|I noticed that the leaves on the lower branches of our dogwood have developed reddish brown spots, giving the
leaves a mottled appearance. We have not had a good rain in over a month and have water restriction due to the
drought. Not knowing much about these trees I have not been giving it a whole lot of water lately; concentrating on our veggies and flowers instead. Are these spots from lack of water or the anthracnose disease? If you think it is drought related, what is my best watering or fertilizing strategy?
|Unfortunately I can't identify the specific cause of the spots you are seeing -- they could be anthracnose but they could also be cercospora or septoria fungus .... or drought stress. You might wish to take a sample to your County Extension (429-7085) where they should be able to help you identify it and suggest the most effective control measures currently used in your area. In any case, remove and destroy any fallen leaves now and in the fall to try to limit reinfection.
These trees prefer an evenly moist yet well drained soil (meaning not soggy) and have fairly shallow root systems so they are very susceptible to drought damage. You might try to water it throughout the root zone (out as far as the branches and often extending further) and then mulch the area with several inches of an organic mulch such as shredded bark to try to keep the soil moist and cool. Dig down a bit and see how effective your watering actually is; it can take an amazing amount of water to do a thorough job. Then, periodically check and see if the soil is dry an inch or two beneath the surface. If so, water again. Water slowly and deeper rather than daily light sprinkling. The frequency will depend on the soil type, the precipitation and the drainage pattern but a rule of thumb is an inch of water a week from the sky or the hose.
These trees are not heavy feeders and any fertilizing would be done in the late fall or early spring. They do require an acid soil. You might wish to run some basic soil tests and find out if you need to take any action. Your County Extension should also be able to help you with the tests and interpreting the results.