytophthora-specific fungicide applications. 

Natalia A. Peres, Marcus Marin, and Juliana S. Baggio

Phytophthora crown rot, caused mainly by Phytophthora cactorum, is an important disease in Florida strawberry fields.

Megan M. Dewdney

2026–2027 Florida Citrus Production Guide (Current Season Spray Guide).