Water Or Soil Problem

Please accept our apologies for the delay in responding! This looks like it could be too much water, and/or a soil drainage problem. If the soil is consistently wet, and does not drain well leaves can turn yellow and develop water-soaked areas (like the dark spots on the leaves, the leaf stem, and the mid-vein). Very heavy clay soils hold too much water and drain poorly; unfortunately many soils in CA are like this. We recommend using a soil probe to determine soil moisture in the root zone water accordingly, allowing the soil to dry down a bit between waterings. Weather conditions determine the rate of evaporation so it varies. Trees weakened by water issues (or other inappropriate soil conditions, as discussed in the following web-link) can make the tree more susceptible to disease. The brown spots may be the result of a fungal or bacterial disease, but we recommend getting the advice of a licensed arborist, or take some leaf samples (sealed in a bag) to your local Dept of Agriculture Office, before attempting to use disease control products. The Ag Dept will usually send the samples to the county plant pathologist and reply to you for free. Be sure to provide as much info about the growing environment and care practices as possible.