Which species is responsible for Phytophthora gummosis in citrus?

Phytophthora gummosis in citrus is specifically caused by the Phytophthora species, particularly Phytophthora citrophthora and Phytophthora parasitica. These pathogens are soil-borne oomycetes that infect the root system of the citrus trees, leading to gummosis, which is characterized by the production of sap-like gum that oozes from the bark and can eventually cause the tree to decline and die if not managed properly. The presence of these pathogens can lead to significant damage in citrus orchards, and recognizing the causal agent is crucial for implementing effective management strategies.

The other species listed are not related to the gummosis in citrus. Pseudococcus longispinus and Planococcus citri are both mealybug species that can cause damage to citrus but are not responsible for gummosis. Icerya purchasi, known as the cottony cushion scale, is another pest that affects citrus plants but does not cause this specific disease. Understanding the specific pathogens and their effects helps in addressing the health of citrus orchards effectively.