As you know we had a great rainfall yesterday (May 18) and last week, so there is a chance the soil is saturated with water. Commercial fruit growers usually rely on irrigation system that is set to water trees couple of times a week. Homeowners who have fruit trees also have simple electric timer to water their trees and landscape plants.
I have visited many citrus groves that trees were suffering from Phytophthora Root Rot because owner did not turn off irrigation system in rainy days. I have seen same case scenario in homeowner’s landscape. So, what to do? Turn of your irrigation until you test the soil and determine that it is not wet.
What is Phytophthora Root Rot?
Phytophthora root rot is a fungal disease and causes a slow decline of the tree, especially in new plantings. The leaves turn light green or yellow and may drop, depending on the amount of infection. The disease destroys the feeder roots of susceptible rootstocks. The pathogen infects the root cortex, which turns soft and separates from the stele. If the destruction of feeder roots occurs faster than their regeneration, the uptake of water and nutrients will be severely limited. The tree will grow poorly, stored energy reserves will be depleted, and production will decline.
Management of Phytophthora root rot involves the use of resistant rootstocks, irrigation management, fungicides, and fumigation.
For more information refer to EDIS and UCANR