Manzanita disease or maybe pest

Asked June 25, 2018, 1:33 PM EDT

My manzanitas are getting spots on leaves then the leaves are turning brown and dying. It is starting at the tops on the fresh leaves.

Josephine County Oregon plant disease horticulture

3 Responses

Manzanita is very vulnerable to a dozen or more fungal pathogens that attack the leaves. The pathogens invade leaves during the wet season. When new growth starts coming out in spring they are at the most vulnerable stage for fungal infection. The fungal spores come from infected old leaves on and around the tree on the ground. To limit the infection you need to limit the amount of inoculum by cleaning up old leaves from around the trees, avoid overhead irrigation that can wet leaves, and prune and space the trees so they dry out better with good air circulation. You can also spray the new leaves in spring with a fungicide like Immunox or Daconil if the trees are in your landscape. This is not practical for wild native acreage.

Thank you for response. I am in a woodland setting and concerned about severity. The manzanita in the picture seems like it may die. Can any of these fungal pathogens do this? There are quite a few nearby that look the same. Can you recommend a book or pamphlet that gives details on all the fungal pathogens. Can any of these affect vegetable garden plants because we have a variety of ones that are dying from some sort of wilt. , simultaneously

Normally trees in the wild develop under natural pressure from these leaf diseases. They can be killed but it often takes repeated disease pressure over many years to do that. Since the weather changes each year the intensity of the disease infection will change from year to year. This spring seemed to cause pretty severe outbreaks with mild temps and enough rain or morning dew to keep the infections going. Native forest species is not something I work with so I don't have a list of books. Just go online and query leaf diseases of Madrone and Manzanita and the same for trunk diseases. These two species have many of the same problems.

Diseases of trees almost never effect vegetable plants. Vegetables can get a few issues when plants are young that are tied to fungal pathogens in the soil, like damping off when the soil is too wet. Most issues I see are insects hitting young seedlings. Of course nutrient deficiency is also an issue if your soil is not fertile.