This work was partially funded by the Stockton East Water District — Crown rot and root rot caused by Phytophthora species are diseases of great concern for almond growers. Many people believe that irrigating with surface water puts your trees at risk of Phytophthora, and that irrigating with groundwater is the best way to prevent these diseases. However, a recent study of Phytophthora in irrigation water and orchard soils tells a different story.
The Bottom Line:
Irrigation management is Phytophthora management. This study showed that Phytophthora is common in orchard soils. Regardless of whether they are irrigated with surface water or groundwater, over 30% of tested orchard soils were positive for Phytophthora. Since water (either standing water or saturated soil) allows Phytophthora to cause disease, good irrigation management is crucial to prevention, no matter what your water source…