Blackened Leaves On Aucuba Shrub
Q: My aucuba shrub has many blackened leaves. About half are either totally black or have black spots. What is going on?
A: I’ll bet dollars to doughnuts that your aucuba has phytophthora root rot. This soil-borne disease affects several shrubs: azalea, rhododendron, daphne and aucuba are common victims. I say ‘victims’ because phytophthora dieback is fatal in most cases. The fungus itself is present in most soils. There is no way to eliminate it. The disease attacks susceptible plants when they become vulnerable due to compacted clay soil, drought stress, or winter injury. The disease works its way up from ground level; little can be done once a plant is affected except removing wilted branches. Nonetheless, a healthy plant in the correct environment can keep the disease at bay. If you decide to replace it, remove all the soil from a hole one foot deep and three feet wide and refill it with a 1:1 mix of native soil and mini pine bark nuggets.